Hello,
My brother has an old Roland GC-408 Amplifier.
It started to make some noise mainly when the reverb is enabled. I think the reverb tank is good, as the noise is sometimes present (but very lower) with the reverb turned down.
Since the amp is old, I think maybe a capacitor is starting to go out of specs or something similar so starting with a basic "recap" maybe would be a good idea.
What do you think?
I post a link to the service manual, I hope someone with skills can point what are the caps to start with.
https://ufile.io/jfc6d
Thanks in advance.
My brother has an old Roland GC-408 Amplifier.
It started to make some noise mainly when the reverb is enabled. I think the reverb tank is good, as the noise is sometimes present (but very lower) with the reverb turned down.
Since the amp is old, I think maybe a capacitor is starting to go out of specs or something similar so starting with a basic "recap" maybe would be a good idea.
What do you think?
I post a link to the service manual, I hope someone with skills can point what are the caps to start with.
https://ufile.io/jfc6d
Thanks in advance.
start with the caps in the supply section (C70 C18 C100 C101 C45 C46 C47 C48) and check the regulator circuit zeners (D15 D20) they are responsible for the voltage rails supplying the op-amps so bad components in this section are a likely source of noise.
any signs of heating around Q11 Q12?
any signs of heating around Q11 Q12?
Thanks for your response turk 182.
I'll start with that caps. I'll check the zeners too 😉.
The amplifier seems to work as expected, except for the slight noise, no excesive heat signs on total, but I didn't checked Q11 and Q12 transistors for heat signs.
I'll start with that caps. I'll check the zeners too 😉.
The amplifier seems to work as expected, except for the slight noise, no excesive heat signs on total, but I didn't checked Q11 and Q12 transistors for heat signs.
Hi Enzo,
the noise is not crackling, I would describe it as hum but not the typical 50 or 60Hz hum, it's a higher frequency.
I tried to capture it but the camera puts its own noise and it's difficult to identify it.
The noise is always light, it increases a bit as you turn the reverb pot more than 12 o'clock.
Thanks for your interest.
the noise is not crackling, I would describe it as hum but not the typical 50 or 60Hz hum, it's a higher frequency.
I tried to capture it but the camera puts its own noise and it's difficult to identify it.
The noise is always light, it increases a bit as you turn the reverb pot more than 12 o'clock.
Thanks for your interest.
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