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I found this talkbass for sale post and it's got a gut shot, and the transistors are installed the same direction.

https://www.talkbass.com/threads/zvex-super-duper-2-in-1-sa-special-edition.1411791/

I see one picture of the guts and I cannot tell which direction they are in. Regardless, it only takes a second to verify if they are in correctly by using a pinout and the schematic.

Yup, I'll do that again tonight just to be sure, and I'll report in.

Well I'll be damned. I diagnosed the transistor correctly then installed the bitch backwards. Great catch, I'm a moron.

Thanks for the help!

I found this talkbass for sale post and it's got a gut shot, and the transistors are installed the same direction.

https://www.talkbass.com/threads/zvex-super-duper-2-in-1-sa-special-edition.1411791/

I see one picture of the guts and I cannot tell which direction they are in. Regardless, it only takes a second to verify if they are in correctly by using a pinout and the schematic.

Yup, I'll do that again tonight just to be sure, and I'll report in.

I found this talkbass for sale post and it's got a gut shot, and the transistors are installed the same direction.

https://www.talkbass.com/threads/zvex-super-duper-2-in-1-sa-special-edition.1411791/

I thought that too, but that's how they were when I opened it up. I only ever pulled the one out. And the one I didn't pull, that is the side that works fine.

Might be worth another look when compared to the transistors installed and the schematic.

I'll definitely double check it. But a week or two ago when I ordered new transistors I remember checking the pinout and it was correct, but the silk screen was wrong.

I'm about ready to breadboard this and see if I can duplicate the issue. I know I'm missing something stupid.

I thought that too, but that's how they were when I opened it up. I only ever pulled the one out. And the one I didn't pull, that is the side that works fine.

I think we need some photos of your build.  Is this a PCB?  Vero?  Perf board?  There's definitely a problem with the power/bias for Q1.

It is an original pedal. Nevermind the resistor on the back of the board, it doesn't go there. It's a pita to get it where it goes, so for testing I slapped it on back.


I'm doing this from my phone, so if the link doesn't work I'll upload them when I get to work in the morning. Home system is shut down for the night.

https://imgur.com/a/twHHJX8

Hi guys, I'm stumped.

First off, here is the schematic that is closest to what I have here:

https://www.pcbway.com/project/shareproject/ZVEX_Super_Duper_2_in_1.html


One transistor is just not biasing properly.

Side 1 is the one I am having issues with. It is sputtering like it is starved for voltage - which as you'll see, it is. I have pulled all the resistors up near it and they have all measured fine. I thought maybe the transistor had failed, so I replaced it, and the voltages are the same.

Here are the voltages I am getting. They are taken with the gain controls (C5K) down:

Side 1
D - 4.8v
G - 1.64v
S - 4.1v

Side 2
D - 7.2v
G - 2.69v
S - 1.83v

I have 9 volts at the front side of both 5k1 resistors, but then the voltage drop across the 5k1 resistors coming from the power rail is:

Side 1 - 4.33v

Side 2 - 1.93v

I have tested the diodes and they seem to have a reasonable voltage drop across all of them.

It is just not making any sense to me. What else could be causing this voltage discrepancy.

Mouser, Small Bear, Antique Electronic Supply, Tube Depot, Amp Repair Parts, Love my Switches, Stomp Box Parts, Digi-Key, Arrow, Ebay (but know what you're looking for), Newark, Tayda.

Thanks. That should give me everything I'm needing.

Thanks. I remembered Love my Switches, their name was hard to forget, lol.

I'll be honest, I completely forgot their original name until I hovered over the link at the top that mauman pointed out. lol

Well it used to be "Bitches Love My Switches", so that stuck out a little better lol. Even though they changed the name, I always say it in my head.

Depends on what I'm getting

Smallbear: hard to find stuff like good LDRs, esoteric caps, WIRE (can't do anything but their prebonded wire), transistors I can't buy in bulk, FETs

Mouser/DigiKey: electrolytic caps, especially bipolar, maybe harder to find buts, but like one-off parts

Love My Switches: certain spec toggles I can't find elsewhere

I tend to shop around if I need premium quality knobs.

Tayda: pretty much everything that I didn't note above. They have the highest concentration of everything, and I hate splitting orders if I can help it at all. They're not paying me to say that, it's just where I've settled down to find nearly everything I need: film caps, resistors (in a much wider array of values), pots (house brand and Alpha), switches (taiway/dailywell, etc), and some which claim to be the same factory as other places' white label switches), and some of their diodes. They also have decent enclosures, as well as drilling, powder coat, and UV printing all from one shop.

PedalPartsPlus: has started a powder coat and UV print service, which appears to be pretty slick. They even do all of the enclosure faces (Tayda, as of now, only does the top), and will do runs of them, for the up-scale builder. I'm interested to see how this works. I haven't priced it or anything, but I'd like to do one in the future.

Thanks. I remembered Love my Switches, their name was hard to forget, lol.

Pedal Parts Plus was one I used but forgot, and Tayda was another. Thanks for reminding me!

I've been getting my toes wet building again on and off for the past few months, and I'm starting to need some stuff. Where is everyone buying parts at now? I still use Mouser for my caps and resistors and such, but I need things like transistor sockets, vero board, etc. Small Bear doesn't seem to have the same selection they did before they were bought out, and I just flat out can't remember the other shops I used.

I fix these all the time, the caps are 50 years old and die, check em with ESR meter. The issue is these were made for 115-117 mains and modern mains can be upwards of 125 volts. It uses a voltage doubler circuit to achive 55-60v, but with an extra 10v going in, it's 20v coming out and the caps aren't rated for that and die quickly.

I usually replace them all with Vishay 105C since the pedal can get pretty warm. It's easy to retrofit a 3 prong cable and fuse in it too to make it safe. I also add a 56v zener to keep the power at a reasonable voltage, and I add some MLCC .1uf bypass caps across the electrolytics to filter out RF racket. I use an 18ga power cable with a Heyco PG7 strain relief, no drilling needed.

Something else that happens is the bulb draws more current than it should and the resistor for it can begin to burn, I replace them with 220ohm 2watt vishay and raise them off the board a bit so they won't damage it if they get a little warm.

The shroud is just some vulcanized paper that's about 1/2mm thick. It's square. They are taped down with DUCK brand black masking tape.

Attached a photo of my PWF (yes I know the fuse is attached to neutral instead of hot, I'll fix it later).

Nice, that is super helpful, thank you.

I'll probably go through and do the couple caps that I didn't replace, I only did the ones I identified as bad, but I just don't like the look of it half done. You really go all out on these, that's great.

This is my first one, but from what I can tell, the transistor bias is what was causing all of my issues, and at the voltage this runs at, it is much more of a problem than a normal stompbox would be.

Thanks for sharing your experience with this, and it's great to see these gut-shots, too.

A cousin of mine is sending me one of these (one of these days...) that he says works intermittently and I'm eager to get in there and see what's what and get it going again. I'm guessing it's something to do with the curtain/box around the bulb. Do you know the voltage coming out of the transformer?

Actually, I have no real problem other than the sweep range without the shield, but the curtain is absolutely needed because it is what blocks the light. (not meaning that to be patronizing).

I have a good copy of the schematic, I would be happy to send it to you, it has the important voltages in it. Off the top of my head its 55v and 25v coming off the power section.

​Well I've been snowed in again for 2 days now. 140 something inches this year. I've had this Power Wah for several years now, I just never got around to getting it fixed.

It would turn on, but it was farting out like it was starving the transistors for voltage. I could get a small response changing the light to the LDR, but those transistors were just being starved. Most notably the photocell that it uses as it's variable for the wah had pieces missing off of it (pictured).

I pulled data sheets for the transistors up, and they just weren't getting the voltage they needed to turn on and off properly, so I ended up having to pull out every resistor and check it for tolerance, and I ended up replacing 2 of them - a 220k, and a 4.7m. I replaced some capacitors, though I don't think those were needed (I do need to trim and finalize placement of the last one pictured). To finalize the fix, I need to order the correct sized resistors, it looks stupid having some 1/4w in there. I have no idea what I am going to do about the shade that goes over the LDR as it was missing when I got the pedal. It doesn't affect the sound, though it does affect the range of the sweep.

But crap, this thing sounds amazing. If it weren't so huge, and needs it's own 120v power, I would be putting this thing on my board for sure.

That is good to hear that Small Bear got bought.