Akai AA-1150 Clicking noise

I took out both big filter capacitors, and turned ON the receiver. (Relay also clicked in).
I repeat this test, and same scenario.
Still vibration noise, and still AC exists T test point #4 and not in test point #3.
Although its very small and simple circuit, i can't see what can be the cause.
Maybe one of the ceramic capacitors?
Ive checked them for short (on l-board) and they are'nt.

Ive tested the big filter caps out of the board.
First for short, they are not.
Then i measured them for capacitance, One of them showed 6600uf, the other 6200uf.
Later Ive charged both of them with external dc voltage supplier, and they both keep it and value go down slowly while measuring with dmm.

What do you think?

Thanks a lot
 
Ok.
Eventhough that also when they are out the circuit, prior to them the two points (3&4) behave differently regarding the AC existance?
Or maybe you talked about the ceramics capacitors?
 
side question.

what if i want to simulate situation in which i operate the receiver as if speakers connected but actually i don't want to play any music?
(like testing the receiver at night)
is it possible to make it variable load? I want to take it to about 60-70-80-90% power.
thanks
 
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Any specs? Recommends?
Maybe DIY?
Safety?

I use only solid states amps/receivers.. No tube amps. Is it any matter?
 
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Updating after making a progress with the 1135.

I replaced 4 diodes rectifiers, and 2 output transistors of one channel.

After that i powered up the receiver thru DBT, for about two minutes, (actually in retrospect i can't even recall if the light bulb was dimm or bright. I do remember that relay clicked IN so i guess no short)
I checked both L/R speakers terminals for DC, and found about 20mv each.

(I forgot performing bias adjustment)
And connected directly to the mains without DBT. After about 10 seconds i saw smoke, and immedietly plug it OFF the wall.

I visually inspected the smoke area and see the big cement (i think they are cement) white resistor looks like it got so hot and something like brown liquid melted at its bottom.

I just wonder if i had already another short that couse to this, or it might be that i didnt make bias adjustment?

Also, its strange for me but the fuse is still like new!
Kind of scary it didnt protect and got burn.

Thanks.

Btw, regarding the VAC i found only in positive (orange) filter capacitor (and no VAC at negative purple filter capacitor) i want to describe more accurate.
It isn't a "real" VAC, but its just a values that "jumps" continuesly 0vac-15vac-30vac-0vac and so on...
So, i guess i was wrong with my previous describe, since if it was a "real" vac i would have seen just one value.
(Im using a cheap uni-t ut136b multimeter)
 
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too much bias might cause it .
your meter might need a low value capacitor in series to block dc when measuring ac .
 
(actually in retrospect i can't even recall if the light bulb was dimm or bright. I do remember that relay clicked IN so i guess no short)

Isnt it imply that the bias was roughly adjusted, and disables the possibility that this is the cause?

Im asking because after i will replace again the shorted outputs... i need to be careful it won't happen again.
By adjusting the bias or maybe look for other possibilities.
 
Hi, now i'm working orderly with the 150 connected directly to the mains (no DBT).
and test it, to see if the clicks appear again.

meantime, i noticed that Left channel (original transistors) is lower volume then the Right channel (new transistors).

is there anything i can do?

thanks
 
Already did (of course).
And also swipe speakers.
To be more sire, I feed a sine wave also and measure with multimeter.
IIRC was 40mvac and 25mvac.

Dont think its related, but bias is set correctly.

Also measure dc at speaker terminals...
Strong channel (right) was about -40mvdc.
And lower channel (left) was about +15mvdc.
 
Mmmm... Negative.

So.. You mean bypasd preamp and then can understand if the issue is within the pream or poweramp?

Great idea.. Will test it tomorrow.
Thanks!

I had experience with akai aa-1030 which was preamp issue that almost didnt send any signal (very low) to the poweramp..

So.. Ill do this test and will be smarter...
 
well...i couldn't wait.
(actually the AA-1135 was already open on bench so i did this test for him.. and notice it's also has (but smaller) difference. so later i will repeat this test also for the 1150..guess it will be pretty same)

so..here is the results

preamp-input:
both 0.165mVAC

preamp-output:
L: 0.16VAC
R: 0.232VAC

poweramp-output:
L: 1.935VAC
R: 2.78VAC

So...the blame is the preamp (at least...in best case)
What next i can do?
thanks in advance...
 
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