glad my 907 is back from restoration, but i found no difference.

[quadklipsh]

yeah.
Its been way over a month that i gave my iMos limited alpha 907 to my tech. After days of poking him, i got it back today. I found that the problem i sent it with was gone . But there was no significant difference after more than a dozen chinese transistor replacements on left channel board with original japanese ones and correction of dc offset .

 

[Hyperion]

Remind me/us what the problem was?...... was it a DC offset & protection issue? - or erroneous speaker cone movement?

I wouldn't necessarily expect you to be able to 'hear' the difference after some transistor changes. Glad you got it back, I hope it now lives up to your expectations - I would expect it is breathtaking :yes:

 

[quadklipsh]

well, it always was breath taking.
But i expected more quality , better imaging , and balance between left and right ch, after the transistors replacements.
The original issue was erroneus speaker cone bulging out with the turn of the knob.i mean ,it just popped out or retracted with the turn up or down of the volume respectively( without playing the cd) .
also, he said that there are three amps that are near the volume knob. One of those could be the cause of the dc offset and speaker oggling and that the previous technnician had always been misdiagnosing the problem and had been replacing all original transistors with the chinese .

 

[pete_mac]

I note that you use the term 'restoration'... was the rest of the amp recapped and restored at the same time, or was this a fault-finding and repair mission only?

 

[BigElCat]

My guess would be that the right channel needs to have the exact same work done to it as the left.

You can hear an "imbalance"?

IIRC, the 907 uses the same circuitry as our AU-X701. I'm still in love with my Alpha.

:scratch2:

 

[quadklipsh]

hell no !!!
It was not repaired like recap . It was working fine. It noticed the popping woofer and so got the amp checked up. It had those non branded transistors. So to kill the fuss in my head , i got it all worked up and he replaced the needful components.
It sounds good. But theres no night and day difference as i had in mind.

 

[JOMARK911]

You will not get theese night and day differences, from a simple transistor swap. In any amp.The big difference comes along with a recap most likely.
Are you sure that the transistors that were chenged were swaped with original ones and matched correctly?

 

[quadklipsh]

yes . The transistor search took time. When he got the right ones he implanted em in an evening and gave me the amp in two days after thorogh testing.
i just asked coz I didnt know that the difference wouldnot be significant.
the amp is running nicely. And sound is very smooth and velvety and also that cone movement problem is gone so its all good.
One more thing.

The recording selector knob on the far right side of the front panel is upside down. I think he fixed it this way by mistake .Is it easy to open ??? . Coz i donot want to take the heavy amp all the way again for this knob.

 

[quadklipsh]

i just opened up the hood. And see that two of brown caps were replaced by blue coloured ones . The original were brown coloured as are on right side. They are 47uF 100v instead of the 50v caps on the original side.
Is that a problem ????

 

[vinyldavid]

i just opened up the hood. And see that two of brown caps were replaced by blue coloured ones . The original were brown coloured as are on right side. They are 47uF 100v instead of the 50v caps on the original side.
Is that a problem ????

Nope, you can go up in voltage on capacitors with nary a problem. They're just fine.

 

[quadklipsh]

awhhhh thankyou !!!!!! Im relieved.