#1
So I traded my bugera the other day for a randall rh50t, and it sounds pretty sick, no doubt. When I traded the amp the guy said that their was a problem with the overdrive channel, when you turned the level up past halfway, the volume would cut intermitently. He attributed this to a bad preamp tube. I figured thats what it was. well, I go home switched the preamps out and it didnt fix it. I thought id have a look at the innards, and while fiddling unplugged the built in the spring reverb. This solved the problem. First I figured that the tank had just gone bad, so i plugged another one i knew worked into the amp. still no dice. I tried new rca cords from the other tank, nothing. So, I come to the brilliant minds of UG to help me. I love the amp, and I can live without the reverb, but its such a bangin' amp, I really want it to work completely. Plus, its spring reverb, c'mon, awesome for when i wanna impersonate old blues and country players. Thanks in advance guys, Im feeling confident I can fix this if I just get some ideas of where to look.
I'm just a kickin' and a gougin' in the mud and the blood and the beer.
#2
i forgot to add, the clean channel is consistently quiet with the reverb plugged, not intermittent like the overdrive channel
I'm just a kickin' and a gougin' in the mud and the blood and the beer.
#3
Hey dude

this seems more like a power tube problem honestly but:

how many preamp tubes are there total?

have you tried contacting Randall?

do you have a schematic?

why did you buy this amp knowing there was this issue?

seriously - if someone told me the volume cuts out after Noon and it is because of a preamp tube, that would have been a warning sign for me. bad preamp tubes usually do not affect the volume. Power tubes do though.

I would hit the reverb jacks, preamp tube pins and power tube pins with some contact cleaner one at a time and work the tubes in and out a bit to get that cleaner down in the socket. Try to avoid spraying it directly into the socket. You can also try swapping some of the preamp tubes around as well as swap your two power tubes around. I don't think you can manually bias the amp but that may be something to do too (but that won't have much to do with the volume problem)

Lastly - it may be a bad Volume pot (potentiometer) You can spray some contact cleaner in there as well if the amp is opened up (can be dangerous).

report back
#4
Is there a tube driving the reverb perhaps?
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#5
Thats what i was thinking. Perhaps i can see if there is, there is a schem, pretty easy to find i googld it no prob. Ill see about the tube driven reverb.

311- I really dont mind sinking some momey into this bad boy if i have to, i really the amp, so thats why i went for the trade. The reason i think its the reverb is it ONLY cuts out when the tank is plugged in, but if their is a tube driving it, then that would explain it. With the reverb not plugged in, it works and sounds great. Im going to try contact cleaner on the reverb inputs and report back.

Cath- im going to look at the schem and figure out if the reverb was tube driven. I have a feeling it might be.
I'm just a kickin' and a gougin' in the mud and the blood and the beer.
#6
Oh, i should mention, the volume doesnt just flat cut, it more kind of jumps every now and then, similar to how id expect the reverb to act if it worked, like in all the places id expect reverberation theres cut. I still havnt tried contact cleaner, i have contacted randall though. Thanks again guys
I'm just a kickin' and a gougin' in the mud and the blood and the beer.
#7
Alright, tried contact cleaner on the inputs and outputs of the tank and the amp, still isnt helping. I found a schematic, If you guys wanna look at it and see if you get any ideas. my schem reading skills are still kinda lousy, im an infant in the electronics world.
http://www.echostar.pl/~zelman/RG50TCSchemat.pdf here it is, it is a schem for the combo version of this amp, which as far as i know should be the same except the inclusion of a speaker in the schem. thanks guys, youll probly have to copy paste it into the address bar.
I'm just a kickin' and a gougin' in the mud and the blood and the beer.
#8
I can't find where the reverb connects in to everything, could any one point me in the general area of where the tank is located on the schem?
I'm just a kickin' and a gougin' in the mud and the blood and the beer.
#9
Quote by dementiacaptain
I can't find where the reverb connects in to everything, could any one point me in the general area of where the tank is located on the schem?


The tank isn't in the schematic, it's not a part of the amp's innards...

The problem may be with the reverb recovery circuit. Not sure how, though.

It could very well still be a power tube problem, though, and you might want to change those regardless of the volume issue since you're using old power tubes from a used amp and all.
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#10
Quote by Raijouta
The tank isn't in the schematic, it's not a part of the amp's innards...

The problem may be with the reverb recovery circuit. Not sure how, though.

It could very well still be a power tube problem, though, and you might want to change those regardless of the volume issue since you're using old power tubes from a used amp and all.


fair enough. It has 5881s in it now, it normally takes el34s. would someone have to change the bias to run the 5881s, and will I have to change it back to run the 34s? those are the only kind of spare tubes I have right now. Also, thank you, I wasnt sure if it would be, since the speaker was on there, and I didnt think the speaker normally would be. so would the inputs for the tank be on there? Im just trying to trace it out so I know what parts I should check.
I'm just a kickin' and a gougin' in the mud and the blood and the beer.
Last edited by dementiacaptain at Sep 29, 2011,
#11
i changed out the power tubes, somehow the reverb is fixed, i think that somehow my noise gate is screwed up though. not a super big deal, but still, hundred dollars of noise reduction gone, and i liked that hundred dollar bill. whenever i activate it sucks away my highs, it muffles it, and it didnt use to do that. weird..
I'm just a kickin' and a gougin' in the mud and the blood and the beer.