Can someone help with a source and part numbers? I want to replace all the electrolytic caps on the pcb’s as well as replace the 4 pots wit multi turn sealed ones. Have no idea what to orde and from where. I have a downloaded service manual but the schematics and text is too fuzzy to be of help. Any help on this would be greatly appreciated.
Nakamichi used good quality parts, caps should be good.
Check with a meter, re capping is a bit of a fad now, and sometimes much larger caps draw too much current from the power supply.
Pots, if noisy, replace with Alps or Bourns units...if anti oxidant spray does not help.
Check with a meter, re capping is a bit of a fad now, and sometimes much larger caps draw too much current from the power supply.
Pots, if noisy, replace with Alps or Bourns units...if anti oxidant spray does not help.
I have just done a PA7- I did replace the lower value caps on the PCB with new ones of the same specification and type. The main caps measured good and I left those in. I did add a 470uf Nichicon MUSE UES biPolar across the 10uf cap as others have suggested.
The amp sounds great., though minimal intervention is my advice
The amp sounds great., though minimal intervention is my advice
I just want to mainly replace those horrible pots as it makes it hard to set the idle current. They are old and glitchy. Then it was recommended I do the pcb electrolytic caps while at it. The 4 power supply 33k’s are fine. Amp sounds beautiful as it has since I bought it in 1987. It is idling hotter i noticed lately so I have been messing with the idle voltage and finally got the temp where I want it. I find the amp sounds very noticeably better if it runs about 50-55c on rear heat sinks at idle.
Pwdia12, what does adding that 470uf do? Is it for a sonic improvement?
Thanks for the replies.
Pwdia12, what does adding that 470uf do? Is it for a sonic improvement?
Thanks for the replies.
the general wisdom is that the additional cap improves the bottom end. According to the manual the idle voltage should be about 40mv.
I did notice that when the amp stabilized the current draw dropped to about 1Amp form 1.5amp, which of course reduced the heat
I did notice that when the amp stabilized the current draw dropped to about 1Amp form 1.5amp, which of course reduced the heat
Voltage at the tp depends on the temp of the amp when you are checking . I use 40mv as starting point. I let idle fo a long time, check the temp at middle of rear heatsink. Slide the top over and adjust both sides. Put top back on and let it stabilize. Repeat until I get the heatsink temp where I want it which is 55-60c
Too cool and it doesn’t good. Too hot is obviously no good. But definitely a better sound running on the warm to hot side. Be cautious of using fans or vented KoolTops. Bias has to be re calibrated or the amp will actually run way to hot.
I set mine once with the top all the way off taking my time (heatsiinks got HOT) and set it to 40mv and when I turned it on the next day with the top screwed back on the amp never got warmed up. I quickly checked the idle voltage and it was 18 ish mv I got it set now so it will read around 40mv with the heatsinks at 55c.
Too cool and it doesn’t good. Too hot is obviously no good. But definitely a better sound running on the warm to hot side. Be cautious of using fans or vented KoolTops. Bias has to be re calibrated or the amp will actually run way to hot.
I set mine once with the top all the way off taking my time (heatsiinks got HOT) and set it to 40mv and when I turned it on the next day with the top screwed back on the amp never got warmed up. I quickly checked the idle voltage and it was 18 ish mv I got it set now so it will read around 40mv with the heatsinks at 55c.
