PUTB v2.b. Help (Solved)

[Anonymous]

Hi! This is my first post so I hope I get everything right. My apologies if I miss something. Please let me know if I do.

Ok, I’ve successfully built a bunch of pedals, most of which I’ve had to problem solve, but with this on I’m stuck.  I am still a noob, but starting to understand what I don’t understand… which is a lot.

It’s the PUTB v.2b. First off is there a difference between it and the V2.1?

Problem:  No sound.  Sometime there is a high pitch squeal when I reconnect the battery. There are also high pitch squeals when I touch the DMM to Two and Three on the IC.

I have reflowed the solder.

Im using a Russian MN20a  hfe are between 100- 120  ( I realize there are low for the board, but I’m waiting on some high gain ones to arrive…)

1.  C -6.0 B. 2.03 E. 0

2.  C  -1.65  B. -2.02. E. 0

3.  C. -6.45 B. -1.38 E. 0

IC max1044

1. 6.58
2. 3.29
3. 0
4. 3.26
5. 6.75
6. 2.51
7. 6.59
8. 6.59

Any help anyone can offer would be appreciated.

Thank you in advance

cheers

Dustin

[Anonymous]

Ohh, sorry the last image has different transistors then the MN20A… (and yes, there NPN to boot).

[Billy]

Your voltages look too low If it’s a battery only you’re using try a fresh one

Pin 8’s your supply voltage should be around 9v with pin 5 your V out – 9v

The readings you’re getting 6.59v going in are more or less a flat battery

Oscillation can be caused by many things one of which is incorrect voltages so hopefully it’s just a dud battery so try a fresh one first

I’ll move your post over to the build support forum

 

[Anonymous]

Thanks Billy, I appreciate it.

update,  switched battery the V came up on T1 (T2&3 were actually lower), yet no sound.  Swapped out transitions, no sound.

When i attached the ‘In’ signal to the C. Of transistor 1 it worked.  Looking at the schematic it seems like c2 or the ‘in’ are the only things that could block the signal?

Ok, off to problem solve.

[Billy]

Do you have the IN ‘T’ pad from the pcb going to your switch

Just in case you don’t know your in and out pads have a small T for tip pad with the other pad being ground can’t see where they go to  or whether your clip is also touching ground on the pins you’ve soldered on the IN and OUT pads

If you’re using an audio probe check from the IN T pad to see if audio gets in there it could be that your connection is grounding the signal just make sure you attach the clip to the T pad without it touching the ground pad next to it

If you’re putting a signal in at Q1 C it tells us everything after it is OK prior to it you have the IN T pad to R1 to C1 to the base of Q1

How are you inputting signal at Q1 C

[Anonymous]

Thanks Billy, I tracked it done to a cold soldier join on c2.

I am still getting a bit of high pitch squeal (oscillation?).  I’m off to re-flo the pico farad caps.  And yes, I get, at least I think I get it, re the T pad.

[Billy]

Reflow all your joints Dustin a dry joint could also cause oscillation also check it isn’t coming from your MAX1044 touch the IC solder joints to see if it affects it

I just realised I’ve been looking at the PUFF schematic instead of the PUTB doh! I’m actually working on a PUFF at the moment

[Anonymous]

Ok, I think I got it.  There is still a bit of a squeal. But I’m getting a gritty fuzz, especially considering how low an hfe of the transistors are.
Do  you know if there is a difference between the v2b and the v2.1?  I’m wondering if the components changed from version to version?

I really appreciate your help.  Thank you.

[Barry]

The change was purely cosmetic.

As Billy pointed out we do not recommend the Max1044 chip.

From the build doc: The charge pump you use must be compatible with the 7660/1044 pin layout. Some charge pumps have a frequency-boost feature which will increase the oscillator from the default 10kHz up to 35-45kHz. We recommend that you use a charge pump with this boost feature to avoid any whine or clock noise. We have seen a high failure rate with some manufacturers’ MAX1044 chips, so we prefer the 7660S (e.g.: TC7660SCPA). 

What is your current bias voltage set at for the collector of Q3?

[Anonymous]

Hi, I switched out the IC and problem solved!

voltages;

C1.  -8.12

C3.   -8.68

No mater where I turn the Trimmer, C3. Stays about -8

thoughts?

 

 

[Billy]

Not sure what C1 and 3 are, are you talking about the collectors on Q1 and 3

You bias Q3 collector to around  -7v using the trimmer or by ear to where you think it sounds good I almost always do it by ear there’s no hard and fast rules if you think it sounds good, voltages are irrelevant from that point of view

As you can see in the build doc people get different results with different bias voltages

[Anonymous]

Yes, Billy, the collectors on Q1 and Q3.  But the trimmer doesn’t drop the voltage down much at all. It tops out about -8.68 and drops to -8.12.  Measured on Q1.

However, I am quite happy with the sound it this point, so in some sense, I’m ready to move on to the next build.

Thank you both for your input, and guidance.  I’m starting to understand more with each mistake I make.

cheers

Dustin

[Author]

Posts