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SX-737, AWR-058, correct caps?

zeferinoj

zeferinoj

Member
Hello!

I'm working on an SX-737's AWR-058 power supply assembly. Apparently it had some repairs done in the past as some electrolytic caps have different voltage and capacitance values.

The service manual does detail an "AWR-058-0" and it follows closely this thread. According to those, C11 and C16 should be 220uF/16v, and mine read 220uF/35v. That should be OK as voltage is higher, but C7 should be 1000F/50V, whereas mine reads 2200uF/63V. Again voltage should be fine but capacitance is higher.

I'm wondering if there are other power supply versions I'm not aware of. It was purchased in Holland a couple of years ago, and the fact the receiver worked as expected up to until a few months ago adds to uncertainty. Here's a picture.

AWR-058 A.png

Any assistance is greatly appreciated.

All the best.
 

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Someone smarter than me will chime in, but until they do, a 2200uf, whether stock or otherwise, is almost certainly fine there. More filtering within reason (too much can strain other components) is a good thing.
 
Unless they've gotten better since the 60's, FRAKO caps generally are not the most reliable stuff out there, IMO. I'd put a 2200uf 63V Nichicon or Panasonic in there. You can use a radial and extend the negative lead, and lay the cap on it's side with a dab of Clear silicone.
 
As a rule of thumb for replacing old caps, I have learned voltage should go one step higher BUT capacity should be always the same as written in the SM. One good extra upgrade can be the cap temperature range up to 105°C instead of 85°C. That’s what I would consider, since this area is the hottest spot inside the SX-737.

For the C7 the SM shows 1000F/50V. Can one give me a hint, why to use a 2200uF/63V and what is the advantage with such a capacity increase in the power supply?
 
I have not looked at the schematic so I am guessing it is the filter cap after the rectifiers. A larger value cap would reduce the AC ripple riding on the DC adding a little more power supply rejection of that ripple or consequential hum reduction
 
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