TS 808 clone can't reach unity gain

[gnugear]

Hey guys,

I just built a TS 808 kit from buildyourownclone.com. It seems to work okay, but the pedal never reaches unity gain when engaged.

The responses on their forum are kind of slow so I thought I would ask you guys. Is there a resistor or something that will increase the output level??

[Dai H.]

have you tried systematically checking for errors (go over from one end of the circuit w/the schematic and instructions comparing with your build)? Also, sometimes, the maker can include the wrong parts, like say--someone mistook a 5.1k for a 51k or whatever. I haven't looked the PCB over carefully, but the kit looks professional (pretty good deal for $75 too, IMO).

[NaBo]

ya might wanna check the resistance range on the relevant pots... sometimes you won't get to the max or min value that you should be getting, just because of a slight mechanical imperfection.  i've had a 500k pot that only made it to 460k, and it produced the same problem.

but 75$ for 1 diy pedal?  ouch.  it BETTER not be a crap pot at that price.  im building mine for 30$ tops

[gnugear]

I'm 99% sure I've got all the right value components. I checked them all with my multimeter and I'm using Dale/Vishay resistors which have the values written on each one.

I never thought about the pots ... how do you check the resistance on those?

[Hal]

with your multimeter!

check the resistance from pin 1 to the wiper (pin2) with the pot maxed and mined.

Then from 2 to 3 with pot max and min.  Then pin 1 to 3.  That'll show total resistance, min resistance both ways, and max both ways....

[cd]

You paid $$$ for a kit and you're not getting the support you need?  IMHO that's unprofessional at best - these new operations should compare themselves to PAiA, who may not have the hippest/latest/greatest, but their service is legendary.

As for your circuit - check the tone control section, a bad pot or solder connection in that area will mess everything up.  Make sure the pot actually goes through the proper resistance range.  Also use the debugging page above.

[gnugear]

Well, I took a reading and my 500k pot only measures 390k  :shock:

I'm guessing that's my problem?

The unit produces overdrives but cuts overall volume when engaged. My Boss SD1, on the other hand, definitely provides a boost.

[cd]

390k won't really make a lot of difference.  That's almost 100x gain, the signal is limited by the clipping diodes anyway (1V peak/peak).  Check the tone control section, that's where most of your volume is being lost.

[gnugear]

Excellent point ... I just figured out that my tone knob isn't even functioning. I'll try working backwards again and then post a pic if I can't figure it out.

[cd]

Check the tone pot, I'll bet it's not sweeping through the proper range or you have the lugs connected to the wrong points.  It's easy to get them messed up.

[petemoore]

"they' Supplied the Pots?
...should' be the right one though, My TS Tone knobs never worked right, or exactly right, takes a wierd taper pot I understand.
 Opamp pin voltages could tell the detale. HAve you taken readings ? Like a thermometer, may instantly tell you what's sick.

[gnugear]

Okay, I give up  :cry:

Here are a couple pics of my board. I'm not sure if you can make anything out, but there's only so much that can go wrong and I'm sure I've got everything in the proper place. I checked the tone pot and it sweeps within its range correctly. Even tried reversing the wires JUST to see if it would make a difference. So far the tone control doesn't seem to function.

[gnugear]

I should note that I replaced a lot of the components like the resistors and some of the caps .... I was trying to make my own boutique version. The actual kit comes with carbon film resistors and those blue electrolytics and green metalized film caps.

I took readings on all the resistors and they're all spot on. Same with the caps. I even changed the op amp and it didn't effect anything.

Can the LED screw things up if it's not wired correctly?

[Fret Wire]

Like cd said, the problem could be in the tone control section. Try two things: get out the maginfying glass and inspect all the solder joints to make sure there are no bridged (touching) solder pads. Second, take the IC voltages and post them, they're helpfull.

Another thing, make sure nothing is grounding out when the board is in place. Did you try it un-boxed?

[Hal]

better pics of the bottom of the board might be helpful for us.  If you have a meter with audible continuity, check to make sure you didn't lift any traces.

[gnugear]

This is the best I can do of the bottom without taking it completely out by unsoldering the wires.

All of my testing thus far has been made without the back cover on.

[bwanasonic]

Transistor pinout for both trannys OK? Not sure you'd get any sound at all if they weren't, but thought I'd mention it.

Kerry M

[gnugear]

Yeah, the circuit board has little outlines of the component shapes so it's pretty hard to screw it up. I'm bummed.  :cry:

[Fret Wire]

Like cd said, the problem could be in the tone control section. Try two things: get out the maginfying glass and inspect all the solder joints to make sure there are no bridged (touching) solder pads. Second, take the IC voltages and post them, they're helpfull.

Did you do this yet? As well as the transistor voltages?

[jmusser]

I've heard that phrase "unity gain" batted around several times, but I'm not sure what it means. I always figured it was max gain for the either the chip or the circuit design, but it's just a guess.