Vintage Akai-52 /turn off when turn volume control/

[coojoe_213]

Hi. I have perfect voltage everywhere, amp work, but if i turn volume from 0 to 1, relay turn off.

If i disconnect input cable, and connect only speakers, and turn volume max, all is normal(relay doesn't turn off)
If i disconnect all cables /output and input/ turn volume max all is normal (relay doesn't turn off)

When i connect input cables and press 'PLAY'' button on cd player or tablet, relay turn off.
I change input cable but without result. I have this problem in every input /tape1, tape2, aux, cd.../

I check voltages on M5218 / M5238 - all normal. I check also idle adj. is 20mv, normal.
Open relay and clean, all normal.
Do you have any idea? ://

[Andrew F. Ali]

Re: Vintage Akai-52 /turn off when turn volume control/

There may be a error in the OUTPUT stages. Look for cold solder joints, open load resistor or weak capacitors. Of course test the pre-amp and output transistors, they might have become leaky due to aging.

[coojoe_213]

Re: Vintage Akai-52 /turn off when turn volume control/

I resolded all joints, I fuseable resistor checked /perfect/. I test some capacitors on input board with esr meter, but they are good.

[budm]

Re: Vintage Akai-52 /turn off when turn volume control/

The speaker relays turn off?
Try turning OFF the SOURCE DIRECT switch #2 as shown on page 4 and see what happen.

[redwire]

Re: Vintage Akai-52 /turn off when turn volume control/

C2 at IC1 should block DC from getting to the volume control.
The protect-relay cap maybe open C115/C116 at IC102. This would make it trip with any "thump".
Otherwise, since this is a DC-coupled power amp with a servo IC101, I would check C109/C108.

[coojoe_213]

Re: Vintage Akai-52 /turn off when turn volume control/

I remove Source Direct, but no result. Check C115/C116/C108/C109, they are good. You can see what happen on my video.
https://www.youtube.com/watch?v=rO5b...ature=youtu.be

[budm]

Re: Vintage Akai-52 /turn off when turn volume control/

How about C119, C117, and as others as marked?

[redwire]

Re: Vintage Akai-52 /turn off when turn volume control/

In the video, IC102 trips when the volume is up.
With BAL control I would see if it is L or R channel doing this or both.
That looked like over-current trip as if shorted loudspeaker or open C113 (by TR112).

[coojoe_213]

Re: Vintage Akai-52 /turn off when turn volume control/

Hi. Thanks for reply. Amplifier work now!!! The problem was ... output wires short on the right chanel in amplifier. Do you have any idea how is possible to short this wires??? Every parts in this amp is perfect (c113 was perfect, tr112 also). Thanks all who reply in my topic.

[budm]

Re: Vintage Akai-52 /turn off when turn volume control/

Good find, but I did not expect you to get sound on both speakers unless it is not a dead short between speaker terminals. It looks like common mode choke to stop RF from coming in to the amp through the speaker outputs.