Messages

[So, if you are using the bypass board then I suggest using isolated jacks like the Lumberg or Marshall type. Or, if you only have metal jacks simply cut the trace on the bottom of the bypass PCB demarked by the green line in the pic below.]

This weekend I went on a building tear and boxed up several boards I had sitting around. I was using the 3PDT Bypass board I gave away last month for all the builds. Two of the builds worked fine. One build, though, caused a major headache. The dry and effect signal were bleeding off in both switch states. I was able to eliminate problems with the 3pdt switch and errors in the bypass board manufacturing. What was different in that last build was that I used metal jacks instead of the isolated Lumberg ones I've been using for the last couple of years.

What's different on the bypass board than the normal wiring I do is that the effect output is also grounded on bypass like the effect input. This is usually a pain when doing the bypass by wiring but easy enough when using a PCB. However, it seems as though grounding the effect output can cause problems when using metal jacks. I'm not totally sure why and maybe someone smarter than me can figure this out. Best I can tell is that if there is a volume pot attached to the effect output it can either cause some kind of impedance issue or provides an AC path to ground via the pot. It doesn't seem like that would happen but it's the best I got so far.

So, if you are using the bypass board then I suggest using isolated jacks like the Lumberg or Marshall type. Or, if you only have metal jacks simply cut the trace on the bottom of the bypass PCB demarked by the green line in the pic below.

Sorry for the mistake. It's something I've never run into! I'll be doing some more of these to give away in December and I will take out the output grounding part for that run.

Here are the pics. There are two jumpers you need to do on the back, it looks like.

There's an entire component buying guide for the 1590G projects linked on the Projects Page: http://www.madbeanpedals.com/projects/1590G/1590G_PartsGuide.pdf

Honestly, if you are happy with how it sounds now it's probably less effort to just get a 1590B and put in that instead rather than trying to desolder parts and replace them. Save the 1590G for a future project.

This is what I could find. Should get you in the ballpark. I can take a picture of my board, too, if that helps.

Quality work right there!

Haha, no. But I can totally see the resemblance.

It's a bit unusual for a 50k trimmer to not be enough to bias, but going up to a 100k should solve the problem. To satisfy my curiosity - where did you get the 2N5457 from?

Before removing it I would suggest audio probing the circuit output on the PCB. If it's good there then there's a good chance that the switch itself may be the problem.

If the board worked on the test rig but not in the enclosure it's almost always a wiring issues, a switch issue or possibly a pot grounding out against the PCB.

Comparing your voltages to the ones in the doc you can see the Vb supply is way off. It should be about 4.5v, and yours is reading 1.3v pretty consistently. So, you need to re-check R35, R36 and C36 to see if they are correct values. Then look at all the areas connected to Vb on the circuit and ensure that there are no solder bridges, etc.

One shortcut is to first remove IC1 and IC4 from there sockets. Then check the Vb voltage in the bare socket (say pin3 or pin5 of IC1). If you suddenly ready 4.5 or so with either IC removed then the problem is likely one of those ICs.

An Hfe of 1400 seems hardly possible. How are you testing these?

J1 is in.

J1 and J2 are for soldering input and output jacks. Use S (send) and R (return) for the FX in and out.

A bit strange sounding. You are getting 15v from the regulator and on one pin of the lamp. But, the pin on the lamp connected to the 15v supply is also connected to the collectors of Q11 and Q12 where you seem to be getting no voltage.

Your transistors are socketed, and that's good. What voltage do you read on the collector socket if you remove them? What I'm wondering is if those transistors are misbehaving they might be sinking current. I have not used 5089 in a Univibe LFO, IIRC, but I don't know if they would have a negative effect or not.

Lastly, the resistance you are measuring is a non-starter. It's not useful because there are still resistors loading the 15v supply which means the measurement is not indicative of anything amiss. If anything, it shows continuity on the 15v rail, which is a good thing.

Okay I have one left. It looks like it has a couple of light scratches but otherwise okay. PM your shipping info.

I can check to see if I have any old ones...might be a couple of "seconds" laying around.