clone theory questions

fatfoot51 · October 11, 2012, 05:03:08 PM

Hey all you pedal geniuses.. It has been a while since I've written any of my pedal queries on this forum but I hope someone out there can lead me in the right direction... I have general questions about my clone theory that I'm getting closer fixing... The voltages fluctuate on the 2n4240(between 1 and 14vdc) on every leg, and the voltage doesn't seem right on the 78L15... Other than that the rest of the voltages seem okay on the other ics since I have another clone theory to compare to... The color knob acts like a volume knob and I can hear the pedal effect when I turn that knob to a lower level and turn the master volume up on my amplifier.. the problematic clone theory is the "b" board version which has a green tantalum capacitor across pin 4 and pin 10 on the cd4047... I desoldered it but what is the purpose of it being there since on the "c" board version its absent? Also what is the 78L15? What are suitable equivalent replacements for the 2n4240 and the 78L15? Someone out there has to know something! Thanks much!

fatfoot51 · October 12, 2012, 01:57:43 PM

I guess I have a few corrections on my earlier findings. Sorry about that... The chorus /vibe knob is the pot that acts like a volume.. The board is the "c" version with the green tantalum on pins 4 and 8... I'm not sure if the jfet is the problem or not.. I have some voltage readings...
The 4558 on top sad 1024 4558 on bottom cd4047
1. 5.05vdc 1. 0 9. 13.99 1. 4-9 variation 1. voltage varies 8. 0
2. 5.07 2. 4.8 10. 7.34 2. 7.35 2. voltage varies 9. 0
3. 4.8 3. 7.34 11. 6.4 3. 7.35 3. 6-7 variation 10. 7.36
4. 0 4. 0 12. 6.4 4. 0 4. 14.7 11. 7.36
5. 4.99 5. 6.77 13. 0 5. 4-9 variation 5. 14.7 12. 0
6. 5.06 6. 6.74 14. 7.34 6. 7.35 6. 14.7 13. variation
7. 10 7. 13.99 15. 4.79 7. voltage jumps 7. 0 14. 14.7
8. 14.6 8. 7.34 16. 0 8. 14.6

pinkjimiphoton · October 12, 2012, 08:31:10 PM

this is the one with the "edge" switch, right?
keep after me, cuz i'm a space shot, and i'll pull my CT tomorrow and see if i can get you some voltage readings.

sounds to me like something stupid with that pot. try re-flowing it's connections.

fatfoot51 · October 15, 2012, 09:31:29 AM

Thanks pinkjimiphoton! It is the one with the edge switch.. Also can anyone tell me the differences between the "b" and "C" boards plus what the green tantalum cap across pins 4 and eight are for on the cd4047! I appreciate it!

Scruffie · October 15, 2012, 10:30:33 AM

Quote from: fatfoot51 on October 15, 2012, 09:31:29 AM
Thanks pinkjimiphoton! It is the one with the edge switch.. Also can anyone tell me the differences between the "b" and "C" boards plus what the green tantalum cap across pins 4 and eight are for on the cd4047! I appreciate it!

That cap is most likely extra supply filtering, it goes from the + connections of the 4047 to the grounds.

The 4047 and LFO look okay, i'd say the issue is with the 4558 'on top'.

Servicing wise, probably a recap job and yes maybe some pot/switch cleaning, plus checking for any bad solder joints (some of those old boards weren't that well done).

As you have 14.6-7V on the chips as main supplies it seems your 78L15 is doing its job.

pinkjimiphoton · October 15, 2012, 12:34:30 PM

+1 on the servicing aspect.

i just won one of these on ebay for a stupidly low sum, as it was "broken"...it needed bad solder fixed on the rate knob, and to be cleaned.

i would also reccomend replacing the carbon comp resistors with precision metal films, it may cut down a little on the noise factor, these are extremely noisy compared to the ones with the vib/flange switch.

bear with me, cuz i'm way behind, will try and post voltages if you still need them, or if you run into any issues, we can compare to my working unit.

the toppopiccione clone theory project is a lot of fun, if ya wanna get a little more in depth with it. i re-drew the vero just to make it a little easier to read, it's on the forum here somewhere.

fatfoot51 · October 20, 2012, 10:27:22 PM

The 2n4240 has erratic voltages on all the legs... Do you think the problem is really in the top 4558? Thanks.. Just another tidbit that I noticed..

pinkjimiphoton · October 21, 2012, 11:48:21 PM

the eratic voltages may be from the thing modulating...sorry bro, above my paygrade..

Scruffie · October 22, 2012, 02:49:06 AM

Quote from: fatfoot51 on October 20, 2012, 10:27:22 PM
The 2n4240 has erratic voltages on all the legs... Do you think the problem is really in the top 4558? Thanks.. Just another tidbit that I noticed..

Easy way to check, turn the rate and depth down, do they jump less than when they're at full?

But yes that should have modulated voltages on it.

If the 'Colour' knob (assume you mean chorus/vibrato) is working as a volume then the issue is in the audio path.

Best bet is to build an audio probe and trace through the path, ignore the 4047 & Bottom 4558 + FET, that's the clock & LFO, if you can hear 'some effect' working then they are most likely okay, plus they're not gunna have your signal in them.

Check pins 1 & 2, 5 & 7 of the 4558 and at the 3 lugs of the Ch/Vib knob for signal.

fatfoot51 · October 28, 2012, 12:53:21 AM

Hey scruffie! Thanks for the reply.. I had the chance to poke around and I wasn't getting sound out at pins 1, 5 and 7... Pin 2 had the high pitched squealing I expected..After I had the chance to solder the green tantalum and a socket for the new 4558 in place, the problem was still there.. So could it be one of the coupling caps somewhere? So close yet so far! Thanks anyway! More ideas?

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clone theory questions