Help me Debug: Rangemaster finally working

[pbrommer]

Hey all-
I need some help debugging my Rangemaster (adapted layout from bigtonemusic.com -- I had the parts to build it before he offered kits). The effect will bypass with a 3PDT switch, but when it is turned on, there is nothing. I did change the transistor from SmallBear's to an OC44 that I had. I once got the circuit to work with the OC44, but then the circuit crapped after that. My guess is the switch itself, after I soldered and desoldered for hours on it. What else could be the problem? I have redone all the joints and checked with a multimeter when my brother brought it (I don't have one). The battery should be fine: it was new when it was put in the enclosure. I'm getting a new DPDT soon, and will check that. Please help my out on my first DIY effect: any and all is appreciated. Thanks.

--Patrick

[Dave Z]

try taking the switch out of the equation....wire it up direct. (I assume you're still in the prototype stage, with the thing on a bench or temporary box.)

If not, well, grab yourself some metal box, buy a couple extra 1/4 inch jacks and make yourself a prototyping box. That way, you can do up a baord, then pop it in & see if the board works. Once you know that, you wire up the actual box, with stomp switch, bypass & DC in & LED, and - without the curcuit board -- test for bypass - should work. Ten turn on power - all you have hooked up at that point is the LED - that should glow. Then, putting in the circuit board, which, since you prototyped it, you know it works. If the final product has problems then you have MANY fewer possible things wrong.

meanwhile, even a cheap Rat Shack multimeter is crucial. Don't have even that? YOu can check continuity (closed circuit, good ground etc) with 2 wires, a battery and a light bulb!

[petemoore]

I used to use 3906 or any run of the mill PNP to test my Rangemaster type circuits and FF's...haven't built one for a while.
  I replaced a few 470k's with actual 470...R's, color codes used to get me.
 DMM...and check out GEO's 'technology of the Rangemaster", voltage readings and Beep mode make it possible to debug....
 Transistor orientation...My Ge's arrow [the way the pins come out of the body forms and arrow head] points toward output...PNP neg ground...I'm not certain yours does...must be in there the right way or it won't work.

[Phorhas]

you can go over the switch problem with a couple of audio probes for the debugging stage (one of the most important tools I have along side my DMM). also be sure to chek pin voltages and leg placement.

http://www.geofex.com/FX_images/audioprb.gif

[petemoore]

Audio probe is expecially helpful when there are more than one active component...bias the tranny on the Rmaster, and input to base has to cause output from collector...worth a try anyway, and very useful tool to have around...I use the 'thumbuzz' method...never had to mess with Audio Probe much...anyway I'll bet the transistor is where the sound is lost...that or a cap isn't connected right...the probe might help find that.
 First thing I'd do is check for short between + and - with the DDM beep mode, then check transistor pin voltages from ground.

[GreenEye]

Mine did the same thing.  My problem was bad/sloppy off-board wiring.  I cut off all the wires, wired it up outside of the box using alligator clips, determined the board was fine, then re-did it.  Took forever, but it works now.  I also recommend GGG's wiring diagrams and pics of insides of pedals.

[pbrommer]

Thanks for the help. Here's a little more from a couple weeks ago (been to busy to touch it lately) that might help.

Orginally, with smallbear's tranny, it was perfectly fine -- switches, jacks, etc. -- everything worked fine. No problems... But when I took wires off to mount the parts in the box, and rewired everything, then replaced that tranny with the OC44, nothing would work. It did work ONE time with everything in place.

By the way, I'm new to this, so putting this in really plain English helps (i.e. I don't know everything). Questions: What am I listening for with the audio probe that is plugged into the guitar amp? Hiss? Buzzing? 'Thumbuzz'? Explain how you do that.

For me, it may just be crappy offboard wiring. Again, thanks for the help.

[petemoore]

plug a cable into your amps input, turn the amp on, try pushing the tip into carpet, the touch your thumb to tip and sleeve of the plug, the signal your thumb produces is not high amplitude, but you should be able to hear on and off.
 You've just verified your cable and amp work, at least a little bit.
 Now plug that in the effects unit's jack, you'l hear a buzz or clicks when this is done.
 >>>Don't try this little trick on a HIGH Potential possible lethal voltage...I'm talkin' stompboxes with batteries for testing purposes...
 OK...plugged the cable from the amp to the effects' out jack...now grab a shank [screwdriver], and touch the metal between your thumb and your output jacks tip connector...hear a buzz...should be the same volume [especially when in bypass] as touching the cable ends with your thumb...[ive found grounds to output jacks tip lug before]...anyway you should hear a buzz when your thumb's connected...follow the signal path through the schematic, from output toward the input of the circuit, the next step would be try the other side of the output cap [assuming you've eliminated the switch as an added variable I like to have a circuit 'pass' signal before figuring in the switch etc anyway]...the buzz, if it's went through the cap, especially if it's a small cap, may sound less bassy/loud, but you should be able to hear a buzz there and by the collector of the Q.
 At this point the DMM will probly have to step in and say "hey...what's the voltage on this tranny...
 Otherwise, get one, but build a board with trimpots all over it, [as V/R's variable reisitors to bias the tranny] and 'unlock' the bias...start with low here...then 'index the others, then 1 here, index the others....or just start cranking them this way and that try...DAFT...just do it by ear...thing is tho...if there's a like miswire, back to DMM time for helping find it...
 Thing is to build a fixed version of the Rangemaster you've perf/breaded you'll need a DMM to read the resistances you've found...
  Look at the nodes [where one or more leads meet], when building, and after, circuit may look simple but it's a law matter of 'work' or don't work' when initially debugging, which means set up right or not.
 resistor values...who knows really depends on the tranny
 cap orientation [value to a lesser degree....as long as it's close it sould work]
 Transistor orientation
 Correct wiring...
 Battery + and - connections
 Could be any one, one or two bads hidden in the rest goods...I'd have to say consider putting it aside 'till you get a DMM...
 I just like the Rangemaster protoperf with a buncha trimpots for trying out my different Ge's in...set up so I can read the resistances after I bias one that sounds good...some resistors can't be read in circuit, the current may have another path around it...so I figure out on my test boards which ones I have to make liftable [pull one end of a resistor from circuit for reading it's value] so I can take it's reading easily.

[pbrommer]

update:
Well, I redid all the wiring for the board and jacks. There seems to be about 4 spots where there's a problem, two are fixable (bad solder to lugs). The other two cause much louder hissing overall from the effect.
With the thumbuzz method, I get buzzing to the Base, but nothing from the Emitter, and very very very little from the Collector. Otherwise, there is nothing. Nothing at all. My guess is bad tranny. Let me know.

Patrick

[pbrommer]

^^BUMP^^

Move this up for some more help.
Like I said, pretty much a nice buzz through to the base of the transistor, but a really narrow sounding buzz comes through. Nothing at the base or emitter. This is the layout:

http://www.bigtonemusic.com/rangerpopulating.html

thanks

[R.G.]

The buzzing you're getting sounds about right. Try the thumb buzz test at the other end of a guitar cord plugged into the input jack.

My best guess is that you have a wiring problem with the wiring into the circuit card. There's no way to tell any more than that from what you have told us.

While you're at it, measure the DC voltages from signal ground to all the transistor pins. That's the single best first debugging test. Often it's enough for one of us to tell you what's wrong. If you don't have a voltmeter, get one unless you never plan to make another pedal. They're available for under $20 if you look the right places. Or take it into a Radio Shack or other electronics store and ask to use the store's meter if there's no other way.

[pbrommer]

I finally got this sucker up and running last night. Somehow, I think the main problem was a bad guitar cord or something. I really don't know what the exact problem was. I socketed the new tranny I had (unfortunately I broke the OC44 trying to put it in the socket - the leads were bent pretty hardcore). Thanks for the help.

patrick