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svengali
Bronze Member
Australia
111 Posts |
 Posted - 07/25/2007 : 13:00:29
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hello, i just fixed an od 1 (jrc4558d) that was hissing. It was hissing awfully with both dials at twelve oclock.
Sounded like a stock ge 7 with some sliders turned up.
Anyway, i replaced the four polarised caps with new ones and bingo. No hiss. These 8 pin od 1 pedals are good btw
svengali |
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Dr. Bob
Moderator
Australia
6593 Posts |
Posted - 07/25/2007 : 16:00:12
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Hi svengali
Thanks for sharing your Technical & repair knowledge about your OD-1.
You obviously changed the 4 small value interstage caps?
In the audio path.
There is also a 5th cap, the 100uf in the power supply section.
Did you change that as well?
Edited:
Sorry svengali & Guys
I was looking at the 14 pin IC version, it has 5 caps
The 8 pin $558 version only has 3 interstage caps & the filter cap 
Did you use electrolytic caps, or mini non-polarized types?
I am fortunate enough to own an ESR Meter.
I have been measuring lots of various caps from a collection of assorted pedals, & it does seem that a lot of the caps are exhibiting High ESR.
I would be interested in measuring the value of the caps you just replaced in your OD-1; If you still had them.
I'm guessing, we are going to see many more faults associated with caps that have risen in ESR
Do you do much Tech work? Or is this a hobby for you.
Regards Dr. Bob 
PS -- ESR Equivalent Series Resistance -- Internal resistance of the capacitor, Low = Good .... High = Bad.
For more info Search your favorite search engine.
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Edited by - Dr. Bob on 07/25/2007 16:14:13 |
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svengali
Bronze Member
Australia
111 Posts |
Posted - 07/26/2007 : 02:14:01
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hello doctor bob.
electronics is a hobby of mine, but i play in a band and i am always torturing the neighbours at home. Lately ive been getting too many complaints which has rekindled my interest in od pedals, which allow me to play quiter, but retain some grit.
I tested these polarised caps after i replaced them. Interestingly, they were not far off spec ( 10-20 percent ) . from memory, they were a 100 uf, 47 uf, a 10(1?) uf and a 1 uf.
I replaced them with polarised electrolytic caps of the same value.
Also, it was obvious after i changed out these caps that the tone thickened up considerably, the pedal now isnt as bright. To try and find the culprit, i did smell each cap and in fact it was the 100 uf that had the most electrolytic odour.
Pls note that the hiss made this pedal almost unusable.
Inspired, i then replaced the five polarised caps in my fourteen pin rc3403adb od 1, which did function without hissing. These caps all reeked of that electrolytic smell.
The result being that again, the tone has 'thickened' up, and both these pedals sound more tubey, more like a ts9 if that makes sense.
regards
svengali
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ChristoMephisto
Platinum Member
Canada
1288 Posts |
Posted - 07/26/2007 : 17:12:29
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When you worked on your 14 pin od-1, did you replace the caps with the same value? I ask because the od-1s have a slighty different cap and resistor setups. It gives you the same corner frequency of 338MHz.
Your saying its beefier now, could you have lowered your lowcut/hipass adding more bass. Or anywhere along the tone line.
I don't have the references with me, far from home...
A point of interest, the ts9 and the sd-1 are similar in design (i would say the od-1 also, but it has no tone knob)
Pacifelix has some good pics of his two od-1s, with bth 8 pin and 14pin versions.
A popular modding trick is to replace the electro caps with nonpolarized caps like a metalfilm. This gives better fidelity |
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stahlhart
Platinum Member
1318 Posts |
Posted - 07/27/2007 : 00:20:43
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quote:
Originally posted by Dr. Bob
I'm guessing, we are going to see many more faults associated with caps that have risen in ESR
What I find to be most daunting is that capacitors don't have date codes, and the troubles associated with electrolytics are primarily due to aging of the dielectric materials.
It makes it somewhat challenging to buy replacements, as you're going to have to trust that they were more recently manufactured than the ones they're replacing. Here in my neck of the woods, there's an electronics store that has stock hanging on the pegs that's so old that the blister packaging has yellowed.
Used to be that old tube equipment (amplifiers, radios, etc.) was what was most often in need of being "re-capped"... now we've all been at this long enough to see solid state gear start to share the same fate. 
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svengali
Bronze Member
Australia
111 Posts |
Posted - 07/27/2007 : 01:59:09
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hello again,
i did manage to replicate the capacitance values exactly in both pedals, but not the voltage. That is, the voltage rating on the replacement caps did not match the originals. We are talking 25 volts instead of 16 etc. Im sure this will not affect tone.
after the cap swap, the tone was definately thicker,at least in the mids to upper register, and definately not as clear, refined. This may be a consideration for someone who does not have a malfunctioning pedal, and who does not want their tone altered in any way.
A nice mod, if one wanted to bother, would be to attach a switch and several caps to the most relevant interstage junction.
Note here that analogman writes that it was the changing of caps, not the ic chip, that mostly altered the tone of his first od 1 experiments.
I do think that mods of this type to this pedal are a waste of time.
I mean, just plug the thing in and let it rip.
svengali |
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hissing pedal fix
