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Electronics => Repair => Topic started by: toomuchesr on October 12, 2017, 12:27:05 pm

Title: Exact Electronics Model 516 Functiongenerator Schematics
Post by: toomuchesr on October 12, 2017, 12:27:05 pm
Hi everyone,

I recently bought a old function generator from the 70thies(?). It's an Exact Electronics Model 516.

I noticed  that the Multiplier had been removed before and put back together the wrong way. I already figured out how to fix that on my own. But I have spotted some "lightly" :) black resistors in the output amplifier stage. I guess they got sometime back quite hot, but they seem to work (for now). However they got as black as unreadable, so I don't know what resistance/wattage/accuracy they should have.

Searching the Net, I found some manuals from other Exact models that all included the schematics, but they differ in most parts from my model. Mine came without any paper.

So to help use, calibrate and maybe repair this functiongenerator any further, it would be of great help to have the manual and schematics. It would be awesome if someone here could help me out on this.

Thank you and br,

Hendrik
Title: Re: Exact Electronics Model 516 Functiongenerator Schematics
Post by: bd139 on October 12, 2017, 01:46:59 pm
I had a new in box Exact function generator a number of years ago. Not the same series. It didn't come with the schematics and they were unobtainable when it blew up. I did however manage to trace it out and fix it when there was a problem which turned out to be a dry solder joint!

If there are black resistors in the output stage, this usually means that someone overloaded it. That is very common on function generators; I've seen lots of them which have smoked resistors There's usually a push-pull amplifier on the output with a couple of resistors on the emitters and then a series resistor with the output to impedance match to 50 ohms. Any of them eventually get smoked if you short the output.

I would desolder the leg of one of them, measure it, then make an educated guess :)
Title: Re: Exact Electronics Model 516 Functiongenerator Schematics
Post by: toomuchesr on October 12, 2017, 02:21:43 pm
Quote from: bd139 on October 12, 2017, 01:46:59 pm
I would desolder the leg of one of them, measure it, then make an educated guess :)

Yes this is the backup plan - however I prefer to now the supposed values. :)
Title: Re: Exact Electronics Model 516 Functiongenerator Schematics
Post by: PA0PBZ on October 12, 2017, 02:35:48 pm
Looks like someone here has/had the manual: https://www.eevblog.com/forum/reviews/old-waveform-generator-exact-electronics-model-502-lcs-question/msg100237/#msg100237 (https://www.eevblog.com/forum/reviews/old-waveform-generator-exact-electronics-model-502-lcs-question/msg100237/#msg100237)
Title: Re: Exact Electronics Model 516 Function generator Schematics
Post by: lowimpedance on October 13, 2017, 12:17:22 am
Quote from: PA0PBZ on October 12, 2017, 02:35:48 pm
Looks like someone here has/had the manual: https://www.eevblog.com/forum/reviews/old-waveform-generator-exact-electronics-model-502-lcs-question/msg100237/#msg100237 (https://www.eevblog.com/forum/reviews/old-waveform-generator-exact-electronics-model-502-lcs-question/msg100237/#msg100237)
Indeed I do still have both generator and manual  :).
As I scan the circuits I will post them up here.
Title: Re: Exact Electronics Model 516 Functiongenerator Schematics
Post by: lowimpedance on October 13, 2017, 12:46:24 am
Okay here is the manual, broken up to get past the posting size restrictions.
Title: Re: Exact Electronics Model 516 Functiongenerator Schematics
Post by: lowimpedance on October 13, 2017, 12:47:44 am
Next part!. Circuit diagrams.
Title: Re: Exact Electronics Model 516 Functiongenerator Schematics
Post by: lowimpedance on October 13, 2017, 01:07:33 am
Last part.
Title: Re: Exact Electronics Model 516 Functiongenerator Schematics
Post by: toomuchesr on October 13, 2017, 04:45:22 am
So much more than I hoped for! Thank you so much!