I thought I'd start my own thread on my on-going Pioneer SA-9800 restoration and upgrade. I bought this amp a while ago, it was missing the top and bottom covers, and three of the smaller sized knobs. I have a "wanted" ad posted on Barter Town, but so far no results.
I brought the old thing up from the holding area (basement) to the workbench (kitchen table) after everyone had gone to bed, and took some measurements. The results are interesting to say the least...
4 fuses on PSU board all good. Amp power light comes on, protection relay clicks after 5 seconds, no display. I was assuming I should measure from the pins listed to a suitable ground (like pin 8). The voltages I measured are show below in red.
pins 1&2: -6.2v, should be -52v, regulated
pins 3&4: +4.2v, should be +52v, regulated
pins 5&6: -0.3v, should be +32v, regulated
pin 7: -0.3v, should be +18v, regulated, provides power for display circuit
pin 8: 0v, ground
pin 9: raw, -75.3v, unregulated
pins 10&11: -0.2v, should be -32v, regulated
pin 12: raw, +74.6v, unregulated
pin 13: raw, +74.6v, unregulated
pin 14: 0v, ground
pin 15: raw, -75.5v, unregulated
pin 16: +6.6vac
pin 17: +56.6vac
pin 18: +56.5vac
Looks like mine is losing power somewhere. There was a red 2.2k resistor, I believe it was R5, that was getting hot.
In addition, while probing around the board, I measured 165v AC between the positive of C2 and the ground. How is this even possible? The capacitor is only rated at 80v. I was so surprised, I got another meter, an old analog one this time, and measured it again. Same voltage.
Lee.
I brought the old thing up from the holding area (basement) to the workbench (kitchen table) after everyone had gone to bed, and took some measurements. The results are interesting to say the least...
4 fuses on PSU board all good. Amp power light comes on, protection relay clicks after 5 seconds, no display. I was assuming I should measure from the pins listed to a suitable ground (like pin 8). The voltages I measured are show below in red.
pins 1&2: -6.2v, should be -52v, regulated
pins 3&4: +4.2v, should be +52v, regulated
pins 5&6: -0.3v, should be +32v, regulated
pin 7: -0.3v, should be +18v, regulated, provides power for display circuit
pin 8: 0v, ground
pin 9: raw, -75.3v, unregulated
pins 10&11: -0.2v, should be -32v, regulated
pin 12: raw, +74.6v, unregulated
pin 13: raw, +74.6v, unregulated
pin 14: 0v, ground
pin 15: raw, -75.5v, unregulated
pin 16: +6.6vac
pin 17: +56.6vac
pin 18: +56.5vac
Looks like mine is losing power somewhere. There was a red 2.2k resistor, I believe it was R5, that was getting hot.
In addition, while probing around the board, I measured 165v AC between the positive of C2 and the ground. How is this even possible? The capacitor is only rated at 80v. I was so surprised, I got another meter, an old analog one this time, and measured it again. Same voltage.
Lee.
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