Strange PT-80 Problem

[jkokura]

Hey,

So I built a PT-80, and put the Ptap circuit in so I can use tap tempo to set the delay. I thought I had something wrong with the circuit - I turned it on and there was no delay. Because I hadn't put any knobs on I had no idea that my delay knob was set fully clockwise. By accident, while I was testing it again, I turned the delay knob a little bit CCW, and wham! Delay happens. Basically, the delay pot works backwards. I know that this should be an easy fix, except that the delay pot has the Ptap circuit on it - so I don't want to mess around and try out various potential fixes and make a big mess. So I guess what I'm asking is if there are any Ptap experts who've installed the unit into a PT-80 and can show me EXACTLY how to wire it in?

To give you an idea, looking at the PT80 layout diagram, (http://www.generalguitargadgets.com/pdf/ggg_pt80_lo1.pdf) the wire from the pad marked "T1" goes to the middle pad on the Ptap board, then links to the square pad on the right; the pad marked T3 is wired to the far left. This assumes the silk screen markings face up, and the diode is down looking at the top of the board. I thought this was precisely what it should look like.

So my options are - flip the PTAP board over so the Square solder pad is on the 1st leg (it's currently on 3), switch the two wires at the board, or do i have to take it all apart and do a lot of adjusting?

jacob

[slacker]

Are you sure you haven't just wired up the delay time pot backwards, that would cause the same thing.

[jkokura]

That's what I've done, wired the pot wrong. I'm just wondering if someone who has a PTAP on their PT-80 who could tell me which wire goes where, and which way up the PTAP board would be. That way I don't have to try a bunch of different ways to figure it out. I'll be trying tonight to figure it out, so if I don't have an answer from someone here, I'll see what I can figure out this evening.

Jacob

[jkokura]

I tried switching the wires at the board - nothing resolved. The weird thing is that even when the ptap is turned off, the Delay pot is still backwards.

I'm thinking about flipping the board over on the Pot so it's reversed.

Jacob

[BAARON]

Reversing the wires won't change anything.  You need to change which lugs they're wired to on the pot.

For example, if you are using the left and center lug, you need to use the RIGHT and center lug instead.  (Or vice versa, whichever the case may be.)

[ppatchmods]

the ptap is tricky because of the digital pot. more than likely you have the 1&3 swapt going to the ptap board from the pt80 board. you can't change one and solve it, you have to change both sets of wires. (to the ptap board from the pt80 and from the ptap to the pot)

[slacker]

From this schematic and this PCB it should be wired like this.

T1 on the PT80 board goes to pin 5 of the MCP41050 (U3 on the PTAP board).
T3 on the PT80 board goes to pin 6 of the MCP41050.

The wiper of the delay time pot goes to pin 2 of the ATiny45 (U1 on the PTAP board), the middle pad of the 3 under where it says R1.
The anti clockwise lug of he pot goes to the pad nearest where it says R1 and the clockwise lug goes to the other pad.

If it's still backwards then like BAARON said you need to connect T1 to pin7 of U3 instead.

[decc]

I think the problem is that the GGG PT80 PCB is wired for the delay pot to be "speed", not "time", so it has the opposite turn.

Changing the link shown from 1 (CCW) to 2 (W) and instead linking 3 (CW) and 2 (W) should fix this.