Hi all, a small problem with my B-2 that i'd like to diagnose before I go replacing un-necessary parts..
It has been cutting out on the left hand channel most days, rhs stays level, just the left drops out - it goes quieter sometimes and then cuts out completely sometimes, no pattern no continuity.
I thought the first port of call might be the front panel switches, so cleaned all these with deoxit. It seemed to help but doesn't solve it - it's still cutting out on the lhs.
So I swapped the rca inputs from one input to the other (controlled by a switch on the front panel) and the same problem persists.
Then swapped the speaker output from speakers A to speakers B and it seems to work perfectly.
So is my problem the speaker A selection switch on the front panel? Or the internal relays??
Thanks!!
It has been cutting out on the left hand channel most days, rhs stays level, just the left drops out - it goes quieter sometimes and then cuts out completely sometimes, no pattern no continuity.
I thought the first port of call might be the front panel switches, so cleaned all these with deoxit. It seemed to help but doesn't solve it - it's still cutting out on the lhs.
So I swapped the rca inputs from one input to the other (controlled by a switch on the front panel) and the same problem persists.
Then swapped the speaker output from speakers A to speakers B and it seems to work perfectly.
So is my problem the speaker A selection switch on the front panel? Or the internal relays??
Thanks!!
I have worked on a few of these amps.
You should never bring this unit using a Variac (not good). Follow precautions in service manual.
Look for cold soldered joints.
Clean connectors and switches.
Replace all electrolytic capacitors.
Jam
You should never bring this unit using a Variac (not good). Follow precautions in service manual.
Look for cold soldered joints.
Clean connectors and switches.
Replace all electrolytic capacitors.
Jam
This amp has separate relays for Speaker A and Speaker B.
Your problem will be with one of the contacts in the Speaker A relay.
You could remove the cover of A relay and scrub/burnish the contacts with thin card soaked in solvent.
Just as easy to leave your speakers connected to Speaker B.
Ignore the advice from Jam.
Dan.
Thanks Dan & Jam.. Thought as much Dan, I'll get some relays ordered and leave them on the bench for the next time I have it apart. I don't like to 'replace all caps' as a blanket fix as you suggest Jam, the caps in these amps are very good and all look fine. I like to leave alone if poss.
I'll leave speakers connected to output B and replace both relays if and when it starts to play up on this output.
Thankyou!!
I'll leave speakers connected to output B and replace both relays if and when it starts to play up on this output.
Thankyou!!
Don't bother cleaning the relays, or replacing the caps. Brand new relay and you're good to go. Speaker B relay is probably unused anyway though so no need to actually do anything with the amp.
Considering the age of the unit it is rather short sighted to ignore the other things I mentioned. I worked for a Yamaha service center and that was Yamaha's advice on older units like the B1 and B2. It better you take care of it now rather than face catastrophic failure later and if that happens the output devices are unobtainable.
The output devices are depletion mode devices and will likely blow if you try to bring the amplifier up with a variac.
Apart from switches and contacts cold soldered joints were the number one source of failure of these amplifiers, due to heat. A little bit of preventative maintenance can't hurt as long as it is done with care.
The amps are over thirty five years old and are loaded with electrolytic's, you might want to do some research into the life expectancy of electrolytics especially in high temperature conditions.
The output devices are depletion mode devices and will likely blow if you try to bring the amplifier up with a variac.
Apart from switches and contacts cold soldered joints were the number one source of failure of these amplifiers, due to heat. A little bit of preventative maintenance can't hurt as long as it is done with care.
The amps are over thirty five years old and are loaded with electrolytic's, you might want to do some research into the life expectancy of electrolytics especially in high temperature conditions.
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After changing to speaker B output and therefore using the B relay rather than the A one, everything has worked perfectly since...
Yes I understand the need to have these old components 'serviced' which I do, but I'm not into changing caps just because it's the fashionable thing to do. If they are in spec, they stay. 🙂
Yes I understand the need to have these old components 'serviced' which I do, but I'm not into changing caps just because it's the fashionable thing to do. If they are in spec, they stay. 🙂
You miss my point, this has nothing to do with fashion there is a possibility that if some caps fail due to age which will cause the amp to blow you will now have an expensive doorstop but then again it's your amp. 😉
yes, the advise is to shut the power off and say a prayer or two that the vfets are still OK.
- make sure the unit is unplugged, bulk caps are fully discharged.
- test the vfets individually without mixing them.
- If the vfets are still OK, look for someone to rebuild that unit. After ~45 years of service it should not be operated without proper restoration.