RM22 Bias setting

[crazyeddie]

Maybe I'm losing my mind but for the life of me I can't find the bias voltages for an RM22. HELP!!!!

 

[JKD]

EL84s - 18 to 22mV from memory.

 

[crazyeddie]

Thanks JKD. After looking again I found the following thread:

http://mtsforum.grailtone.com/viewtopic.php?t=17188

 

[crazyeddie]

*Update* Concerns NEW amp purchase. PLEASE read...

I probably should know better but when i received my new RM22 I just plugged her in and fired her up. I was having a good ole' time when I decided to try out the boost function after about a half hour of tweaking the settings. There was a popping sound and all of a sudden it was like I turned the amp down to where it was barely audible. I thought maybe I had the boost volume turned down. No, that wasn't the case. In fact it was almost at 3/4 volume. I put it in standby mode for about five minutes after killing the boost and after taking it off of standby the amp was purring along again. I decided to shut it down until I could check the bias setting on the power tubes.

I have only had the amp for a week and only just had a chance to fire it up yesterday. After finally finding the bias adjust voltage settings I set it up and checked the voltages. My readings were test pt#1 = 15.7mv. Test pt#2 = 8.5mv. So after attempting to get the tubes biased my best results were test pt#1 = 20mv and est pt#2 = 13.6mv. Readings should be between 15mv and 20mv. Also, according to other MTS amp bias instructions when I plug my black lead into test pt#1 and red lead into test pt#2 I should preferably have a reading less than 5mv. I am at right around 7mv. I'm thinking new tubes are needed.

Since I just got this amp last week should I contact the place I got the amp from or should I contact Randall directly ( I don't want to mention the dealer, but they are an authorized Randall dealer)? I haven't even registered the amp yet. I think I should be getting a new set of power tubes since the manual explains that tubes carry a 90 day warranty. However it also states that I have to ship the entire unit for service?

Anybody run into this type of situation before? I have a full 30 day no questions asked return policy from the place of purchase, but from the short time I had with it I would rather keep the amp. I just don't want to be jerked around having to ship the amp for service. I will need backup tubes and will get probably a couple of sets if I keep the amp but it still frys me that my new amp already needs new tubes after a half hour of operation.

 

[BigBrewtus]

I would ask the store to see what they could do. The tubes just are enough of a match obviously but I am not sure they will do more than maybe try another tube or replace both. Hoping that the volume problem you had was just a tube mix-match though. Either way I would let the store know and see what happens.

 

[crazyeddie]

Unfortunately the tubes weren't the main problem. Installed a new set of tubes and the bias was easy to dial in. less than 1mv difference. After about 5 minutes of less than moderate volume it just stopped producing any sound whatsoever. I immediately put it in standby mode and turned down all of the control pots to re-check the bias. The bias readings were 70mv and climbing and I couldn't dial it in any more. So I shut it down immediately and will be taking it in to the shop for repair. I think I have a blown OT. Surprised I didn't pop a fuse, hoping I didn't fry the new tubes....

 

[crazyeddie]

Dropped off the amp today. Hope to have it back in a few weeks.....Thankfully the RM50 is still chugging along just fine.....