Origin 5 input mod problem

Dave_11

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I did the Class 5 input mod, which is supposed to work the same for the Origin 5, tonight on my Ori 5:

Replaced R20 with a 1 Meg ohm resistor
Removed C10

But now there is no sound. All tubes are glowing. When I turn the amp up I can hear a light hiss, but no sound from the guitar. Tried 2 cords and 2 guitars, and got the same result. Re-flowed the solder connections on R20, but still no sound. What looks like a little jumper wire coming from the input jack is plugged in snugly on both sides.

I'm no electronics guru, but this seems like a fairly straightforward mod. Any ideas what is wrong?
 

Dave_11

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Thanks - I plan to do that tonight with the resistor. Unfortunately I broke one of the legs off the cap when pulling it and don't have another. I may be able to cannibalize an old radio for one. I think this cap is specd at 500V - does it have to be that high?
 

Dave_11

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Replaced the original resistor, but still no sound. I plugged the guitar into the effects loop and got sound, although the tone is very bassy with no treble. I guess I'll have to order a new cap to see if that restores functionality.
 

Brek

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Replaced the original resistor, but still no sound. I plugged the guitar into the effects loop and got sound, although the tone is very bassy with no treble. I guess I'll have to order a new cap to see if that restores functionality.
I have done same mod on mine, don't you have to bridge c10? cannot be 100% on that though did my mod a couple years ago.
 

Gene Ballzz

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Yes, there needs be be a jumper wire in place of that capacitor! I did all the full Lyle Calwell mods to my Class5 and decided I liked it better stock and simply enjoy it for what it is! With my new SV20H and a 5E3 Tweed Delue "in da house", the Class5 is pretty lonely!
Just Screechin' & Squawkin'
Gene
 

Dave_11

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Thanks for the tips. I soldered a jumper into the C10 position but still get no sound -- with either the original resistor or the 1Meg resistor. I get sound with a guitar plugged into the effects loop.
 

thetragichero

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cap on the input prevents dc from going in (or out). if it's sufficiently big enough to allow the full signal through (without the schematic in front of me i'm guessing it's a larger than needed electro cap, in the range of 10-47uf like you might find in a slo)
 

Dave_11

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I found a 47pF cap in a junk radio and soldered that in, but still no sound. I guess I'm out of ideas...
 

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