Date   
Re: TR502 A120 Assembly Required.... transistor update

Craig Sawyers <c.sawyers@...>
 

It never ceases to amaze me what an incredible resource of knowledge we have within this
community :)...... like the other thread on "sooty cable".... Radon decay and..... a "Geiger
counter"
group!

Now I've got to arrange a small work-jig to hold the tiny module stationary while I work on it.

Nigel G8AYM
I'm reading this thread with great interest! You might still have problems soldering, because
alumina has a high thermal conductivity. At 35W/mK it is 140 times more conductive than FR4 circuit
board material, and only 6 times less conductive than aluminium.

Good luck

Craig

Re: 575 curve tracer on UK eBay

NigelP
 

Aha now the curve tracers are coming out of the wood-work :). Indeed a very useful tool. I have a 577 and an 7CT1N, both of which I've needed to repair and used a 576 at work (as well as that actual aforementioned 577 :)). The 7CT1N is a bit limited compared to the 577 but it's much quicker to plug that into the mainframe and check some devices than to drag the 577 out from under the bench (don't have a workshop big enough to put it all out on show) .

Beauty is in the eye of the beholder and if I had a decent sized workshop I'd probably be buying too many of these wonderful beasts and my wife would be saying (yet again) "just WHY do you need another oscilloscope, and why are they filling up the attic?"..... she gets the room crammed full of musical instruments, but scopes ??????

Nigel G8AYM

Re: TR502 A120 Assembly Required.... transistor update

NigelP
 

Ed, indeed it is "greyish" in colour! Now you've provided that useful insight I guess I can assume the silver loading is helping to conduct the heat away from the back of the substrate and making it difficult for unsoldering (at least I HOPE it is!!).

It never ceases to amaze me what an incredible resource of knowledge we have within this community :)...... like the other thread on "sooty cable".... Radon decay and..... a "Geiger counter" group!

Now I've got to arrange a small work-jig to hold the tiny module stationary while I work on it.

Nigel G8AYM

Re: 575 curve tracer on UK eBay

 

Talking of Deane: What happened to his hoard?

Dave

Re: Type 503 Oscilloscope Issues

Albert Otten
 

Evan, note that a simple DMM or analog voltmeter might not respond properly to an AC ripple component of several kHz (the oscillator frequency).
IIRC you would have had another scope available last weekend to perform waveform measurements?
Albert


---In TekScopes@..., <polara413@...> wrote :

Measuring the AC voltage to GND on the -100V bus will be a good first
check. It should be very low as has been previously mentioned.
--

Dave Casey

Re: Tek Blue paint source?

Jan Bottorff
 

I see Krylon Bahama Sea spray paint is available on amazon https://www.amazon.com/Krylon-K09102000-COVERMAXX-Spray-Bahama/dp/B013LT52E0/ref=sr_1_1?ie=UTF8&qid=1494317136&sr=8-1&keywords=krylon+bahama+Sea

Jan

From: <TekScopes@...> on behalf of "Chris Elmquist chrise@... [TekScopes]" <TekScopes@...>
Reply-To: "TekScopes@..." <TekScopes@...>
Date: Sunday, May 7, 2017 at 7:39 PM
To: "TekScopes@..." <TekScopes@...>, "Gary Robert Bosworth @grbosworth [TekScopes]" <TekScopes@...>
Subject: Re: [TekScopes] Tek Blue paint source?



On May 3, 2017 9:49:15 PM CDT, "Gary Robert Bosworth @grbosworth [TekScopes]" <TekScopes@...> wrote:
Krylon "Bahama Sea" is very close. It cannot be used as touch-up, but
is
near perfect if sprayed on all over. It is called Colormaster gloss.
Sherwin-Williams orders it for me and does not charge for the service.
Each can is about $6.00.

On May 3, 2017 6:03 PM, "Chris Elmquist chrise@... [TekScopes]" <
TekScopes@...> wrote:



Wondering if there is still a source for Tek Blue spray paint?

I've tried to contact Stan Griffiths here,

http://www.reprise.com/ash/clients2/parts_shop/contact.html

but the email is bouncing. He used to be able to supply it in spray
cans, apparently having it mixed by the same Sherwin-Williams outfit
in
OR that Tek did.

I may have missed a discussion that Stan is no longer with us or no
longer in that business.

Any other sources or perhaps knowledge of the mixing codes so we can
get our own mixed locally?

Thanks and 73,

Chris NØJCF
--
Chris Elmquist



Gary,

This was a great recommendation. I happened to find a can of Bahama Sea while at the local farm store today. $3.50. Promptly cleaned the top of the TM-504 I am refurbing and sprayed it in the backyard. It looks great! It's just a tiny bit more green than the original blue on the rest of the box but it is definitely close enough for government work (as we say in government). So, I am happy with this easy solution.

Thanks again for the suggestion,

Chris
--
Chris Elmquist

Re: 575 curve tracer on UK eBay

Craig Sawyers <c.sawyers@...>
 

Chuck and Tom

That is a really interesting application - and thanks to the late and great Deane Kidd. I'll have to
give that a try.

If you have a 175 high current adaptor for the 575 you could test some serious batteries - it can
deliver up to 200A at up to 20V. I have one with Tek's original label tied around one of the handles
(so never had much use, clearly). A real beast, nearly 20lb heavier than the 575 (it is 83 1/2lb,
38kg) and wired internally with welding cable. When I got it, I randomly tried out a TO220 cased
transistor, and without much effort at all blew a red hot metal tab across the room in a hail of epoxy
shards.

Craig

-----Original Message-----
From: TekScopes@... [mailto:TekScopes@...]
Sent: 09 May 2017 06:12
To: TekScopes@...
Subject: Re: [TekScopes] 575 curve tracer on UK eBay

It's really pretty easy, set up the curve tracer for any DC sweep, such as you would do to test a
diode,
and put the current up pretty high.

For a good low impedance battery, you should see something that looks a lot like a zener diode knee.
No current drawn until you get to the battery voltage, and then the current will go sky high.

The shape of the knee, and the slope of the curve above the knee are indicators of the charging
current ability.

If you use AC, and a charged battery, the curve will show the charging impedance and the discharging
impedance.

OBTW, the slope of the curve above the knee is an amalgam of the load resistor you have selected,
and the impedance of the battery.... Z=V/I.

Try it, you will like it!

-Chuck Harris

Merchison Burke merchison@... [TekScopes] wrote:
Hello Tom,

Is there an article on-line which describes the method of testing
Ni-Cad batteries as you mentioned?

Thank you


On 2017-May-08 5:52 PM, ae5i@... [TekScopes] wrote:
Craig, you are so right! A 575 is one of the most useful instruments I have. For hand-selecting
transistors/diodes/etc, there's nothing like it. For sorting, testing, matching so many components.


It's also a good tool for assessing the condition of NiCad batteries. By sweeping the battery
and
looking at the curve, you can see an indication of the source impedance of the battery which is a
guide
to its overall condition. Deane Kidd taught me that trick.


Definitely the sort of instrument that you'd want to have a backup unit for.... :-) Just too
handy to
be without it when you need it!


Tom


------------------------------------
Posted by: Merchison Burke <merchison@...>
------------------------------------


------------------------------------

Yahoo Groups Links




------------------------------------
Posted by: Chuck Harris <cfharris@...>
------------------------------------


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Yahoo Groups Links


Re: 575 curve tracer on UK eBay

Chuck Harris
 

It's really pretty easy, set up the curve tracer for
any DC sweep, such as you would do to test a diode, and
put the current up pretty high.

For a good low impedance battery, you should see something
that looks a lot like a zener diode knee. No current drawn
until you get to the battery voltage, and then the current
will go sky high.

The shape of the knee, and the slope of the curve above the
knee are indicators of the charging current ability.

If you use AC, and a charged battery, the curve will show
the charging impedance and the discharging impedance.

OBTW, the slope of the curve above the knee is an amalgam of
the load resistor you have selected, and the impedance of the
battery.... Z=V/I.

Try it, you will like it!

-Chuck Harris

Merchison Burke merchison@... [TekScopes] wrote:

Hello Tom,

Is there an article on-line which describes the method of testing Ni-Cad
batteries as you mentioned?

Thank you


On 2017-May-08 5:52 PM, ae5i@... [TekScopes] wrote:
Craig, you are so right! A 575 is one of the most useful instruments I have. For hand-selecting transistors/diodes/etc, there's nothing like it. For sorting, testing, matching so many components.


It's also a good tool for assessing the condition of NiCad batteries. By sweeping the battery and looking at the curve, you can see an indication of the source impedance of the battery which is a guide to its overall condition. Deane Kidd taught me that trick.


Definitely the sort of instrument that you'd want to have a backup unit for.... :-) Just too handy to be without it when you need it!


Tom


------------------------------------
Posted by: Merchison Burke <merchison@...>
------------------------------------


------------------------------------

Yahoo Groups Links



Re: 575 curve tracer on UK eBay

Merchison Burke
 

Hello Tom,

Is there an article on-line which describes the method of testing Ni-Cad batteries as you mentioned?

Thank you

On 2017-May-08 5:52 PM, ae5i@... [TekScopes] wrote:
Craig, you are so right! A 575 is one of the most useful instruments I have. For hand-selecting transistors/diodes/etc, there's nothing like it. For sorting, testing, matching so many components.

It's also a good tool for assessing the condition of NiCad batteries. By sweeping the battery and looking at the curve, you can see an indication of the source impedance of the battery which is a guide to its overall condition. Deane Kidd taught me that trick.

Definitely the sort of instrument that you'd want to have a backup unit for.... :-) Just too handy to be without it when you need it!

Tom

Re: Suggestions for rehabbing a 466 w/ DM43

Fabio Trevisan
 

Hello Ryan,

You said "Okay, definitely going to need pictures on this one. =) I didn’t
actually see any way to GET to the pin header on the scale illumination
wire. And sadly, it seems to go right under the CRT. =/"

It seems you`re trying to find a pin header at the wrong end of the cord...
at the the lamp assy`s end the cord is soldered... it comes out from the
back of the lamp assy`, enters underneath between the tube and its tunnel,
and through a small hole in the tube`s tunnel that you're not seeing,
because the lamp assy is covering it and the cord is simply too short that
it won't let go a single millimeter.
The pin header I'm talking about is at the other end of the cord, where it
comes out from underneath the storage board, in the very tight space
between the storage board and the interface board, nearby a 4cm aluminum
block where two small power transistors are screwed.

I took some pictures of the way how the cord goes in and out of the lamp
assy, into the scope.
You can find the pictures here at Imgur: http://imgur.com/a/e1ihJ

You wrote
"I may need to take things apart anyway to replace a couple axial caps
(unless I just cut the leads on both ends and tack a replacement in… which,
is sounding more and more appealing. Or is the bottom board single sided
and I can just unsolder from the top and resolder without worrying about
back side connections"

To replace the axial electros and/or most of the components on the bottom
board, you can unsolder them from the component side and solder the new
ones cutting the excess leads to size before soldering the new ones in
place.
Unlike what you seem to be thinking, although all boards in this scope are
double sided, they don`t rely on the components' leads to connect to tracks
on the back side... the through holes have their inner walls metallized,
therefore assuring the connection between both sides regardless of the
component's leads.
As long as you`re careful while unsoldering / removing the old component to
not rip-off the metallized through holes, you can safely solder the new
components only from the component's side, and the metallized holes will
spread the solder by capillarity to the other side, and even if it doesn't,
it won`t matter, because the holes themselves connect the two sides.

You asked
"Is the scale illumination stuff IN the manual? I can’t seem to find it in
the schematics… which, I’d give my grandfather a hard time about (since he
probably helped write the manual) if he were still around"

The mechanical drawing is not clear enough to illustrate how the lamp
assy's wiring goes into place, but the lamp assy, as well as its
controlling circuit are described in the electrical diagrams...(you called
it schematics, but you will soon find out that in Tek jargon they're called
DIAGRAMS, so it's better getting used to it).
I don't have the 466 manual, but assuming it's similar to mine in that
respect, the lamp assy and the voltage controller circuit are described in
the same diagram where the low voltage power supplies are drawn (where you
will find the input power transformer, all the full-wave rectifier bridges
and the voltage regulator transistors).
In the pages just prior to each diagram, you will find the corresponding
pictures of the boards and/or parts of boards containing the components
drawn in the following diagrams.
In those pictures you will find the visual references to locate the
connector P1791, where the lamp assy's 2 pin header goes.

I must say that, if your grandfather helped written the manual, he did a
heck of a good job (although sometimes I also want to shout at them, as
they become hard to understand because they're split apart in so many
pieces)...
My entire Kenwood oscilloscope's diagrams fits into 3 tabloid pages (11 x
17 inch) and are much easier to put everything together in mind!

I will post the other pictures of the lamp assembly modded to LEDs as soon
as I can.

Rgrds,

Fabio


2017-05-08 19:01 GMT-03:00 Ryan Stasel rstasel@... [TekScopes] <
TekScopes@...>:



Hi Fabio,

Okay, definitely going to need pictures on this one. =) I didn’t actually
see any way to GET to the pin header on the scale illumination wire. And
sadly, it seems to go right under the CRT. =/

I may need to take things apart anyway to replace a couple axial caps
(unless I just cut the leads on both ends and tack a replacement in… which,
is sounding more and more appealing. Or is the bottom board single sided
and I can just unsolder from the top and resolder without worrying about
back side connections.

Is the scale illumination stuff IN the manual? I can’t seem to find it in
the schematics… which, I’d give my grandfather a hard time about (since he
probably helped write the manual) if he were still around.

Do let me know if you have pictures. The LED mod sounds like a nice
addition. =)

-Ryan Stasel
IT Operations Manager
School of Journalism and Communication
University of Oregon

Re: Type 503 Oscilloscope Issues

Dave Casey
 

Measuring the AC voltage to GND on the -100V bus will be a good first
check. It should be very low as has been previously mentioned. We also
might be able to find a good place to isolate the rest of the -100V
circuitry from the supply to see how well the supply operates completely
unloaded. It may then be able to reach -100V, but if we can't adjust it
much higher than that with R641, that's a pretty good indication that those
capacitors are leaky. You might even be able to prove them bad with just an
ohm meter once you've disconnected them.

Dave Casey

On Mon, May 8, 2017 at 6:57 PM, enchanter464@... [TekScopes] <
TekScopes@...> wrote:



Thank you all for the direction on looking at the capacitors. Sorry for
the delay in my reply. I have not gotten the chance to look at the scope
since doing the tube-removal checks a few days ago.

I had checked the capacitors C611 and C612 previously, as they were
suspected to be an issue early on (but both checked out okay with the
resistance test), but I never checked any of the others in the power
circuit.


I can check the C682 and C684 later tonight or tomorrow, based on the
instructions from Trevor. Unfortunately, I do not have a capacitance meter
available for use, but I have gotten in my probes for the analog meter, so
I can check the caps with both the DMM and analog meter, and then report in
my findings. I also got in more silver-bearing solder, so removing any
components to get the readings won't be an issue.


I recall from earlier postings that the non-ceramic capacitors are prone
to failure in the older scopes, so are there any other capacitors that I
should check as well for potential failure? (there appear to be quite a few
other EMC/PTM capacitors in the scope, based on the manual)


- Evan



[Non-text portions of this message have been removed]



[Non-text portions of this message have been removed]

Re: Type 503 Oscilloscope Issues

Evan
 

Thank you all for the direction on looking at the capacitors. Sorry for the delay in my reply. I have not gotten the chance to look at the scope since doing the tube-removal checks a few days ago.

I had checked the capacitors C611 and C612 previously, as they were suspected to be an issue early on (but both checked out okay with the resistance test), but I never checked any of the others in the power circuit.


I can check the C682 and C684 later tonight or tomorrow, based on the instructions from Trevor. Unfortunately, I do not have a capacitance meter available for use, but I have gotten in my probes for the analog meter, so I can check the caps with both the DMM and analog meter, and then report in my findings. I also got in more silver-bearing solder, so removing any components to get the readings won't be an issue.


I recall from earlier postings that the non-ceramic capacitors are prone to failure in the older scopes, so are there any other capacitors that I should check as well for potential failure? (there appear to be quite a few other EMC/PTM capacitors in the scope, based on the manual)


- Evan

Re: Suggestions for rehabbing a 466 w/ DM43

R. Stasel
 

Hi Fabio,

Okay, definitely going to need pictures on this one. =) I didn’t actually see any way to GET to the pin header on the scale illumination wire. And sadly, it seems to go right under the CRT. =/

I may need to take things apart anyway to replace a couple axial caps (unless I just cut the leads on both ends and tack a replacement in… which, is sounding more and more appealing. Or is the bottom board single sided and I can just unsolder from the top and resolder without worrying about back side connections.

Is the scale illumination stuff IN the manual? I can’t seem to find it in the schematics… which, I’d give my grandfather a hard time about (since he probably helped write the manual) if he were still around.

Do let me know if you have pictures. The LED mod sounds like a nice addition. =)

-Ryan Stasel
IT Operations Manager
School of Journalism and Communication
University of Oregon

On May 8, 2017, at 14:44 , Fabio Trevisan fabio.tr3visan@... [TekScopes] <TekScopes@...> wrote:

Hello Ryan,

It seems we're almost in sync regarding the repairs we're doing, you to
your 466 and me to my 464, which are mostly the same.

I just finished refurbishing the Scale Illumination assembly on my 464 and,
as though I had to remove the A6 Interface board out (for other reasons), I
could see that there's actually nothing that prevents pulling that assy'
out, besides its own 2 pin header (harmonica header) P1791 being attached
to the A6 interface board, just next to its controlling transistor Q1792.
Just pulling out the header connector already make the assembly loose and
allow you to pull it out (the 2 wire cable is short).

The problems you may face (if your storage controller board isn't removed
yet and if you don't plan to take it out) are:
1. To move / slide the 2 pin header between the Interface board and the
Storage board, so that it can run freely underneath the Storage board...
2. To run the wire and header back into place, after you clean / refurbish,
do whatever you need to do to the lamp assembly.

For problem 1, my advice is that you just take the pins out of the header's
plastic holder... without the holder and the 2 pins separate from each
other, is much simpler to slide them under the Storage board and pulling
out the lamp assembly from the scope's front (BUT WAIT, don't do it before
reading below)...

For problem 2, I advice you to attach (with scotch tape or insulating tape)
some thin leader to the tip of the lamp assy wiring, so that you can pull
it back afterwards.
One of the wires from a piece of rigid CAT5 network cabling will do nicely.

I did replace my lamps for 10cms worth of flexible LED stripes (6 leds, two
segments of 5cm) and I`m almost ready to post the pictures of the whole
process, at the TekScopes photo area.
To account for the fact that the LED stripes work with 12Volts, and also
for the fact that LEDs are more dimmable by controlling their current
instead of their voltage, I modified slightly the lamp control circuit,
turning it into a variable current sink, instead of a variable voltage
source.

The modification is 4 steps:
1. remove P1791 (2 pins) altogether and mount a 150Ohm 1/3Watt resistor in
there (150Ohms yields about 42mA under 6.3V which is just over the LED's
nominal current of 20mA per 5cm).

2. Change the voltage source of Q1792, from +5 UNREG to +15UNREG, by
cutting the track to the collector of Q1792 at 2 places...near the +5V
UNREG rectifier bridge and near Q1792 itself.
2.a. 1st cut near the rectifier bridge CR1761 (on the component side), It's
a less than 10mm segment of track between the bridge and a via.
2.b. 2nd cut near the Q1792 itself, leaving some space around the cut to
solder on both sides before and after the cut. (e.g. don't cut right near
Q1792 collector, but some 5mm away)

3. Connect, with a 3.5cm piece of insulated wire, the +15V UNREG voltage to
the via (mentioned on point 2.a. above). This will bring approx 23V on top
of the led stripe (instead of the original 10V from the former +5V UNREG).
Since Q1792 is rated for 40V there's no problem here and dissipated power
won't be a problem either, as the LEDs will draw only one tenth of the
current of the 2 lamps set.

4. For this, I used 2 pins from a right angle pin header, but any thicker
component lead will do (0.6mm dia), and pulled out and reinserted the pins
so that each L points outwards, and soldered the headers FLAT, right on the
track near Q1792 transistor, so that each pin is soldered on each side of
the cut performed on step 2.b.

I tested it already and it illuminates the scale bright and evenly all the
way through the screen's height... million times better than the uneven and
weak illumination from the original 2 lamps set.

Rgrds,

Fabio

2017-05-08 14:17 GMT-03:00 Ryan Stasel rstasel@... [TekScopes] <
TekScopes@...>:



Hi Everyone,

Thanks so much for the input on this. Some Deoxit later, and I have a
largely functional scope with two remaining issues (one being recapping the
PSU and main board).

The other being replacing the graticule illumination lamps. I can’t figure
out how to get them out… they’re in a holder, which has seen better days
(being plastic from 1976). But the cord that powers them runs into the guts
of the scope… Do I really have to pull the whole thing apart?

Thanks!

-Ryan Stasel
IT Operations Manager
School of Journalism and Communication
University of Oregon

On May 3, 2017, at 21:24 , Fabio Trevisan fabio.tr3visan@...
[TekScopes] <TekScopes@...> wrote:

David,
Yep, essentially that is the idea but the solder doesn't actually need
to
touch the board (although it doesn't hurt either).
Since molten solder has a high surface tension, you fill the crucible
with
enough solder so that the molten solder surface is above the crucible
edges
so, when you get the board closer and closer, the solder touches first
the
tip of the components and it's surrounding solder... In that moment, the
solder around the leads immeditaly melts and is "pulled" by the
Crucible's
solder (by capilarity or surface tension, I'm not sure exactly what's
the
name of mechanism by which it happens).
You don't actually need to take the board closer than that because at
this
point, the solder around all pins is already molten and the component is
free to be pulled from the other side.
In practice you apply some pulling force to the component before and as
you
get the board closer and closer to the crucible.
At some point the component gets free and comes out and you can lift the
board away from the crucible.
If you apply some flux to the board before is even better as it helps
the
molten solder to "wet" the pins/pads.
When you lift the board, it leaves the pads with an even and thin solder
coating.
Large holes are drained out and smaller holes remain filled with solder
as
the hole's capillarity "hold" the solder inside them.
As with everything else, some practice is required and you can train
yourself on scrapped PCBs of any unrepairable device or equipment, such
as
of computers, laptops and modern scopes :-).
Kidding... One cheap stuff that is often discarded such as desktop PC
power
supply boards usually have the kind of bigger components (like big
transistors hooked together with their solderable heat sinks) that allow
you to get the "touch" quickly.

Brgrds,

Fabio

On May 3, 2017 10:01 PM, "David Berlind david@... [TekScopes]"
<
TekScopes@...> wrote:

So, the PCB essentially had to make contact with the melted solder in
the
crucible?

On May 3, 2017 8:07:40 PM "Fabio Trevisan fabio.tr3visan@...
[TekScopes]" <TekScopes@...> wrote:

Hi David,
I didn't but I wish I did because now I'm having to work around quite
a
few
lifted pads and stripped-off metalized vias.
I do have, however, experience of a former job at a computer
manufacturer
in Brazil where we had small crucibles, of about 3 cms diameter, to
unsolder hard stuff just like this... Multi pin connectors where the
pads
were big (and retains a lot of solder and drains a lot of heat) all
that
were a pain to remove by any other means, and were so easy to remove
using
the crucible.
It was just a matter of carefully turning the PCB solder side down
over
the
crucible so that it would melt all the pins simultaneously, wait for
no
more than 2 seconds and pull the connector away.
They would come out so quickly that we could hold the connectors bare
handedly.
Of course that it has its down side...
It takes you to remove the board (which is not easy on the 4xx series
scopes), and sometimes takes additional measures such as removing
components around the area where the crucible will have to get close
to
the
PCB, either not to damage the components or to clear the area so that
you
can actually put the board in contact with the molten solder.
Back then, at a factory, we did that simply because it was faster and
cleaner, and usually there wasn't the down-side of having to
disassemble
the equipment, because it was already disassembled.
At a repair shop, dealing with equipment that's still current, I think
it
wouldn't be practical for the day to day use, due to the down-sides
and
due
to the availability of parts to replace, should they get damaged in
the
removal process..
Back to the restoration business (where we are) when a PCB that is, at
least, hard to get, and when you also don't want to destroy the old
caps,
because you want to use their packaging as mechanical support for the
new
ones, as I had to, I think that the additional preparation work is
worth
it.
I wish I had a small crucible at hand when I started removing the
caps.
But I fooled myself I would do it easily and I must confess I regret
for
having insisted on doing it the hard way.
Later I went on looking for crucibles and found small ones for as
cheap as
Brazilian 110,00 which is roughly 30,00 dollars.
I will look after one to have it around for the next occasions.

Brgrds,

Fabio


On May 3, 2017 7:06 PM, "David Berlind david@... [TekScopes]"
<
TekScopes@...> wrote:



Hi Fabio,

I suspect that I will one day end up having to recap my 466... I was
curious about this statement:

*"get yourself asmall soldering crucible... because it takes too long
to
unsolder thecapacitors using regular solder wick and solder
vacuum-pump
and
the PCBsuffers. It's almost impossible not to end-up lifting some
pads
and/ortracks or ripping-off some of the metalized thru holes
(vias)."*

Can you explain how specifically you ended up using the crucible?

Thanks.

On Wed, May 3, 2017 at 5:43 PM, Fabio Trevisan
fabio.tr3visan@...
[TekScopes] <TekScopes@...> wrote:



Hello Ryan,

I have a 464 (they're quite similar to the 466, exception to the
H.V.
section that is simpler than that of the 466s) which I have went
through
all sort of minor problems since I bought it about 9 months ago.
Last "event" was that if finally blew one of its large P.S.
electrolytic
capacitors, the 1200uF x 120V.
On this last event (quite recent), I posted a question on this
forum,
for
which I had quite some good advice from the folks.

Search for the thread:
Tek 464 - Big Caps recommnedation - Pot grease recommnedation

The original caps "form factor" is not in use presently and most
you
will
find on the market are plain "Radial" caps, (with plain leads) or
"Snap-In"
caps that are usually short and fat (and some of them won't fit on
the
1"
available space).
Neither fits-in mechanically / physically as the originals and both
require
some adaptation.
In recapping yours, you will have to make up your mind on either
following
the path of that guy you mentioned who recapped his 465 with
Snap-In
capacitors (and connected them with wires and held them with
plastic
brackets)... Or...
Buy pairs of smaller valued capacitors and mount them "In" the cans
of
the
original caps (after opening them up and disposing their original
innards).

I followed the latter path and I`m just about to finish doing
it...As
soon
as I can I will post to the pictures area of Tekscopes.
My solution was as follows:
500uF x 50V was replaced by 820 x 100V (it fits inside the can).
250uF x 150V was replaced by 330uF x 250V (if fits inside the can)
3 x 5500uF x 30V were replaced by 3 pairs of 3300uF x 63V (and each
pair
fits well inside the can)
1200uF x 100V were replaced by a rather long pair of 680uF x 160V
(I
wish I
could have found shorter ones) They were 2 inches tall (each) and
the
association didn't fit inside the can and I had to open the top of
the
can
to mount them inside.

You will notice the C and V values are larger in all of them than
the
originals, and this is not by chance. It's rather an advice from
the
folks
of this forum to make up for the overall smaller ripple current
ratings
of
the modern electrolytics.
Another advice is to try to have them all of 105C grade (the
original
ones
were all 85C).

Last but not the least, on desoldering the old ones, if you plan to
follow
the 2nd path (and re-use the old capacitors base and cans), get
yourself
a
small soldering crucible... because it takes too long to unsolder
the
capacitors using regular solder wick and solder vacuum-pump and the
PCB
suffers. It's almost impossible not to end-up lifting some pads
and/or
tracks or ripping-off some of the metalized thru holes (vias).

If you don't plan to use the older capacitor bases and cans, its
better
to
just cut the old ones with a dremel cutting disc and pulling the
terminals
one by one.

Rgrds,

Fabio

2017-05-03 17:17 GMT-03:00 Ryan Stasel rstasel@...
[TekScopes]
<
TekScopes@...>:




Hi All,

I picked up a Tek 466 w/ DM43 locally for $30 this week, and
after
replacing the main fuse, it powered up, and after fiddling with
things
for
a while, it’s mostly “working”. Checking all the voltages, things
seem
good
and within tolerance. But it’s obvious all the caps are original
to
the
unit… which, I have no good date on since I can’t find a serial
anywhere
(there is a hand written label on the tube shielding that says
92615).

Anyway, it’s pretty clear all the switches and pots need cleaning
(do
most
suggest just using Deoxit spray, and maybe Fader Lube for the
pots?),
and
the main caps need replacing. I’m also seeing a couple axial
electrolytic
caps on the “main” board (looking at the screen, the board along
the
right
hand side) need replacing (they’re showing corrosion on the
leads).
But
I’m
also curious if I should pull any of the socketed transistors or
ICs
and
spray the sockets with cleaner and reseat, etc. The unit still
acts a
bit
weird from time to time (screen blooms like it’s doing some
storage
mode,
not showing both traces, not properly grounding the inputs when
gnd
is
selected, etc).

I’m happy to link to pictures, etc… everything looks good, but
obviously
hasn’t been touched much since the unit was built. I’m also
really
interested in what caps I should use for recapping the Power
supply.
They’re a very odd size (tall and skinny), and looking online, I
see
someone recapped a 465, but the new caps didn’t really match in
size
at
all
so jumpers were needed. I’m pretty sure these size caps aren’t
really
made
anymore, so I’m all for suggestions.

If anyone’s interested, it looks like my unit was tested by a
Kreurauko
(or something like that)… and the DM43 has “Donna” written on the
board
in
“Sharpie”. =)

Thanks very much!

-Ryan Stasel

[Non-text portions of this message have been removed]


[Non-text portions of this message have been removed]



[Non-text portions of this message have been removed]
[Non-text portions of this message have been removed]

[Non-text portions of this message have been removed]



[Non-text portions of this message have been removed]


Re: 575 curve tracer on UK eBay

Tom Brown
 

Craig, you are so right! A 575 is one of the most useful instruments I have. For hand-selecting transistors/diodes/etc, there's nothing like it. For sorting, testing, matching so many components.


It's also a good tool for assessing the condition of NiCad batteries. By sweeping the battery and looking at the curve, you can see an indication of the source impedance of the battery which is a guide to its overall condition. Deane Kidd taught me that trick.


Definitely the sort of instrument that you'd want to have a backup unit for.... :-) Just too handy to be without it when you need it!


Tom

Re: Suggestions for rehabbing a 466 w/ DM43

Fabio Trevisan
 

Hello Ryan,

It seems we're almost in sync regarding the repairs we're doing, you to
your 466 and me to my 464, which are mostly the same.

I just finished refurbishing the Scale Illumination assembly on my 464 and,
as though I had to remove the A6 Interface board out (for other reasons), I
could see that there's actually nothing that prevents pulling that assy'
out, besides its own 2 pin header (harmonica header) P1791 being attached
to the A6 interface board, just next to its controlling transistor Q1792.
Just pulling out the header connector already make the assembly loose and
allow you to pull it out (the 2 wire cable is short).

The problems you may face (if your storage controller board isn't removed
yet and if you don't plan to take it out) are:
1. To move / slide the 2 pin header between the Interface board and the
Storage board, so that it can run freely underneath the Storage board...
2. To run the wire and header back into place, after you clean / refurbish,
do whatever you need to do to the lamp assembly.

For problem 1, my advice is that you just take the pins out of the header's
plastic holder... without the holder and the 2 pins separate from each
other, is much simpler to slide them under the Storage board and pulling
out the lamp assembly from the scope's front (BUT WAIT, don't do it before
reading below)...

For problem 2, I advice you to attach (with scotch tape or insulating tape)
some thin leader to the tip of the lamp assy wiring, so that you can pull
it back afterwards.
One of the wires from a piece of rigid CAT5 network cabling will do nicely.

I did replace my lamps for 10cms worth of flexible LED stripes (6 leds, two
segments of 5cm) and I`m almost ready to post the pictures of the whole
process, at the TekScopes photo area.
To account for the fact that the LED stripes work with 12Volts, and also
for the fact that LEDs are more dimmable by controlling their current
instead of their voltage, I modified slightly the lamp control circuit,
turning it into a variable current sink, instead of a variable voltage
source.

The modification is 4 steps:
1. remove P1791 (2 pins) altogether and mount a 150Ohm 1/3Watt resistor in
there (150Ohms yields about 42mA under 6.3V which is just over the LED's
nominal current of 20mA per 5cm).

2. Change the voltage source of Q1792, from +5 UNREG to +15UNREG, by
cutting the track to the collector of Q1792 at 2 places...near the +5V
UNREG rectifier bridge and near Q1792 itself.
2.a. 1st cut near the rectifier bridge CR1761 (on the component side), It's
a less than 10mm segment of track between the bridge and a via.
2.b. 2nd cut near the Q1792 itself, leaving some space around the cut to
solder on both sides before and after the cut. (e.g. don't cut right near
Q1792 collector, but some 5mm away)

3. Connect, with a 3.5cm piece of insulated wire, the +15V UNREG voltage to
the via (mentioned on point 2.a. above). This will bring approx 23V on top
of the led stripe (instead of the original 10V from the former +5V UNREG).
Since Q1792 is rated for 40V there's no problem here and dissipated power
won't be a problem either, as the LEDs will draw only one tenth of the
current of the 2 lamps set.

4. For this, I used 2 pins from a right angle pin header, but any thicker
component lead will do (0.6mm dia), and pulled out and reinserted the pins
so that each L points outwards, and soldered the headers FLAT, right on the
track near Q1792 transistor, so that each pin is soldered on each side of
the cut performed on step 2.b.

I tested it already and it illuminates the scale bright and evenly all the
way through the screen's height... million times better than the uneven and
weak illumination from the original 2 lamps set.

Rgrds,

Fabio





2017-05-08 14:17 GMT-03:00 Ryan Stasel rstasel@... [TekScopes] <
TekScopes@...>:



Hi Everyone,

Thanks so much for the input on this. Some Deoxit later, and I have a
largely functional scope with two remaining issues (one being recapping the
PSU and main board).

The other being replacing the graticule illumination lamps. I can’t figure
out how to get them out… they’re in a holder, which has seen better days
(being plastic from 1976). But the cord that powers them runs into the guts
of the scope… Do I really have to pull the whole thing apart?

Thanks!

-Ryan Stasel
IT Operations Manager
School of Journalism and Communication
University of Oregon

On May 3, 2017, at 21:24 , Fabio Trevisan fabio.tr3visan@...
[TekScopes] <TekScopes@...> wrote:

David,
Yep, essentially that is the idea but the solder doesn't actually need
to
touch the board (although it doesn't hurt either).
Since molten solder has a high surface tension, you fill the crucible
with
enough solder so that the molten solder surface is above the crucible
edges
so, when you get the board closer and closer, the solder touches first
the
tip of the components and it's surrounding solder... In that moment, the
solder around the leads immeditaly melts and is "pulled" by the
Crucible's
solder (by capilarity or surface tension, I'm not sure exactly what's
the
name of mechanism by which it happens).
You don't actually need to take the board closer than that because at
this
point, the solder around all pins is already molten and the component is
free to be pulled from the other side.
In practice you apply some pulling force to the component before and as
you
get the board closer and closer to the crucible.
At some point the component gets free and comes out and you can lift the
board away from the crucible.
If you apply some flux to the board before is even better as it helps
the
molten solder to "wet" the pins/pads.
When you lift the board, it leaves the pads with an even and thin solder
coating.
Large holes are drained out and smaller holes remain filled with solder
as
the hole's capillarity "hold" the solder inside them.
As with everything else, some practice is required and you can train
yourself on scrapped PCBs of any unrepairable device or equipment, such
as
of computers, laptops and modern scopes :-).
Kidding... One cheap stuff that is often discarded such as desktop PC
power
supply boards usually have the kind of bigger components (like big
transistors hooked together with their solderable heat sinks) that allow
you to get the "touch" quickly.

Brgrds,

Fabio

On May 3, 2017 10:01 PM, "David Berlind david@... [TekScopes]"
<
TekScopes@...> wrote:

So, the PCB essentially had to make contact with the melted solder in
the
crucible?

On May 3, 2017 8:07:40 PM "Fabio Trevisan fabio.tr3visan@...
[TekScopes]" <TekScopes@...> wrote:

Hi David,
I didn't but I wish I did because now I'm having to work around quite
a
few
lifted pads and stripped-off metalized vias.
I do have, however, experience of a former job at a computer
manufacturer
in Brazil where we had small crucibles, of about 3 cms diameter, to
unsolder hard stuff just like this... Multi pin connectors where the
pads
were big (and retains a lot of solder and drains a lot of heat) all
that
were a pain to remove by any other means, and were so easy to remove
using
the crucible.
It was just a matter of carefully turning the PCB solder side down
over
the
crucible so that it would melt all the pins simultaneously, wait for
no
more than 2 seconds and pull the connector away.
They would come out so quickly that we could hold the connectors bare
handedly.
Of course that it has its down side...
It takes you to remove the board (which is not easy on the 4xx series
scopes), and sometimes takes additional measures such as removing
components around the area where the crucible will have to get close
to
the
PCB, either not to damage the components or to clear the area so that
you
can actually put the board in contact with the molten solder.
Back then, at a factory, we did that simply because it was faster and
cleaner, and usually there wasn't the down-side of having to
disassemble
the equipment, because it was already disassembled.
At a repair shop, dealing with equipment that's still current, I think
it
wouldn't be practical for the day to day use, due to the down-sides
and
due
to the availability of parts to replace, should they get damaged in
the
removal process..
Back to the restoration business (where we are) when a PCB that is, at
least, hard to get, and when you also don't want to destroy the old
caps,
because you want to use their packaging as mechanical support for the
new
ones, as I had to, I think that the additional preparation work is
worth
it.
I wish I had a small crucible at hand when I started removing the
caps.
But I fooled myself I would do it easily and I must confess I regret
for
having insisted on doing it the hard way.
Later I went on looking for crucibles and found small ones for as
cheap as
Brazilian 110,00 which is roughly 30,00 dollars.
I will look after one to have it around for the next occasions.

Brgrds,

Fabio


On May 3, 2017 7:06 PM, "David Berlind david@... [TekScopes]"
<
TekScopes@...> wrote:



Hi Fabio,

I suspect that I will one day end up having to recap my 466... I was
curious about this statement:

*"get yourself asmall soldering crucible... because it takes too long
to
unsolder thecapacitors using regular solder wick and solder
vacuum-pump
and
the PCBsuffers. It's almost impossible not to end-up lifting some
pads
and/ortracks or ripping-off some of the metalized thru holes
(vias)."*

Can you explain how specifically you ended up using the crucible?

Thanks.

On Wed, May 3, 2017 at 5:43 PM, Fabio Trevisan
fabio.tr3visan@...
[TekScopes] <TekScopes@...> wrote:



Hello Ryan,

I have a 464 (they're quite similar to the 466, exception to the
H.V.
section that is simpler than that of the 466s) which I have went
through
all sort of minor problems since I bought it about 9 months ago.
Last "event" was that if finally blew one of its large P.S.
electrolytic
capacitors, the 1200uF x 120V.
On this last event (quite recent), I posted a question on this
forum,
for
which I had quite some good advice from the folks.

Search for the thread:
Tek 464 - Big Caps recommnedation - Pot grease recommnedation

The original caps "form factor" is not in use presently and most
you
will
find on the market are plain "Radial" caps, (with plain leads) or
"Snap-In"
caps that are usually short and fat (and some of them won't fit on
the
1"
available space).
Neither fits-in mechanically / physically as the originals and both
require
some adaptation.
In recapping yours, you will have to make up your mind on either
following
the path of that guy you mentioned who recapped his 465 with
Snap-In
capacitors (and connected them with wires and held them with
plastic
brackets)... Or...
Buy pairs of smaller valued capacitors and mount them "In" the cans
of
the
original caps (after opening them up and disposing their original
innards).

I followed the latter path and I`m just about to finish doing
it...As
soon
as I can I will post to the pictures area of Tekscopes.
My solution was as follows:
500uF x 50V was replaced by 820 x 100V (it fits inside the can).
250uF x 150V was replaced by 330uF x 250V (if fits inside the can)
3 x 5500uF x 30V were replaced by 3 pairs of 3300uF x 63V (and each
pair
fits well inside the can)
1200uF x 100V were replaced by a rather long pair of 680uF x 160V
(I
wish I
could have found shorter ones) They were 2 inches tall (each) and
the
association didn't fit inside the can and I had to open the top of
the
can
to mount them inside.

You will notice the C and V values are larger in all of them than
the
originals, and this is not by chance. It's rather an advice from
the
folks
of this forum to make up for the overall smaller ripple current
ratings
of
the modern electrolytics.
Another advice is to try to have them all of 105C grade (the
original
ones
were all 85C).

Last but not the least, on desoldering the old ones, if you plan to
follow
the 2nd path (and re-use the old capacitors base and cans), get
yourself
a
small soldering crucible... because it takes too long to unsolder
the
capacitors using regular solder wick and solder vacuum-pump and the
PCB
suffers. It's almost impossible not to end-up lifting some pads
and/or
tracks or ripping-off some of the metalized thru holes (vias).

If you don't plan to use the older capacitor bases and cans, its
better
to
just cut the old ones with a dremel cutting disc and pulling the
terminals
one by one.

Rgrds,

Fabio

2017-05-03 17:17 GMT-03:00 Ryan Stasel rstasel@...
[TekScopes]
<
TekScopes@...>:




Hi All,

I picked up a Tek 466 w/ DM43 locally for $30 this week, and
after
replacing the main fuse, it powered up, and after fiddling with
things
for
a while, it’s mostly “working”. Checking all the voltages, things
seem
good
and within tolerance. But it’s obvious all the caps are original
to
the
unit… which, I have no good date on since I can’t find a serial
anywhere
(there is a hand written label on the tube shielding that says
92615).

Anyway, it’s pretty clear all the switches and pots need cleaning
(do
most
suggest just using Deoxit spray, and maybe Fader Lube for the
pots?),
and
the main caps need replacing. I’m also seeing a couple axial
electrolytic
caps on the “main” board (looking at the screen, the board along
the
right
hand side) need replacing (they’re showing corrosion on the
leads).
But
I’m
also curious if I should pull any of the socketed transistors or
ICs
and
spray the sockets with cleaner and reseat, etc. The unit still
acts a
bit
weird from time to time (screen blooms like it’s doing some
storage
mode,
not showing both traces, not properly grounding the inputs when
gnd
is
selected, etc).

I’m happy to link to pictures, etc… everything looks good, but
obviously
hasn’t been touched much since the unit was built. I’m also
really
interested in what caps I should use for recapping the Power
supply.
They’re a very odd size (tall and skinny), and looking online, I
see
someone recapped a 465, but the new caps didn’t really match in
size
at
all
so jumpers were needed. I’m pretty sure these size caps aren’t
really
made
anymore, so I’m all for suggestions.

If anyone’s interested, it looks like my unit was tested by a
Kreurauko
(or something like that)… and the DM43 has “Donna” written on the
board
in
“Sharpie”. =)

Thanks very much!

-Ryan Stasel




[Non-text portions of this message have been removed]



[Non-text portions of this message have been removed]
[Non-text portions of this message have been removed]

[Non-text portions of this message have been removed]




[Non-text portions of this message have been removed]

Re: Type 503 Oscilloscope Issues

Dave Casey
 

I've mentioned the caps as a possibility, but I haven't yet heard anything
back on them being checked. I agree that it's looking more and more like
they are to blame.

Dave Casey

On Mon, May 8, 2017 at 7:52 AM, Trevor Marshall trevorjmarshall@...
[TekScopes] <TekScopes@...> wrote:



Measurements point towards open or very leaky -100 volt rail filter
capacitors C682 and/or C684. Electrolytics can fail such as to become
leaky, or fail such that they have greatly reduced capacitance, many times
essentially zero, when they fail open circuit. Disconnect one lead of each
of these caps to facilitate leakage measurement with your DVM.
Then, if you lack a capacitance meter, another more crude capacitance test
is as follows: Put your DVM in the resistance mode on the 20k scale and
probe the two cap terminals, and watch the meter reading. If the capacitor
is functioning properly, the reading will start low and increase over the
course of a few seconds or so, as the meter charges to cap, and then read
"ol" (or whatever indication the meter gives for off scale readings.) You
can repeat the test, but will have to first discharge the cap by shorting
it.Ideally, the correct polarity should be employed, meaning that the DVM
positive lead should connect to the capacitor positive lead. In practice,
at the <2 volts applied, polarity should not matter. If you put the meter
on the 200k scale, the charging process slows down by a factor of ten, so
will be even more easily observed. Going to an even higher scale, 2M, the
capacitor's leakage resistance will begin to interfere with this method.
You can get a rough idea of the value of the capacitor by comparing the
results to another known good capacitor. So if you have an electrolytic cap
that is 20 to 80 microfarads, experiment with it.

Before connecting your DVM or a capacitance meter to any capacitors,
assure that the cap. is discharged. If the scope has been off for some
time, charges tend to decay toward zero. But to be safe. since some types
of capacitors can hold charge for weeks, manually shorting capacitors
before measurement is a good practice.
My apologies to Evan and the mentors if this is redundant advice, it's a
long thread and I did not thoroughly scour it.
Trevor


On Sunday, May 7, 2017 1:38 PM, "'John Snyder' Kochcal@...
[TekScopes]" <TekScopes@...> wrote:


I look like your making progress, some things you try don't reveal
things.

Dave's point of Turning all the front panel adjustments is a good idea to
see if it changes the loading on the -100V, if one has a big change it can
indicate a part of the circuit that is the problem. If the overload is
through one of the tubes the associated adjustment should change the tube
operating point and current that may release the -100V a bit.

But it might not.

I would try other things before changing any other "inside" calibration
adjustments other then R641. The existing calibration can have some value
as
it can take time and equipment to restore.

Other things to look at:

I don't recall if you have already measured the resistance of the -100V bus
to ground (be sure to turn power off, wait, ground -100V bus for a while
remove ground, before testing to remove any charge on the capacitor) that
would be a good starting point.

Have you done a AC voltage reading on the -100V to see if the problem is a
low DC or more of a AC wave on top of the DC resulting in a lower average?

The -100V should have a AC voltage that is very low compared to a volt.

And then the same question as to the +500V on C612

The 500V could have 1's to few 10's of volts of AC but much more then it
would be a concern and need some calulating.

I don't recall or missed if you checked the input DC power caps C611 or
C612.

If you have can you re-report the check?

If you have not, one way to help check those would be to clip on a pair of
350V to 450V caps in parallel with each one. Those generally have a very
large range of value like +20%,-80% so it might only take 30uF's or so to
function. And that would be a good way to help eliminate that possibility
that that part of the power supply that is cutting out 120 times per
second.

The scope is functioning enough that you might be able to use it self to
probe some circuits.

Do you have any probes and if so can you tell us, there nature, model
numbers or ratings? To see if they can be used for the voltages needed for
some tests you can do to help.

John

For later:

You can see on the schematics that there are typical voltages at nodes for
parts of the circuit. (best made if all the scope knobs are set as stated
in
the manual for testing) Measuring those and reporting them, might lead to
clue as to the location of the problem, but with the -100V low most will
readings will be offset in some way, and it will be a bit more challenging
to use them to locate the area of over current. But we might be able to
find
something.

I don't recall if you have done any tests to check D682, C682 C684, a leak
there would be generally independent of the tubes being pulled.

If you are running the scope for a while you can check for the temperature
of D682, C682 C684 if it's different from the other diodes, But be sure to
measure all the voltages 250V 100V -100V to be sure they are discharged be
for sticking a finger in there. Not a great test (see scope probe Questions
below)

You still have a visual check of everything connected to the -100V

And measuring the voltage of across each resistor that is connected to the
-100V

-----Original Message-----
From: TekScopes@... [mailto:TekScopes@...]
Sent: Saturday, May 06, 2017 10:39 PM
To: TekScopes@...
Subject: [TekScopes] Re: Type 503 Oscilloscope Issues

Yes, from the calibrator, the scope is out of spec (at 420 mV and 4.1 mV),
but the calibrator image is not stable. Here is a link to what I mean:
https://goo.gl/photos/BZzZ41sma3vz5R717
https://goo.gl/photos/BZzZ41sma3vz5R717.

From the images, the square wave's magnitude is ~0.8 cm (compared to the
expected full 1 cm). However, as seen in the video, the issue of the waves
"warping" is even more present here, aside from a general instability of
the
trace.


I still have not looked at turning each adjustment knob to see the effect,
but I will try to get that done tomorrow.


- Evan



------------------------------------
Posted by: enchanter464@...
------------------------------------

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Re: 575 curve tracer on UK eBay

Craig Sawyers <c.sawyers@...>
 

I'm see eye to eye with Craig in recognizing the value of curve tracers. I have a 575 (I paid $20
for it),
two 577s, three 7CT1Ns and a 5CT1N. The only curve tracer I don't own is a 576 but I have access
to two
of them if I need them.

Dennis Tillman W7PF
I got my 576 free about 6 months ago. It had the dreaded epoxy potted HT problem, which I overcame
by winding a new one myself and then wax impregnating. The 1400 turns of 40 gauge wire was the
tricky bit.

Works flawlessly with the rewound transformer.

Craig

Re: 575 curve tracer on UK eBay

k1ggi
 

I would be remiss if I didn't mention an unbeatable bargain, kindly offered
by Kurt a couple of years ago, 575 free for pickup.

Splendid working condition, now used most often with a hb tube adapter.

Ed



_____

From: TekScopes@... [mailto:TekScopes@...]
Sent: Monday, May 08, 2017 11:24 AM
To: TekScopes@...
Subject: RE: [TekScopes] 575 curve tracer on UK eBay





I paid $20 for mine. Had to carry it quite a distance to my pickup. That's
when you learn why
there
are two heavy leather handles on the top.

Chris Trask
N7ZWY / WDX3HLB
http://www.home.earthlink.net/~christrask/
That was a nice price for a 575!

Craig

Re: 575 curve tracer on UK eBay

 

A curve tracer is as much of a universal instrument as an oscilloscope. Its
uses are limited by your creativity. They can measure the characteristics of
any electric and/or electronic device, not just transistors.

Until recently the one thing a Tek semiconductor curve tracer could not
measure (except in a very limited case) was vacuum tubes. I took care of
that recently by making an adapter board that would display the
characteristic curves of almost any kind of vacuum tube on any Tek
semiconductor curve tracer. Obviously, you are probably asking who is
interested in measuring tubes these days. The answer is plenty of people.
Audiophiles are one large group that want to do this.

I'm see eye to eye with Craig in recognizing the value of curve tracers. I
have a 575 (I paid $20 for it), two 577s, three 7CT1Ns and a 5CT1N. The only
curve tracer I don't own is a 576 but I have access to two of them if I need
them.

Dennis Tillman W7PF

-----Original Message-----
Sent: Monday, May 08, 2017 8:23 AM
Subject: RE: [TekScopes] 575 curve tracer on UK eBay

I just looked that up. That gigantic thing is only a curve tracer and not
an oscilloscope? Wow, ugh.

I can see the electric meter spinning every time you test a transistor
(does anyone really do that anymore?).

Dave
Well they do more than transistors. Diodes, Zeners, Tunnel Diodes. And you
are pushed to test a TD without a curve tracer. And if you want to match
transistors - particularly FET's both junction and MOS - for audio
applications they are darned useful. And you can test and optimise component
combinations, like cascode. With modest additions, you can also do tubes
(check recent threads about tube curve tracing on a 576).

I have two 575's, one with the high voltage Mod 122C, and also the high
current facility the 175. I also have a 577 with split storage screen, a 576
and a 7CT1N. Because why wouldn't you?

Craig------------------------------------
Posted by: "Craig Sawyers" <c.sawyers@...>
------------------------------------

Re: Sooty cabling

Ed Breya
 

Yes indeed - the radon decay chain has great affinity toward HV stuff. I've seen discussions in the geiger-counter group about measuring the soot/dust, and even collecting it to use as test sources. Needless to say, you want to avoid inhaling the stuff.

Ed