GGG Ross Comp -- Ready to blow brains out...

[camsna]

So. It's my first real troubleshooting investigation. I'm really good with instructions and I'm very careful, so I've never really had to troubleshoot before. I'm sure it's great that I get to, since it'll help me learn. But, that's the thing, I'm almost totally electronically illiterate. So, I need help. Bad.

Here are the relevant build docs from GGG:

Schem:
http://www.generalguitargadgets.com/pdf/ggg_dnr_ross_sc.pdf?phpMyAdmin=78482479fd7e7fc3768044a841b3e85a

Layout:
http://www.generalguitargadgets.com/pdf/ggg_dnr_ross_lo.pdf?phpMyAdmin=78482479fd7e7fc3768044a841b3e85a

Problem:
No signal when effect is engaged (but bypassed signal is fine. LED works correctly)

What I've done:
- Checked and reflowed all solder joints. There are no bridges, cold, or dry joints
- Checked ALL wiring, it's correct according to the layout
- Whipped up an audio probe and went at it

Here's where I'm lost. I built the audio probe, but have no idea, really, how to read a schematic. (I know, I know, I'm embarrassed...) Anyhow, I started with the IN pad on the board -- joy. Then C2 -- joy, R1 -- joy, C1 -- joy, R2 -- joy, R3 -- NO JOY. Also there's no joy on any of the pins of Q1. Nothing on R5 or C6 or anywhere else.

I replaced R2 and double-checked its value (metered 9.9k). Same thing. So, it seems to me (and I'm well aware that I can be, and likely am, WAY off base) like the signal just isn't getting past R2. I even checked for continuity between R2 and R3, which there is.

Am I on the right track? What's next to hunt down? I just don't know where to go from here and am REALLY frustrated. Lil' help?

Thanks!

---
Cam

[k.rock!]

Sounds like you're doing great man I would start by doing a continuity check and make sure everything is connected to where they have to be and not shorting anywhere. This would be done with your meter bascially touching with one probe point A and the other probe on point B, if you get a Beep, you're good to go...Also, on the same test, probe each trace to ground. If you test a trace and it's grounded then your problem lies within one of those components. Check for either a blown component (like a diode) or maybe just a solder bridge to ground.

If all of this passes, try swapping out Q1. From your testing sounds like you got close to Q1 and maybe that's your culprit right there.

I'm sure there's tons of other things to check but at least this is a good start, in my opinion Good luck!

-Kaleb

[maysink]

Shot in the dark: have you adjusted the trimpot at all? If not, set it around 50%. If I recall, full CW & full CCW will 'kill' the effected signal.

[jkokura]

Problem is at Q1? that means that any of the parts in an around Q1 might have a cold joint or something along that line. Can you get voltages on Q1 and we can tell if you they look right. Also, double check the orientation of Q1.

And yes, you NEED to bias the circuit properly using the trimmer.

Jacob

[camsna]

Problem is at Q1? that means that any of the parts in an around Q1 might have a cold joint or something along that line. Can you get voltages on Q1 and we can tell if you they look right. Also, double check the orientation of Q1.

And yes, you NEED to bias the circuit properly using the trimmer.

Jacob

Thanks, guys. WILL do! I've replaced the trimmer in favor of 2 1k resistors. It's what Keeley does and the circuit and board are set up for it.

BOM:
http://www.generalguitargadgets.com/pdf/ggg_dnr_ross_bom.pdf?phpMyAdmin=78482479fd7e7fc3768044a841b3e85a

"TR1 – Trimmer - 2k - Can be replaced by two 1k resistors as shown in the layout"

I'll look around the transistors for bad joints. As for checking their voltages, which voltages do I want? Wow -- that's a dumb way of asking that...what I mean is, do I measure the voltage from each leg to ground? Or leg 1 to 2 or 1 to 3, etc.?

Thanks again!!!

---
Cam

[jkokura]

Put your black lead on your DMM on ground, then measure each pin of the transistor. Write them down and post them for us. If you can look up a datasheet and tell us which pin is which, that's very helpful.

Jacob

[camsna]

Put your black lead on your DMM on ground, then measure each pin of the transistor. Write them down and post them for us. If you can look up a datasheet and tell us which pin is which, that's very helpful.

Jacob

Yahtzee! Will do in the morning!

¡GRACIAS!

[camsna]

Think I figured it out! I subbed some NOS Toshiba 2SC1849s for the 2N5089s. It looks like my 2SC1849s are pinned out differently. The 2N5089s are EBC, while the Toshibas are BCE. I should just be able to carefully bend some leads and be fine.

Took HOURS of web scouring to figure this out. Turns out that the 2SC1849 comes in both pinouts. I found some legacy BYOC docs that explained that trannies with "C1849" have a different pinout than the ones labeled "2SC1849." The ones with the "C1849" label have to be turned, blah blah. Then ANOTHER legacy BYOC build doc out and out says that some 2SC1849s have the BCE pinout, which makes sense of the other build doc...Anyhow. I think that's it. I'll put it together in the morning and report my mileage.

Thanks again for the help, fellas!

---
Cam

[camsna]

Welp. It appears I was wrong...

I've put installed these trannies in damn near EVERY configuration -- exact same problem. As I poke around with my audio probe, I get signal at Input, C2, R1, C1, and R2 (though it's quite quiet there...). Then -- NOTHING! If I'm reading the schematic correctly (and that is questionable...), then I should be getting signal AT the base of Q1, but I get nothing...And nothing at the emitter either.

I'm almost certain, after much testing and scouring, that the pinout of my trannies is standard (that is, EBC, looking at the flat side, pins down). I've reflowed every solder joint and 20-tuple checked the wiring. I've exhausted my imagination about what might be wrong. So...here's what's going on.

Same thing -- no output when engaged (bypass is fine). Switch works correctly. LED fires as expected. The only subs I've made are 2SC1849s in place of 2N5089s. IC is CA3080E (not a sub). Here are the voltages I'm getting on the trannies (Trannies are labeled differently on the schematic than they are on the layout. The following accord to the schematic)...

Q1: E - 2.38v, B - 2.94v, C - 6.86v
Q2: E - 2.09v, B - 2.65v, C - 7.13v
Q3: E - 0.4mv, B - 0.5mv, C - 9.11v
Q4: E - 0.5mv, B - 0.8mv, C - 9.1v
Q5: E - 8.63v, B - 0.5mv, C - 9.15v

So...uh...yeah. I have no idea what that all means, but there it is. What's my next move?

Thanks again, fellas!

---
Cam

[maysink]

Do you have any 5088/5089's to try? You can use them to eliminate the pinout confusion of the other transistors and see if the problem lies there or elsewhere. Also, try just one 1K resistor in place of the trimpot as I'm pretty sure I remember setting the trimmer full on and full off = no sound. Subbing two 1K resistors is the same as a 2K trimpot full on.

One more shot in the dark: is the IC orientated correctly?

[camsna]

Do you have any 5088/5089's to try? You can use them to eliminate the pinout confusion of the other transistors and see if the problem lies there or elsewhere. Also, try just one 1K resistor in place of the trimpot as I'm pretty sure I remember setting the trimmer full on and full off = no sound. Subbing two 1K resistors is the same as a 2K trimpot full on.

One more shot in the dark: is the IC orientated correctly?

Thanks! That's kind of what I was planning. I just hate to irder a buck worth of transistors and pay the shipping...but it's what I think I must do.

I replaced the 1K resistors with a 2K trimmer. I set it to half way. I guess I can monkey with it and see if it's the problem. I considered the IC also. It's oriented correctly. And I'm losing signal before I even make it to the IC. So...poo...

Thanks for the help! I gotsta get this fixed!

[Smeero]

Did you check all your diodes? If not you should make sure none of them are dead.

[maysink]

If you live near a radio shack, they should have 5088/5089's. They'd have replacement diodes, too, if needed.

[jkokura]

Q's 3-5 look suspicious to me, but if sound isn't even getting by Q1...

Yes, you NEED to have a trimmer in there, not the 2 1k resistors. There's a sweet spot for the trimmer, and you'll need to be able to dial it in. If you haven't got a trimmer in there, install one and begin to try again. Once that's done, you should be able to hear things. If not, use the recommended transistors instead of the ones you're using.

Jacob

[Smeero]

I put this same project together this weekend, used a trim and it worked on the first try. Adjusting the trim was easy, I'd get those resistors out of there.