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Old 14th Aug 2022, 11:41 am   #1
John_BS
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Default Tek 1502 TDR - loss of trace

A wonderful piece of equipment, capable of operating underwater! So I've never attempted to remove it from its case... unitl this weekend, when switch-on resulted in no trace - nothing.

It turned out to be couple of 100uF electrolytics, both on the "raw DC" side of the 10V regulator. They must both have leaked something which caused the -ve leads to competely corrode o/c. So if this happend to anyone else, it's C6525 and C6429. They are effectively paralleled via a 100uH choke.

The rest of the inside looked like it just came out of the factory

John
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Old 14th Aug 2022, 1:22 pm   #2
Diabolical Artificer
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Default Re: Tek 1502 TDR - loss of trace

Interesting bit of kit John, can you still get the graph paper? I see the mains tfmr is made by multicomp not Tektronix, I thought Tek always designed and wound their own tfmr's.

Andy.
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Old 14th Aug 2022, 1:54 pm   #3
John_BS
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Default Re: Tek 1502 TDR - loss of trace

Quote:
Originally Posted by Diabolical Artificer View Post
can you still get the graph paper? I see the mains tfmr is made by multicomp not Tektronix, I thought Tek always designed and wound their own tfmr's.

Andy.

Not sure about the paper. Lots on the roll. I'm pretty sure they did design the tfmr, they must have sub'd the manufacture.
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Old 14th Aug 2022, 2:08 pm   #4
Craig Sawyers
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Default Re: Tek 1502 TDR - loss of trace

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Originally Posted by Diabolical Artificer View Post
Interesting bit of kit John, can you still get the graph paper? I see the mains tfmr is made by multicomp not Tektronix, I thought Tek always designed and wound their own tfmr's.

Andy.
I got several rolls of paper from either Deane Kidd (RIP) or Stan Griffiths (also RIP). Both of these worked all their lives at Tek Beaverton, and acquired huge stocks of Tek parts when they retired. They were a great resource.

But since they have gone to paint the pearly gates in Tektronix blue, the source of expertise and spares has totally dried up.

Craig

PS This might be worth a try. Also Beaverton based https://vintagetek.org/
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Old 14th Aug 2022, 7:36 pm   #5
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Default Re: Tek 1502 TDR - loss of trace

Quote:
Originally Posted by John_BS View Post
A wonderful piece of equipment, capable of operating underwater! So I've never attempted to remove it from its case... unitl this weekend, when switch-on resulted in no trace - nothing.

It turned out to be couple of 100uF electrolytics, both on the "raw DC" side of the 10V regulator. They must both have leaked something which caused the -ve leads to competely corrode o/c. So if this happend to anyone else, it's C6525 and C6429. They are effectively paralleled via a 100uH choke.

The rest of the inside looked like it just came out of the factory

John
Those look to be wet tantalum capacitors, the outer cases are either sliver or tantalum, to resist corrosion from the acid electrolyte. I've had a few fail in the same way in Tek scopes, the gold plated tracks underneath were also eaten away.

David
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Old 15th Aug 2022, 10:15 am   #6
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Default Re: Tek 1502 TDR - loss of trace

David: I'm pretty sure you're right: they feel too heavy for aluminium electrolytics. All the other "canned" caps on the supply are glass sealed, but these two have a black hard-rubber-like plug. I've also managed to identify the WRONG PAIR! Should be C6341/C6246 and they'r on the +25V rail, which explains the 30V rating.

Mods; don't know if it's possible to amend the first post?

Waning powers
John

Last edited by John_BS; 15th Aug 2022 at 10:29 am.
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