Just learning still but trying to fix this for a friend and hoping it's something I can do. Would appreciate any help beyond the user and service manual which I have.
This is a very clean unit. I cannot tell if anyone has been into it before, but there are blue felt tip pen marks on each of the power supply caps and similar red marks on many of the main board caps. I do not have the remote.
Here's the symptoms:
-- In standby mode and high volume there is bleed-through with CD input regardless of which source is selected. I am "guessing" that this is normal.
-- The protection relay engages instantly when the unit is turned on (no delay). This may be normal, but I haven't seen one of these units before and don't know.
-- Once turned on, the amp is dead quiet at the speakers and headphone output regardless of source, tape settings, or volume level.
-- The CD Direct light stays engaged and does not respond to being pressed.
Diagnostics I have been able to do so far:
-- CN55/56 on the power supply board read -38/38. Service manual says it should be 36. I don't know if this is enough of a difference to be a problem, but leads me to believe problem is not in the power supply?
-- Bias current at CN59/60 on the power amp boards was very high, between 35-40 mV. I was able to adjust with VR53/54 to the recommended 11mV.
No changes to symptoms. Not sure where to go next and hoping these symptoms sound familiar to someone. Schematics attached.
Thanks,
Michael
This is a very clean unit. I cannot tell if anyone has been into it before, but there are blue felt tip pen marks on each of the power supply caps and similar red marks on many of the main board caps. I do not have the remote.
Here's the symptoms:
-- In standby mode and high volume there is bleed-through with CD input regardless of which source is selected. I am "guessing" that this is normal.
-- The protection relay engages instantly when the unit is turned on (no delay). This may be normal, but I haven't seen one of these units before and don't know.
-- Once turned on, the amp is dead quiet at the speakers and headphone output regardless of source, tape settings, or volume level.
-- The CD Direct light stays engaged and does not respond to being pressed.
Diagnostics I have been able to do so far:
-- CN55/56 on the power supply board read -38/38. Service manual says it should be 36. I don't know if this is enough of a difference to be a problem, but leads me to believe problem is not in the power supply?
-- Bias current at CN59/60 on the power amp boards was very high, between 35-40 mV. I was able to adjust with VR53/54 to the recommended 11mV.
No changes to symptoms. Not sure where to go next and hoping these symptoms sound familiar to someone. Schematics attached.
Thanks,
Michael