FuzzDog Super Skwisher power problem - Help

[ANTHROTONY]

Hi everyone, first time here, and my first pedal build for 40 years. I hope it's ok to post debugging questions for this brand here.

Full disclosure first: I originally trained as an EE and remember just enough to be only slightly dangerous. More importantly, I bought this kit to get some hands-on experience before starting a 5e3 amp build (for which I have all the parts ready, not a kit). I've had a neurological disorder for 10yrs which makes my hands shake, but I was hoping that with a lot of patience and care, and no caffeine for a few weeks, I would be able to manage this little pedal -- my first few solder joints were a bit dull; a few flecks of solder dropped on the board occasionally; my iron was terrible, too hot, and I destroyed one pad which I resolved by using a new iron and an under-board jumper wire to rejoin the two connection points. Other than that, I think I have fairly decent soldering although I'm constantly verifying and re-verifying under a loupe in case there are some solder bridges or cold joints. Anyway, I sincerely don't want sympathy, but some debugging help would be very much appreciated!

The problem: Before wiring up the 9VDC power socket, I rigged a test harness to use a battery. The new battery (now) reads 8.5VDC, but when I test the voltage at where the battery wire is soldered to the pcb I'm reading only 0.9VDC. The Ground and Voltage joints have no direct connection, confirmed by a continuity test. The battery feels warm. I'm assuming that something on the board is drawing all the current to ground. The schematic is here http://pedalparts.co.uk/docs/SuperSkwisher.pdf  I'm building the Mark Hammer modded version shown on page 5, and I'm using the LM13700 IC.

Someone previously kindly suggested elsewhere that I check C9 and D1 for polarity as they go straight to ground. They are oriented correctly.

So, before I check other voltages, I think that it's most important to seek your collective advice first, to see if my own initial diagnosis seems logical in which case I'm not actually sure where to begin with the other checks -- I'd expect everything to be skewed because there's such a low voltage going into the circuit?

Cheers,
tony

[GibsonGM]

Hi Tony, welcome!  Debugging ?'s here is absolutely OK. 

You have a short.  The battery is draining thru near zero, or very low, ohms, so it's trying to source infinite current, and it gets hot!   So, like all of us, you have to go back thru and find where it is.   Usually, the eyeball method will reveal a blob of solder that snuck over to a neighbor and is causing it!   Or maybe the jack is miswired somehow? (by your harness)   

Gotta be the problem; check with that meter again, perhaps the continuity test 'cuts in' at 50 ohms, and you have just over that present, fooling it......try reading actual ohms....


Hope that helps!  A pic of the front & back of the board may be useful!   

[antonis]

Someone previously kindly suggested elsewhere that I check C9 and D1 for polarity as they go straight to ground. They are oriented correctly.

C9 (as well as C12) only matters in case of been shorted.. 
In case of C9 wrong polarity placement (C12 doesn't mind..) you might have a blown open cap..

I strongly recommed you to double check for D1 correct polarity or maybe for a short between Anode/Cathode..
(close enough due to vertical placement..)

P.S. Welcome...!! 

[ANTHROTONY]

Hi GibsonGM and antonis, thanks for the input. It makes me feel a little better knowing that I was on the right track, so to speak. I will look much more closely at the circuit a little later (I'm in France, nice weather, and garden work is required) and take some photos as suggested. they'll clearly help even me by being able to look at them at full screen size on my laptop.

When I decided to do this project, I honestly hadn't even thought about how small the board would be and how close the pads for clean soldering! But it's been fun so far, and if/when I can find the problem, I will feel much better about myself (I have high self-expectations and the older I get the harder they seem to become to achieve) So I'll do my best to trace through the circuit looking everywhere for soldering issues or contact issues, and I'll report back just as soon as I've taken those photos.

Regarding D1, I agree that I need to be absolutely sure. Through my magnifying lens everything looks fine, but again, perhaps the photos will show something up.

Thanks so much guys for your help. Looking forward to solving this so I can rebuild a bit of self-esteem and start building my amp -- at least the parts are generally much bigger!

Cheers,
Tony
PS, The security questions for posting are really quite amusing. I'm a tele player and a question about knobs came up. I really had to think about it!

Oh, and thanks for the kind "welcomes"

[GibsonGM]

Here, I gave you your first "like", too, for self confidence Everyone stumbles when they're getting up to speed!  And sometimes after, too, ha ha ha.   Spend some time with it, and ask more if the trouble can't be found.

[duck_arse]

also welcome, and do you mind if we have the coffee?

voltages! #1. and - check your R21, R22 values. [how I hate schems that don't put the value on the part.] another thing to ponder - what sort of DC socket is it, not the open metal frame type by any chance?

[Kipper4]

Yer nice one. Welcome aboard.
Diysb with a neuro disorder. Amazing you sound like your smashing it already.

My tuppence is on the diode......

Bienvenue

[PRR]

> Super Skwisher

Where did you get your '3080??

There are many more fakes sold than real ones left. A fake may be any 8-leg chip, washed and re-printed. So it could turn out to be a diode-drop where a real '3080 has V+ and V-.

Small Bear is a reliable source. There may be others people here know. eBay et al are *not* reliable.

There's no point looking at the rest of the voltages while it only has 0.9V on it. Nothing works "right" at 0.9V. (Well, an LM10 might, but that's obsoleter than a '3080.)

[ANTHROTONY]

@duck_arse - lol. I used up the real coffee and then started drinking unleaded. But you're welcome to share a coffee any time you're in France!

@PRR sorry, I should have been clearer -- I'm using an LM13700...

@Kipper - any easy way to test the diode?

Well I got some photos which show the naked truth of my soldering joints The first thing I should explain is the jumper wire under the board. My initial iron was too hot and it massacred the pad under R13, causing some of the trace to come away from the board. This trace would have gone towards the top left of the board (component side) and then went horizontally right under those caps, ultimately joining C16. Rather than try to stick the trace back to the board I decided it would be safer to run the jumper wire. I measure 10Kohms between the two connections so that appears correct, although I suppose it is possible that I've messed up something else at either end of the jumper, or even causing a short to ground at some point - but I thought that the correct resistance measurement does not support that idea.

My photos show some solder splashes and some joints that look a little dark/dull.

It is very difficult to see the D1 in the lower left quadrant, mounted vertically.

Anyway, I hope this might help shed some light on the problem.
Cheers,
Tony

[Kipper4]

I was thinking you might have the psu protection diode wrongly orientated. Causing a short at the input.

[ANTHROTONY]

@Kipper4  Thanks - I thought that was what you were suggesting. I really don't think this is the issue but I will triple check as soon as I'm able.

@duck_arse -- sorry I didn't respond to the question about the DC adaptor. It's one of the plastic enclosed types.

[Slowpoke101]

What is the polarity of the DC adaptor?
If you have wired the DC jack as per the instructions then the plug on the DC adaptor should be centre pin negative. Also it should be 9V DC of course.

[ANTHROTONY]

I should have made it clearer that I was not using the DC jack for this test, just using the batter connector. But thanks to  duck_arse and Slowpoke101 for their thoughts about the power jack, I did check my battery wiring a few times. Finally, I figured out that there was nothing wrong with that side of the harness, but where the wires join the board, there had apparently been a production problem and the labels were not printed onto the pcb. I contacted FuzzDog who confirmed that the actual order of the pads was the same as shown on the pdf photo of the previous production pcb. I had actually soldered a red wire to the G pad and of course, the green wire to the V pad... So D1 was doing its proper job after all.

So as things stand right now, I have switched the two wires provisionally to the proper connector boxes, and reverified the voltages at the battery, the pads on the board, and just for good measure on pin 6 on the IC (ground) and pin 11 (V+) -- all are absolutely correct. So I'm suitably confident to move forward to an audio test as soon as I can power up my amp... and then hopefully find no more problems!

Thanks to everyone who has been very welcoming here and extremely forthcoming with suggestions. I very much appreciate it and will report back as soon as I can.

Cheers,
Tony

PS Yes, I feel really ticked off at myself for missing the crossed wiring despite many visual checks. I'll definitely learn from this experience, humbling as it has been

[ANTHROTONY]

So I just got five minutes to power up my amp. No signal from the output -- totally silent. I can't say I was actually expecting this to work just like that however So I'm going to spend some time exploring what could be going on. If I can find no solution, should I post back here, or open another thread? Perhaps someone knows the proper protocol...

Thanks,
Tony

[bluebunny]

Keep this thread going, Tony.  You can change the title when you next post.  Good news getting to the bottom of the power issue.  I'm sure we can sort out the silent output too.

[Kipper4]

Have you a full set of ic and transistor voltages ?
Now that you have power.

Do you have an audio probe.

At least the ic are in sockets.

[ANTHROTONY]

Hi guys, I'm getting a few minutes here and there to start testing my circuit - several months ago we rescued five very young kittens, and right now one is recovering from a dog attack a couple of days ago, and the other from an infection in the unfortunate area following his sterilisation: trying to stop them from escaping or getting into mischief with the others is almost a full time job

So first, @bluebunny, I can't see where I would change the name of the thread. No biggy, but if you can easily describe what to do please...?

@Kipper4 I will obtain full IC voltage readings as well as transistor readings and post them as soon as I'm able. I'm just about to build an audio probe -- I think I have a spare capacitor around to do this with a simple guitar cable.

General question as I'm reading contradictory advice on the web... I'd like to measure the three diodes, especially the main D1. I thought that I could disconnect power (easy as I'm using the battery harness) and measure either resistance through the diode in both directions while it is still on the board, or use the diode setting on my DMM the same way, but I've read several times that the diode has to be partially lifted from the board for this to be accurate. Can anyone help me understand which method is correct please? I figured it would be good to know if they are functioning correctly before getting into serious diagnostics

Cheers,
tony

[bluebunny]

So first, @bluebunny, I can't see where I would change the name of the thread. No biggy, but if you can easily describe what to do please...?

You can overtype what's in the Subject: box.  (I just did it.)

General question as I'm reading contradictory advice on the web... I'd like to measure the three diodes, especially the main D1. I thought that I could disconnect power (easy as I'm using the battery harness) and measure either resistance through the diode in both directions while it is still on the board, or use the diode setting on my DMM the same way, but I've read several times that the diode has to be partially lifted from the board for this to be accurate. Can anyone help me understand which method is correct please? I figured it would be good to know if they are functioning correctly before getting into serious diagnostics

Ah, the web.  Hours of endless fun sorting the golden nuggets from the brown ones...   

Anyway, "it depends".    Most of the time, anything in the circuit will be in parallel with everything else.  (Big generalisation, but you get the drift.)  So it's best to lift one end of the diode before you measure.

TBH, voltages at the transistors and opamp will probably be more useful.  Or just follow the step-by-step instructions in the sticky "Debugging" thread.  They really work. 

[ANTHROTONY]

OK thanks for the continuing advice -- yeah, I see far too many brown nuggets!

I'm probably going to go quiet for a day or two while I wait for a few necessary things to arrive chez moi, notably alligator clips and a cap specific for the audio probe. Meanwhile I'll go ahead and read those voltages on the IC and transistors ready to post.

Many, many thanks!
Tony

[Kipper4]

I use a 100nf ceramic cap for my probe.
I think I'd dare go much smaller and much bigger too.