Author Topic: double flush debug  (Read 1561 times)

eniacmike

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double flush debug
« on: December 11, 2010, 06:31:52 AM »
I built my double flush up and I have alot of issues. The led isn't flashing and I am getting a super fuzz sound. Also when I play the attack comes on then the signal drops and then slowly returns. also my volume knob is working backwards even though I have the cold lug wired to ground. The intensity knob is working properly increasing brightness of the LED.

I thought maybe the my IC3 had a weird marking so I flipped it backwards and it kind of tremoloed for a second but then it started burning up and getting hot so I pulled it. I have tried replacing all the ICs and nothing seems to be working including substituting different ICs (suggestions on the build instructions.)

Here is my voltages

IC1 JRC5558
1 7.85
2 7.21
3 1.29
4 0
5 4.0
6 7.29
7 7.28
8 8.50

IC2 LF351
1 0
2 0
3 (alternating between aprox. 2-3) vd?
4 0
5 0
6 7.52
7 8.50 vc
8 0

IC3 TL062
1 (alternating between approx. 1-5)
2 .70
3 2.35
4 0
5 2.35 vd
6 2.41
7 (alternating between approx 2-3)
8 8.47

madbean

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Re: double flush debug
« Reply #1 on: December 11, 2010, 07:13:17 AM »
Something is wrong with the Vb supply. There's no way you should be getting such high voltages on IC1. Pins 1,2,5,6 and 7 should all read closer to 4.5v.

Your supply is a little low at 8.5v, too.

Could be an iffy resistor on R20 or R21.

Here are the two supply rails you need to examine more closely to figure out why you Vb supply is so high.

[attachment deleted by admin]
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eniacmike

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Re: double flush debug
« Reply #2 on: December 11, 2010, 11:34:50 AM »
thats what I noticed too. my supply off the breadboard is 9.45.

at 9v I get 9.45 and after the diode 1n4148 I get 8.50. I swapped the diode and the same results applied. I checked the direction, and it looks the same as your picture too.

I also thought pins 3 and 5 should read the same thing because they both basically are connected to VB via a 470k resistor.
« Last Edit: December 11, 2010, 11:46:11 AM by eniacmike »

madbean

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Re: double flush debug
« Reply #3 on: December 11, 2010, 01:07:46 PM »
You can swap in a 1N4001 or 1N5817 for lower voltage drop. That will solve one problem.

What reading do you get at the junction of R20 / R21?
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eniacmike

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Re: double flush debug
« Reply #4 on: December 11, 2010, 01:45:30 PM »
I just did a second build. I am getting flashing on the LED and all the knobs appear to working correctly. It is working however I am still getting FUZZ.

I swapped in the 1N5817 and I am reading 8.99 after the diode.

on the new build I am getting 3.88 at the r20/r21 junction (VB)

IC1
1 7.85
2 3.93
3 .77
4 0
5 2.6
6 7.73
7 7.85
8 8.61

IC2
1 0
2 3.59
3 3.77 vd
4 0
5 0
6 3.52
7 8.59 vc
8 0

IC3
1 4
2 .75
3 3.7
4 0
5 3.7
6 2.46
7 3.75
8 8.57

on this second build I changed cap brands. on the first build I was using some new short electrolytic caps that I have never used before (nichicon 50v 5mm tall) I used lelon 25v electrolytics in the new build.
« Last Edit: December 11, 2010, 01:55:21 PM by eniacmike »

eniacmike

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Re: double flush debug
« Reply #5 on: December 11, 2010, 02:09:48 PM »
got board #2 working. found two solder bridges.

it sounds great! thanks.

http://www.youtube.com/watch?v=pAVhKjsImeI
« Last Edit: December 11, 2010, 02:12:20 PM by eniacmike »

madbean

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Re: double flush debug
« Reply #6 on: December 11, 2010, 02:10:44 PM »
Mike, try disconnecting your LDR on build #1, then demo it just on with the mix knob all the way to the un-effected side. Do you still have distortion? Are your voltage readings any different?
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eniacmike

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Re: double flush debug
« Reply #7 on: December 11, 2010, 02:34:22 PM »
Mike, try disconnecting your LDR on build #1, then demo it just on with the mix knob all the way to the un-effected side. Do you still have distortion? Are your voltage readings any different?

I stole the pots for build #2. I have to leave for austin for a gig right now, but I will fix it when I get a chance tomorrow.

G.G.

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Re: double flush debug
« Reply #8 on: December 13, 2010, 09:33:12 AM »
http://www.youtube.com/watch?v=pAVhKjsImeI

HAHA! I have always loved that short curly cable in this vid.  A buddy of mine used to have one like that so he would look like Fogerty but every time he took a step forward it almost pulled his amp over.  :D

eniacmike

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Re: double flush debug
« Reply #9 on: December 13, 2010, 10:49:13 AM »
I got both working now. I had more solder bridges on the other build.

I switched my solder tip from a screwdriver tip to a needle point tip.