|
Home
/ FAQ
/ News Classifieds / Events |
Audio Asylum Thread Printer |
Get a view of an entire thread on one page |
66.32.82.115
In Reply to: RE: Runaway 7581A posted by FenderLover on July 03, 2009 at 05:38:01
I will certainly check the resistors on the sockets. I have seen them burned completely open on other Fender amps.
What I think I'll do is offer to sell my friend the pair of used/good GE 6L6GCs I have. They match well, and look *exactly* the same as some GE 7581As on eBay at the moment. They also showed the least sign of even incipient grid emission of any pair of tubes I tried in the amp. I'll let him play the amp and see if he likes them. I'm not a guitar player myself, and I have no amps that use a pair of 6L6s. The Leslie amps I have require a matched set of four. I have two other GE 6L6GCs, but one of them is extremely microphonic, as I found when I installed them in the Leslie. It set up an interesting howl.
David
They sit in a pretty hot enviroment most of the time (during use, of course). Use same wattage rating resistors, nothing fancy, as you want them to act as "fuses" for the power tubes*.* (I know that you prolly already know that, but Fender INSISTS on the disclaimer). :^)
Edits: 07/04/09 07/04/09 07/04/09 07/04/09 07/04/09 07/04/09 07/04/09
T, since you've worked on Fenders, ever see a pink ceramic based STR 415 (6L6GC) or STR 416 (6CA7). I believe both were special issues the 415 for Fender's Evil Twin and the STR 416 for the Mesa Boogie Mark III. I'd love to get a pair or two of each, NOS.
I have to talk to old guitar amp nuts who actually remember these tough, great sounding tubes. I remember someone actually put nearly 700 VDC on those STR 416 and they hardly glowed. Remember the blue and red glass Tesla E34L's?
I've heard of those pink-based tubes, but I've never seen one.
I'm just starting to work on Fender amps. Some of the designs seem pretty hard on the miniature tubes, running them at excessive plate voltages, etc... I guess these were designed back when tubes were cheap.
Yeah, but a lot of amps run plates at high voltage. I remember working on a CJ monoblock that ran a hefty voltage on the 6CG7. Gotta be sure that the cathode resistor/bypass caps are within tolerance, so the current draw is ok. And coupling caps are ok.
BTW... if you drop the plate voltage, sometimes the great headroom of the amp kinda goes away. As well as the crunch in the overdrive. Anyhow, need for quiet gain stage tubes (esp the first stage) is a must. I like BP RCA 7025 or Euro (TFK or Philips made) ECC83 in that position. They give nice overdrive and stay quiet, despite the crazy abuse.
Post a Followup:
Top of Page ]
[ Contact Us ]
[ Support/Wish List ]
[ Copyright © 2009, Audio Asylum, all rights reserved ]
[ Go Green ]
[ Take5 ]