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AU-888 recap

R

RAOF

New Member
Hi,

Today I connected for the first time a Lenco 75 to my AU-888 and I had a lot noise as soon as I connect the cables. I think the phono stage capacitors are dead. Everything else is working good as it was. Tuner ok, Aux ok, Tape ok.

As I have to see what's wrong with the phono stage, I think I'm going for a full recap. What do you think?

Anyone has already a list of the parts?

Suggestions regarding the capacitors? Elna? Others?
 
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Just before you go in for the whole 9 yards of a recap, have you made sure the turntable is grounded back to the amp?
I recently put a Rotel RP-830 on my 888 and had quite a bit of noise until I hooked up the ground wire from the table to the amp properly.
 
The turntable is correctly grounded to the 888.

And the turntable in another system is ok.

Perhaps I didn't explain correctly. The noise is horrible. The question is not music with noise. It's only noise.
 
RAOF said:
Hi,

Today I connected for the first time a Lenco 75 to my AU-888 and I had a lot noise as soon as I connect the cables. I think the phono stage capacitors are dead. Everything else is working good as it was. Tuner ok, Aux ok, Tape ok.

As I have to see what's wrong with the phono stage, I think I'm going for a full recap. What do you think?

Anyone has already a list of the parts?

Suggestions regarding the capacitors? Elna? Others?
Click to expand...

Noise on phono only? Check the transistors on the phono board. Any 2SC458s? They are known to go noisy. Repacement is KSC1845F. Dirt cheap at Mouser of DigiKey.
 
RAOF said:
Hi,

I think I'm going for a full recap. What do you think?

Anyone has already a list of the parts?

Suggestions regarding the capacitors? Elna? Others?
Click to expand...

I would suggest replacing the coupling caps with mylar film types. Wima MKS2 or Kemet R82. 30 vac. 50vdc. We are experimenting with doing this and have done a 5000A. The idea is to remove all electrolytics from the signal path. The results seem to be very good so far. We are going to do a 9090 next.

I briefly looked at an AU888 schema and jotted down the following coupling caps that could be changed to Mylars. some of them may already be Mylars.

F1228
C603
C613
C609

F1208
C711
C717

F1209
C719
C725
C727
C737
C755
C735

F1282
C801

These miniataure Mylars are only available up to 10uf. On the smaller valued ones, I would at least double the cap value for extended low end. For example the F1282-C801 is a 1uf cap (probably a mylar). I would increase it to 2.2 or 4.7uf.

Here is a link to Mouser for the 4.7uf Wima cap.
http://www.mouser.com/Passive-Compo...apacitors/_/N-9x371?P=1yznbzrZ1z0wrjcZ1z0x7y9
 
Last edited:
I did a complete recap along with transistor replacement on a 888 a while back. After the work everything worked great except the phono board. I then stumbled across a thread started by Zekeman regarding phono noise on Sansui AU-555. After reading the thread I realized the 1845fta replacements for the 458's were the source of my problem. When I reinserted the original 2sc458's, the phono board worked just fine. When working on that board I would leave the 458's in until the last replacement to ensure easy troubleshooting. I believe the 1845's have too much gain.
 
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