Need help repairing amp

[JimiRayHalen]

I have a Randall solid state amp that my son loaned to a friend. Needless to say , it was brought back with a broken volume pot. It was broken completely off the board. Of course, they say it “just fell out” but the indicator plate the pots are bolted on to tells a different story. Anyway, I changed the pot ( put a 500 ohm in place of a 100 ohm) and turned the amp on, plugged a guitar in ( with a good chord, mind you), and… NOTHING! My question is, could the pot not have a good connection? Could other pots be broken internally causing this issue? Or, could it be a jack? I tried both jacks ( one is active and the other passive) and I get the same thing on both ends ( just a very faint electrical hum) and when I turn any of the pots, I’ve got nothing. Any ideas anyone? Where do I start?

[tedmich]

Pictures please! I typically start with the most obvious damage, like you did, then proceed from there! 100 Ohm volume pot is a bit odd but SS can be that way, a picture is worth 1000 words (maybe more here ; )

[Enzo]

OK, so the broken pot. Was it broken off where the three legs come out? I'd wager what happened to that pot probably happened to others on the panel. They could be not snapped off completely but still cracked. ALso check the pc board they solder to for cracks.

How do pots break? SOmething can fall onto them, like a guitar propped up that falls over, and the headstock WHAXKS the controls. Or the amp falls on its face onto something. Or bouncing around in a car trunk it gets whacked. An amp that gets dropped can snap off parts. Etc etc.

[Jazz P Bass]

"Randall solid state amp"

Amplifier model please?

[Amptech47]

Hello to all, new member but not new new to the amp repairs trade...I second what Enzo stated, check the whole front end under strong light with magnifier glass and as for the pot being a 100 ohm thst is a little low for that as it may be 100k or 50k.

I'd look at the schematic drawing and trace it out.

If more help is needed I'm sure your find it.

Kind regards.

[vintagekiki]

Randall schematics

https://el34world.com/charts/Schematics/Files/Randall/Randall_Schematics.htm
https://www.schematicsunlimited.com/r/randall
https://elektrotanya.com/showresult?what=RANDALL&kategoria=All&kat2=All
http://spaceryerson.com/pics/img%20RG80-A-SCH234.jpg
https://www.scribd.com/doc/278908103/Randall-RX120D-Amplifier-Schematic ¹⁾
etc ...

[vintagekiki]

#5
pot being a 100 ohm thst is a little low for that as it may be 100k or 50k.

Do you have a measuring instrument, for example an ohmmeter and measure it.