Hi, can anybody help me with this amp I have for repair. A schematic would help, but what I need to know is the type number of the thermistor that sits in the heatsink. There are 2 of them, they are coded TTC 050, but that can be many different values. One I have broken trying to get it out of the board (I have a replacement board which was supplied without any of the componants that attach to the heatsink.
If anybody can help out I would be most grateful.
Dave
If anybody can help out I would be most grateful.
Dave
On the B3000T I see two thermistors. COmponent number R7 and R8 on the board.
R7 is the bias thermal compensation. and is a 50 ohm NTC thermistor. Description is just NTC-500, Behr. part number: 804-15000-20589
R8 is the fan speed control sensor, and is a 100 ohm PTC thermistor. Description is PTC-101/01, Behr. part number: 804-21001-29294
R7 is the bias thermal compensation. and is a 50 ohm NTC thermistor. Description is just NTC-500, Behr. part number: 804-15000-20589
R8 is the fan speed control sensor, and is a 100 ohm PTC thermistor. Description is PTC-101/01, Behr. part number: 804-21001-29294
Thanks Enzo, the replacement board was not fitted with those componants, I was told to transfer them from the old board. The PTC one fell to bits when I tried to get it out of the board, the leads were a "good fit" in the through plating.
Do you have any info on how to set up the presets, Vr1, Vr2 & Vr3 ?
Do you have any info on how to set up the presets, Vr1, Vr2 & Vr3 ?
VR1 is your bias, and it is adjusted like any other. I'd use a scope and watch my crossover notch. The cheap way is to monitor mains current at idle, advance the control from the coldest setting until the mains current just starts to ramp up with the adjustment, then back off a hair from that point. I am sure someone may have a favorite idle current through the ballast resistors, but I don;t like that method, I find it arbitrary. Are R13,14 6.8 ohm resistors? Spec says 140mv acros each.
The other two are current limiters and are probably best just left where they are.
This amp adjusts like the QSCs it resembles.
The other two are current limiters and are probably best just left where they are.
This amp adjusts like the QSCs it resembles.
Thanks again Enzo. The resistors are indeed 6R8. Unfortunately I have to do something with the other 2 pots, it's a new board so they haven't been adjusted. I could measure the settings on the old board, not very scientific though!
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