Date   
Re: Another scope 7854

 

what is the fastest setup I can get with this 7854? The 7A24 with its 50 Ohm 400MHz inputs?
The 7854 is specified to have 400 MHz vertical bandwidth (BW) when using either a 7A19 or 7A29 plug-in amplifier.
The 7A24 amplifier is specified to have 400 MHz BW when used in a 7104 mainframe. The 7104 is specified as quite a bit faster (1 GHz with 7A29) than the 7854. It is therefore to be expected that the 7854 / 7A24 combination may have trouble reaching the 400 MHz mark if you ignore the fact that actual BW of mainframes and plug-ins usually is significantly higher than the specification.

And the 7B85 ?
The 7854 has a specification of 500 ps/div. maximum horizontally. The 7B85 is specified at only 1 ns/div. max, when using the 10x magnifier and so would be the limiting factor.

Just trying to figure out the ideal plugins to look out for.
To fully utilise the horizontal and vertical speeds that the 7854 is capable of, a 7A19 (or 7A29) amplifier and a 7B92(A) would be a very nice setup. Be aware that the 7A19 and 7A29 are single-channel and that the 7B92(A) is a dual time base with delay.
With a 7B92(A) you'd have one horizontal slot unused. A 7D15 counter/timer would be nice to have real-time frequency and timing info.

What happens if you try to run the 1GHz plugins in the 7854? Are they just limited to 400MHz or what?
See above. It's not a matter of "trying to run": It just runs at at least 400 MHz BW without a problem, as described above.

If you like cheating:

The fastest setup by far would use a sampling set (7S12 or 7S11 with 7T11A). Top BW would be around 14 GHz, depending on sampler. That would only work for repetitive signals though.
Although a sampling setup only needs a very slow 'scope (a few MHz would do nicely), the storage and processing capabilities make for a very nice set and beautiful screen traces.

Raymond

Re: AF501 woes

EJP
 

Thanks Dave.

I added two more photos.

- The one with two traces shows the trigger pulse (top) and the input signal (bottom).

- The one with three traces shows trigger (top), signal (middle), and output at pin 7 of the comparator (bottom).

The glitch is towards but slightly before the bottom of the cycle, so there is a phase advance happening as well as the frequency doubling.

The comparator output doesn't change, apart from size and frequency, when I vary the amplitude or frequency into/out of the problem zones that exhibit the trigger glitch.

However I finally measured the comparator supply voltages and they are +15V and -9V, which should be +15/-3V, so the zener VR272 is faulty, which I will fix ASAP, and I guess we now have to wonder whether that is a possible cause.

TIA

EJP

Re: Another scope 7854

ArtekManuals
 

JOE

The 1GHz plug-ins will be just fine in the 7854 up to 400MHz. Yes you are limited by the 7854 but you might find it is good to 450MHz or even 600MHz with reduced sensitivity , dimmer waveform etc.

Dave

manuals@...

On 5/3/2017 8:50 PM, Joe Laffey joe@... [TekScopes] wrote:

What happens if you try to run the 1GHz plugins in the 7854? Are they just
limited to 400MHz or what?
--
Dave
Manuals@...
www.ArtekManuals.com

Re: Another scope 7854

John Griessen
 

On 05/03/2017 08:24 PM, David DiGiacomo telists@... [TekScopes] wrote:
Why would you say that?

Forgot. I use mine in store mode where there IS a 100MHz sampling speed that limits one shot events.

Thanks for correcting. It's one of 3 that are above my bench all the time: R7844, 2230, 7854

Re: Another scope 7854

David DiGiacomo
 

On Wed, May 3, 2017 at 7:20 PM, John Griessen <@jgriessen> wrote:
On 05/03/2017 07:50 PM, Joe Laffey joe@... [TekScopes] wrote:
What happens if you try to run the 1GHz plugins in the 7854? Are they just
limited to 400MHz or what?
I think they are limited to 100MHz+.

Why would you say that? The 7854 is a 400MHz mainframe.

Re: Another scope 7854

John Griessen
 

On 05/03/2017 07:50 PM, Joe Laffey joe@... [TekScopes] wrote:
What happens if you try to run the 1GHz plugins in the 7854? Are they just
limited to 400MHz or what?
I think they are limited to 100MHz+.

For fast try a 7904A, and then of course, a 7104.

Re: Tek 549 - HV transformer

zerousair
 

Good to know and thanks. Just a matter of checking the HV while it's in fail mode, I think.




Garrett

Tek Blue paint source?

Chris Elmquist
 

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

Re: Suggestions for rehabbing a 466 w/ DM43

David Berlind
 

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]

Another scope 7854

Joe Laffey
 

Hello all,

Well, I am now the proud owner of another scope I don't need... a Tek 7854.

It came with a 7A18 (70MHz dual input) and a 7B53A (100MHz dual time base).

The 7A18 has some issues. Channel 1 seems fine, but Channel 2 has a lot of noise on it (need to check the exact value, but the line is about 4 times thicker than Channel 1). It also seem to have all of its attenuator values off by around one click of the switch (not exactly). All waveforms have much greater vertical amplitude then they should. The readout display is correct based on the switch position.

I tried cleaning all the basic switches and pots, but I have not disassembled the cam based switches on the attenuator controls. I was wondering what special tricks there were to dealing with those. I am guessing one of the contacts is dirty/bad.

I will try to use the Open/Closed table for the attenuator and the amount of increase vertical scale to determine which contacts are bad. I just need to sit down with the unit and the service manual and see what I can discern. Any info is appreciated.

The scope also seems to have trouble triggering cleanly off Channel 2. I will occasionally see a glitch waveform. I do not see this on Channel 1. Also the glitches go away if I toggle the Channel 2 polarity switch to invert mode. They also go away if I use DC Offset (Option 06) mode on the 7A18.

I am guessing I should start with the cam switches, but do those trigger glitch criteria ring any bells with anyone?

Also, what is the fastest setup I can get with this 7854? The 7A24 with its 50 Ohm 400MHz inputs? And the 7B85 ? Just trying to figure out the ideal plugins to look out for. I'd like this to be my fast scope, possibly supplanting the 2465 (300MHz).

What happens if you try to run the 1GHz plugins in the 7854? Are they just limited to 400MHz or what?

This thing is pretty amazing considering the date of manufacture. Of course it was over $30k in today's dollars...

Thanks,

--
73
Joe Laffey
The Stable
Visual Effects
http://TheStable.tv/?e40763M/

Re: Suggestions for rehabbing a 466 w/ DM43

Fabio Trevisan
 

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]

Re: 485 1ns & 5ns/div

 

I love it when a plan comes together...

Raymond

Re: 485 1ns & 5ns/div

Christopher Kuni
 

Progress! And lots of it. Many thanks to David, George, Raymond, etc for useful comments.

The trouble was C615 and C617. I had noticed early in the saga that these trimmers made only slight changes in the trace. I took any change as evidence that they were OK. Nevertheless, I removed them and checked them with an LCR meter -- they tested good. BUT -- my LCR meter defaults to 100Hz when turned on. Today after reading the comments in the thread I removed them again and subbed fixed caps with values in the middle of the ranges of the trimmers. That made a big improvement. Re-checked the trimmers with the LCR bridge, this time at 100KHz, at which frequency the capacitance values were much lower and didn't change much with rotation. Furthermore, the D values, good at 100Hz, were terrible at 100KHz. How can a ceramic trimmer do that? Now I know why I keep my ancient Boonton Q meter, which goes up to 75 MHz.

I wired in replacement trimmers that I had on hand and got the result shown in the photo that I will upload. I measure the aberrations at about 2.5% P-P, less than the 4% limit quoted in the manual. I used the 50-ohm inputs and will get to the high impedance inputs soon.

I finally understood David's comments about viewing the external trigger signal. I've been using internal triggering, so at first it didn't make sense. When I did use external triggering (from the generator that drives my pulser) the trigger signal did indeed show the troubling distortion, which, in retrospect, it had to do.

Oh, BTW, don't go anywhere, as the project is not quite finished.

Re: Suggestions for rehabbing a 466 w/ DM43

 

I agree with Fabio, with a few remarks (hi Fabio!):

1. It's a good idea to use higher working voltage power supply caps but as to higher capacity, not so much, since their ESR will be lower still which causes a larger inrush current through the rectifier bridges. These are a bit underdimensioned in that respect. ESR of same capacity modern caps is already lower than that of the original caps. I don't think that ripple currents in these 'scopes is high enough to threaten modern good quality caps.

2. Very important: The original caps' sockets are part of the PCB continuity with their multiple case lugs. Make sure to replace their connections with wires.

3. Make sure you don't leave any contact cleaner residue, especially not in "open areas": Since these 'scopes pull air through their innards, dust carried by it will stick.

4. Lastly, you can find production date codes on the large PS caps: They contain 4-digit YYWW codes (Y = year-1900, W = calendar week), e.g. 7834 means week 34 of 1978. Other caps and IC's may have similar codings. Compare a few and you know which groups show the date code.

Re: Suggestions for rehabbing a 466 w/ DM43

David Berlind
 

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]

Re: 485 1ns & 5ns/div

 

And sometimes the caps rotate but the capacitance does not change because the screw driver slot
is disconnected from the rotating plate. I have replaced several of these faulty trimmer caps in my
485 and other Tek stuff.
Exactly my experience. BTW most often, the plate rotates but the metal layer is disconnected. Recently in a 7904A mainframe and a 465 portable.

Raymond

Re: Suggestions for rehabbing a 466 w/ DM43

Fabio Trevisan
 

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

Re: Tek 549 - HV transformer

widgethunter
 

To my knowledge, no vintage of the 551/555 are subject to this issue as
their xfrmrs are potted in wax.
The 556 is another story...
Sounds like you need to go through the HV supply.
Bernd Schroder

In a message dated 5/3/2017 2:35:24 P.M. Pacific Daylight Time,
TekScopes@... writes:




Bernd,
Without me looking up the thread, do you know of a source for rewinding
these HV transformers. I'm starting to lose the lower trace on my 555 and I
suspect this is the problem. After the scope is on for more than 20 minutes,
the trace never disappears. Don't have a high voltage probe so haven't
checked it. Thanks for any info.


Garrett Fulton


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






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

Re: Tek 549 - HV transformer

Jerry Ingordo
 

I'm sorry to say I have quite a few 500 series Tek scopes with bad hv
transformers and it usually takes 15 minutes for the hv to fall. The first
indication the deflection sensitivity increases. The trace starts to widen
and after about 30 minutes the display dims then disappears. 60 seconds
seems to soon for the hv transformer. You might have an other hv problem.
Jerry
W2JI

Re: Tek 549 - HV transformer

zerousair
 

Bernd,
Without me looking up the thread, do you know of a source for rewinding these HV transformers. I'm starting to lose the lower trace on my 555 and I suspect this is the problem. After the scope is on for more than 20 minutes, the trace never disappears. Don't have a high voltage probe so haven't checked it. Thanks for any info.


Garrett Fulton