I just performed a Fromel Electronics Supreme Mod Kit modification to a Fender Blues Jr. Before there was no really noticeable noise while idle (no input signal), but as soon as I performed the mod there seemed to be an excessive amount of static-y noise while idle. Is it possible that the mod just exacerbated the noise? Or did it cause it? Anyway, I followed the mod instructions to a tee. All solder work is solid (I have extensive soldering experience). There seems to be isolation and continuity where there should be (with regards to modified parts of the circuit: a few large electrolytic filter caps (C25, C26, C27, C28), filter caps on each of the EQ bands of the preamp (C5, C6, C7), a new bias resistor (R52), a couple small filter caps (C1 & C4), and a new input jack). Electrolytic caps were installed with correct polarity. I was also instructed to twist the heater wires. The power and preamp tubes are new (I even swapped out some of the old tubes one at a time to see if it was a defective new tube). I have double checked my work. Any suggestions for troubleshooting this noise? It's really unusable as is.
Mostly loud crackles and pops. Schematic here:
https://www.thetubestore.com/lib/thetubestore/schematics/Fender/Fender-Blues-Junior-Schematic.pdf
https://www.thetubestore.com/lib/thetubestore/schematics/Fender/Fender-Blues-Junior-Schematic.pdf
Thanks, but we will also need the
The original schematic as shown had no problems.
schematic and instructions.
The original schematic as shown had no problems.
then it should be dead quiet...you need to revisit your solder technique.....with a magnifying glass and some flux
My soldering is not the problem. I used magnifier, flux and tested for isolation/continuity. And I have extensive soldering rework experience. Just don't work on guitar amps all that much.
ok so it's a case of the input being miswired because without a jack inserted your input should be seeing ground and if it's not quiet then watch out snap and crackles are usually an indication of an intermittent connection or it's due to new mods!
i've reversed and refitted a few Fromel mods but most of the troubles where due to poor workmanship...
i've reversed and refitted a few Fromel mods but most of the troubles where due to poor workmanship...
Ok, cool. Thanks. Maybe I'll just try putting the old jack back in first. See if that helps at all. There really wasn't anything wrong with it.
i guess i also would be questioning the validity of the mods but even with 30+ years in servicing and building can't count how many times i've been caught with overlooking simple things.
if there really wasn't anything wrong with it why in god's name would you mod it?
if there really wasn't anything wrong with it why in god's name would you mod it?
Well, if it is, then it's the new jack that's causing problems (might be the soldering, might be the jack itself).
If it is not, then something else went wrong.
If it is not, then something else went wrong.
I believe not.
I suspect the input-to-ground connection (which should be present when nothing is plugged in) is bad. If the input-to-preamp connection was bad, we'd already heard about it, I presume.
I suspect the input-to-ground connection (which should be present when nothing is plugged in) is bad. If the input-to-preamp connection was bad, we'd already heard about it, I presume.
FWIW Fromel Mod instructions DO NOT MATCH SCHEMATIC nor show a schematic of its own, so *anything* might have been done to that poor amp.
Fromel says ... then reality:
* Treble cap numbered C5 ... schematic calls it C25
To boot original is perfectly competent "250pF x 1kV", presumably ceramic ... Fromel substitutes it with 250pF silver mica, unknown insulation voltage.
Myth says "they sound brighter ... more transparent" .
fact is they were preferred for RF circuits ... in the 40´s ; in any case no difference at audio frequencies.
* then they replace other caps by WIMA brand ones.
I would expect any changes to be caused by different capacitance, not brand.
And again part designations do not match.
Fromel says ... then reality:
* Treble cap numbered C5 ... schematic calls it C25
To boot original is perfectly competent "250pF x 1kV", presumably ceramic ... Fromel substitutes it with 250pF silver mica, unknown insulation voltage.
Myth says "they sound brighter ... more transparent" .
fact is they were preferred for RF circuits ... in the 40´s ; in any case no difference at audio frequencies.
* then they replace other caps by WIMA brand ones.
I would expect any changes to be caused by different capacitance, not brand.
And again part designations do not match.