Trace Elliot AH300 GP12 series6

[MARSHALL BUSTER]

Hi guys
I'm looking at a Trace Elliot AH300 GP12 that has a red hot 220r 5w resistor at R118 on the front preamp board.


I have replaced the 10k at R117 because someone had put a 4.7k in there and i noticed on the schematics that its a 10k but R118 still gets red hot!

Any suggestions please??

BTW the amp is working perfect i noticed the resistor when i was servicing the amp.

Trace Elliot AH300 series 6.pdf

Cheers guys

[Enzo]

Your schematic says 15k for R117.

I expect R118 to get good and hot. According to the schematic it drops 21 volts across its 220 ohms, and that is a 2 watt dissipation. Pretty hot.

The things to find out are:
is there about 33v across ZD2?
what voltages are on the ends of R118, you get about 59v on the end by the connector and about 38v on the other?
do you get the two preamp supply voltages +30 and +15? Looks like just measure acrooss R115 R116.

[MARSHALL BUSTER]

Hi Enzo how are you buddy.

Yes your right it does say 15k, i went straight to the parts list where it says 10k

Ok then ZD2 = 34v

R118 connector end is showing 74.5v other end 52v

Preamp supply 17.4v on R115 and 33.3v on R116

I just notice the cooling fan is not running.

[Enzo]

So all the voltages are within reasonable bounds. Your 15 and 30 are a couple volts high, but we can live with that. You have roughly the 20 volts across the big resistor as it was intended, so I'd have to think the heat is normal.


If it really bugs you, remove the resistor, get one of the same value in a heavier package, like 15-20 watts, in the type with the aluminum housing and fins, with mounting tabs on the ends. Screw it to the chassis wall somewhere and run wires back to the circuit board. Now no more heat on the board.

HS10 220R 1% Arcol | Mouser

[rf7]

I've seen that before in those amps, they just run that resistor hot. Upping the wattage as Enzo suggested will definitely help it live longer.