Tube Amps / Music Electronics
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|9/25/2000 4:03 PM|
||SF Deluxe reverb, output tube problem|
Could not get a set of Phillips JAN 6V6 to bias without some red glow. They sounded awful. While adjusting bias current down, ( reducing but not eliminating glow), fuse blew, rectifier tube blew ( also a phillips 5u4gb).
I replaced rectifer with a GE,replaced the fuse and used two old RCA's from my Champs. Bias set up mid range and the amp sounds great.
Did I exeperience the fabled deluxe problem of newer tubes exceeding their rated plate voltages ?
The plates are running at 427 volts.Randy
|9/26/2000 1:25 AM|
You know more about biasing and such than i but i have heard that Philips 6V6's don't sound good in Fender BLK/SLVFC Deluxes.
|9/26/2000 3:19 PM|
That's not true. These tubes sound fine in Fender amps. They may not be as desireable as RCA's but are a huge step up from the Russian and Chinese 6V6s.
|9/26/2000 7:42 PM|
Speaking of 6V6's! Anyone knows how Sylvania 6V6GTA (USA) sounds and works? Do they handle 400+ Volts?
|9/26/2000 9:23 PM|
I believe these are essentially the same tubes as the JAN Philips 6V6GT. During the mid-1980's, when Sylvania halted production of the STR 6L6GC tubes, PhilipsECG bought all the tooling and continued to make these exact same tubes (only for a couple of more years, unfortunately) but now with their own labeling. My guess is that the same thing happened with Sylvania's 6V6GTA tubes.
Does the tube you're talking about have a black plate structure, where there's a vertical seam in the middle of one of the curved sides but not the opposite one? If so, then I'm pretty sure its the same tube. It should handle well over 400 volts. Probably even up to 460 volts or even more, as long as it's biased such that plate dissipation is kept within reason.
No matter which 6V6 tubes you wind up using in a Fender Deluxe or DR, it's a real good idea to increase the screen resistors from 470 ohms to 1K/2W, for a some extra screen grid protection. I've started to do this in my customers' amps.
|9/27/2000 5:23 AM|
Yes, the plates looks just like that!
I have a small stock of these tubes, that I've got from an air base, and it's good to know what they're capable of. They are probably made around 1970-71, since they were first tested in nov. 1971.
|9/26/2000 3:07 AM|
Are you sure you were reducing the bias current (raising the fixed bias voltage, if modded, or increasing the cathode resistor value)? If you've blown a fuse, and the rectifier (5U4s are really rugged beasts) it sounds like your current was increasing.
While excessively higher voltages do shorten tube life they generally don't kill tubes with a shot to the head - more like a tobacco smoker's demise.
What is, and was, your measured bias voltage and idle current and how did you measure these?
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