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I'm fixing a pair of Quicksilvers for a friend. The biggest problem is in the picture but not so obvious.
Follow Ups:
Is it the KT-88's in an amp that was designed for 8417's? As a Dyna Mk VI owner, I've seen that mod (clumsily) committed against amps in the past.
Yeah, whomever did this should be shot through the head, drawn, quartered and then hung. This is gross criminal assault on what is or was a nice power amp. I remember the first time I heard them. It was with a set of M-L CLS full range e'stats. The combo made me feel the CLS was maybe what Art Janszen would have liked if he made a new ground up electrostatic panel and full range replacement for the KLH Nine and Koss One.
Don Brian Levy, J.D.
Toronto ON Canada
"I remember the first time I heard them. It was with a set of M-L CLS full range e'stats."Was that at Arthur Salvatore's store on Queen St? That's where I first heard that combo and the Wilson Watt / Entec and a lot of other interesting equipment besides. He had a passion for high end gear and a great collection of records.
Edits: 03/31/15
Thanks ALL for your comments;
The first BF Cap after the rectifiers was 650uf, 6x the max ratings. Diodes worked well but had ~ 8 amp turn-on surge (tuff on fuses). The 2x 100mf cap (500v) took care of PS issues well enough that JJ 5ar4s work OK.
The owner wanted the amp as original (as close as reasonable). I converted it back to 8417 with changes to the bias arrangement + it now has dual bias pots and simple meter test points.
Listening: Interesting sound, I am normally not too thrilled with UL type sound. These are better than any I've heard. They have a clean and punchy sound.
Its a tween amp. QS ran one recifier then two then back to one.
If you don't have a stash of Sylvania type 8417, place a 100 volt 5 watt zener in line with the ultralinear tap and you can run the GE 8417's (their S2 voltage can not exceed 400 volts)
Thanx
That's good usable info.
Wrong tube and 'de inductor is over 20 Ohms in DCR .
That one cap looks to be about 1/4 inch from that power tube. Won't last more than a few years like that.Overall shoddy workmanship, that is the choke tapes around the caps like that. Not to mention the easily touched exposed B+.
And if you are trying to be funny, the 20-22ga wires on that choke, black insulation to boot, can't be good for sonics!
Edits: 03/29/15
Close.... The amps had chronic rectifier failure. The solution is in the background.
...Why, the "solution" must be the fitting of a reasonably sized filter I nput cap like the LCR in the background so the problem must be either excessive or defective filter caps in current setup. Legend has it that some Quicksilver amps overdid the input cap to the point that only US mfg 5AR4s would survive. Could this be one of those legendary amps?
Looks to be the QS KT 88 60 watt monoblock. Yeah it ran a GE 5AR4 hard, pushing a 320 uF cap. You could optional have a 70 uF cap right after the rectifier. The GE's lasted, though as did the Mullards and Mastushitas.
Commie tubes provided fireworks, with or with the 1812 playing.
The cap seems to installed in the space for the rectifier, which may be marginal for the space required by the screw terminals. don't know how that large cap is installed
"Yeah it ran a GE 5AR4 hard, pushing a 320 uF cap."
Why would anyone do that?
Torture the tube, transformer and the first cap with those high charging currents?
A 5ar4 has a limit for the first cap of 60uf and that's only when the proper resistance per plate (rt) is provided (different values ranging from 75 to 200 ohms depending on the AC voltage applied).
If you increase this resistance the cap value can be a higher value but without the proper resistance the cap would need to be lower in value.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
But, I've seen this in several 1980-90 era amps. Seems almost like it was done on purpose, to keep you buying $$$ tube rectifiers. Should have used solid-state rectification, if large first stage filtering was needed.
routinely did this on the early 60 watters,8417 and KT 88, at least as long as the GE's were available. Tough damn tube.
I remember asking him about the over valued caps in the first stage. His reply was have you had any issues? I had to say no, none at all, and as a matter of fact, those GE's ran for years.
Curiously, with the advent of the commie crap, we have to toe the line concerning the ratings, and even allow for greater allowances....
Mike ended the practice when the GE plant closed down of course.He did briefly modify the units for two 5AR4's, but returned to the single GE's.
Having a design solely dependent on one type/make of tube is kinda odd. I can understand this philosophy in the 1940-50s, when tubes were plenty and really the only choice. But, in the 1980-90s, when it was well known that most tube manufacturers were closing their doors... strange.
Ever try on of those Weber Copper Head replacement rectifiers in those AS amps?
Thanks!
Mike started building in the early 80's. tube production was still going on strong. GE was not to close their plants til 1992. In 18989 Mike told me he had something like 4000 5AR4s. he has 6000 sylvania 8417's too
Matstushita 5AR4's and Mullards could hold up to the stress he loaded them with. I believe he ended all rectifier tube production in the mid 90's, because the new stock were horrible.
Those are just silicon rectifiers (most likely 1N4007) with a 53 to 100 ohm wire wound resistor to drop/sag voltage and a NTC Inrush limiter. Not bad if you don't want to modify your equipment, but not really a tool for sound improvement. I would not want to bake a pair of diodes in a metal can with a power resistor and an inrush limiter.
Edits: 04/02/15
Fixed by removing a BFC that had been added right after the rectifier?
100uf.
That was my first guess but I don't see a rectifier tube.
SS diodes wouldn't care.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Looks awful tall even for a 12bh7 and plate structure doesnt look right. Love the sidecar choke.
mt
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