Hello. Accuphase P-102 here. Intermittent fault, like scratches in right channel, resembling the sound of loose interconnect wire. Bias and DC offset are fine. No visible reasons, internals are clean and free of dust and rust . Power supplies are good. Schematic / Service manual would be highly appreciated.
........if it sounds like a loose connection.......
have you searched for a bad soldering point or sowhat?
(press with a stick of wood lightly on some places of the pcb and
listen if the scratching sound changes)
have you searched for a bad soldering point or sowhat?
(press with a stick of wood lightly on some places of the pcb and
listen if the scratching sound changes)
have you tried to find out if the noise comes out
of the psu or of one of the amplifier(halves) in the right channel?
of the psu or of one of the amplifier(halves) in the right channel?
Well, there's some progress, but still to many reasons of the fault.
What I did:
1. Localised the failed module. There are four similar amplifier modules, easily interchangeable. Swapping them in different combinations, I figured the only one producing the noise.
2. Given the above it is not PSU, neither input board or relay switches.
3. I disconnected the final stage from the front end (see picture) by raising fets gates, connecting them with 2x1k resistors, grounded in just between.
So, what I get is: no noise with separated front end. Apparently this is a front end and possibly dc servo opamp.
Need some methodic for next steps, otherwise I have to change almost all parts in particular module.
What I did:
1. Localised the failed module. There are four similar amplifier modules, easily interchangeable. Swapping them in different combinations, I figured the only one producing the noise.
2. Given the above it is not PSU, neither input board or relay switches.
3. I disconnected the final stage from the front end (see picture) by raising fets gates, connecting them with 2x1k resistors, grounded in just between.
So, what I get is: no noise with separated front end. Apparently this is a front end and possibly dc servo opamp.
Need some methodic for next steps, otherwise I have to change almost all parts in particular module.
sounds
recorded by phone mic close to speaker's twitter and midrange. Eventhough it is not that loud, its clearly audible. Unfortunately I can't trace it with the scope.
View attachment scratches.mp4
recorded by phone mic close to speaker's twitter and midrange. Eventhough it is not that loud, its clearly audible. Unfortunately I can't trace it with the scope.
View attachment scratches.mp4
all resistors in output stage are fine, however, blue ones are all measured 2 ohms, are fusistors, replaced them all. Moreover, having the gates of fets disconnected from front end and grounded via 1kohm (each side) makes no noise at all. So the problem apparently somewhere in the front end.
I swapped regulator transistors, and even couple behind them, also swapped one of the double jfets (J109) with other channel with no result. Rubbing my head...
databook says j76/k213 are mosfet, these need some voltage on their gates for currentflow i guess........
you right, it needs 2-4 volts gate to source to open them. Missed this point, will try again.
Nevertheless I changed them for J313/k2013, eventhough source and drain are reversed, the clicks were still there.
Nevertheless I changed them for J313/k2013, eventhough source and drain are reversed, the clicks were still there.
Hello arky,
please forgive me if I overlooked it, but have you replaced (or cleaned) the Output Relay (contacts!)?? This would be the first thing I'd recommend to check given the failure description and the age of the Amp. Alternatively to Relay replacement (especially if you can not get the original 😉) consider the application of Solid State Relays in the place of the original electromechanical parts. If you should decide for that, I'm ready to advise.
Good luck and best wishes for success!
Winfried
please forgive me if I overlooked it, but have you replaced (or cleaned) the Output Relay (contacts!)?? This would be the first thing I'd recommend to check given the failure description and the age of the Amp. Alternatively to Relay replacement (especially if you can not get the original 😉) consider the application of Solid State Relays in the place of the original electromechanical parts. If you should decide for that, I'm ready to advise.
Good luck and best wishes for success!
Winfried
Hi. Relays were changed at once. The failure is in particular amp module, the machine has four similar modules, all of them can be exchanged with each other. Several relocations and I got this particular module which produces the clicks.
sounds
recorded by phone mic close to speaker's twitter and midrange. Eventhough it is not that loud, its clearly audible. Unfortunately I can't trace it with the scope.
I have also the same problem with my P102 I just put a drop of isopropyl in the potentiometer and rotate it in clockwise and anticlockwise direction the problem solved.try it
recorded by phone mic close to speaker's twitter and midrange. Eventhough it is not that loud, its clearly audible. Unfortunately I can't trace it with the scope.
I have also the same problem with my P102 I just put a drop of isopropyl in the potentiometer and rotate it in clockwise and anticlockwise direction the problem solved.try it
It was an issue caused by pre-driver transistors heatsinks. It is unclear whether the heatsinks were original or modified by previous owner in Japan. Nevertheless, they were not attached to the board firmly, so the legs of transistors caused cracks in the soldering points of these BJTs.