RT2/50 "humming"

[m0jo]

You have a ground loop. What else is in your rig? Have you tried the preamp directly into the power amp with no other connections to outboard gear?

Its not a ground loop, I know what those sound like. I just have the RM4 going straight into the RT. Once again, the hum isnt there when I plug it into the Marshall PA, so Im going to bet its the tubes...

Can you record the hum?

Or describe it: very low or not, sizzling, buzzing or just a smooth tone?

Haha, yea I can definitely do that. Where can I upload it when its ready? Its really hard to describe, & perhaps hum isnt the proper description. Ill plug it in again later & see.

Ehm just throw it on filedropper or something no need for a whole soundclick account or whatever.

Yeah that's why I asked for a recording, hum/buzz/noise is very hard to describe.

Well this really sucks...I turned the amp on & now channel 1 doesnt work at all! All tubes are lit, I even tried 3 different 12ax7's. Tested tubes fron the front as well, they all get a reading. What the heck!?

Okay turn the amp off and don't turn it on again till you get advice from Randall customer support.
You can reach them at [email protected] It's said they're very quick to respond and respond adequatly, so let's put that to the test

The strange thing is, when I hear this I'd say dying tubes, but than the failure warning leds should go on and you would get a very strange reading from the bias.

 

[Eptesicus79]

You have a ground loop. What else is in your rig? Have you tried the preamp directly into the power amp with no other connections to outboard gear?

Its not a ground loop, I know what those sound like. I just have the RM4 going straight into the RT. Once again, the hum isnt there when I plug it into the Marshall PA, so Im going to bet its the tubes...

Can you record the hum?

Or describe it: very low or not, sizzling, buzzing or just a smooth tone?

Haha, yea I can definitely do that. Where can I upload it when its ready? Its really hard to describe, & perhaps hum isnt the proper description. Ill plug it in again later & see.

Ehm just throw it on filedropper or something no need for a whole soundclick account or whatever.

Yeah that's why I asked for a recording, hum/buzz/noise is very hard to describe.

Well this really sucks...I turned the amp on & now channel 1 doesnt work at all! All tubes are lit, I even tried 3 different 12ax7's. Tested tubes fron the front as well, they all get a reading. What the heck!?

Okay turn the amp off and don't turn it on again till you get advice from Randall customer support.
You can reach them at [email protected] It's said they're very quick to respond and respond adequatly, so let's put that to the test

The strange thing is, when I hear this I'd say dying tubes, but than the failure warning leds should go on and you would get a very strange reading from the bias.

Yea, I think there is a much bigger problem. I took a pair of EL34's from my other amp & put them into the 6L6 channel...still nothing. Took the cover off just to check other fuses & see if there was any evident damage, looks clean. Channel 2 still works fine.

 

[m0jo]

You have a ground loop. What else is in your rig? Have you tried the preamp directly into the power amp with no other connections to outboard gear?

Its not a ground loop, I know what those sound like. I just have the RM4 going straight into the RT. Once again, the hum isnt there when I plug it into the Marshall PA, so Im going to bet its the tubes...

Can you record the hum?

Or describe it: very low or not, sizzling, buzzing or just a smooth tone?

Haha, yea I can definitely do that. Where can I upload it when its ready? Its really hard to describe, & perhaps hum isnt the proper description. Ill plug it in again later & see.

Ehm just throw it on filedropper or something no need for a whole soundclick account or whatever.

Yeah that's why I asked for a recording, hum/buzz/noise is very hard to describe.

Well this really sucks...I turned the amp on & now channel 1 doesnt work at all! All tubes are lit, I even tried 3 different 12ax7's. Tested tubes fron the front as well, they all get a reading. What the heck!?

Okay turn the amp off and don't turn it on again till you get advice from Randall customer support.
You can reach them at [email protected] It's said they're very quick to respond and respond adequatly, so let's put that to the test

The strange thing is, when I hear this I'd say dying tubes, but than the failure warning leds should go on and you would get a very strange reading from the bias.

Yea, I think there is a much bigger problem. I took a pair of EL34's from my other amp & put them into the 6L6 channel...still nothing. Took the cover off just to check other fuses & see if there was any evident damage, looks clean. Channel 2 still works fine.

Crazy idea: check that the mono/stereo switch is in the right position!

BTW: this is epic quotage btw haha, stand back kids, don't try this at home!

 

[Eptesicus79]

Haha...

Yea, it was in the right mode. Just as a test, I threw it into Stereo mode & connected both jacks to my cab. Still, only Channel 2 outputs volume.

Im just baffled at what this could be. It worked until I changed the preamp tubes around. Maybe I loosened a solder joint somewhere?

 

[m0jo]

Haha...

Yea, it was in the right mode. Just as a test, I threw it into Stereo mode & connected both jacks to my cab. Still, only Channel 2 outputs volume.

Im just baffled at what this could be. It worked until I changed the preamp tubes around. Maybe I loosened a solder joint somewhere?

I don't think so, if that was it there would probably still be some buzz or something coming through..
I'd say something near the powertubes.. maybe the transformer.

But you really need some tech help, I think this is beyond forum advice

 

[RockManiac]

Did you change the tube fuse for your 6L6 channel or did you just took a look at it? Sometimes a fuse looks good, even if it is not working correctly. So to make sure, you should try a good fuse for that channel or put the fuse of your EL34 channel into the place for your 6L6 channel.

 

[Eptesicus79]

Did you change the tube fuse for your 6L6 channel or did you just took a look at it? Sometimes a fuse looks good, even if it is not working correctly. So to make sure, you should try a good fuse for that channel or put the fuse of your EL34 channel into the place for your 6L6 channel.

OK, heres something interesting that I totally overlooked before. The fuses for CH1 are both 400mA! The front panel clearly says to use 250mA for both channels. I thought they looked different than the ones for CH2, but didnt realize until I looked again.

That being said, I tried using the fuses from CH2, but still no dice. I could technically replace all the fuses on the PCB board & see what happens.

 

[Julia]

Fuses are easy to check. Put an ohm meter on it. If it reads anything other than "0" the fuse is toast.

 

[Eptesicus79]

Fuses are easy to check. Put an ohm meter on it. If it reads anything other than "0" the fuse is toast.

OK, I found a 160mA fuse on the motherboard that reads 0.01. All the other ones read 0. Not sure if that small increment means something, but Im going to get a bunch of replacements just in case. Thanks for the tip!!

Looks like this thread is going to become the official RT troubleshooting thread :lol:

 

[Shinozoku]

I might have suggested checking the preamp tubes but you seem to have already checked that out...

 

[Eptesicus79]

I might have suggested checking the preamp tubes but you seem to have already checked that out...

Yea, tried swapping those out already.

 

[Eptesicus79]

Get ready to laugh...

The middle preamp tube had a broken pin so it wasnt outputting to Channel 1, even though Channel 2 was still working! I guess through all the craziness, I overlooked double-checking that tube again. I assumed that only the dedicated preamp tubes on the side would be a cause of the problem.

That being said, its probably my fault that the pin was broken after I pulled it out the first time. At least it wasnt anything serious...

Thanks for all your comments!