I finally got this beast to function...I re flowed and messed around, redid a few components and then slapped a JRC4558 in there and it freaking works...don't ask me how...
This one gave me the most trouble of all.....
Let me know if I need to post any other info....
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Start by getting the right voltages, lift the regulator output leg and make sure the charge pump is actually doing it's job of getting 17.1V on the regulator input and the regulator is providing 15V out, then you know if the circuit is causing an issue or if you need to debug your power section.
Pulled output pin from 7815T
Pin 1 is 16.50v
Pin 3 is 14.80
Looks good so far...
I pulled the v regulator out completely and was getting proper input voltage from pad 1 to ground. When I checked the output PAD 3, it was showing the 9v from the external power supply from the pad to ground. Is that 9v supposed to be there? Sorry if that is a dumb question...
Are you saying you have 9V on ground? If you're saying what I think you are, that you have 9V on the regulator output pin without the regulator in place, then no that's not right and what's causing your issue, you probably have a solder hair or short somewhere round IC7 & 8.
Looking at the schematic and the voltages above, I'm seeing the voltage divider output (VB) after IC5 in the power supply circuit, showing up at various IC pins on the rest of the circuit, but I'm also seeing the 9.22v from the bench supply showing up on other IC pins. So that seems to be a clue. The input voltage of 9.22v isn't supposed to be going anywhere but to the charge pump as far as my meager reading of the schematic goes. Can someone verify that?
Or is that a wrong assumption?
I just verified that and see that the Pins that are reading 9.22v are to ground.. See if I can fix it tonight....
Quote from: blearyeyes on May 21, 2014, 07:28:53 PM
Looking at the schematic and the voltages above, I'm seeing the voltage divider output (VB) after IC5 in the power supply circuit, showing up at various IC pins on the rest of the circuit, but I'm also seeing the 9.22v from the bench supply showing up on other IC pins. So that seems to be a clue. The input voltage of 9.22v isn't supposed to be going anywhere but to the charge pump as far as my meager reading of the schematic goes. Can someone verify that?
Or is that a wrong assumption?
No that's a right assumption, so you likely have a short or solder hair somewhere, start searching around the power section of the PCB and 9V & Gnd pads.
Thanks Scruffie... It helps to have someone with experience to point you in the right direction. I've learned a lot from this one. I know just enough to get into trouble. Hope to have it up and running tonight.
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Ok I found where the power is getting to the output of the voltage regulator. It is the 9v pad and the output of the voltage regulators trace that runs around the outside of the board. I am trying to cut between the trace and the 9v input pad as you can see. They are connected and I wonder if we ever get bad PCBs or did i do something somehow to connect them. I don't see how I could have but then what do I know? I guess it could be connected somewhere else but I'm flummoxed fer sure....
Its rare but you can get bad pcbs. Usually its not a short but an open trace/thru hole in my experience. I don't believe you can cause a short under the soldermask in the manner you seem to have.
That is a good catch, hard to see with the silk screen over it and all.
Last time I had an IC get hot (really hot..!) was when I installed a dual opamp in backwards. Didn't have a notch at the top like many do, and I forgot which side had the bevel before I installed it.
Oh Bean, help me for I am lost and forsaken. Wondering in the wasteland of mediocrity.
OK that was the issue, 9v pad was connected to the 15v trace. cut it with an exacto knife and now will sleep. as I am tired and must try to live another day! Tomorrow I will set bias and try to get this thing to sing.....
Very nice catch, wouldn't have guessed that was the issue but glad you spotted it.
Everything lines up pretty much with the voltages in the build docs with the exception of ICs 3 & 4...the ones marked with an asterisk... Oh, I also replaced both opamps with no effect. The only thing is scruffies suggested swap of the two 15uF caps configured as a Bipolar cap in the LFO with 10uF and 33uF
voltages with 12.02v regulated power pulling 55ma {bench supply}
IC#1 ALL GOOD
7.37v
7.37v
7.37v
0 v
6.97v
7.38v
14.75v
IC#2 ALL GOOD
7.37v
7.37v
7.33v
0 v
7.37v
7.37v
7.37v
14.75v
IC#3 BAD ***
1.40v
7.49v
8.89v
0 v
7.58v
10.55v ***
14.76v
IC#4 BAD
1.217v **
2.218v **
1.375v **
0 v
7.34v
7.38v
7.39v
14.76v
IC#5 ALL GOOD
14.76v
7.37v
7.38v
7.38v
7.38v
7.38v
7.38v
0 v
7.38v
7.38v
7.38v
7.38v
100+ mv fluctuating
7.38v
7.38v
100+ mv fluctuating
IC#6 ALL GOOD
7.38v
7.38v
14.50v
0 v
7.38v
0 v
0 mv
14.75v
14.77v
10.87v
14.77v
14.77v
14.77v
IC#7 ALL GOOD
1.45v
6.07v
0 v
6.4mv
203.6mv
2.571v
1.447v
12v
IC#8 ALL GOOD
22v
0 v
14.77v
IC#9 ALL GOOD
14.77v
7.37v
7.79v
1.6v
0 v
7.37v
7.491v
7.481v
IC#7 charge pump is no longer getting hot after I fixed shorted 9v pad to 15v trace. the voltages above are new.. I have checked all caps and resistors for values but I have missed stuff before. I have searched for cold solder joints and bridges. I have re-flowed any suspect joints. This one has been difficult. When I set the Bias I can hear the effect kick in but the sweep is not oscillating. When changing any of the controls or the trimmers the effect is obvious on the guitar signal.
Any help is appreciated.
That's getting very close so your audio path is all fine, power is fine, your clock is fine, it's your LFO not kicking in and seeing as the half the opamp of the width control that is in the audio path is fine and the other half isn't, we can pin point it down to anything following the 4013.
So IC4A (not B) & IC3 are the most suspect.
All the values in that section checked? Transistors all confirmed against the datasheets (for the particular brand) to be orientated correctly? Hopefully no more bad traces...
Will do, thanks.
I'm getting 13+ volts from pin one and three on the Sweep pot.. Trying to stare at the circuit board to figure out how that could happen. Pin one looks like it is to ground although the schematic is not clear. I used a standard pot instead of a reverse taper (C) and wired it backwards... I'm not getting that voltage from other ground sources...
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Quote from: blearyeyes on May 27, 2014, 10:13:03 PM
I'm getting 13+ volts from pin one and three on the Sweep pot.. Trying to stare at the circuit board to figure out how that could happen. Pin one looks like it is to ground although the schematic is not clear. I used a standard pot instead of a reverse taper (C) and wired it backwards... I'm not getting that voltage from other ground sources...
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Pin 1 of the sweep pot is not grounded, just floating, unless you meant the manual pot?
Just in case though, check that the power trace running next to pin 1 of the sweep pot isn't connected to it.
After that, check your values for R26 & 47 and then if they're right it might be worth pulling out IC3 and seeing if the voltages on IC4 pins 1, 2 & 3 stabilize.
Well if pin one is floating then I'll just remove the wire from the pad to the pot. If that works then the trace is connected to the pad.. If not then onward!
So you can have a pad just floating and use it for component support. Who woulda thunk?
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OK here's my guess:
Either pin 1 of the sweep pot is connected to the 15v trace or the positive pad of C13 is connected to the 15v trace as they both lead to to pin 6 of IC3b where the 10+v reading is where it shouldn't be... When I get home the truth will be revealed! At least I freakin hope so!!!
My brain hurts... How do Beans function at this level without going Mad?
Removed wire from Pin 1 on SWEEP Pot no change. Checked C13 pad and found no connection. checked R26 & R47 both 470k. Pulled IC#3 and IC#4's voltages did not stabilize; Still 2.2v on 1,2,3 and 0 on pin 4.
IC#3 pin 6 = 10.55v.
SWEEP POT Pin1 Disconnected shows floating at the pad. on the Pot shows 13.33v CCW and 14.08 Fully CW
SWEEP POT Pin2 Shows 14.02v fully counter clockwise and 14.08 fully clockwise
SWEEP Pot Pin3 Shows 14.02v fully counter clockwise and 8.84v fully clockwise.
Is that correct?
Going to re-check all values in area after cd1430.
Once again any help is appreciated......
I'll have to come back to this one... Collosalus has kicked my butt....
You said you got 2,2V on pins 1,2&3 with IC3 out, that's fine so let's just focus on IC3 as the culprit.
I think... I would just try replacing IC3 with another OpAmp, just to be sure it's not bad, obviously check all your values in that LFO area though, make sure the electros are orientated correctly and reflow the joints too and that there's no shorts or solder hairs.
Think you're almost there :)
Did all of the above, replaced IC 3, checked values, cap polarity, went over soldering top and bottom re flowed and checked with continuity checker adjacent pads and pads to ground just because. LFO still not ocillating.
Really has a great sound when I mess with the trimmers!
It's got to be right in front of my face!
Sorry this is taking so long... I really appreciate the support!
Dan.
If you lift the pin of the width pot coming from the LFO then you have it isolated which might help you debug it.
What IC are you using? A 4558? Might be worth trying a 1458.
@12.00v
After lifting pin 2 on width control, IC4a pins 1,2,3,4, are showing higher voltages
of 5.1v 4.9v 4.71v and 0v
IC3 is 1.4v 7.49v 8.9v 0v 7.58v 12.92v 7.37v 14.76v
=================================
Oh and previously IC4 was showing 2.22v on 1,2,3 with IC3 in or out (no change)
Lift pin 3 of the width, then check all the LFO traces to make sure there are no more traces joining that shouldn't, also did you try a 1458 (or LM358/TL022) for IC3? Then reflow all the joints in the LFO area, triple check all the values (R20-25 & C12-14) then cry if it still doesn't work ;)
Well there is another alternative, which involves a hammer, or I could build an external LFO and insert it into the 4013. I know, I'll take the portion of the schematic after the 4013 and work it up in Eagle, send it off to Oshpark and glue it on top of this board then epoxy the whole thing into a clear brick and frame it. ;-D
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Actually I'm going to pull every part in the LFO and check it with a meter. Then run continuity on the board. I have never had to admit defeat yet..
Or I'll just do what I stated previously.
I think I have an LM358. I'll give it a try.
Maybe a trace under the chip is goofy.
Then if that doesn't work I will Brutalize this PCB removing every part of the LFO and checking it with a meter.
I will not admit defeat! ........yet
LFOs are finniky!!!
My go-to LFO op amp is the LM358. I have has TL072, RC4558s, JRC4558s, TL082s, and many other NOT work as an LFO but.... never had a 358 NOT work.
I know the circuit is usually built to support the op amp used but, I have always had good luck with the 358.
Im betting that is the culprit. ;) Good Luck
Remember.... the original used the LM1458 for the LFO which is a low-current dual op amp as well.
Thanks, I'll pop one in there tonight.. Fingers crossed.
I didn't have a LM358 but tried everything I had and a NE5532P fired up... So I'm gonna get a few 358s and try those as now the speed range is limited. I'll work with the pot and other resistors when I get the opamps to get the range right. Thank you guys for all the help and especially Scruffie who worked overtime.. You guys are awesome!
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An NE5532? Usually an awful LFO OpAmp haha, congrats though! Glad it got there in the end.
Well it's not really there but on the back burner till I get the LM358s
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I finally got this beast to function...I re flowed and messed around, redid a few components and then slapped a JRC4558 in there and it freaking works...don't ask me how...
This one gave me the most trouble of all.
I know I wouldn't have that pitbull tenacity that you seem to sport to see this sort of thing through... ::)
Hat's off, man!
Huzzah! Congrats
Well thanks! In the few moments while enjoying this colossal triumph, I built a Pork Barrel and it worked out of the gate! Well except for one bad MN3101. Figuring I bought 10 MN3101s and 10 MN3007s off of eBay blind, having them work at all is a blessing!
Thanks again!
Dan.
Well done! My first 'you little Bastard' build was Brian's electric mistress board... you always remember the first ;)
Yes in deed! Onward my friend!
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