a question : what is normal temperature of this amplifier? It is known that they run warm but I have not found more specific information
background:
- a few weeks back I got hk 665vxi to my must have vintage collection. Unit I got was working but gave every now and then static noise at random. Pots were scratchy end push pull button were causing huge voltage swings at speaker terminals. After connecting to scope I got quickly distortion in one channel and strange drifting of complete sine wave around screen
- I read forums, download manuals and watched several great videos about pm665 and started to dig into it.
- initially I tried to set idling and offset but it was impossible- no scale on pots
- I have cleaned it, replaced all caps that were out of spec or bulged, replaced several bad resistors, some where lose, checked all transistors and refreshed paste, some transistors seem to drift away from spec hFE and where stuck to heat sink (not sure if I should change them in the future). Several components and jumpers were completely corroded
- after complete work I had started with dim bulb. It behaved strange (bright for a second, dim, and slowly bright after which pulsating every 1second) . Initially I thought it was a short but after checking it appear to be wrong idle and offset. It took me good one hour to set it back to what is specified.
- test speaker went grea, putting my better speakers as well but after some time I noticed that it runs hot. Transistor are at 60-75C when in a long listening session at elevated temp
- phonostage still doesn’t work but I will look at it later.
any advice from experienced folks? I started my vintage hobby a few months back and did 4 projects where forum was great tool ;-)
Adding some photos for the library.
Thank you in advance!
background:
- a few weeks back I got hk 665vxi to my must have vintage collection. Unit I got was working but gave every now and then static noise at random. Pots were scratchy end push pull button were causing huge voltage swings at speaker terminals. After connecting to scope I got quickly distortion in one channel and strange drifting of complete sine wave around screen
- I read forums, download manuals and watched several great videos about pm665 and started to dig into it.
- initially I tried to set idling and offset but it was impossible- no scale on pots
- I have cleaned it, replaced all caps that were out of spec or bulged, replaced several bad resistors, some where lose, checked all transistors and refreshed paste, some transistors seem to drift away from spec hFE and where stuck to heat sink (not sure if I should change them in the future). Several components and jumpers were completely corroded
- after complete work I had started with dim bulb. It behaved strange (bright for a second, dim, and slowly bright after which pulsating every 1second) . Initially I thought it was a short but after checking it appear to be wrong idle and offset. It took me good one hour to set it back to what is specified.
- test speaker went grea, putting my better speakers as well but after some time I noticed that it runs hot. Transistor are at 60-75C when in a long listening session at elevated temp
- phonostage still doesn’t work but I will look at it later.
any advice from experienced folks? I started my vintage hobby a few months back and did 4 projects where forum was great tool ;-)
Adding some photos for the library.
Thank you in advance!
