working on a vintage luxman r1040 , I'm getting what seems to be dirty pot noise , have cleaned as well as I know how with very good cleaner and still get an intermittent large dose of R channel static .
Question : is there a practical way to isolate the power amp section of this piece ? Also , if someone wants to recommend a repair for the existing problem please do.
thanks
Question : is there a practical way to isolate the power amp section of this piece ? Also , if someone wants to recommend a repair for the existing problem please do.
thanks
You may have to replace the 200k dual volume control (use a 250k replacement), but first you could try
replacing the coupling capacitors C301a/301b, in case they are leaky.
Board PB-1009 is the power amplifier. Its inputs are P201a and P201b. Just disconnect the existing leads,
and connect these input terminals to a pair of unneeded RCAs on the back. Use a nearby ground on PB-1009
for the wires from the RCA grounds. Use either shielded cable or twisted pairs for the connections.
Luxman R-1040 - Manual - AM/FM Stereo Receiver - HiFi Engine
replacing the coupling capacitors C301a/301b, in case they are leaky.
Board PB-1009 is the power amplifier. Its inputs are P201a and P201b. Just disconnect the existing leads,
and connect these input terminals to a pair of unneeded RCAs on the back. Use a nearby ground on PB-1009
for the wires from the RCA grounds. Use either shielded cable or twisted pairs for the connections.
Luxman R-1040 - Manual - AM/FM Stereo Receiver - HiFi Engine
Last edited:
Thank you , is it possible the caps 301a/b are causing the problem or just maintenance ? Do you think the noise is in the volume control ?
luxman r1040 contd
Thanks Rayma , I used your layout info and isolated the pre/power amps . Am I correct , the only thing remaining in the power amp side is the speaker a/b ? Still getting what sounds like pot noise so I bypassed the speaker selector switch . Any ideas where to look for this or just go through a items and connections in the power amp section ? Seems like a waste to invest much time into but this is a sweet sounding amp , not sure what I would need to spend to better it aside from spring for one of Nelson's first watt amps , don't have the budget for that .
Thanks Rayma , I used your layout info and isolated the pre/power amps . Am I correct , the only thing remaining in the power amp side is the speaker a/b ? Still getting what sounds like pot noise so I bypassed the speaker selector switch . Any ideas where to look for this or just go through a items and connections in the power amp section ? Seems like a waste to invest much time into but this is a sweet sounding amp , not sure what I would need to spend to better it aside from spring for one of Nelson's first watt amps , don't have the budget for that .
Noise in the power amp section could be bad solder joints, a bad resistor, pots,
bad connector contact, etc. You could use freeze spray to try to localize the problem,
if it happens often enough.
You could bypass the speaker switch easily enough, if it could be the problem.
bad connector contact, etc. You could use freeze spray to try to localize the problem,
if it happens often enough.
You could bypass the speaker switch easily enough, if it could be the problem.
Last edited:
I have bypassed the speaker selector so I believe the problem is in the power amp section . Are there pots in that section ? The noise is almost constant .
Sounds like a bad connection or bad resistor. Could even be a bad semiconductor.
You'll have to use freeze spray to localize it further, unless the pencil eraser trick works.
You'll have to use freeze spray to localize it further, unless the pencil eraser trick works.
What is the eraser trick ? I will have to import freeze spray from the US . Could one use an infrared thermometer to search for hot spots ?
With the amplifier power on and some junk speakers hooked up, poke around gently with an insulated tool
such as a pencil eraser or stick. Stay away from the AC line area. You may cause quite loud sounds doing this.
If you find a noise trigger, poke more carefully until you locate the source, which could be a bad component
or connection. This will only work on some noise problems, but the freeze spray will find others, like bad
resistors or semis. This particular problem does not seem likely to be a capacitor.
Use only one hand, and keep the other hand in your pocket, for safety.
Last edited:
Well it's beyond solder joints , i dont really see change in device manipulation but using an infrared thermometer with the amp on I see cap and resistor temp differences from channel a-b 80F - 115F other channel same device. I see several devices ch to ch with 20-40F differences. Do I just start repopulating these boards ? I'm actually considering punting and looking for a pair of populated boards that work within the voltage/wattage parameters. Any input would be appreciated even in an experimental spirit . I'm game at this point . I'm actually considering removing the transformer and power supply board , buying a pair of clone boards and fitting it all into a new enclosure .
Last edited:
It's usually best to repair problems before taking any further action.
A can of freeze spray would be much cheaper than more drastic measures.
Temperature differences of parts can be due to the environment on the board
and in the chassis, rather than differing power dissipation.
A can of freeze spray would be much cheaper than more drastic measures.
Temperature differences of parts can be due to the environment on the board
and in the chassis, rather than differing power dissipation.