hifiaf
pfm Member
I recently bought some CB Nap 135s, which after recapping are sounding very good. There are two quirks in operation, though.
I should note here that I only recapped the amp and regulator boards, not the fan boards — and I didn’t replace the zener diodes on the amp boards. I did test that the fans worked by turning up the fan trim pot (they both came on) and then returning them to their pre-set positions. I do now have the caps in hand for recapping the fan boards, so if that’s all that’s needed, it’s easily done.
First, one of the amps likes to suddenly mute its output. It doesn’t turn right off, because the idle hiss is still audible when it goes. It seems to do this only if I’ve been driving it relatively hard (about 9 o’clock on my 32.5) for about 20 minutes or more. If I then turn it off and back on, it plays happily once again. The case is not hot to the touch at any point. The fan never turns on. I thought maybe that the process that is supposed to trigger the fan is instead triggering this self muting.
The other amp doesn’t self-mute but it’s a bit overzealous with its fan. My speakers are relatively efficient Yamaha NS-1000Ms, so I wasn’t expecting to hear the fans at all unless I really got things loud. The other day I left it turned on and noticed that the fan was running when I came back in the room — it was a hot day, but still... I see where the trim pot is for the fan — I figure I just need to turn it down a bit. But is there a standard way of setting this pot?
Thanks for your help!
I should note here that I only recapped the amp and regulator boards, not the fan boards — and I didn’t replace the zener diodes on the amp boards. I did test that the fans worked by turning up the fan trim pot (they both came on) and then returning them to their pre-set positions. I do now have the caps in hand for recapping the fan boards, so if that’s all that’s needed, it’s easily done.
First, one of the amps likes to suddenly mute its output. It doesn’t turn right off, because the idle hiss is still audible when it goes. It seems to do this only if I’ve been driving it relatively hard (about 9 o’clock on my 32.5) for about 20 minutes or more. If I then turn it off and back on, it plays happily once again. The case is not hot to the touch at any point. The fan never turns on. I thought maybe that the process that is supposed to trigger the fan is instead triggering this self muting.
The other amp doesn’t self-mute but it’s a bit overzealous with its fan. My speakers are relatively efficient Yamaha NS-1000Ms, so I wasn’t expecting to hear the fans at all unless I really got things loud. The other day I left it turned on and noticed that the fan was running when I came back in the room — it was a hot day, but still... I see where the trim pot is for the fan — I figure I just need to turn it down a bit. But is there a standard way of setting this pot?
Thanks for your help!