Randall RD50 question?

[chris osborne]

Hi everyone! I bought one of the older rd50 combos from a guy locally and it had supposedly received the fortin mod from a local amp tech. What I've noticed so far is that there doesn't seem to be as much gain as there should be, it's quite harsh and bright, and if the volume is ran past 4oclock with the gain also fairly high then it sounds as though the speaker is blown. Back off the volume control a bit and it goes away. Does this at any master volume setting and on both channels with the gain and volume both up and boost engaged. Not sure what could be wrong or what to do as I can't find a schematic online for the amp as it should be with the Fortin mod in place. I did roll all the preamp tubes to rule that out. Any help would be much appreciated!

Chris

 

[squank]

Are you sure it's not the speaker?

 

[chris osborne]

Positive. The actual volume can be cranked via the master and the speaker is clear. The issue occurs when the overall gain is increased by running the channel volume very high.

 

[nico22]

maybe you could try with new pre tubes...

I have the RD50 schem with the fortin mod, from sloclone forum, pm me your email....

 

[crankyrayhanky]

To 100% rule out your current speaker, try connecting another speaker cab if you can. Your poor experience is not what I had with the rd50 head at all.

 

[squank]

Positive. The actual volume can be cranked via the master and the speaker is clear. The issue occurs when the overall gain is increased by running the channel volume very high.

Ok, then it's most likely a bad preamp tube. Swap them out one by one (powering down the amp each time you do it, of course), and you'll probably find the culprit.

 

[chris osborne]

Thanks so much for the replies! I tried rolling a new tube although it i possible that more tha one tube could be in trouble. Pm sent on the schematic!

Chris

 

[chris osborne]

maybe you could try with new pre tubes...

I have the RD50 schem with the fortin mod, from sloclone forum, pm me your email....

Since I don't have many posts here yet, the PM function is unavailable to me but I did send you an email. If you didn't get it though my email address is chris@swordpolish.net. Thanks so much for offering the schematic, that will definitely help!