Timmy Clone- Tommy PedalPCB problems

[Big mike 1100]

Hey All,

Been a while since I've been here.  This forum has been extremely helpful in diagnosing Pedal problems- Can't thank you enough!!

Here's the issue.  I'm building a Timmy Clone- The Tommy PedalPCB and it's not working.  Here's some additional info.

https://www.pedalpcb.com/product/tommy/


I tried using an audio probe and am only hearing sound at R1, C1 and Pin 7
Regarding voltages-
1 0
2 0
3 0
4 9.35
5 0
6 0
7 9.35
8 0

Not sure where to check next.

[Slowpoke101]

Hi Mike, long time no see. I'll PM you a bit later on and catch up.

1st thing to check with this Timmy clone is your IC. I think that it may be inserted the wrong way around.
Your voltage measurements don't make sense so check it out.
2nd thing is to give the solder side of the board a good clean and see if there are any bits of solder where they should not be. Let us know what you find.

[Big mike 1100]

Thanks!  Might take a bit.  I switched the IC chip and the Led light went out.  Now there's no voltage.  I'll clean the board and see if I need to replace the LED and IC chip.  I might have fried something in the process.

Stay tuned!

[Big mike 1100]

OK- got that straightened out.  Led is back on and the IC chip I believe is orientated correctly now.
I've also cleaned the solder side of the board to catch any potential stray stuff.

New Pin voltages:
1 8.47
2 8.24
3 9
4 0
5 8.42
6 8.45
7 8.46
8 9

[willienillie]

Something is very wrong.  It's possible the chip is now dead from having been inserted backwards.  Your voltages suggest maybe it's internally shorted in both halves, but maybe there's an error with your Vref supply.

The link you posted is for a newer version of the PCB, so it's hard to check with nothing to refer to.

[Big mike 1100]

I scanned a copy of the schematic.  Hopefully this will help.  I put in another IC chip a TL072 as I think I fried the other one.

[Slowpoke101]

Check R2. It should be a 510K resistor but it looks like you may have a 100R in there.
R8 and R9 for the Vref voltage divider so it may be helpful to measure the voltages on each leg of those two resistors.


Edit: I think that this a link to the correct documentation;

http://www.pedalpcb.com/docs/Tommy.v1.pdf

[willienillie]

Check R2. It should be a 510K resistor but it looks like you may have a 100R in there

I was looking at that too.  The newer version specs a 1M, but I can't tell what he has installed.  Definitely not 510K.  Easy enough to check Vref, just pull the chip and read voltage at socket pin 3.

I put in another IC chip a TL072 as I think I fried the other one.

Anything change?

[Big mike 1100]

I'm attaching the other piece of documentation, noting where R2 is on the board.  I re-measured and it reads 510k ohms.  (I assume thats the same as 510K)  Also attached a pic of the resistors, in case I'm missing something obvious :-)

***I think I'm missing something obvious- .510 is not the same as 510 I'm betting******

Socket pin 3 with the chip removed reads 9.06V
R8 and R9 both read 9V

[MikeA]

That would do it!  510 ohm in the 510k spot (R2) between Vref and Pin 3 of the op amp.  You'll probably need a new op amp.  I've more than once put a 47k in a 470k spot, easy to do...

[PRR]

> .510 is not the same as 510

I *HATE* displays with dinky dots!!

I have thrown-away otherwise good TI-30 calculators because their dots were too shy. (They change the LCDs every few years.)

BTW, in text it is a good idea to always have a leading zero: not .510 but 0.510. (And your post shows why.)

[willienillie]

Socket pin 3 with the chip removed reads 9.06V

That's another problem, it should read around 5V even with the wrong R2 value.  Check that one end of R9 has continuity (0 ohms) with ground.

Edit:  I'm making the assumption that this pedal is running at 9V, not 18V.  It doesn't actually say on the schematic.

[Slowpoke101]

Here are the voltages on R8 and R9 (assuming 9V supply );



If you are measuring 9V on each leg of the resistors then you are missing the 0V connection to R9 (leg closest to the switch ).

Also I see that in your latest pictures that the bag of resistors shown is labelled as being 510 Ohms (always measure components - it is not uncommon for the wrong part to be placed in the bag )....Meters can be difficult to read at times. Still annoys me after all these years particularly when using different meters.

[Big mike 1100]

I'll make these changes and get the measurements.  Turns out I don't have a 510K resistor, but have TONS of others.  Can I substitute another Value? (1meg?) Or just bite the bullet and order them?

[willienillie]

1M, 470K, two 1Ms in parallel (500K), any of these will work fine.

[Big mike 1100]

I replaced the 510k with a 1M at R2 and took new readings

R9 Left leg 0 RT leg 9 (not the 4.5 needed)
R8 Left leg 9 RT leg 9 (not the 4.5 needed)
Pin 3 on the IC reads 8.24 (not the 4.5 needed)

[Slowpoke101]

OK. I see that the left leg of R9 is at 0V therefore R9 is open circuit (faulty ) or some high value greater than 1M,
Replace R9, 10K I think but do measure the replacement resistor to make certain that it is the correct value.

[Big mike 1100]

I reflowed all of the solder around R8 and R9
New readings look better I think!

R9 L-0 R-5.0
R8 L-0 R-5.0
Pin 3- 3.9

Sound better?
Also
IC voltage
1-5.0
2-5.0
3-4.5
4-0
5-5.0
6-5.0
7-5.0
8-9.0

[Slowpoke101]

Looking much better.
Voltages on the IC seem to be within expected values and Vref is also good.
I suspect that you mislabelled R8 left leg as 0V and not 9V.

So, have you connected up your guitar and amp to see if this pedal sounds good?

[Big mike 1100]

Yes, sorry!  Left Leg of R8 is 9V and not 0 as reported.

Will plug it in tomorrow and report back.  Thanks for your help as always!