Problems with RG50TC

I need help with my first tube amp, it is a Randall RG50TC.

The clean channel sounds nice, the volume is fully working, and all the tubes are warming up but the overdrive channel is sounding like ****, like a low gain SS amp, I have 3 more 12AX7 that I replaced and tested in different ways but the problem persists, almost no gain and ****ty sound on the distortion channel.

I don't know, maybe all my preamp tubes are bad? Maybe somebody experienced this before.

Something strange happened when I was testing the tubes.

One of them is a 12AT7EH and is known as the phase inverter (or someting like that), this tube was working nice but suddenly stopped working and I had to use one 12AX7 in replacement (when it happened the volume in both channels got reduced like 80%). Anyway the problem is still there, is like the distortion I am getting is not from the tubes, just the circuit gain or something.

I noticed something else too, when I try to play in the overdrive channel with the channel volume almost maxed the sound fade in and out when I hit the strings hard.

try another 12at7. The 12ax7 is a higher gain version of the 12at7. It might be overloading it. I would try some more 12ax7's in the pre amp and see if that makes any difference. Other than that, there sounds like theres something wrong with the drive channel. take it back.

thanks for the help. This is the mail I sent to the randall contact that is in the webpage.

It looks like I am screwed. I am really dissapointed and sad, for this amp I saved money for two years , when I had the chance to travel to the USA I bought it but I made a big mistake, buying it online, then I hadn't time to try it or return it, I had to come back and I just took the risk, I was thinking about getting a Bugera but I didn't because of its realiability issues and look what happens.




So, if anyone knows another contact to try, maybe another mail it would be a great help. Thanks.

Try ringing them, the number is at the bottom of the web page.

Just to add, you can either use 6l6 valves or EL34's in the amp. The amp just needs to be re-biased for either sets.

My tech said me today that he cant find the problem, he says that all the tubes are working fine and it looks like everything works fine in the amp so its strange and he cant do anything more for me. The problem is he doesn't have all the troubleshooting info about this amp like some points to measure the voltages and that because it isn't a very common amp.

I am calling them if they not reply my mail. Thanks.

Now I am taking the amp to another technician , It looks like a problem in the circuit and only in the Overdrive Channel part.

And I am convinced that the problem is related to the fade in and out that is produced when I turn up the overdrive channel volume, I read that it could be a resistor.

As amps go this one's a very complicated amp. It does sound like you have some sort of component faliure. Bummer, hope you get it sorted out.

Yeah, it looks like some component is failing and is up to the tech saving my *** now. I will have news in some days but this is my last chance here, then I will have to look for help in the guarantee and thats in the USA, that would cost a lot from shipping.

Thanks for answering, this forum looks like a desert sometimes.

Aye, I noticed not everyone replies to threads, even if they have nothing to add!! :wink: Where abouts are you? If your in England there's a guy here thats helping me out modding mine. If your over here I can pass over his number.

Thanks but sadly I am not in England , I am in South America .

Hopefully I can find another technician , but I have hope in this one.

Hey, don't feel bad. I'm in the US and we've got techs here who only think they know what they're doing and are very poor at communication -- I think that last part comes from being in a back room with a lot of equipment daily with little or no human contact.

I looked at the manual online and it doesn't really tell you anything.

Please list your amp settings.... these can have something to do with it. Don't run your bass too high. That will cause mud.

Typically you can replace a 12AX7 with a 12AT7 but usually it doesn't work well going from a 12AT7 to a 12AX7. Get yourself some JJ ECC83s or Tung Sol 12AX7s for your 12AX7, and get a Tung Sol 12AT7.

Also turn your amp so you can watch the power tubes. While they may be in range, you may just have a weak tube, but check this first.

Unplug your guitar cable at the amp, unplug your cables to and from the effects loop, turn all the volume knobs to zero. Now turn the amp on like you normally do. Turn off the lights in the room so it's dark. Watch the tubes for about 20 to 30 minutes. Look for any blotches of red on the tube plates. If you see them you may have 1) too hot a bias setting, or 2) a tube failing, or 3) both.

Now if everything looks normal, turn the amp on standby and plug in your guitar. Now turn on the amp and play in the dark and watch the tubes. If one starts doing the blotchy red thing or starts glowing on the plates you've got a bad tube. I've had this happen and it'll make the amp sound like feces. The amp will be as loud as ever but .... turn it off and it's time to replace the power tubes and rebias the amp.

I know. More money going out.

Thanks for the support, I am waiting for news in the nex two days, the last thing I am gonna do if everything fails is change the tubes, but I dont think that's the problem since the tech that saw them says they are ok.

I tryed with a lot of different settings too but I am sure the problem doesn't come from that way.

Anyway thanks for the tips, I am gonna play in the dark a little

Today my technician found and replaced some shorted components in the amp (like 3 resistors) that were causing the sound fade out I mencioned before, now it sounds better but there is still some problem with the tone. He will be looking for more bad components in the pre stage.

I really have bad luck, a lot of shorted components in a new amp? WTF?

There's nothing worse than having a new toy not work properly. I'm gutted for you mate. Bummer.