TS 9 - drive pot does nothing

[Arangonix]

Hi guys, need some advice. Just finished and fired up TS 9 clone. Here's the layout:



My changes compared to the layout are minor: 20k lin tone pot, 2k2 led resistor, 2N3904 trannies, double pair germanium diodes, 47p ceramic cap.

Everything works fine despite drive pot. It does nearly nothing. Double checked the wiring, everything's fine, double checked the board, every part is on its place, no shorts, no cold joints. IC and trannies are oriented correctly, voltages are in norm.
Knowing that the drive pot varies resistance between IC 1 & 2 lug I put my multimeter there and while turning the knob resistence variation was minimal between min and max. Pot, mechanically, works good.

Drop me an idea guys, where should I looking for mistakes now

[antonis]

Resistance between pin1 & 2 sould vary between 51k & 551k with diodes OUT of circuit..
(lift one leg of each one diode and take measurement agian..)

P.S.
Check for 4k7 resistor proper value..
(the one going to pin 2 and 47nF cap)

[duck_arse]

Resistance between pin1 & 2 sould vary between 51k & 551k with diodes OUT of circuit..
(lift one leg of each one diode and take measurement agian..)

P.S.
Check for 4k7 resistor proper value..
(the one going to pin 2 and 47nF cap)

.... or show the photos so we can triple-double check.

[Arangonix]

antonis, resistor is ok, 4k7. It's kinda weird, but at drive pot minimum I have 114.
500 is when the pot is somewhere around 3/4, after that it starts galloping to 2000

duck_arse, heres some photos:

[antonis]

.... or show the photos so we can triple-double check.

You're now welcome to triple-double check all vertical carbon comp 1/2W resistor values, Stephen.. 

It's kinda weird, but at drive pot minimum I have 114.
500 is when the pot is somewhere around 3/4, after that it starts galloping to 2000

1. Above numbers refer on Ohms..??
2. Are measurements taken with diode pair out of circuit..??

[Arangonix]

Yup, all diodes were out of circuit and yes, measurements refers to ohms.

[iainpunk]

well, that's a ... special ... way of soldering resistors, it looks cool tho, and easy to get to with probes, i like it.

what is the resistance of the pot out of the circuit?
and the resistance between the socket's pin 1 and 2 if you take out the diodes AND the chip?

cheers, Iain

[PRR]

well, that's a ... special ... way of soldering resistors...

What, upright? That was common all the way back to the Regency.

https://i.postimg.cc/bv8dgjHf/NV-1004-Lowrey-Figure04-1.jpg

[stallik]

Are those diodes oriented the same way?

[iainpunk]

well, that's a ... special ... way of soldering resistors...

What, upright? That was common all the way back to the Regency.

https://i.postimg.cc/bv8dgjHf/NV-1004-Lowrey-Figure04-1.jpg

i am familiar with upright, i do most of my resistors, diodes etc upright, but normally the return pin goes straight down, to save real estate, angling them like OP does kinda defeats the purpose of upright, but it looks cool as heck.
i even have some 4148 diodes that came with pre-bent upright leads


cheers, Iain

[Arangonix]

stallik, diodes are reversed to each otcher to get standard, symmetrical clipping. After I fix the issue, I'll try different configurations to find the best voicing for my ears.

iainpunk, I'll check the pot after work.

[anotherjim]

They are waiting for the penny to drop. A 500k pot should reach a reading around 500000 ohms, not 2000. The rapid change toward one end of travel is correct for a log taper pot. Does your meters resistance range only go to 2000ohm? Does it read close to zero ohms with the probes touching each other?

[Arangonix]

Ok guys, I made few measurements. My multimeter was set to 2000k, as this is the closest to 500k pot value I can get while using it.

only pot: 0 - 463
no IC & no diodes in a circuit: 051 - 515 (I did measurement touching the rails were IC socket is soldered)
with IC in a circuit: -105 - -106 (I did measurement touching ICs lugs)
                            -005 - -038 (I did measurement touching the rails were IC socket is soldered)
with IC & diodes in a circuit: 0 - 0

So, pot is working good Board shows proper resistance without IC & diodes. Could the IC cause the problem? Voltage on every lug is excellent. I don't have any IC to swap.

[antonis]

Sorry but we still are confused..

Did you take negative resistance measurements..?? 

[iainpunk]

when the IC is out of the socket, what is the resistance between the socket hole (component side) and the solder track? becaue these numbers shouldn't be different:

with IC in a circuit: -105 - -106 (I did measurement touching ICs lugs)
                            -005 - -038 (I did measurement touching the rails were IC socket is soldered)

cheers, Iain

[Arangonix]

Yup, the numbers were strange, but I wrote down what my multimeter has shown. Will check it once again today.

[Arangonix]

Ok, sorry for those yesterday's mess Multimeter set to 2000k ohm and here we go:

no IC & no diodes - 51 min - 519 max
with IC - 51 min - 519 max
with IC & with diodes - 006 min - 007 max

All measurements were done touching socket's pins/holes or IC lugs. Numbers were the same when touching solder tracks.

[iainpunk]

those values seem alright, what does the pedal do without the diodes? does the gain control still do nothing when the diodes are out of the pedal? if not, you might have blown diodes.

cheers

[Arangonix]

Truly, didn't check that I'll warm up my amp and do some testings. I have dozens of ge diodes left. Will swap em too.

[Arangonix]

Ok, I can see that this circuit doesn't like germanium diodes Each one I put in it caused the problem with drive pot. When any other diodes type is in, it works perfectly So, thanks for help, it was a pleasure to cooperate with you all guys