Tech help please! Randall RT2/50 - resistor sparking

[cyndicate]

My RT2/50 was working properly until a few weeks ago.. I have the bias set right, powered it on, switched it off of standby to play position and then it starts "sparking" and making some electrical noise. I opened it up to see that the resistor on A19 is sparking, looking from the front, its on the far right. At first I thought it was the preamp tube, but its not. It only does this for about 10 seconds and you hear "pops" coming out of the speaker. Any thoughts?

**edit** I think its R19..I can barely tell if its a A or a R

 

[jkdsteve]

Will..don't have a schematic,....nor am I an amp expert but I'm thinking A19 is a tube socket and I think you already tried a new tube right?

Basic troubleshooting....if you had a schematic/spec to compare and measure what the voltage across that resistor is supposed to be...

If it's sparking at the joint, maybe it's loose...?

If it's arcing around the resistor then maybe there's some other issue (spill or conductive material across the tube socket/component?)...usually end up with carbon residue/evidence of this at some point...depends on how high the voltage is and how long it's been doing it.

IN any case I'd replace the resistor as first step...if I couldn't get anywhere after that...tech time.

 

[cyndicate]

Will..don't have a schematic,....nor am I an amp expert but I'm thinking A19 is a tube socket and I think you already tried a new tube right?

Basic troubleshooting....if you had a schematic/spec to compare and measure what the voltage across that resistor is supposed to be...

If it's sparking at the joint, maybe it's loose...?

If it's arcing around the resistor then maybe there's some other issue (spill or conductive material across the tube socket/component?)...usually end up with carbon residue/evidence of this at some point...depends on how high the voltage is and how long it's been doing it.

IN any case I'd replace the resistor as first step...if I couldn't get anywhere after that...tech time.

It's sparking accross the resistor. I swapped that preamp tube a couple of times, it looks like its for Ch. 2, I guess its just arcing at that one resistor, I don't see any carbon residue or anything, but I haven't left it on long enough for it to burn the board or anything. I pm'd Steve to help with troubleshooting it. If you want the schematic I just got one from Randall.

Let me know your email and I can forward it to you if you want it for future reference.