Troubleshooting Tone Bender MK-II

Fret Wire · October 09, 2004, 01:30:10 AM

Time to take a break for a day or two, and come back with a fresh mind. No sense in wiring up any offboard connections till the board is straight. Then you can concentrate on the jacks, pot, and switch.

Sometimes the harder ones go together easy, and you get one like this that mystifies you. Walk away then come back, and it will go together. We'll be here to help.

Fret Wire · October 09, 2004, 01:40:56 AM

Those last set of voltages look much better than the first page set does. The voltages are closer, but don't respond to biasing. Sometimes a tranny doesnt respond to biasing when it is leaking heavily.

I still think theres a solder or component problem. The voltages are off, but proportional to each other. And Q1 & Q2's emitters are at zero. Something is staring us right in the face, and we're missing it.

mrsage · October 09, 2004, 01:47:56 AM

Quote from: RDVUh...when you turned this all back to positive ground, did you turn the electros back around?

Those voltages tell a tale of unrestrained DC all through that circuit, which is why I asked about the electrolytics.

I turned them in the correct directions when I rewired. One needed turning, and I needed to move the jumper from one place to another. The other two caps kept their original orientation (according to the layout on GGG, anyway...let me know if that's wrong...)

I'll take a break for a few days. I need to play more guitar anyway.

On the bright side, I got a vintage Big Muff working again. Found it on eBay for like $35, and it turned out to be a simple fix. That's always nice. I'm going to try a tremulus lune next...maybe I'll order that and get it going while this one is resting.

Thanks for the help thus far. I'll check back in later!

Fret Wire · October 09, 2004, 02:06:27 AM

Tremulus Lune? Are you going with Tonepad's layout or Commonsound's?

mrsage · October 09, 2004, 02:08:04 PM

Commonsound's...are they significantly different?

Fret Wire · October 09, 2004, 02:15:35 PM

No differences, really. Commonsounds is where it originated. Their DIY link has a host of mods. Tonepad even links to it. The Tonepad layout is nicely done. You could put it in a 1590b box sideways with 16mm pots.

mrsage · October 14, 2004, 10:01:22 PM

Okay...I'm ready to try again.

I just desoldered everything and I'm going to start from scratch.

I have an HFE tester on my multimeter...what values should I be looking for on the trannies? Are there any other things I should be testing other than hfe?

I want to make sure they're okay before I put them back in. I'm thinking I might have fried at least one of them and that's why it hasn't been working right.

RDV · October 14, 2004, 10:13:45 PM

Measure Q1 thru 3 and post the readings.

RDV

mrsage · October 15, 2004, 05:00:03 PM

okay, here's the values from the hfe tester.

Q1: 75
Q2: 106
Q3: 168

mrsage · October 17, 2004, 05:22:04 PM

bump

petemoore · October 17, 2004, 09:42:53 PM

What are the transistor pins and battery voltages on the rebuilt one?
I think the gains are in the right order for Q's 1, 2, and 3...

Fret Wire · October 17, 2004, 11:31:59 PM

Quote from: mrsageOkay...I'm ready to try again.

I just desoldered everything and I'm going to start from scratch.

I have an HFE tester on my multimeter...what values should I be looking for on the trannies? Are there any other things I should be testing other than hfe?

I want to make sure they're okay before I put them back in. I'm thinking I might have fried at least one of them and that's why it hasn't been working right.

Because of Ge leakage, the readings from your DMM won't be accurate, but they will tell you that you have the pinout right, and that they still work.

If you haven't started rebuilding yet, check the unpopulated board for broken traces with a magnifying glass. Then, check the value of each component before you put them in. When it comes to electro caps, make sure polarity is right before you put them in. As you solder each component in, check the solder joints with the magnifying glass to make sure they aren't bridged before you go on to solder the next joint. When the board is done, hook up the battery and check voltages before you do the off board wiring. You also might want to check your switch with a DMM before you trust it again.

mrsage · October 20, 2004, 11:20:32 PM

So I reconnected everything and I'm still getting 9 volts on that Q3 collector, regardless of whether it's an 8k2 resistor or a 10k.

What should the voltages be at each end of that Q3 resistor without the resistor in place?

What I mean is, if I remove that resistor I've been changing the value of, what should the voltage be at either of the ends where it was connected?

I'm getting about 2 volts on the transistor end and 9 volts on the other end...does that sound right?

mrsage · October 21, 2004, 08:50:37 PM

bump

mrsage · October 22, 2004, 04:21:46 PM

Okay...I'm getting the feeling that people are pretty much done with this topic this time around.

Any last suggestions before I order a whole new set of trannies and parts? Is there any way to test the capacitors other than just replacing them?

aron · October 22, 2004, 05:26:19 PM

I doubt it's the resistors or capacitors. It's probably a wiring mistake I would guess. Either that or some bad solder joints and a combination of wiring and solder.

I assume you went through this page:

http://www.diystompboxes.com/pedals/debug.html

mrsage · October 22, 2004, 06:18:29 PM

Yeah...I went through the debugging.

I even desoldered everything, checked the board over very carefully, removed all excess solder from the board, examined the traces, then carefully re-wired it all.

I seem to be having the same problem as before, even after all that. I guess it's possible that I wired it incorrectly twice in a row, but it doesn't seem likely...especially since I was doubly careful the second time around.

aron · October 22, 2004, 06:20:36 PM

What layout, what schematic?

mrsage · October 22, 2004, 08:02:04 PM

It's a PCB purchased from General Guitar Gadgets, and I'm using their layout for the PNP positive ground version.

Reading schematics is probably the next hurdle I need to tackle, but this is only my second full DIY build...

brian wenz · October 22, 2004, 08:12:42 PM

Hello Hello--
Don't give up! I still have times when I've gone over everything 3 times and it's PERFECT but still won't work. Give it some rest and then slowly start again!
Good luck--
Brian.

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Troubleshooting Tone Bender MK-II