a few years ago my friend built me this hybrid amp,now he move to other country and i lost contact with him.
this amp now damage,it has distort sound,such like clipping on every volume.
after i turn off the amp,i measure the dc offset on one channel,it show -50vdc,after the relay click on.
somebody can help me please..
here is the schematic for input stage (tube) & output stage
lot of thanks for the help
this amp now damage,it has distort sound,such like clipping on every volume.
after i turn off the amp,i measure the dc offset on one channel,it show -50vdc,after the relay click on.
somebody can help me please..
here is the schematic for input stage (tube) & output stage
lot of thanks for the help
Attachments
Banned
Joined 2002
q45= c3281 ,4 pcs each channel
q52= a1302 ,4 pcs each channel, toshiba's
So are you saying there is 55V on the speaker output ?
.
You verify before the fuse on negative and positive rail. If it is Ok, then it miss the bias in the upper half. If fuse is broken, then you have a transistors short circuit in the relative side.
Francesco.
thank you,all transistors were check and they are normal,the fuse also ok,and i don't know where to set the bias for that amp,there is no bias pot as you see on schematic
cheers
Yes, i not be seen your answer before: if you have dc offset only with relay on, then you have the 0,22 cap in short.
Francesco.
thank you very much,i was ever try to swap the cap 0,22uf for left channel and right channel,but the problem is still on same channel,the tubes was swap also for left and right,the result is the same
uuufffhhh... very headache
Are you saying you have swapped the cap and it's still faulty ?
If you only get an offset when the relay at the output of the valve closes then either the cap must be leaky or there is some strange wiring fault/short etc.
It's not possible for it to be anything else.
Remove the cap and see if the offset problem remains when the relay closes.
Extremely obscure is the posibility that the valve stage is oscillating, you would need a scope to check... or remove the valve.
If you only get an offset when the relay at the output of the valve closes then either the cap must be leaky or there is some strange wiring fault/short etc.
It's not possible for it to be anything else.
Remove the cap and see if the offset problem remains when the relay closes.
Extremely obscure is the posibility that the valve stage is oscillating, you would need a scope to check... or remove the valve.
thank you ,yes i swapped the cap and the problem still there,when relay is not connect with the valve stage (relay shorted to ground),there is no dc offset on output
yes,the circuit is correct,and the relay is true on there,between valve stage and amp stage
thanks
very sorry,i forget something on circuit,there is caps 47pf on collector to base q42 and q58, if i remove those caps the 50vdc is gone,but this happen only in one channel,the other channel still fine altough the caps still on there.
and the other problem,the sound is very distort on both channel,very weak,such like clip on every volume
thank you
and the other problem,the sound is very distort on both channel,very weak,such like clip on every volume
thank you
Hi Tomat,
You need to step back and start again
The relay is drawn incorrectly... you mention it shorting the input to ground... yes !
If so it's possible there is a problem in the power amp and the effect of shorting the input is masking the problem... particularly with you saying removing 47pf caps stops problem.
You need to isolate the where the fault lies, power amp or valve stage/relay.
You need to step back and start again
The relay is drawn incorrectly... you mention it shorting the input to ground... yes !
If so it's possible there is a problem in the power amp and the effect of shorting the input is masking the problem... particularly with you saying removing 47pf caps stops problem.
You need to isolate the where the fault lies, power amp or valve stage/relay.
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