20 Most Recent Crate Blackheart BH15 112 Handsome Devil Guitar Amp Combo, 15W All Tube with Attitude - Page 4 Questions & Answers

Shorted instrument cable. Try a different cable.

Are all the tubes lighting up? they should glow like dim light bulbs. If not, replace them with the same model type (12ax7, or EL34 for example).Often there are two fuses, one to protect the speaker and another to protect everything, it sounds like the latter fuse may be burned out. take it out and take it to radio Shack for exact replacement.

A possible problem MIGHT be marginal switch contacts on the external foot controller cable. If you are not using the foot pedal, these contacts must maintain contact to keep the same channel selected.

Power light means very little. If unit has a preamp output, plug a set of headphones into it and see if you can hear anythin going through. (it will be weak). If you can, the power amp section is bad. Take in for service.

NEVER use switch cleaner such as DeOxit on pots !!!!!

I have used CRC226 available at Home Depot electrical dept.

I SUSPECT that the resistance element in that pot is cracked. This is common if the knob sustained a hit. Replacing the pot is the only cure if the element is cracked.

Reviewing the schematic, ALL audio passes through the wiper on the HIGH tone pots. If the wiper is intermittent, so will be the sound.

If your unit is solid state amp, the pot looks like a 10K ohm LINEAR taper.
If you have a tube type, then the pot is a 250K ohm LINEAR.

Note that the other tone pots in the units are AUDIO tapers, but the high is a linear taper.

Get repair parts from either DigiKey.com or Mouser.com

Looking over the schematic I see all sorts of poor design. The reverb is driven by IC TL072 chip and the output is received by the same.

This chip is supplied with +/- 15.5 volts UNREGULATED which is stupid! If you get a power surge, the IC will be destroyed. Myself I would put at least a shunt Zener regulator on these voltages. Use a 100 ohm resistor in series and Zeners to ground for both the plus an minus 15.5 lines.

First thing check those 15.5 volt... the plus is on C23 pos term and the neg is on C24 neg term.

They have a 1 meg resistor to ground from pin 3 of the chip to bias the + input of the chip. This is TOO big as the input leakage current can be too much. I would reduce this resistor to 220K and increase C22 to 0.0047 mfd.

Check the DC voltage at pin 1 of the chip (IC1). It should be VERY near zero.

The output buffer for the reverb has better design. Check for zero volts or very near it on pin 7 of the chip. Be careful not to short to pin 7 which is pos 15.5.

If either of the above tests show a voltage over 0.5 volts from ground, replace the TL072 chip as it is likely fried by power surge..

Since there is high voltage (320 volts) use great caution when working on this amp.

Check for bad tube... it HAPPENS that brand new ones fail... USUALLY if they last 50 hours, they will last for the expected life. The bad tube would likely NOT be the main power tubes, as the amp would still run on one cylinder...

I can understand your confusion... and a lot depends how you are going to use this. There are some caveats regarding the connections,
If you use the 1/4 outputs on the GSP, there is a speaker modeling like function that is NOT available, that IS available IF you use the XLR outputs.
The STP is an "Insert Snake" which is not really what you want as it is intended to send and receive (audio going both directions in the cable.
If you want that speaker function, then you should get two XLR to 1/4 TRS cables and go from the XLR's on the GSP to the Left and Right inputs on the back of the Crate. Your audio or guitar then is connected to the GSP guitar input.
If you connect the guitar to the crate and then use the STP, Plug the TRS single connector into the Left/Mono/send/rtn on the Crate. The Send cable of the Y should go to the Send jack on the back of the GSP and the return should go to the left return jack of the GSP. This connection I would NOT recommend as it will be noisier and you will lose the stereo effect capabiltiy since the effect is inserted as a mono.

I believe you would be happier with using the XLR's to carry left and right to the Crate and run your inout to the GSP. In short, you have the wrong cable to do the best job.