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Vintage Test Gear and Workshop Equipment For discussions about vintage test gear and workshop equipment such as coil winders.

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Old 28th Oct 2020, 2:53 pm   #21
John_BS
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Default Re: Tektronix 7623A poser

Colin: do you have an orignal Tek paper service manual for this?

John
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Old 29th Oct 2020, 10:24 am   #22
ColinTheAmpMan1
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Default Re: Tektronix 7623A poser

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Colin: do you have an orignal Tek paper service manual for this?

John
Yes, I do, John. I have replied to your email re this. It is the proper 7623A paper Manual, too. If you recall, I bough this scope off you before you moved out of London.
Colin.
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Old 29th Oct 2020, 6:24 pm   #23
ColinTheAmpMan1
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Default Re: Tektronix 7623A poser

Well, this gets curiouser and curiouser, as Alice might say. I have removed the inductor L1198 and it was fixed to the A10 HV board at three points! When removed, there are two wires at one end with continuity between them (about 5 ohms) and the connection at the other end is only going into the ferrite and shows no connection (infinity) to the two connections at the other end. The end where the connected wires emerge has some broken "glue" around it, which convinced me that there was some damage underneath that I couldn't see. Not so; it looks as though L1198 is fine, but C1198 is no longer a capacitor. I will put a bit more Araldite around the cracked end of the inductor L1198 and remove the capacitor to give it a fully out-of-circuit check.

Who would have thought that an inductor would have both of its connections at one end and a support-wire at the other?

I will also have to re-think the checking of the connections to the inductor; I may have assumed that the support-wire was a genuine connection.

Colin.
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Old 31st Oct 2020, 6:45 pm   #24
ColinTheAmpMan1
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Default Re: Tektronix 7623A poser

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. I will put a bit more Araldite around the cracked end of the inductor L1198 and remove the capacitor to give it a fully out-of-circuit check.

Who would have thought that an inductor would have both of its connections at one end and a support-wire at the other?

I will also have to re-think the checking of the connections to the inductor; I may have assumed that the support-wire was a genuine connection.

Colin.
OK, so the capacitor measures ~3000pF and more than 20 Mohms out-of circuit. My Peak Atlas ESR70 doesn't recognise it as anything. I have put a little Araldite on the end of the inductor to strengthen and stabilise the end winding.
I have checked the connection between the 15V unstabilised pad that the inductor was soldered to and the fuse (which is still o/c and in place) and there is continuity.
I think I may be good to go on refitting the old and new components once the Araldite has set hard.
Colin.
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Old 5th Nov 2020, 6:11 pm   #25
Outposter30
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Default Re: Tektronix 7623A poser

I have found that there are numerous circumstances where the ESR-70+ and similar ESR meters can not be relied upon. Further, to be certain of what I've noticed I've removed numerous electrolytics which tested fine for ESR with the ESR-70+ but fail when tested for leakage at their working voltages using my Sprague TO-6 cap tester.

I've also noticed that if the cap under test in circuit has a parallel path to ground, such as a parallel cathode bias resistor of anything less than 3K ohms, the ESR-70+ reads the low resistance as leakage. You can throw a low value resistor across an electrolytic and check out how your ESR meter responds to the ckt for yourself.

Because of these and related issues with my ESR-70+, I believe that such testers might help in a rapid service application to eliminate potential problems, but are not up to snuff in serious restoration or complex repair work...Of course, your position may vary from mine....!!!

I seldom use the ESR-70+ anymore, and I've only had it for 4-5 months. I get
more reliable accurate information from the TO-6 and a digital multi-meter...
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Old 6th Nov 2020, 10:47 am   #26
dave cox
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Default Re: Tektronix 7623A poser

That capacitance is way too low for the ESR70, 1 uF is minimum!

To somewhat defend the ESR, it is actually very useful in its own domain. Measuring 'in-circuit' is always a bonus and need to be interpreted carefully. Out of circuit I have found it accurate and quick. The only limitation is that you can't alter things like the ESR test frequency but given its tiny size I can forgive that

dc
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