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Monster Fender rig - 400 PS
Rob:
--- Quote from: Psycho Bass Guy on January 24, 2014, 04:43:25 PM ---They DO NOT have three output transformers. They have three taps on the transformer secondary split from a single primary winding. I HAD one until I sent it away for cosmetic restoration and it, the nice set of NOS GE 6550A's, and the custom roadcase it was in disappeared into New Jersey.
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Thanks PBG! I was trying to figure out what the third trans would be for :o
Ummm Jersey Devil?
Psycho Bass Guy:
--- Quote from: pilgrim9 on January 24, 2014, 06:29:09 PM ---I saw a head with one cabinet in a pawn shop 35 years ago. The guy turned it on and it started on fire so I never got the chance to try one.
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Yeah. They'd do that. The amp runs its six 6550A output tubes so hard that it uses a 6L6GC for a DRIVER tube and has a large interstage transformer, a pretty rare thing for a bass amp. CBS Fender was trying to compete with Ampeg's SVT and Acoustic's 360, and it was probably some marketing "genius" who came up with the idea of requiring three cabinets to get full power out of it- to increase cabinet sales of course. I'm sure the design engineers were cussing them up and down, because making it with a single output like of all the OTHER amps on the market would have done nothing to increase the cost and would have made the amp far more reliable, but once the custom OT was in place, there was no going back. I suppose if you knew how to wind transformers, nowawdays a person could make a single replacement OT for it. If it were a toriod, it wouldn't even be much bigger than the original, but that output stage is VERY unforgiving: Class AB2 AIN'T for the average Marshall or Fender tinkerer.
Fender ALMOST learned its lesson and gave the 300PS, the 400PS's lesser powered successor, a single output, but to save money on the output transformer, that single 300 watt output was at 8 ohms ONLY. Folks who put a four ohm load on it were treated to watching their output tubes literally melt because unlike most other tube amps, the 3/400PS had a supply (HUGE power transformers) capable of delivering the extra current the tubes were trying to dissipate and where they were being asked to get hotter with current instead of being the voltage amplifiers they were designed to be, they overheated and melted their envelopes. The 300PS used a quartet of 6550A's with a 6V6 for a driver.
Psycho Bass Guy:
--- Quote from: Rob on January 24, 2014, 07:43:42 PM ---Thanks PBG! I was trying to figure out what the third trans would be for :o
Ummm Jersey Devil?
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No. It MAY be recoverable, but with my health and employment situation, I've not had the money or energy to chase it.
fealach:
That's pretty impressive looking. Tough to find someone local who likes that sort of thing and has the money and space for it. I have no idea what the cabs sound like, but I like my 400PS head. I could live without its bizarre output configuration, but it sounds good to me so I'm happy. At least until the day it needs work.
--- Quote from: Psycho Bass Guy on January 24, 2014, 04:43:25 PM ---They DO NOT have three output transformers. They have three taps on the transformer secondary split from a single primary winding. I HAD one until I sent it away for cosmetic restoration and it, the nice set of NOS GE 6550A's, and the custom roadcase it was in disappeared into New Jersey.
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That's terrible. Especially with those tubes!
Tim Brosnan:
My understanding on the guy who designed that amp-if you called him up with a technical question about it, he would make you prove to his satisfaction that you were competent enough to work on it, otherwise he would tell you to buzz off, he wouldn't help you. Anybody know if thats true?
Now, if that amp had the kind of transformer that the SVT had-one that allowed you to put the power to one cab-could it have seriously competed with the Ampeg?
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