Author Topic: Adret 742A Signal Generator  (Read 214 times)

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Offline e_pigreco

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  • Posts: 1
  • Country: gb
Adret 742A Signal Generator
« on: December 06, 2019, 09:24:59 pm »
885440-0Hi guys,
I am trying to repair an Adret 742A SG that was going to be skipped, so might be a bad starting for a beginner !
Anyway looking at the unit, it seems that main problem are 2 desoldered cables for which I might be able to solder and another problem are the big PSU capacitors that were missing from the unit. Well, there was only one inside but without screws. I guess there was some attempt to repair... or maybe that was the only good...
So looking at some online info they look to be all the same as the one which was there...so 6800uf 40V each.
Anyone has an idea how they screw to the board ? So for example in pairs of 2  ++  and -- or any combination or anyone has a photo ?
Please do not send schematics as first of all I am a novice in electronics, just an appassionate of radios and secondly I have a degenerative problem to my sight due to diabetes so I would struggle with small writings anyway  :(.
A photo or anything like this would help showing me the correct position of the caps (+ and minus).
I will try as well to add some photos later.

Thanks a lot for the patience in reading and anyone who can help.
I know that I should not plug the psu directly...no worries, I will try first to check if all psu outputs are fine because I can see there are values on test points... and then check at the rest of the unit.
Thanks a lot !
« Last Edit: December 06, 2019, 09:51:48 pm by e_pigreco »
 

Online George Edmonds

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  • Posts: 32
  • Country: gb
Re: Adret 742A Signal Generator
« Reply #1 on: December 07, 2019, 10:42:09 am »
Hi

STOP, before wasting any time on the 742A you MUST check the condition of the CPU board.  Looking from the front of the instrument with it the correct way up it is the first board on the left hand side, this board has a rectangular Saft backup battery on board which invariably leak and damage the board.  The repair of this board is very difficult as the corrosion products get under the IC's some of which must be removed to effect a valid clean up of the board and to repair damaged track work.  Be very careful of the correct orientation of the plugin ribbon cable.  Please note that Adret use an absolutely unobtainable PCB edge connector.

The power supply is a bad joke with all of the French Pink electronic capacitors going open circuit.  These can be replaced by modern designs as the screw fixing ones are virtually unobtainable.  Power supply diodes also go short circuit and the power supply output ribbon cables (IDC?) burn out.

Adret was purchased by Marconi Instruments to obtain access to patents and then quickly put out of its misery.

If you do want to try to repair it I can provide details of the capacitor orientations, but please check the CPU board first.

Regards

George G6HIG

 

 


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