Recapping a Sansui AU-2900

Flapper

Member
Hi all,

Recently I loaned my AU-2900 to a friend who returned it as dead. It turned out to be nothing more than the neutral lead had disconnected in the mains plug, but I'd opened up the case to have a look and it looks like a recap of the AU-2900 would be a pretty straightforward operation. One of the caps was noticeably leaking, although the sound doesn't seem to be noticeably affected.

I have recapped nothing more complex than some Celestion 33 speaker crossovers. I noticed a big difference in sound for these.

For the Sansui I think I'll just replace the main board caps at first.

I have a few questions that I'd appreciate advice on:

1) I don't want to spend huge amounts so will probably just replace electrolytics with electrolytics. I have used Alcaps in speaker crossovers, but I guess I need to fit unipolar replacements in the amp. Any cost-effective recommendations? ( I'm in the UK)

2) Are there any spots on the main board where it would be worth using polypropylene? Again - I don't want to spend loads!

3) Any benefit in upping the voltage on any of them or should I match as closely as possible?

Here's a list of the caps I can see on the main board for reference:

Elna 3300uf 35v - x2
? Light blue 220uf 35v - x2
? Light blue 100uf 35v - x2
Elna 33uf 50v - x2
Elna 47uf 50v - x2
Elna 47 or 4.7uf ?v - 1 (hard to see exactly)
? Light blue 47uf 6.3v - x2
? Light blue 1uf 50v - x2
? Orange 1uf 50v - x2

Thanks for any advice on the above and any stupid mistakes that I should avoid.

Sam
 
The leaking you see is probably glue ?

You must be sure it's 4.7 or 47uf look on a schematic if not sure, but there sometimes are mistakes in schematics, the part installed is more exact.

But for Voltage rating, you can go higher in a range of about 50% higher without risk.

The 1uf 50V may benefit from replacement by 1uf 63V WIMA MKS2 if you have room.

For polar electrolytics, I prefer Elna Cerafine and order at PartsConexion in Canada, for some values you are OK with Elna Silmic II
 
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Sansui and the other Japanese manufactures of the era used ordinary general purpose caps in almost all locations. There was no effort made to match a particular brand or color of cap to a specific location. If you look at several AU-2900s you will see a random mixture of caps from all the Japanese suppliers.

The one exception are the bright orange caps. They are considered "low noise." They are generally small values and can benefit from a WIMA cap mentioned above. Since then, electrolytic capacitor technology has improved substantially. Today, any quality electrolytic cap will be better than what was in that amp originally.

Make a list by reading the values on each of the caps. Draw a diagram of the board outlining the location of each cap. Mark the orientation of the negative lead of each cap on the diagram. Don't use the parts list in the service manual. Sansui routinely made substitutions in production that are not reflected in the service manual. There are also likely to be "non polar" or "bi polar" caps. These caps have no polarity and can be installed either way.

Please post the serial number for the database. Click on the link in my signature block below.

- Pete
 
Today, any quality electrolytic cap will be better than what was in that amp originally.

I generally agree, however in order to match the leakage specs of the original orange low leakage / low noise caps, the Nichicon UKL series (or decent film caps) are required.

For the rest of the caps, go for your life! :)
 
Thanks all that's very helpful. I'll post my serial number for the AU-2900 in the database thread. (I also have an AU-317 but the serial number label has dropped off that one)
 
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