Howdy
My Krell FPB200 seems to have developed a problem. There's a hum coming from the right channel and occasional static-like noise. (The left channel is fine.) At the moment the problem is still periodic, sometimes there and sometimes not, but it seems to be increasingly prevalent. I am a newbie to amps (so far I have been mucking around with power supplies only) and I am wondering if such a repair, with guidance from good folk here, is within my grasp or whether I just have to face up to what might well be an expensive repair bill (just because they think they can stiff a Krell owner).
If I am going to poke around in the amp I may as well replace the main power supply caps as well.
Any ideas as to what the problem may be and the potential complexity of fixing it?
Thanks in advance
Steve
My Krell FPB200 seems to have developed a problem. There's a hum coming from the right channel and occasional static-like noise. (The left channel is fine.) At the moment the problem is still periodic, sometimes there and sometimes not, but it seems to be increasingly prevalent. I am a newbie to amps (so far I have been mucking around with power supplies only) and I am wondering if such a repair, with guidance from good folk here, is within my grasp or whether I just have to face up to what might well be an expensive repair bill (just because they think they can stiff a Krell owner).
If I am going to poke around in the amp I may as well replace the main power supply caps as well.
Any ideas as to what the problem may be and the potential complexity of fixing it?
Thanks in advance
Steve
I should add that the problem only happens when a cable is connected to the right channel XLR balanced input. (Shifting this cable to the left input doesn't create the hum in the left channel so it's not the cable or upstream therefrom.)
Do you get a hum in the right channel when a single-end RCA input is used?
Do you get a hum in the right channel when the XLR balanced input is grounded?
Do you get a hum in the right channel when a single-end RCA input is grounded?
Can you get an O'scope?
The main output power supply is shared between the two channels, but there are separate power regulators for each channel front-end ckts. There are also small value high frequency filter capacitors around the input circuit which can generate a hum if they are faulty(some leakage to ground). These caps are very close to the input terminal.
I suspect you will need some local help finding the problem if it goes beyond the input stage.
Hi LineSource
Thanks for responding. I will try to get answers to your questions. (I do have an oscilloscope.) The issue is periodic and so I have to wait for it to return. I have found in the past that disconnecting and reconnecting the balanced connection a few times cleared the issue.
This evening it reappeared. I had a faint hum in the right channel - no static - even with no input connected. When I connected the balanced input the hum was more pronounced and the 'static' appeared in the right channel.
I decided to take a look inside (unfortunately before I checked grounding the input). This was enough for me to realise I haven't a hope of hunting this down with my current knowledge level. The FPB200 is a real beast. (BTW the channels don't appear to share anything other than control circuitry.)
When I replaced the lid and reconnected everything the issue was still there but a disconnection and reconnection cleared the problem (at least for now).
Ugh...
Thanks for responding. I will try to get answers to your questions. (I do have an oscilloscope.) The issue is periodic and so I have to wait for it to return. I have found in the past that disconnecting and reconnecting the balanced connection a few times cleared the issue.
This evening it reappeared. I had a faint hum in the right channel - no static - even with no input connected. When I connected the balanced input the hum was more pronounced and the 'static' appeared in the right channel.
I decided to take a look inside (unfortunately before I checked grounding the input). This was enough for me to realise I haven't a hope of hunting this down with my current knowledge level. The FPB200 is a real beast. (BTW the channels don't appear to share anything other than control circuitry.)
When I replaced the lid and reconnected everything the issue was still there but a disconnection and reconnection cleared the problem (at least for now).
Ugh...
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