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I have a Kustom Quad 200HD guitar amp that's having a problem with the built-in effects. It would work intermittently whenever you flip the power switch off and on. Is there something quirky with the voltage supply or do I have a bad effects board?
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Does physical stimuli (like a good smack) do anything, or does it only respond to cycling the power switch?Originally posted by Enzo
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Kustom Quad 200HD Schematic
Here is the schematic.
The FX runs off of +5Vdc.
So you can check that the supply is stable.
I would look for signal going into IC1 pin 86 & 87.
If that is good, look for the signal coming out. Pin 7 & 8.Comment
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There may be an issue with the design of the +/-15V supply, this is derived from the +/-45V supplies, through 100 ohm resistors to the input of the 7815 / 7915 regulators
The regulators have a max input voltage of 35V.
As you are working on it anyway, it might be an idea to change R34 & R40 to get the input voltage of each regulator down to below (say) 33V
Measure the voltage drop across each of R34 & R40. With this you can work out the current through each one.
Calculate the new resistor value.
eg, R34 has 3V across it & the DC rail is 45.0V
current through the resistor is 3 / 100 = 30mA
We need to get the input volts to the reg at 33V, so we need to drop 45 - 33 = 12V across the resistor.
12V / 30mA = 400 ohm, use 390 ohm. Power dissipated is I^2 x R = .03 ^2 x 390 = 0.35W so use a 1W resistor.
These are just an example, using a guess, you will need to measure & work out the right values of resistor to use
You may find the regulators will work OK up to 45V input, but they are being used beyond their limits, and this may cause you a problem down the track. For a few resistors & a little time, we can stop this happening.Comment
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I just talked to tech support. He said to check C28, C34, IC8, and BR3. I'll see what happens.Comment
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