Date   
Re: Digital multimeter DM502

 

Well, I was close or at least we were heading in the right direction.
I am glad you found the problem because my next step was to do a
detailed analysis of the circuit up to that point. I know generally
how delta Vbe thermometers work but Tektronix's implementation is a
little different.

That is a good job finding that kind of problem; a couple months ago I
found a bent IC pin like that on a 7B80 timebase resulting in the
trigger level not working correctly. I suspect I bent it when
reseating the ICs years earlier.

On 01 May 2017 07:36:39 +0000, you wrote:

David,

Thank you very much for help!

It is working now! The fault was not the capasitor C263. There was no signal on pin 1 of the IC U250A. Pin was bent and had no contact. My eyesight to near objects is not in first class condition anymore!

Eino

Re: Tek 465 multiplier

 

A vacuum pump is better - what ever you use, make sure that there is a filter in the line so that you don't get any resin in the compressor/vac pump

Robin

Sent from my iPhone

On 2 May 2017, at 09:28, David @DWH [TekScopes] <TekScopes@...> wrote:

I read somewhere about someone using a hand operated vacuum pump
normalized used for bleeding brake systems for this. The air inlet
for an air compressor will also work to draw a vacuum.

On Tue, 2 May 2017 00:04:38 +0000 (UTC), you wrote:


To the Group,
Many thanks for ALL explanations concerning the multiplier construction.
The first one is running just fine,besides the 3kV capacitors, but the second one will be with a pair of 3kV in series. Acrylic resin was used. Next unit for the 468 will be with epoxy filling.
The only doubt is the vacuum proccess of getting the air bubbles off.
I Hope I can repair the 468 too!
Regards to ALL,
Sam

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

Re: Type 503 Oscilloscope Issues

ykochcal
 

A few thoughts in general come to my mind

One: removing one end of a resistor in a tek and measuring a resistor works
but can cause collateral damage.

Two: most times only one or a few parts are bad so if you can find them with
other means I would do that first.

Three: If there is a capacitor in parallel with the resistor it's best to
measure with the + lead on the capacitor + and then let the resistance rise
as the capacitor charges then take reading.

Four: (and this one has caught me before) if taking a lot of in circuit
resistance readings too fast there might be a charged capacitor which can
make a resistance look high, To be sure sometimes I clip a low ohm resistor
on to discharge everything and come back after lunch remove it and read
again.

Five: In circuit the resistance should always be lower then the value plus
tolerance (but many times things will work with +20% +50% so it's not a sure
thing it's "the" problem)

Six: Most times there is one or more resistors in parallel in some way and
that will make a lower reading so generally it's good to be lower but it
takes more effort to check for sure.

Seven: Often, If there is a more complicated resistor network (or transistor
junction), then you can connect/short some nodes in ways to get down to one
or a few resistors in parallel to simplify calculating what the reading
should be. (be sure to remove before applying power as this is only a test
to check resistors with power off).

Eight: (This happened to me) I generally clip on my resistance meter between
the resistor body and the ceramic strip. The clip leads can put enough force
on a resistor that is open to connect making it look good. So after a few
passes I clip on to the lead of the other part the resistor is connected to.
One resistor I must have measure as good a dozen times before I figured that
out and found it was open.


So if you want to learn to solder do #1, if you want to learn about
circuits, as I do (that's the fun part after all) then take some time to see
if you can figure what part is bad by looking at the circuit and estimating
what the resistance should measure in circuit . That way the oscilloscope is
useful in both states, working and when it's not working, it's teaching as
you fix it.

Good luck and keep reporting in

John

-----Original Message-----
From: TekScopes@... [mailto:TekScopes@...]
Sent: Tuesday, May 02, 2017 12:09 AM
To: TekScopes@...
Subject: [TekScopes] Re: Type 503 Oscilloscope Issues

I replied before I saw Dave's last message, but in checking R624 again
(holding the probes while the capacitor charged up), the final resistance
measured was 33.2 ohm, which is higher than the rated 22 ohm. I also caught
my mistake in reading the resistor codes when comparing to the manual, and
the previous update I sent out was in reference to the correct values (as
displayed on the image).

As for the transformer, I will take a look at that later today or tomorrow
and see what happens once wired in place.


- Evan






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


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

Yahoo Groups Links

Re: Tek 465 multiplier

 

I read somewhere about someone using a hand operated vacuum pump
normalized used for bleeding brake systems for this. The air inlet
for an air compressor will also work to draw a vacuum.

On Tue, 2 May 2017 00:04:38 +0000 (UTC), you wrote:


To the Group,
Many thanks for ALL explanations concerning the multiplier construction.
The first one is running just fine,besides the 3kV capacitors, but the second one will be with a pair of 3kV in series. Acrylic resin was used. Next unit for the 468 will be with epoxy filling.
The only doubt is the vacuum proccess of getting the air bubbles off.
I Hope I can repair the 468 too!
Regards to ALL,
Sam

Re: Type 503 Oscilloscope Issues

Dave Casey
 

I would recommend replacing R624 and R632 toward your goal of correcting
the supply voltages.

Dave Casey

On Tue, May 2, 2017 at 2:08 AM, enchanter464@... [TekScopes] <
TekScopes@...> wrote:



I replied before I saw Dave's last message, but in checking R624 again
(holding the probes while the capacitor charged up), the final resistance
measured was 33.2 ohm, which is higher than the rated 22 ohm. I also caught
my mistake in reading the resistor codes when comparing to the manual, and
the previous update I sent out was in reference to the correct values (as
displayed on the image).

As for the transformer, I will take a look at that later today or tomorrow
and see what happens once wired in place.


- Evan




Re: Type 503 Oscilloscope Issues

Evan
 

I replied before I saw Dave's last message, but in checking R624 again (holding the probes while the capacitor charged up), the final resistance measured was 33.2 ohm, which is higher than the rated 22 ohm. I also caught my mistake in reading the resistor codes when comparing to the manual, and the previous update I sent out was in reference to the correct values (as displayed on the image).

As for the transformer, I will take a look at that later today or tomorrow and see what happens once wired in place.


- Evan

Re: Type 503 Oscilloscope Issues

Dave Casey
 

All of the resistances that you have cited as low or very low need to be
measured out of circuit to get an accurate reading. This type of resistor
tends to drift high, not low. You can get a sense of whether or not
anything is drastically wrong here by measuring voltages as marked in the
schematic. Because you do not have the correct supply voltages, you cannot
expect the same bias voltages as what's marked, however everything should
be proportionally correct within an order of magnitude (i.e. V634 pin 3
should be approximately 60% of whatever the +100V bus is measuring). You
can also check the resistors one at a time by desoldering one of the leads
from the terminal strip.

R632 is just barely out of tolerance, and you may replace it if you so
desire.

R692 does sound a bit high, but I believe you previously reported a
measurement for R692 (before you removed and replaced V692) that was within
reason. It's unlikely that R692 has suddenly gone high. Perhaps you're not
making good contact for your measurement, or you have a less than perfect
connection with your soldering job? Regardless, if V692 is glowing gently
and you get a trace on the CRT, I wouldn't worry too much about R692.

You should know where R641 is as you've adjusted it before with no effect,
have you not?

As I stated earlier, you should be able to measure R624, so if you are
unable to get a measurement there, you need to determine why.


Dave Casey


On Tue, May 2, 2017 at 1:22 AM, enchanter464@... [TekScopes] <
TekScopes@...> wrote:



Thanks Dave for that correction on R692. I had mistyped the color code in
my resistor calculator, and it did not click in my mind that the units from
my multimeter did not match (just assumed it to be of the same magnitude).

As for matching the resistors to the manual's diagram, I updated the
figure with the corresponding part labels (again, can view at
https://goo.gl/photos/JUFwEfmnyFAcYtp6A https://goo.gl/photos/
JUFwEfmnyFAcYtp6A). They should all be labelled correctly, although some
wires are difficult to trace and the resistors could be mixed up.


To simplify things, I have each resistor listed below as well:
- R611 = 151.2 k (good)
- R612 = 140.5 k (good)
- R621 = 94.7 k (good)
- R623 = 4.65 k (good)
- R624 = ? (could not get a measurement)
- R626 = ? (could not locate)
- R628 = 508 ohm (good)
- R630 = 537 k (low)
- R631 = 752 k (very low)
- R632 = 116 ohm (high)
- R634 = 20.5 k (low)
- R635 = 22.3 k (very low)
- R637 = 400 k (low)
- R640 = ? (could not locate)
- R641 = ? (could not locate)
- R642 = ? (could not locate)
- R644 = 465 k (good)
- R646 = 15.3 k (good)
- R659 = 77.9 k (low)
- R692 = 8.9 ohm (very high)




- 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
 

Thanks Dave for that correction on R692. I had mistyped the color code in my resistor calculator, and it did not click in my mind that the units from my multimeter did not match (just assumed it to be of the same magnitude).

As for matching the resistors to the manual's diagram, I updated the figure with the corresponding part labels (again, can view at https://goo.gl/photos/JUFwEfmnyFAcYtp6A https://goo.gl/photos/JUFwEfmnyFAcYtp6A). They should all be labelled correctly, although some wires are difficult to trace and the resistors could be mixed up.


To simplify things, I have each resistor listed below as well:
- R611 = 151.2 k (good)
- R612 = 140.5 k (good)
- R621 = 94.7 k (good)
- R623 = 4.65 k (good)
- R624 = ? (could not get a measurement)
- R626 = ? (could not locate)
- R628 = 508 ohm (good)
- R630 = 537 k (low)
- R631 = 752 k (very low)
- R632 = 116 ohm (high)
- R634 = 20.5 k (low)
- R635 = 22.3 k (very low)
- R637 = 400 k (low)
- R640 = ? (could not locate)
- R641 = ? (could not locate)
- R642 = ? (could not locate)
- R644 = 465 k (good)
- R646 = 15.3 k (good)
- R659 = 77.9 k (low)
- R692 = 8.9 ohm (very high)




- Evan

Re: Type 503 Oscilloscope Issues

Dave Casey
 

Evan -

I've sent the schematic to you in a direct e-mail where the attachment
shouldn't get stripped. Let me know if you continue to have issues, and I
can put it on imgur or something.

Before you go trying to solve problems you don't have, I would wire in the
new transformer and see if the scope works again. It probably will. The
issue will just be that the power supply voltages are not to spec. It may
have always had this problem and you weren't aware of it because the scope
worked well enough for your purposes.

It's very likely that at least some of the resistors are now out of
tolerance, but you will have a hard time determining that by measuring them
in circuit as you've done. You are correct that the measurements are skewed
by the other components. One of your EE friends who has done the basic
circuit theory coursework can help you determine approximate measurement
values by performing nodal analyses using the schematic. Even though they
are not familiar with tubes, this being a tube scope doesn't complicate
things very much for these types of measurements. When everything is
powered off and you're just checking resistances with a DMM, it's basically
as though the tubes aren't even there.

The resistor you couldn't measure (???), which is supposed to be 22 ohms,
is R624. Your difficulty in measurement may be due to C624 (the little
yellow electrolytic on the back of V620). You should be able to read get a
solid reading on that resistor if you keep your leads connected long enough
for C624 to charge. If you can never get a stable reading, C624 may be
faulty. The presence or absence of V620 should not affect this measurement
either. If the measurement changes when the tube is removed, then V620 has
developed some internal shorts and needs to be replaced.

You've mis-read the values of several resistors. All those you've marked as
48 are actually supposed to be 47. Violet is 7, black is 0. Due to math and
the way resistors are made, 47 is a common value whereas 48 is not. Google
"standard resistor values" and have a look at the E12 series to get a sense
of the common significant figures you can expect to encounter in this
scope. (or just see here:
http://www.rfcafe.com/references/electrical/resistor-values.htm ).

I will look over your measured values as I have time, but I would recommend
you take a close look at R624 in the meantime.


Dave Casey


On Mon, May 1, 2017 at 11:21 PM, enchanter464@... [TekScopes] <
TekScopes@...> wrote:



It has been a while since last posting, but I have only gotten time
recently to work on the scope (in the midst of final exams).

Taking Dave's advice, I went ahead and measured the resistance of the
resistors surrounding V620 and V634 (basically everything on the ceramic
strips). I have a photo of my measurements here: https://goo.gl/photos/
JUFwEfmnyFAcYtp6A https://goo.gl/photos/JUFwEfmnyFAcYtp6A


I was unable to measure the resistor across V620, which is why there are
"???" for that value. Those values reported in red were the ones outside of
the tolerance range. Suffice to say, the majority of the resistors gave
values that were outside of their range. However, I am not sure if this is
due to how some are soldered together, which could affect the values (for
example, the resistor at V692 giving a resistance value of just the tube
itself, since its expected value is relatively small). In addition, only
one resistor (a 100 ohm) had values higher than its range, while the others
were all below their tolerance limit.


Before looking at getting a replacement tube for V620, would it be best to
replace these resistors? Or is there a better way I can test resistance to
confirm that the values I measured are accurate?


Also, a side note for Dave, but the schematic for wiring the 6.3 VAC
transformer did not get added to your posting. Would you be able to share
the image as a link (since the forums don't support attaching photos)?


- Evan


[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
 

The lower right one is R692. Evan has listed the marked value, the allowed
range factoring in for tolerance, and the measured value in that order for
each resistor he's measured. However, he's mis-read R692 as 0.43 ohms
instead of 4.3 ohms, and he's accidentally marked it as 0.42 ohms even
though his tolerance range is correct for the incorrect value he's read off
the bands.

Dave Casey

On Mon, May 1, 2017 at 11:55 PM, 'Tom Miller' tmiller11147@...
[TekScopes] <TekScopes@...> wrote:



What is the one in the lower right 0.42 ohms? That is way out of range,
maybe open?

----- Original Message -----
From: enchanter464@... [TekScopes]
To: TekScopes@...
Sent: Tuesday, May 02, 2017 12:21 AM
Subject: [TekScopes] Re: Type 503 Oscilloscope Issues

It has been a while since last posting, but I have only gotten time
recently to work on the scope (in the midst of final exams).

Taking Dave's advice, I went ahead and measured the resistance of the
resistors surrounding V620 and V634 (basically everything on the ceramic
strips). I have a photo of my measurements here: https://goo.gl/photos/
JUFwEfmnyFAcYtp6A https://goo.gl/photos/JUFwEfmnyFAcYtp6A

I was unable to measure the resistor across V620, which is why there are
"???" for that value. Those values reported in red were the ones outside of
the tolerance range. Suffice to say, the majority of the resistors gave
values that were outside of their range. However, I am not sure if this is
due to how some are soldered together, which could affect the values (for
example, the resistor at V692 giving a resistance value of just the tube
itself, since its expected value is relatively small). In addition, only
one resistor (a 100 ohm) had values higher than its range, while the others
were all below their tolerance limit.

Before looking at getting a replacement tube for V620, would it be best to
replace these resistors? Or is there a better way I can test resistance to
confirm that the values I measured are accurate?

Also, a side note for Dave, but the schematic for wiring the 6.3 VAC
transformer did not get added to your posting. Would you be able to share
the image as a link (since the forums don't support attaching photos)?

- Evan

[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:

The edited image/photo of the 503 chassis is interesting, with the indicated resistances, but is not easily correlated to resistor identifications (such as "Rxyz") on the Tektronix documentation schematics. Can you provide a list of measured vs. design resistances that is keyed to the resistor identifications that are indicated in the Tektronix documentation; specifically that is keyed to the resistor identifications shown on the "Power Supply" schematic diagram in the Tektronix 503 user/owner's/service manual? Any diagnosis of issues is most easily accomplished (for me, at least; I suspect also so for other Tekscopes members) when reference can be made to schematic diagram(s). I believe it also simplifies email discussions, since it's easier to refer to a specific Tektronix resistor ID (e.g., R640, R642...) from a schematic within the Tek documentation rather than referring to an photographic image.

Thanks!

Mike Dinolfo N4MWP

On 05/02/2017 12:21 AM, enchanter464@... [TekScopes] wrote:


It has been a while since last posting, but I have only gotten time
recently to work on the scope (in the midst of final exams).

Taking Dave's advice, I went ahead and measured the resistance of the
resistors surrounding V620 and V634 (basically everything on the ceramic
strips). I have a photo of my measurements here:
https://goo.gl/photos/JUFwEfmnyFAcYtp6A
https://goo.gl/photos/JUFwEfmnyFAcYtp6A


I was unable to measure the resistor across V620, which is why there are
"???" for that value. Those values reported in red were the ones outside
of the tolerance range. Suffice to say, the majority of the resistors
gave values that were outside of their range. However, I am not sure if
this is due to how some are soldered together, which could affect the
values (for example, the resistor at V692 giving a resistance value of
just the tube itself, since its expected value is relatively small). In
addition, only one resistor (a 100 ohm) had values higher than its
range, while the others were all below their tolerance limit.


Before looking at getting a replacement tube for V620, would it be best
to replace these resistors? Or is there a better way I can test
resistance to confirm that the values I measured are accurate?


Also, a side note for Dave, but the schematic for wiring the 6.3 VAC
transformer did not get added to your posting. Would you be able to
share the image as a link (since the forums don't support attaching
photos)?


- Evan



Re: Type 503 Oscilloscope Issues

 

What is the one in the lower right 0.42 ohms? That is way out of range, maybe open?

----- Original Message -----
From: enchanter464@... [TekScopes]
To: TekScopes@...
Sent: Tuesday, May 02, 2017 12:21 AM
Subject: [TekScopes] Re: Type 503 Oscilloscope Issues



It has been a while since last posting, but I have only gotten time recently to work on the scope (in the midst of final exams).

Taking Dave's advice, I went ahead and measured the resistance of the resistors surrounding V620 and V634 (basically everything on the ceramic strips). I have a photo of my measurements here: https://goo.gl/photos/JUFwEfmnyFAcYtp6A https://goo.gl/photos/JUFwEfmnyFAcYtp6A


I was unable to measure the resistor across V620, which is why there are "???" for that value. Those values reported in red were the ones outside of the tolerance range. Suffice to say, the majority of the resistors gave values that were outside of their range. However, I am not sure if this is due to how some are soldered together, which could affect the values (for example, the resistor at V692 giving a resistance value of just the tube itself, since its expected value is relatively small). In addition, only one resistor (a 100 ohm) had values higher than its range, while the others were all below their tolerance limit.


Before looking at getting a replacement tube for V620, would it be best to replace these resistors? Or is there a better way I can test resistance to confirm that the values I measured are accurate?


Also, a side note for Dave, but the schematic for wiring the 6.3 VAC transformer did not get added to your posting. Would you be able to share the image as a link (since the forums don't support attaching photos)?


- Evan

Re: Type 503 Oscilloscope Issues

Evan
 

It has been a while since last posting, but I have only gotten time recently to work on the scope (in the midst of final exams).

Taking Dave's advice, I went ahead and measured the resistance of the resistors surrounding V620 and V634 (basically everything on the ceramic strips). I have a photo of my measurements here: https://goo.gl/photos/JUFwEfmnyFAcYtp6A https://goo.gl/photos/JUFwEfmnyFAcYtp6A


I was unable to measure the resistor across V620, which is why there are "???" for that value. Those values reported in red were the ones outside of the tolerance range. Suffice to say, the majority of the resistors gave values that were outside of their range. However, I am not sure if this is due to how some are soldered together, which could affect the values (for example, the resistor at V692 giving a resistance value of just the tube itself, since its expected value is relatively small). In addition, only one resistor (a 100 ohm) had values higher than its range, while the others were all below their tolerance limit.


Before looking at getting a replacement tube for V620, would it be best to replace these resistors? Or is there a better way I can test resistance to confirm that the values I measured are accurate?


Also, a side note for Dave, but the schematic for wiring the 6.3 VAC transformer did not get added to your posting. Would you be able to share the image as a link (since the forums don't support attaching photos)?


- Evan

Re: Tek 465 multiplier

Samuel Rocha <py1dkw@...>
 

To the Group,
Many thanks for ALL explanations concerning the multiplier construction.
The first one is running just fine,besides the 3kV capacitors, but the second one will be with a pair of 3kV in series. Acrylic resin was used. Next unit for the 468 will be with epoxy filling.
The only doubt is the vacuum proccess of getting the air bubbles off.
I Hope I can repair the 468 too!
Regards to ALL,
Sam




Enviado do Yahoo Mail. Baixe o aplicativo

--------------------------------------------
Em seg, 24/4/17, Fabio Trevisan fabio.tr3visan@... [TekScopes] <TekScopes@...> escreveu:

Assunto: Re: [TekScopes] Tek 465 multiplier
Para: TekScopes@...
Data: Segunda-feira, 24 de Abril de 2017, 17:37


 









Hello David,



Sticking up my nose...



It grabbed my attention that Sam mentioned in his initial
post he'd be

using 3kV caps and I`m confused about that...



Isn't it that the capacitors need to withstand the
peak-to-peak voltage

(i.e. 5kV) ?



As I saw it, I got doubtful if it's the peak voltage or
peak-to-peak...



If it's peak-to-peak, I suppose he need to use - at
least - 6.8kV caps.



Rgrds,



Fabio



2017-04-23 21:55 GMT-03:00 David @DWH
[TekScopes] <

TekScopes@...>:



>

>

> I added a couple of new columns in my spreadsheet for
these

> oscilloscopes.

>

> The 465 and 468 both use the 152-0552-00 5kV
peak-to-peak x3 to 15kV

> multiplier which has a 510 kilohm output resistor. So
as you

> identified, it has 6 diodes. It looks like this except
for a high

> voltage 510 kilohm resistor in series with the
output:

>

>
http://www.nutsvolts.com/uploads/wygwam/NV_0198_Marston_Figure05.jpg

>

> I would air wire it pretty much as shown in the
schematic making sure

> that all joints are nicely rounded by solder to prevent
points which

> would otherwise cause electric field concentrations.
Wrap the solid

> leads around each other before soldering; do not rely
on just the

> mechanical strength of the solder. Then I would coat
all exposed

> wiring in several coatings of corona dope, and then
vacuum pot it.

>

> More than one high voltage resistor can be used in
series adding up to

> about 500 kilohms to get enough voltage rating. The
resistance is not

> critical

>

> For a potting material, I would use wax if I did not
have a suitable

> epoxy resin.

>

> A vacuum chamber can be made from a mason jar and air
compressor. Run

> a test before potting the circuit.

>

> Do not use polystyrene Q dope as corona dope because it
has bubbles in

> it.

>

> On Thu, 20 Apr 2017 19:14:33 +0000 (UTC), you wrote:

>

> >To the Group,

> >I have a 465 and 468 and both scopes need a new
multiplier.

> >I am trying to build one with six diodes and six
2k2 3kv caps since I

> cannot find the original one.

> >

> >Does anyone has a diagram and tips to epoxy the
case?

> >

> >Thanks Very much for any help!

> >Sam

> >Brazil

>

>

















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Re: FG504 died - Now fixing

Joe Laffey
 

After much further troubleshooting, lifting legs and testing things I was able to nail down the source of my 6-10 Ohm short across the +15V rail. It wasn't any of the poor capacitors and diodes that got their legs unwillingly lifted.

It turns out it was Occam's Razor... literally slicing a wire!

One of the wires connected to the Symmetry switch/pot combo was rubbing up against another metal contact on that switch combo. It had worn through the insulation and was making contact. I guess it was heat expansion that caused it to fail when left on for a while.

So I am a happy man with my FG504 working smoothly again. It is such a nice little generator. 40MHz analog.

--
73
Joe Laffey

Re: TM503B question

gmail
 

Got some life into the FG5010. The mistake i made was to leave the resistor in feeding the zener with the 33.5V. It was still connected to the transistor which the plugin uses. Oops. Luckily i was monitoring everything and it only ran like this for a very short time. After removing the resistor in the TM and putting the FG back together, all started working with the external supplies. Some buttons are sticky, the output shapes are not perfect, but no errors and basic functionality (shape, amplitude, offset and frequency) is there.

But it is very power hungry: +26V at 0.9A, -26V at 0.5A and 8V at 2.5A. And then it also uses two AC windings to make + and - 35V itself. Inside are a lot more regulators and four use the NPN/PNP transistors of the mainframe. Crazy really.

Most caps measured ok-ish, but it would not hurt to replace them. It gets quite warm, i think i need to look at forced cooling, like the TM5xxx mainframes.

Re: FG504 died - Now fixing

David Kuhn
 

I've had CERAMIC capacitors short; its rare but does hsppen. A silly little
.001uf/100v sitting on a 12 line in a power supply; dead short..., and they
don't do you the honor of smoking or even getting hot usually like tantalum
does. They be sneaky suckers when they go!


On Mon, May 1, 2017 at 10:14 Vince Vielhaber vev@... [TekScopes] <
TekScopes@...> wrote:



On 05/01/2017 03:40 AM, Joe Laffey joe@... [TekScopes] wrote:

Thanks to Jerry kindly sending me the ends I got two extenders all
soldered up and going. So I finally got a chance to look into this.

I found that in my TM5006 when I connect the FG504 other plugins stop
working in the TM5006 as well (while the FG504 is connected).

First off, to anyone else who might think that connecting just one of the
extenders is a good idea as a troubleshooting measure... uh, don't. I
unplugged the extender to the main board (after pwoering off) and ended
up
vaporizing a trace on the axillary board (after powering on). I was able
to repair it. I was also able to determine that the issues lies in the
path on the main board connector, since the other plugins started working
again. Of course there are easier ways to figure this out (Ohm meter for
one).
Thanks for the advise. I could see myself doing that.

I measured the resistances on the extender connector to the main board (I
actually did this before I tried disconnecting one extender, but I think
I
must not have been methodical enough). I found that pin 11B to ground
reads 6 Ohms. Basically the +15V rail has a short someplace.

I was able to narrow it down to the Loop Board. The +15V rail to ground
on
the Loop board (with the header form the Main board power supply section
disconnected) is 6 Ohms.

I checked C1672 and it seems fine.

I pulled each of the ICs and checked the resistance on the rail with each
one removed. No change.

I am trying to find someplace where a failed component on the +15V rail
would cause a reading of just 6 Ohms if shorted. Most uses of the +15V
have a number of resistors, and are unlikely to get to 6 Ohms with a
single failure (maybe multiple failures).

I guess I should check C1671 (ceramic cap, not likely)
Don't think it's not likely that a ceramic can fail shorted. My low
band rig is a Collins KWS-1/75A4. Years ago while it was idling, the
shack filled with smoke. An electrolytic failed open in the grid supply
causing the screen supply's protection circuit to trip and blow the fuse.

Problem was, the fuse, which was supposed to be 1/4 amp, was a 25 amp.
The dot before the 25 on the silk screen looked more like a spec of dust
and someone put a 25 amp fuse in it. So when the 2D21 tripped the fuse
didn't blow, the power transformer for the screen supply did, along with
the 2D21 and the screen supply's rectifier.

Anyway, after replacing all of that (and the adventures of trying to
find a 2D21 - I now have 5 spares) it still didn't work. I traced it
down to a .01 ceramic disk cap in the power connector box on the back of
the transmitter (for those that don't know the transmitter and power
supply are separate - the power supply stands about 3 feet high). A
Collins doesn't use cheap parts, it's built to mil spec.

Morrow of story, if it's a cap, it can short!

Vince - KA8CSH.
--
Michigan VHF Corp. http://www.nobucks.net/ http://www.CDupe.com/
http://www.metalworkingfun.com


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

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


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

Yahoo Groups Links



Re: Tek 2465B high serial repair -- help needed

 

That looks like a proper loadboard.  I concur, your LVPS is likely ok.  Each supply line to A1 is separately regulated.  Which ones measure ok on J119?

From: "@rodd [TekScopes]" <TekScopes@...>
To: TekScopes@...
Sent: Monday, May 1, 2017 7:59 AM
Subject: [TekScopes] Re: Tek 2465B high serial repair -- help needed

  I am sorry for that. Here goes the link: https://groups.yahoo.com/neo/groups/TekScopes/photos/photostream/lightbox/357254485?orderBy=mtime&sortOrder=desc&photoFilter=ALL#zax/357254485 https://groups.yahoo.com/neo/groups/TekScopes/photos/photostream/lightbox/357254485?orderBy=mtime&sortOrder=desc&photoFilter=ALL#zax/357254485


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

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Re: Rare Variac find (I think)

David Berlind
 

thanks @Peter. Was reading that document and it's hard to believe how bad
the documentation is.

so, questions:

- You say the fuses are protecting the meters? Or are you saying that
the variac is essentially fused according to which range in the meters I'm
using (and how the switches are set)? I'm assuming the latter.
- So, the same 5amp fuse is engaged for either the ammeter, the
wattmeter, or both (simultaneously) depending on how the switches are set?

I am assuming it's entirely based on load. For example, if I don't know
what the load is, I should start with the high ammeter setting. If I
anything >0, leave it on high. If it stays at 0, switch to low. Over on
the watts side, this will depend on volts. For example, if I'm at 3 amps
and 30 volts (~90 watts), then I need to have the watt switch on low. But
once the math works out to anything >150 watts (ie: 3x60), switch to high.

Does that sound right?

On Sun, Apr 30, 2017 at 9:42 AM, Peter Reilley preilley_454@...
[TekScopes] <TekScopes@...> wrote:

From the schematic available here:
http://bama.edebris.com/download/gr/w5mt3/W5MT3A,%
20W5MT3W%20and%20W5MT3AW%20Metered%20Variacs.pdf

The 1 amp fuse protects the amp meter on low range.
The 5 amp fuse protects it on high range.
The 2 amp fuse protects the watt meter on low range.
The same 5 amp fuse protects the watt meter on high range.

Pete.


On 4/30/2017 7:12 AM, David Berlind david@... [TekScopes] wrote:

What about the 3 different fuses? When/how do they come into play?

On April 27, 2017 10:42:05 AM "Peter Reilley preilley_454@...
[TekScopes]" <TekScopes@...> wrote:

Yes, that would be my guess. You could easily test it by plugging
in a 100 watt lamp. That won't damage anything no matter what
the position of the switches.

Pete.

On 4/27/2017 10:30 AM, David Berlind david@... [TekScopes]
wrote:

thanks @PeterR.

So, do you think it's possible that the left side low/high switch
on this
older unit is for ampmeter range and that the low/high switch on
the right
is for the wattmeter range? I don't have the unit in my possession
yet. A
friend is picking it up today.

On Thu, Apr 27, 2017 at 10:21 AM, Peter Reilley
preilley_454@...
[TekScopes] <TekScopes@...> wrote:

I have the same unit but a newer version. My unit is a W5MT3AW as
well
but the knob and printed panel are gray.
The switch on the left is labeled "ampmeter range" and 1A on the
left
with 5A on the right.
The switch on the right is labeled "wattmeter range" and 150W on the
left with 750W on the right.
The amp and watt meters have two printed scales. I cannot see them
in
your picture.
Otherwise mine looks exactly the same.

Pete.



On 4/27/2017 10:02 AM, david@... [TekScopes] wrote:

As some of you know from previous threads, I've been in the
market for
both a variac, and advice on configuring it into a setup that
includes
an isolation transformer and current limiting. I'm good on the
advice
and I acquired a nice variac (no chassis) off of eBay.


But, when I came across this little General Radio gem for $30,
I could
not resist buying it. Since first starting to look for a variac
several months back (almost 6 at this point), I have not seen
anything
like this. The model number is w5mt3aw and there's a newer
version on
ebay for $589. It appears to have three modes of operation for
1, 3,
and 5 amps. The gauges are for watts, amps, and volts. Has anybody
seen one of these before and if so, do you know how exactly the
two
low/high switches work?


https://goo.gl/photos/BdasmYAwxJXNhjXy7
https://goo.gl/photos/BdasmYAwxJXNhjXy7









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Yahoo Groups Links








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Yahoo Groups Links



Re: FG504 died - Now fixing

Vince Vielhaber
 

On 05/01/2017 03:40 AM, Joe Laffey joe@... [TekScopes] wrote:

Thanks to Jerry kindly sending me the ends I got two extenders all
soldered up and going. So I finally got a chance to look into this.

I found that in my TM5006 when I connect the FG504 other plugins stop
working in the TM5006 as well (while the FG504 is connected).

First off, to anyone else who might think that connecting just one of the
extenders is a good idea as a troubleshooting measure... uh, don't. I
unplugged the extender to the main board (after pwoering off) and ended up
vaporizing a trace on the axillary board (after powering on). I was able
to repair it. I was also able to determine that the issues lies in the
path on the main board connector, since the other plugins started working
again. Of course there are easier ways to figure this out (Ohm meter for
one).
Thanks for the advise. I could see myself doing that.

I measured the resistances on the extender connector to the main board (I
actually did this before I tried disconnecting one extender, but I think I
must not have been methodical enough). I found that pin 11B to ground
reads 6 Ohms. Basically the +15V rail has a short someplace.

I was able to narrow it down to the Loop Board. The +15V rail to ground on
the Loop board (with the header form the Main board power supply section
disconnected) is 6 Ohms.

I checked C1672 and it seems fine.

I pulled each of the ICs and checked the resistance on the rail with each
one removed. No change.

I am trying to find someplace where a failed component on the +15V rail
would cause a reading of just 6 Ohms if shorted. Most uses of the +15V
have a number of resistors, and are unlikely to get to 6 Ohms with a
single failure (maybe multiple failures).

I guess I should check C1671 (ceramic cap, not likely)
Don't think it's not likely that a ceramic can fail shorted. My low band rig is a Collins KWS-1/75A4. Years ago while it was idling, the shack filled with smoke. An electrolytic failed open in the grid supply causing the screen supply's protection circuit to trip and blow the fuse.

Problem was, the fuse, which was supposed to be 1/4 amp, was a 25 amp. The dot before the 25 on the silk screen looked more like a spec of dust and someone put a 25 amp fuse in it. So when the 2D21 tripped the fuse didn't blow, the power transformer for the screen supply did, along with the 2D21 and the screen supply's rectifier.

Anyway, after replacing all of that (and the adventures of trying to find a 2D21 - I now have 5 spares) it still didn't work. I traced it down to a .01 ceramic disk cap in the power connector box on the back of the transmitter (for those that don't know the transmitter and power supply are separate - the power supply stands about 3 feet high). A Collins doesn't use cheap parts, it's built to mil spec.

Morrow of story, if it's a cap, it can short!

Vince - KA8CSH.
--
Michigan VHF Corp. http://www.nobucks.net/ http://www.CDupe.com/
http://www.metalworkingfun.com