Randall Clean Mods Question

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lightwoheat

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@ Grail.com the following is listed as a mod

Randall Clean Mods
There was an issue discovered after several production runs in all the clean to mid-gain Randall models including the Clean, Blackface, DLX, Top Boost, Plexi, JTM, & Brown, that causes excess distortion overloading the input gain. Too eliminate this issue and clean up these modules, position R1 which is a 470 ohm 1/2w resistor, needs to be changed to a 150 Ohm 1/2w resistor. This is only the early production Randall models and some of the early Egnater models. The new modules have been fixed at the factory but you should check any current module that you have. You can identify what value is in your module by the color bands located on the resistor, 470 ohm resistors have yellow, purple, and brown color bands, where the correct 150 ohm resistors have brown, green, brown color bands.

R1's purpose is to control the Opto Coupler (Optical Switch) and has no connection to the actual audio signal, thus I don't understand why this would have an overloading affect on the input signal causing distortion. Also all of the PCB files (Top level view of board) show R1 as still being 470 Ohm and not 150 as mentioned above.

Does R1 actually have the affect as mentioned above? If it does can you explain why?

Thanks,
FM
 
I made the mod to my TopBoost and it made a substantial difference in the nasty input distortion that I was getting with fairly hot pickups.
 
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