No bias reading rm50

[zombieskank]

I am not getting any bias reading I replaced the 2 back 250mA fuses. The tubes glow still I am not sure about sound because I just shut it down quickly

 

[shortlife]

I had the same issue with my Rt2/50.
I had a bad 12ax7 and a bad power tube, after I changed them everything worked normally again.
I don't know how a Rm50 has all the tubes in the power section laid out but I imagine it is a similar issue.

 

[warmachine67]

There are some internal fuses on the
RM50s that you can only check with the chassis out.

I think you may have blown an internal 100mA fuse (F3 maybe) on the bias circuit only.

A decent tech should be able to replace it, or you can if you are knowledgeable about the dangers inside a tube amp.

 

[zombieskank]

How dangerous or difficult would it be to do this on my own?

 

[warmachine67]

They are inside the amp. Based on your response, I would say take it to a tech. I don’t know your skill set and wouldn’t want something bad to happen. It would probably be a $50 fix.

Don’t mean to discount you in any way, electricity is invisible, so the risks aren’t apparent.

Mattfig with motorcitymods has a tutorial on YouTube showing how to install a salvation mods MDA board that would be worth viewing.

Worse case is you could suffer electrical shock, worst case is an electrical burn and possibly death. Even worst than that, you might foul up your amp.

 

[Spencer4hire]

Are you sure the amp is in play mode and not on standby? You will not get a reading if it is on standby.

 

[warmachine67]

Spencer brings up a good point.

Anyways, with the amp not on standby and the master all the way down, if the tubes aren’t red plating, you should be ok to play with your multimeter for a few minutes and rule that out.

As long as the speaker is connected and the amp all the way down, it won’t let the smoke out immediately.

 

[zombieskank]

I checked the stand by thing as the first thing I tried because I have made that mistake before haha. That’s a good tip