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Old 17th May 2023, 6:23 am   #21
Craig Sawyers
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Default Re: Gould J3B

I have two J3B's. Both handsomely exceed specification regarding distortion on both the balanced front panel outputs and the rear panel low distortion output.

The only repair that was necessary on one was a previous, and professional looking repair to replace the series pass transistor in the regulator, had also replaced the previous transistor with the wrong polarity. That turned the series pass transistor hard on - only spotted while checking distortion. Just shows that the "calibrated" stickers meant nothing at all! It actually took quite a while to find the cause of the hard on series pass.

I have not replaced a single electrolytic on either of mine. Or taken any boards out. They work just fine as they are.

You are though playing with fire messing with those boards. They are single sided, and you run the risk of lifting pads. And getting the wires off the turret tags without burning the insulation, and running the risk of breaking the unobtanium glass encapulated thermistor etc etc.

I'm really uncertain why you are taking these risks to deal with a bit of corrosion that you would not have seen had you not taken the casework off.

Craig
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Last edited by Craig Sawyers; 17th May 2023 at 6:30 am.
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Old 18th May 2023, 12:44 am   #22
Philips210
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Default Re: Gould J3B

Craig, as pointed out earlier, the chassis is damaged possibly due to being dropped so I would like to repair that to start with. The signal generator has obviously been stored in damp conditions and a fair amount of corrosion is evident and my main worry was if it was a passivated cadmium plated finish. The chassis plating certainly looks quite dusty in places due to the corrosion. I felt it would be wise to deal with this rather than to just leave it.

The unit can be dismantled without having to remove the circuit boards or desoldering any of the wires to the two PCBs. I've managed to remove the damaged chassis side panel for straightening.

I notice that most of the electrolytic caps are the generally good Philips axial lead types but in my experience, they're not above suspicion. I've come across quite a few with excess leakage current not helped if they've been out of use for several years.

I know what you're saying about damage to the PCB foil but I've been in the repair business since the early 1980s and have considerable experience in handling a wide range of equipment. I've very rarely done any damage to equipment that I repair. It's all down to experience.

Regards,
Symon
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Old 18th May 2023, 1:23 am   #23
Chris55000
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Default Re: Gould J3B

I am in whole–hearted agreement with Craig & Symon – I have a (slightly dented here and there!) Advance J3B myself, and apart from opening the case to take some internal pictures suitable for the appropriate Chapter of my T & M Theory and Repair Book, I have no need to do any repair work whatsoever to mine!

Unless you're unlucky enough to get a "butchered" one or one that's been robbed for bits, you can confidently buy these in the expectation that they'll work, and prices are starting to rise towards "foolery" levels!

Chris Williams
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Old 18th May 2023, 8:52 am   #24
Philips210
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Default Re: Gould J3B

Craig,

I don't suppose you have an original copy of the user manual for the J3B by any chance?
I was only looking for a decent copy of the fold out circuit diagram. The rest of the information I have is clear enough to interpret. Thanks.

Regards,
Symon
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Old 18th May 2023, 1:07 pm   #25
Craig Sawyers
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Default Re: Gould J3B

Mine it a copy alas. And the diagrams, even on A3, are no better than the downloadable version from https://www.kevinchant.com/uploads/7...operating..pdf

Craig
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Old 18th May 2023, 2:59 pm   #26
Philips210
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Default Re: Gould J3B

Thanks anyway Craig.

I have a genuine copy of the Advance J3 which is very similar to the Gould J3B. That will help confirm many unclear component reference numbers on the J3B circuit diagram. The previous owner of the manual has done some quite extensive modifications so I'll have to put that diagram back to its original state.

Like most of us, I do like to have a decent, clear circuit diagram to hand when doing any servicing work.

Regards,
Symon
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