This thread is the follow up of a discussion started by myself in a thread about different speaker cables lengths because I wanted to know if that could be the case, in my ignorance. I don't want to keep polluting that thread so I start this one.
The last intervention by @restorer-john, which seems to have some consensus it points to the right diagnosis, is this one. I paste it here:
This is the audio of what happens. It's a 440 Hz tone. As described above, the audio is distorted and unstable before it's solved by turning up the volume. This happens only in the B channel, which I believe I hasn't been used since I bought the amp, 10 years ago. This relay has been waiting for 10 years... Does that make sense? Lack of use can be a triggering factor?
I'm not completely sure about which is the suspicious relay. I've taken some pictures.
I think the one (this is a relay, right? ) I'm pointing with the wood is the one that controls the B channel, the lower one, the only that has the problem. Does that make sense? There are another pair of white relays in the main board, but I think they control other things. I'm reluctant to disassemble more pieces so I don't have access to the rear of this vertical PCB where the speaker terminals are attached to be sure the current arrives just at this point to verify this is the correct relay.
I've tried hitting it with the wood (I've hit all the relays nearby in fact ) but the results are not conclusive. Sometimes, with a hit, the sound changes abruptly, apparently as a result of the hit, but it doesn't get solved.
I can keep trying. I'm on the right track?
Thanks a lot!!
The last intervention by @restorer-john, which seems to have some consensus it points to the right diagnosis, is this one. I paste it here:
You have most likely, an oxidised/pitted set of speaker relay contacts. Very, common.
The 'burst' of volume is required to 'cut through' the oxide and then all is well until next time or a period down the track.
Prior to turning it up, one speaker is lower in level and/or distorted.
To confirm it is the relay, take the cover off the amp, turn it on and play at the level where the issue occurs. Tap the speaker relay firmly with a wooden chopstick (safety first) and see if it instantly solves the issue. All you need do is either replace (preferable) the relay or alternately, remove it, pop the cover and clean the contacts with some 2000+ grit wet and dry cut into a thin streamer-like strip, folded over and pulled through the NO contacts.
This is the audio of what happens. It's a 440 Hz tone. As described above, the audio is distorted and unstable before it's solved by turning up the volume. This happens only in the B channel, which I believe I hasn't been used since I bought the amp, 10 years ago. This relay has been waiting for 10 years... Does that make sense? Lack of use can be a triggering factor?
I'm not completely sure about which is the suspicious relay. I've taken some pictures.
I think the one (this is a relay, right? ) I'm pointing with the wood is the one that controls the B channel, the lower one, the only that has the problem. Does that make sense? There are another pair of white relays in the main board, but I think they control other things. I'm reluctant to disassemble more pieces so I don't have access to the rear of this vertical PCB where the speaker terminals are attached to be sure the current arrives just at this point to verify this is the correct relay.
I've tried hitting it with the wood (I've hit all the relays nearby in fact ) but the results are not conclusive. Sometimes, with a hit, the sound changes abruptly, apparently as a result of the hit, but it doesn't get solved.
I can keep trying. I'm on the right track?
Thanks a lot!!
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