So this was started on another thread and it's time to move it to the tech help section. I really some magic smoke ad now the phase 100 doesn't phase. Here's what I know thanks to Jon probably the IC's,so here are my voltages. There are 6 of them and they are all TL072.
IC-1 (Im guessing this one has the issue)
4.5
4.5
0
0
9.1
.6~8.4 fluctuates
5.3
3-5.5 fluctuates
IC-2
4.5
4.5
4.3
00
9.1
4.5
4.5
4.0
IC-3
4.5
4.5
4.0
0
9.1
4.5
4.5
4.3
IC-4
4.5
4,5
2,1
0
9
4.5
4.5
4.0
IC-5
4.5
4.5
3.9
0
9
4.5
4.5
4.2
IC-6
4.5
4.5
4.3
0
9
4.5
4.5
4.3
I'm thinking it's IC-1 because the voltages are fluctuating and that doesn't look to be normal. (Like how I figured that one out? I'm a sharp one.)
Magic smoke bump
Coupla things:
1) Can you put up a link to the schem?
2) without the schem I'm only guessing here, but the fluctuating voltages on IC1 would suggest to me that ic1 is the lfo?
Maybe some pics? And if its smoked, check for solder bridges and anything that might've cooked ;D
Jeremy
Quote from: the3secondrule on March 25, 2013, 07:06:50 PMCoupla things:
1) Can you put up a link to the schem?
2) without the schem I'm only guessing here, but the fluctuating voltages on IC1 would suggest to me that ic1 is the lfo?
Maybe some pics? And if its smoked, check for solder bridges and anything that might've cooked ;D
Jeremy
Will do, it worked before it smoked. I was wiring up the selector knob. ;D http://generalguitargadgets.com/pdf/ggg_p100_lo.pdf?phpMyAdmin=78482479fd7e7fc3768044a841b3e85a
For reference, here's the schematic:
http://generalguitargadgets.com/pdf/ggg_p100_sc.pdf?phpMyAdmin=78482479fd7e7fc3768044a841b3e85a
Jimi, post some pics when you get a chance.
Also, I'm not sure how you've measured the voltages on the op amps, but you should post them in the pin number order:
1 8
2 7
3 6
4 5
In any case, it looks like IC1A pin 3 is grounded or not connected to anything. This is a bad sign: it should be tied to Vb via a 100K resistor, and it should be close to the voltage of the component it's directly connected to, IC2 pin 7, and, being constructed identically, it should also be close or identical to the other pins in the phasing stages (all the + inputs of those op amps in the center of the schematic). You've either got a short, a broken trace, or the chip is bad. I'd actually replace the chip first if you used a socket (then test it in another working build that uses a dual op amp before tossing it if you like) to avoid the frustration of troubleshooting around a blown component.
Ohhhh I did 1-8 sorry about that. I'll start with that op amp and socket it. I bought it from a guy over on byoc. It was working then I shorted it out. Definitely my error.
So I replaces IC 1 and bow have voltage on pin 3 but still no phasing. What should I check next? I didn't pull the vactrol.
Bump before it's #1 in a box of fail bump
Quote from: jimilee on March 28, 2013, 03:08:09 AM
Bump before it's #1 in a box of fail bump
Sorry, Jimi. I could recognize what was wrong in the op amps, but my experience with this circuit is basically nil.
Did you check if the LED in the vactrol isn't blown (measure for continuity across it ... you don't want continuity.)
Have you checked the vactrols yet? You can do this in one of two ways. Remove them from the circuit and check from the center lead to each end lead (the side with 3 leads), if you get resistance, it is good. Or, use your volt meter and check them in circuit while powered up. You should have fluctuating resistance on each vactrol. Be very careful doing this as you don't want to short out anything
. Also, set the rate to a slow sweep so the meter has time to rect.
Also, since IC1 was part of the LFO, check the transistors in the LFO circuit. Or, better yet, temporarily add an LED is parallel with the LED side of the vactrol and you could tell right away if the LFO is working (just make sure to have it connected with correct polarity). Once verified, remove the temporary LED.
You said you replaced IC1 and got voltage on pin 3, what are the voltages for the IC's now? Did any voltages change for any IC?
Jim
Jimilee,
Did you get this going?
Jim
Nope. I still need to check the transistors next though. Sometimes you gotta let it be and think on it.
Quote from: electricstorm on March 31, 2013, 02:23:43 AM
Jimilee,
Did you get this going?
Jim
Ok , so I have resistance that fluctuates on each of the vactrols,BUT an led in parallel doesn't light up,so I would assume that the transistors are non functioning? Also I measured for continuity across the LED side of the vactrols. The first vactrol on the lower left has continuity but the other 2 do not.
OK, if two vactrols don't show continuity, you shouldn't have any fluctuation of resistance (unless I'm reading the schemo wrong). Use you voltmeter and check the voltage on the collector of Q1 and Q2 (they form a darlington transistor). Set the rate of the LFO to a slow to medium setting so the meter has time to react. If you have fluctuating voltage, the LFO is working. I don't recall seeing a depth control, so the speed should be all you need to adjust to check this.
If the right most two vactrols don't have continuity, place an LED on each of them as before (one on each that didn't read continuity) and they should light up as the LFO sweeps. Or you could place a single LED from 9vdc through a 470 ohm resistor and connect the other end to the collector of Q1/Q2 to verify the LFO works (this is if you don't want to use the volt meter). If this is the case, the LEDs in the vactrols are bad for sure.
I touched an led to each vactrol the and nothing lit up. The right most vactrols gave me fluctuations through the volt meter. I will test the trannies with a volt meter next.done,the collectors fluctuate.
QuoteThe right most vactrols gave me fluctuations through the volt meter.
These should be working then.
QuoteI will test the trannies with a volt meter next.done,the collectors fluctuate.
Your LFO should be working. If you were getting fluctuations on the vactrols, the LFO is working.
So this leaves the vactrol on the left (this should be OC1 or VR1).
QuoteThe first vactrol on the lower left has continuity but the other 2 do not.
Was there continuity in both directions on this vactrol (LED side reversing the leads to check each direction)? There should be no reading in one direction and a reading when the leads are reversed (or vice versa). If it gives a reading in both directions (when it's out of the circuit) then it is bad. Like Jon said, you don't want continuity. If the other two vactrols are good, you should have some (maybe small amount of) phasing.
Could you post your voltages again since you replaced IC1? You should have fluctuating voltage on the following ICs that are controlled by the vactrols:
IC1, IC3 and IC5 - Pin 3
IC2, IC4 and IC6 - Pin 5
Your pin 8 voltages seem too low on all the ICs.
Jim
Well sure, I'll do that tonight after work. I really appreciate your help, knowing this was a bone headed move on my part. I'm not too stressed about it. It's a neat challenge to find out what happened, and a great learning process.
Woops! waited a couple of days,so here we go.
IC-1
1 4.5 8 9.1
2 4.5 7 1.3-8.4
3 4.0 6 3.7-5.5
4 0 5 3.2-5.5
IC-2
1 4.5 8 9.0
2 4.5 7 4.5
3 4.3 6 4.5
4 0 5 4.5
IC-3
1 4.5 8 9.0
2 4.5 7 4.5
3 4 6 4.5
4 0 5 4.3
IC-4
1 4.5 8 9.0
2 4.5 7 4.5
3 2.1 6 4.5
4 0 5 4.5
IC-5
1 4.5 8 9.1
2 4.5 7 4.5
3 4 6 4.5
4 0 5 4.3
IC-6
1 4.5 8 9.1
2 4.5 7 4.5
3 4.3 6 4.5
4 0 5 4.0
Only IC-1 is fluctuating on pins 5 and 6.
OK, voltages look better. And your LFO should be working as you said the collector of Q1 and Q2 had fluctuating voltage on it (the darlington setup). This basically feeds a fluctuating ground path to the LEDs in the LDRs. What I think is wrong is one or more LDRs have a bad LED.
I am looking at the GGG Phase 100 schematic and board layout. Assuming you have the same board, use your volt meter (negative lead connected to ground, probe with the positive lead) to find the vactrol that has 9v going to the + (anode) side of the LED. Next go to the - (cathode) side of that vactrol with the meter, there should be approximately 8.3v there. Go to the next vactrol and check the - side, there should be approximately 7.6v. Now, go to the - side of the last vactrol, there should be approximately 6.9v or a fluctuating voltage. The first vactrol that gives a 0v reading is the bad one. Replace that vactrol, then if there is still no phasing, do the procedure again to find the next bad vactrol.
If you are getting signal but no phasing, one or more of the vactrols has to be bad.
Let me know how it goes.
Jim
Edit: You may want to check both sides of the LED side of the vactrols in the steps above just to make sure there are no open traces from one vactrol to the next. Also, if you have 9v on both sides of the LED, it is bad (if it shorted). If you find this situation, check the resistor on the emitter of Q1 to see if it is burned or looks brown. I don't think it is bad if you have fluctuating voltage on Q1/Q2 collectors, but worth checking. Then you can decide if you want to replace it too.
The vactrols are about 9.00 each (x3). I don't know yet if I want to spend that much on this particular circuit. I'm going to look around and see what I can find.
Were they actually bad? How many were bad if they were?
Quote from: electricstorm on April 06, 2013, 03:08:48 AM
Were they actually bad? How many were bad if they were?
I haven't tested the vactrols at this point but I think we concluded that it was the vactrols just from the testing we did. I haven't puled them out of the circuit to test them.