Tonepad Pulsar near total failure, need help

[jjjwwt]

i searched the forum and internet but couldnt find any solutions. i just finished building pulsar from tonepad (http://www.tonepad.com/getFile.asp?id=29). i followed the layout as good as i can except 2 100k resistors in series instead of 200k ones and bc239's instead of 2n5088's(they are hard to come by here). i checked the pinouts and reversed the transistor positions accordingly. i checked the solders and there are no solder bridgesor cold solders (or i couldnt find at least)

the tremolo doesnt work when i turn it on. i get clean sound with some ticking(which doesnt change when i play with pots but goes away when the toggle is on down position).

i can post pictures if needed.

i really need this pedal to work because i cant afford to buy another pcb right now(they make custom pcb's very pricey here in turkey). so every bit of help is appreciated greatly.

[blackieNYC]

does the ticking change with the rate pot?  If it does, you have oscillation, which is a good start, but your transistor sub might not be acceptable.  I'm not sure.  the toggle you mention - it probably is ticking in square wave "chop" mode, and gets quiet in the non-chop triangle mode.  (Don't worry about the ticking until you get the thing working.)
2n5088s have very high gain.  might you have a BC549?  Or maybe a 2N5089, 2N3904, 2N3906?
Do you get the same sound level out of it that you're putting in, or is there a loss?  If you have a voltmeter you may have to go to the "Debugging" thread and post some voltages.  But a bit of transistor swapping (NPN) shouldn't hurt.

[jjjwwt]

i dug through my part pile and found some 2n5088s, i put them in but nothing changed. the ticking doesnt change with rate or depth pot. there is no noticable difference in volume when i turn it on.


Q1
C=0.00
B=0.57
E=0.00

Q2
C =8.50ish
B =0.8ish
E =0.00

Q3
C =0.9
B =0.50ish
E =0.00

u1
pin1: 5.82
pin2: 5.84
pin3: 5.52
pin4: 0
pin5: 0
pin6: 10.48
pin7: 10.48
pin8: 11.10

[GibsonGM]

Hi JJJ, welcome.  Time to get use to how to 'debug' 

Ok - what is your battery or power adapter voltage? (actually measure it please)

For the PCB you used - did you use Tonepad's design, or make your own?  Are you sure the "open arrows" at the top of the resistors (R8, 17,18,19,20) are connected to power?

What voltages do you read on each TL072 pin?

When this happens, you have to look at EACH part, many times, to be sure the correct value resistors are in each place, and that you have not put the IC in backwards, etc.   

With some more information, we can help you get it working   "ticking" is a good sign right now.

Direct link to schematic: http://www.tonepad.com/getFile.asp?id=29

[jjjwwt]

i used the pcb design from tonepad. the resistors are connected to power. i updated the readings on the previous post with TL072 pins. my adapter voltage reads 12.62-12.68(it says 9v on the cover though, kinda confused me now. never thought of checking it before).

[jjjwwt]

just as i posted i noticed i used 33k instead of 330k resistor. i placed the correct one and effect is working! rate and depth pots doesnt do anything though. clicking is also in tolarable range in square wave mode. nearly no noise too

[GibsonGM]

We get frustrated and are convinced we have no errors.  Then we find an error!! 

Sounds like you are most of the way there.   Trace your wiring for the rate & depth pots, be sure they are hooked up properly, and are the correct values.   

[jjjwwt]

i checked the connections and values as you suggested and they were fine. maybe the pots are broken? how can i tell if they are broken with out pulling them out? its really crowded in there.

[GibsonGM]

If you can reach the pot lugs with your meter, set the meter to its resistance scale (ohms).  Measure between the 2 outside pot lugs - you should read just about the rated resistance of the whole pot.    If you then measure from one leg to the wiper (the center lug), you'll find that the number changes while you turn the knob.    This indicates normal operation.   

I would be more concerned that the full value is correct, and that the wiring is not mistaken.   Pots rarely go bad like this unless you apply too much power to them...and they usually become noisy before failure.  That is not likely. 

You might want to see if R6, 11, 14, 16 are the correct values, since they 'help' the pots change the voltages the transistors will see.  If they are not the correct values, that may affect operation!  And also be sure the wiper is tied to the right end of the pot... 

[duck_arse]

I'd put money (I have none) on pot wiring being bad before bad pots, as Gibson says. was there any photos posted, cause I'm inclined to miss them ..... ?

and, we should get that circuit board layout "fixxed". this is the second pulsar in recent times, and the voltages show that the unused half of the IC (don't start me on 1/2 unused dual opamp layouts) is latching.

[edit/s :] if bluebunny, with the powerful remembering comes past, he might tell us if the experts here have said/disected what happens to a latching opamp.

[jjjwwt]

Well, you would lose that bet cause it turns out that the rate pot had gone poop for some reason I changed the pot and verything works now. rate pot is hard to use a bit, but i can live with that.

Thank you so much for all the help guys. You really saved me.

[GibsonGM]

Good work, JJJ - of COURSE this is the time when the pot IS bad, and I told you it shouldn't be, ha ha ha!  Murphy's Law.
Enjoy the pedal!! 

[duck_arse]

in my defence (yer not getting any money ....), Gibson told me to say that.

can I ask, what is that black thing wrapping your board I see in the pictures thread?

[jjjwwt]

i wrapped my board with medical bandages and wrapped with insulating tape on top of them  seemed like a good idea to insulate the board without getting any adhesive on it from the tape 

[bloxstompboxes]

Probably not going to hurt anything, since I suppose it is all wired together and in an enclosure, but I would be worried about ESD and frying your IC. Can't see the image at the moment here at work, so I am not sure how you did it. Suspose it might matter what material the bandages are.

[bluebunny]

if bluebunny, with the powerful remembering comes past . . .

Powerful remembering?  Crikey, if only you knew, duck!      I surprise myself with the long-ago stuff I can recall, but my short-term memory ... what was I saying?   

[GibsonGM]

We could make a new topic on this, of course (be warned not to go too far off topic!), but -  I find that getting my PCBs into their enclosure, solder side 'down' (towards the floor), then lying a sheet of non-conductive foam across the board...and screwing the back lid on...is just great for insulating!  You 'hook' the foam to the little tags that protrude from your solder joints, and it does not move. 

I've used old mousepad material, 'egg crate mattress' foam, etc.  Never an issue.  I think the static issue goes away if the circuit is complete and you've accounted for the risk (protection diodes on MOSFETs and so on).   Plus, my wiring is pretty tight, so the board will 'ride' on that anyway.    Just a thought for the OP...since it's the last thing needed to do before closing the back, doesn't get in the way when working on the thing...

[duck_arse]

We could make a new topic on this, of course (be warned not to go too far off topic!),  .......

I think the correct term is "bww-haarrr-harr-haahhhh", dunno the spelling tho. too far? really.

I was asking about the black wrapping because it looked a little like an anti-static black plastic bag, is all. now, back on topic .....

[GibsonGM]

No, it's NOT ON TOPIC, DUCK.  Look where this has gone!!!?  How DARE YOU???  First Pulsar, then PLASTIC BAGS??
AAAAHHH!!!!