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Topic: Looking for someone to repair my volume pedal |
Mark Wayne
From:
Wisconsin, USA
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Posted 6 Jul 2007 3:23 pm |
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| I have a Goodrich photo-cell pedal back from the 80's and was wondering if anybody knew who could repair it. The pot is functional which led me to believe it's with the electionics. There is no signal that comes from the pedal. I know Goodrich will not repair them. Anybody? |
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George McLellan
From:
Duluth, MN USA
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Posted 7 Jul 2007 5:06 am
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Hi Mark. If you do find someone to do the repair work on your pedal, Dave Slattery is also in the same boat with no luck finding someone to fix his. He'd appreciate the help. He doesn't monitor the Forum.
Geo |
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Jim Palenscar
From:
Oceanside, Calif, USA
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Posted 7 Jul 2007 7:53 am
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| I don't understand- a photocell pedal has no pot |
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Harvey Richman
From:
Georgia, USA
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Posted 7 Jul 2007 8:32 am photocell pedals
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I've never seen one of these so I don't know what's in there. The only way way I could imagine a pot being in there (I agree with Jim) is if it were to control volatge to the light source, but most photocell pedals I've seen aren't set up that way. I recently successfully restored a 1960s Edwards light beam pedal I picked up from a forum "yard sale." However, I don't know if your pedal is as simple electronically as this one, the Edwards is really just a light source and a photocell wired across the signal. As you move the pedal, an opaque piece of plastic of changing density controls the level of light that falls on the photocell. The photocell had gone bad, resulting in very low output. Maybe you could post a pic of the inside of your pedal.
Best Regards
Harvey |
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Mark Wayne
From:
Wisconsin, USA
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Posted 7 Jul 2007 9:25 am
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This particular pedal does have a pot. Would it not be considered a photo-cell pedal then?
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Jim Palenscar
From:
Oceanside, Calif, USA
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Posted 7 Jul 2007 10:32 am
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| It is not a photocell pedal- what number is printed on it? |
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Mark Wayne
From:
Wisconsin, USA
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Posted 7 Jul 2007 10:38 am
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| The number is worn off, but it says PH-2 in the inside. |
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Jim Palenscar
From:
Oceanside, Calif, USA
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Posted 7 Jul 2007 10:57 am
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| Seems to me that was a photocell # but I don't see one anywhere- call Goodrich 231-893-5702- Ollie and Curt are great folks to deal with |
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Mike Wheeler
From:
Delaware, Ohio, USA
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Posted 7 Jul 2007 11:30 am
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It looks to me to be an impedance matching circuit, but no photo cell arrangement...Hi-Z input, Lo-Z output.
If it was originally a photo cell pedal, it isn't now. Maybe it was retrofitted with the different circuit.
_________________
Best regards,
Mike |
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Harvey Richman
From:
Georgia, USA
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Posted 7 Jul 2007 11:40 am photocell pedals
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Thanks for posting the pic Mark. It certainly does have a pot. I'm no expert on Goodrich pedals so this is just a guess from looking at the pic. If there's no photocell or light, it could be that the pot electrically controls the circuit to change the signal level. That's actually pretty common on keyboard volume pedals, but again, that's nothing more than a guess. I'm curious now so please let us know what you find out. Just in case you're interested, this pic is typical of what an older type photocell looks like. It's resistance changes as more or less light falls on it. I imagine modern ones may look different.
Regards
Harvey
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Mark Wayne
From:
Wisconsin, USA
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Posted 7 Jul 2007 11:53 am
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That's neat, Harvey.
If the electronics are bad in there, can I bypass all the electronics, buy some jacks and wire the pot to the jacks like a standard volume pedal?
Would anybody have a diagram for that? |
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Jon Light
From:
Saugerties, NY
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Posted 7 Jul 2007 12:15 pm
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| No, Mark---assuming that all that circuitry is indeed in the signal path and not just a bypassed vestige, that pot will not be the 500K that you need. On the other hand, stick a 500K pot in there and it wouldn't take but a couple of minutes to reroute the jacks (no jack replacement necessary) and have yourself a basic passive pedal. |
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Greg Cutshaw
From:
Corry, PA, USA
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Posted 7 Jul 2007 12:28 pm
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If it's not a 500K pot, replace it with a 500K pot. Wiring instructions and pics here:
Pot Pedal Wiring
Greg |
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Mark Wayne
From:
Wisconsin, USA
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Posted 7 Jul 2007 12:42 pm
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| Thank you Jon, Greg, Harvey, Jim, Mike and Geo. I think I'll go that way for now. One benefit out of all this is realizing the spring that's connected to the pedal underneath the heel area (connecting the 2 main parts of the pedal). I was wondering why this pedal is so much smoother than the others I've had and I think that's the reason. |
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Harvey Richman
From:
Georgia, USA
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Posted 7 Jul 2007 1:21 pm If all else fails, why not...............good idea!
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I don't see why it couldn't be converted to a regular pot pedal if you can't get it fixed. Nothing to lose in trying. However, you might (or might not) have to get a new pot. As the one in there is not serving the standard function it may be of an odd resistance "value" that won't work right (you might get lucky though, a pretty wide range will work). Resistance is measured in ohms and typical volume pedal pots have values in the tens or more often hundreds of thousands of ohms. I think 250,000 (250K) and 500,000 (500K) are the most common. The value is often marked on the casing (e.g., something like 100K or 500K). The exact value (along with other things) will affect the "feel" and "movement" characteristics of the pedal. Even if yours is of a value that will work, it could be scratchy just like any pot that old (maybe not though). And, of course, that would be a mono (not stereo) pedal unless you got a stereo pot. The jacks are reusaable and of better quality than than you will find in most stores that sell them.
Taking those things into account, I would say yes, it can be done (with a little trial and error) and a working pot pedal is better than a high tech paperweight.
I do hope you can get it fixed though.
If you do decide to modify it, you might want to make a diagram of how it was wired just in case. Also, before you tear into it, please don't forget to make sure it's unplugged first. I've made that mistake!
Regards
Harvey |
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Harvey Richman
From:
Georgia, USA
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Posted 7 Jul 2007 1:27 pm
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| Wow, step by step instructions! Can't beat that. |
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Jerry Erickson
From:
Atlanta,IL 61723
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Posted 8 Jul 2007 9:35 am
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| Looks like there are 4 transistors on that board. Also 3 Vactrol optocouplers, ceramic and tantalum capacitors and carbon film resistors. Some of the same on the other boardbut can't tell all what's there. |
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Michael Brebes
From:
Northridge CA
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Posted 9 Jul 2007 12:10 pm
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The 3 Vactrol's are enclosed photocells with an internal LED, usually, as the light source. It is probably some kind of hybrid where it uses a pot but only as a control voltage for the Vactrol's. If you are still interested in getting it fixed, I can probably do the job. Email me. If you can get Goodrich to cut loose with a schematic that would be great. If not, it's going to cost you for me to draw one out from the circuit.
_________________
Michael Brebes
Instrument/amp/ pickup repair
MSA D10 Classic/Rickenbacher B6/
Dickerson MOTS/Dobro D32 Hawaiian/
Goldtone Paul Beard Reso
Mesa Boogie Studio Pre/Hafler 3000
RP1/MPX100 |
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Mark Wayne
From:
Wisconsin, USA
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Posted 10 Jul 2007 11:07 pm
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Thanks guys...Sounds like you know your stuff with electronics.
There are some 500k pots at http://allparts.com Would one of these pots work as the 500k pot that's needed? |
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Harvey Richman
From:
Georgia, USA
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Posted 12 Jul 2007 7:53 pm
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Hi Mark, did you ever figure out the value of the pot that is already in there or tried wiring it up? I'm going to check out the allparts site.
Regards
Harvey |
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Mark Wayne
From:
Wisconsin, USA
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Posted 12 Jul 2007 8:39 pm
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Hi Harv,
It's a 100k pot in there. I haven't tried the different wiring yet.
I talked to Goodrich directly today, and they said they have no schematic to offer me on this pedal that needs repair. It seems they have quite alienated themselves from this pedal, but will repair the 10k pedals for $27 + $8 for shipping (pots etc. extra).
There was a possibility that Michael could repair it, but the labor might exceed the cost of the pedal because of no schematic. I've been using my Hilton as a back up, but it isn't for me. You'll probably see me selling it for another Goodrich pedal (sigh)  . In 2 weeks I had 2 pedals go. This pedal, and a different 10k pedal. Never changed anything, just coincidence.
Any new info I get I'll post. |
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Harvey Richman
From:
Georgia, USA
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Posted 13 Jul 2007 6:36 am
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What I would suggest is before you start spending money, go ahead and wire up the pot that is in there. 100K will function and you may even be satisfied with its performance. It will at least give you a feel for what you are working with.
When modifying things like this, you never know exactly what will surprise you. There is a chance (albeit a very small one) that the amount that the pot gets rotated from pedal up to pedal down position could differ in this pedal (vs. the normal 500K pot pedal). I strongly doubt that's the case but if so, you might not want a 500K pot, a 250 or even 100 might be better (it's a trial and error thing). You can buy low quality pots very inexpensively from radio shack if you want to experiment with different values before buying a good one.
I saw allparts had a wide range of pots. I've used their inexpensive ones on regular guitars but never the better ones, so no knowledge there. Probably the Allen Bradley or Dunlop for around $25-30 is the way to go.
IF you want to give it a try, I think I would disconnect the white, yellow, green, and orange wires at the pot and jack ends (and use those two jacks). You might want to make a diagram so the pedal could be returned to original if you decide to. If you don't have a lot of soldering / desoldering experience, you might clip the white and yellow wires an inch or two away from the pot and solder to the wire ends. You can damaage these pots very easily if you overheat the terminals (the jacks are pretty tough).
If you need advice on soldering technique (and desoldering technique) or in relating that schematic to the parts actually sitting in front of you let me know.
If this all gets to be too much, you could see about swapping with someone for a less exotic but working pedal.
Regards
Harvey |
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Mike Wheeler
From:
Delaware, Ohio, USA
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Posted 13 Jul 2007 6:53 am
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Mark, you have mail.
_________________
Best regards,
Mike |
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Mike Wheeler
From:
Delaware, Ohio, USA
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Posted 18 Jul 2007 5:22 pm
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Mark, you have mail again. 
_________________
Best regards,
Mike |
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Mark Wayne
From:
Wisconsin, USA
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Posted 18 Jul 2007 5:34 pm
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Thank you sooo much, Mike!!!!! You win the "Guy Who Can Fix The Pedal From The Past" award  |
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