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MHZS CD33 distorted and clipped heavily

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him27hk 發表於 2009-7-1 22:37:03 | 顯示全部樓層 |閱讀模式
hi everyone

I hv owned cd33 for a few years. And i hv moded some caps before. After intalled a pair of NOS GE5670 to it today. it played normally at first.

Then after some hours, i turned it on again and it started to distort and clip
heavily.

I am sure that the tubes are normal cause i trace back the distortion to the output pin of the opamp. And i assume the opamp should be normal because i measure the rail it was 30v.

What would be the source of the distortion? :?  
Where should i test?

Last resort would be bring it to the dealer and the warranty was ended.......gonna cost me some....

many thanks~~
alfcat 發表於 2009-7-2 16:13:05 | 顯示全部樓層
Hi,

Can you read Chinese?

There is a thread right above by K.K. Ho on the distortion of the CD 66 Player.

K K suggested changing the Zener diode on the Power Supply board. I have checked the voltage at that point as well; it exceeds the tolerence of the default Zener diode. This MAY be one cause of your distortion

CAT
 樓主| him27hk 發表於 2009-7-2 20:09:18 | 顯示全部樓層
yep. i can read it~~ XP
I hv measured the plate voltage ~80v  should be fine. But thx anyway~~

I suspect there is bad soldering in the DAC board, cause i trace back and found the distortion came from the dac out put . (before 2 100uf coupling cap)

I was fustrated and gave up yesterday. Today morning, i opened the case and it played normally. Then i just closed the case and the distortion came back. (damn it)

So i suspect there was some bad soldering point.
alfcat 發表於 2009-7-2 20:30:39 | 顯示全部樓層
Hi,

So the distortion comes in when the CD gets hot?

I re-soldered many parts of the DAC board and I even changed the tube sockets of my CD 33. You may as well consider that.

I guess there is NO dealer of CD 33 in HK .....

CAT
 樓主| him27hk 發表於 2009-7-2 21:03:37 | 顯示全部樓層
thx for ur kind reply,

i think the distortion is independent of the temperature. I think the vibration caused by sliding the top plate back will make the weak soldering point fall apart.

Anyway, i will get all the joint on dac board re-solder on this weekend. (and mod it as well : )

If i still cant get it fixed, can i take it to hifi fever to ask some experienced hifi-er to help me?

thx~~
alfcat 發表於 2009-7-2 23:12:39 | 顯示全部樓層
Good luck.

I recall I changed most of the caps that lies on the signal path after the DAC to RMG and DALE. The sound quality improved a lot.

You can check the threads here at HiFiFever. We have posted a lot of discussions here. Maybe some will interest you.

You better send a message to K.K.Ho if you want assistance with HiFiFever. K.K. Sir is kind of busy. You will be lucky if he is around ....
mhifi508 發表於 2009-7-8 20:53:44 | 顯示全部樓層
him27hk, I think you have the same problem as we have over here.

http://www.xtremeplace.com/yabbs ... msg423844#msg423844
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