Krell FPB catastrophic protection conditions?

demi884

Member
2013-08-07 9:08 pm
Hi, friends.

I have Krell FPB-300 amplifier, which randomly trips breaker on rear panel. Looks that caused by signal on VCoil of breaker.(from one of CPUs)
It was recapped and checked by service man, he checked everything and told amplifier in perfect working condition.

The strange thing about it, i'v tested it at different places, at two apartments it was working fine without any breaker trips, at other two apartments it's trips breaker randomly.

Does anyone know conditions which force FPB amplifier to trip the breaker? Or, maybe someone has S19 file with dumped firmware(or disassembled), so i will be able to check conditions by myself.

Any ideas welcome...

Regards, Leo.
 
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It may be the load ...different speaker ... different load ... may be a strong dip in impedance curve ... but only if you drive it at very high level ... clipping like mad ....

some speaker wiring fault ... ( any in wall wiring ? with jacks & plug ? or switches ? )

I would also check for DC ofset on mains ... or harmonics ..... if somebody on the same mains circuit use electronics drive for air conditioning or other stuff
 

demi884

Member
2013-08-07 9:08 pm
It may be the load ...different speaker ... different load ... may be a strong dip in impedance curve ... but only if you drive it at very high level ... clipping like mad ....

some speaker wiring fault ... ( any in wall wiring ? with jacks & plug ? or switches ? )

I would also check for DC ofset on mains ... or harmonics ..... if somebody on the same mains circuit use electronics drive for air conditioning or other stuff

It could trip breaker even with detached speakers and inputs.

Looks like only thing that metter is power quality. Going to check how will it working with EMI filter.
 
The house circuit it's plugged into..
Do you know what other devices that particular plug/circuit shares through the house?
It might be near the edge of tripping and your amp pushed it over.
Or that lines breaker is going bad (least likely)
Is it a 20 or 30 amp breaker?

Regards
David
 

turk 182

Member
2012-10-26 3:03 pm
i may be wrong be it does seem he is saying that the circuit breaker on the "back panel of the amplifier"is tripping with no load or input connected (not the circuit breaker supplying the amp and whatever else is on the circuit)
the owners manual does state that a dedicated 15 amp breaker is best (might not be possible in an "apartment" situation)
 

demi884

Member
2013-08-07 9:08 pm
Tauro0221, i'v measured outlet voltage with TrueRMS multimeter, at appartment with "problem" was 224-230V without any visible voltage changes at tripping moment. Im using dedicated 30A breaker for this line.
Appartment without issue shows 220-225V.

turk 182, you are right, amplifier trips his own breaker.

David, is it possible that "noise" from other devices force amplifier to trip the breaker?

Im pretty sure that issue has software roots, cause CPU are able to trip the breaker by apply voltage to breaker VCoil.
Had discussion with collegues, we decide that propably amplifier could trip the breaker on any exception at microprogram.(ex. seg fault or divide by zero)

Could this exception(or cpu insanity) result of electrical noise or EMI?
 
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turk 182

Member
2012-10-26 3:03 pm
not that i would consider the 5 volt difference between the two locations as significant (or should not be) but it may well be the case if it exceeds the device's rating.(internal breaker)
i'm not well enough aquainted with the operation of the amp (as i've only ever heard one, just auditoning it) to say that your "cpu issue" is the cause of the problem or not.
 

demi884

Member
2013-08-07 9:08 pm
tauro0221, its tripping when amplifier is enabled, with and without music. It doesn't tripping at idle mode.
I will try to check CPU breaker leg, but some time ago i checked voltage directly at magnetic breaker vcoil, and wasn't able to detect voltage on it at tripping moment, possibly my multimeter is not fast enought.