Recent content by PJS

Your voltages are not making any sense. Make sure you are numbering the pins correctly - also for the LM13700 it is pins 6 and 11 that are relevant for this.

My understanding is that an op amp works by trying to make the 2 inputs the same. If one of them is tied to a voltage (ground or VB is usual), then it will try and make the other input a steady voltage as well. The output then will be whatever is required to cancel out the input, taking into...

That is crazy good troubleshooting

OK, so probe pin 7 of the TL074. If you are getting dry sound at the mix pot then you should have sound at pin 7 of the op amp. Then probe both sides of C3 and both sides of R3. If you have audio at the op amp, but nothing at the input of the FV-1, then it has to be getting lost at C3 or R3.

I built it and it has unity volume with no mods.

I haven't tried with the wrong value pots but I am reasonably certain it will still work OK. By all means change them but I don't think that is the problem. Do you get audio going in to pin 1 of the FV-1, and it it coming out at pin 28?

It also looks as if you have uses thin tape to insulate the back of the pot that is under the board. I know from experience that cut component leads can pierce even pretty thick/strong tape very quickly.

OK. The dry sound in the arachnid bypasses the FV-1 chip. If you are not getting dry sound through the mix pot then you will not be getting any signal into the FV-1 either, which means that even if the FV-1 is working, you won't get wet sound out of it. You need to audio probe from the input...

Honestly, it may not sound like it, but it may be a good thing. A problem that is there all the time is easier to find and fix than a problem that as erratic. I think I would first be audio probing to see where the signal dies.

Working for 30 seconds sounds like either something gradually heating up until it stops, or a capacitor gradually charging up until it is fully charged and that stops the circuit working. Check (carefully) for over-warm components, check capacitor values and orientation, and check to see if...

The regulator only powers the Belton brick. The datasheet for the brick says that it draws typically 60mA, and 100mA at maximum. The 78l05 can deliver 100mA, so by rights it should power the brick OK. The larger regulator can deliver 1A. It will probably need a heatsink to deliver that...

A few things to double check first. I know it sounds basic, but double check and make sure you haven't plugged the guitar into the output and the amp into the input. Most (all?) of us have done that. Check that the board is getting voltage with a multimeter. The arachnid has a mix pot to...

Your meter is saying that the new speakers should be OK. I think I would be trying the original speaker back in it, just to make sure that the amp is still working.

If you have a mulitmeter and you use it to test the DC resistance of the speakers, you should also see the speaker cone physically move one way or the other while under test. The meter tests DC resistance, while the specification is for AC impedance, so a 4 ohm speaker won't measure exactly 4...

The wiring looks as if it should be correct. Did you try the 2 speakers individually to make sure they are both OK?