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Dynaco St-70 Running On a 83 Murcury Vapor Recitifer!!

Retrovert said:
The Amperite is totally old school. The Tek 500 series had a few of them. I remember my 585 had them. Plus an HP scope of that era. And RF amplifiers used them.

The Amperite, however, has limited current capability, and must drive an external relay. It also does not protect against hot switching because, being hot, it remains closed. (Not that anyone ever does that, or experiences mains dropouts, which never occurs.)

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Vintage applications easily took care of the hot switching potential by using the amperite delay to drive a multi-pole relay that when energized by amperite contact closure would short or “seal” the amperite contacts, remove power from the amperite heater and apply power to the main circuit. As long as a momentary outage didn’t occur within ~ 30s of activation (time nec for the amperite heater to cool / contacts to open), the system was protected against momentary power outages or other causes of short cycling. Brute force and clunky by today’s standards but effective. Recall seeing this arrangement in Amperex app notes but don’t have a copy or link handy. Have an old Kepco regulated DC supply that uses exactly the described arrangement to protect the 872A MV rectifiers.
 
Steve O said:
Vintage applications easily took care of the hot switching potential by using the amperite delay to drive a multi-pole relay that when energized by amperite contact closure would short or “seal” the amperite contacts, remove power from the amperite heater and apply power to the main circuit. As long as a momentary outage didn’t occur within ~ 30s of activation (time nec for the amperite heater to cool / contacts to open), the system was protected against momentary power outages or other causes of short cycling.
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That's why I wrote, "being hot, it remains closed". Once it cools it obviously resets.
 
I have a bunch of Amperite delay tubes in the stash. Anyone have a schematic for a power supply using this scheme?
 
My only experience with the 83 is in my Hickok tube tester. It runs it without preheating, and it's mounted horizontally. It runs the tube well under maximum ratings, so they may be able to get away with it.
 
andy said:
My only experience with the 83 is in my Hickok tube tester. It runs it without preheating, and it's mounted horizontally. It runs the tube well under maximum ratings, so they may be able to get away with it.
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In the Hickok the 83's filaments are activated at power-on so it is always pre-heated.
 
have yet to hear of a tester that pre-heated an 83. there is not much current flow when powered, so that must be how they get away with it.
cheers,
Douglas
 
PakProtector said:
have yet to hear of a tester that pre-heated an 83. there is not much current flow when powered, so that must be how they get away with it.
cheers,
Douglas
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Well, all I can tell you is that when I turn my Hickok 532 on, the 83 filaments are lit before I begin any testing.
 
Pio1980 said:
Waaaay too much work for a light show.
I'd use the big base line testing thread and the time and work to optimize the sonic potential instead.
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It would probably be easier to drill out a the base of a dead tube, smoke the lower part of the glass on the inside and light it up with a couple of blue LEDs. :smoke:
 
IIRC, The Hickok testers are supposed to be turned on for a few minutes before testing any tubes as to let the 83 warm up and vaporize the Hg. No high voltage is applied until the "Test" button is pushed...
 
tenor.gif
Monsters inc...
 
well....a nuclear detonation mushroom cloud can look pretty cool....but that does not mean one should set one off though....looks to me like a case of knowing just enough to be dangerous.....
 
JohnT123 said:
Off topic but Fender used an 83 in the 1958 Tweed Twin amp. I generally replace the socket and install a 5AR4. Didn't want the EPA to show up at the guys gig and put yellow tape around the amp.
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Looking at the original schematic of the 5f8 (and the 5f6), there doesn't seem to be any provision for pre-heating the 83 rectifier. http://www.thevintagesound.com/ffg/schem/twin_5f8_schem.gif

Was the 83 then powered up in the same way as the 5AR4? I assume these amps were not given any special handling as they were humped about from gig to gig. And, looking at a pic online, I see the rectifier was operated upside down.
 
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zackthedog said:
Well, all I can tell you is that when I turn my Hickok 532 on, the 83 filaments are lit before I begin any testing.
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s-petersen said:
I seem to remember that also, but I couldn't find it in print.
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The filaments on the 5Y3GT and 83 tubes on my Hickok 800 are lit as soon as the unit is plugged in, and the 800's switch is in the off position. The other funny thing is the 800 manual does not state anything about a waiting period prior to testing, I can only assume the reason is due to the filaments being on upon plug in, and also the amount of setup time for testing tubes.

Also, the blue glow never illuminates from the Hickok's 83 tube when in use. I've tested a 83 tube on this tester and the blue glow illuminates, but the Hickok's 83 doesn't glow. Swapped tubes and the results remain the same, strange...
 
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Dandy said:
Looking at the original schematic of the 5f8 (and the 5f6), there doesn't seem to be any provision for pre-heating the 83 rectifier. http://www.thevintagesound.com/ffg/schem/twin_5f8_schem.gif

Was the 83 then powered up in the same way as the 5AR4? I assume these amps were not given any special handling as they were humped about from gig to gig. And, looking at a pic online, I see the rectifier was operated upside down.
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It was used and powered just like any other rectifier they had, that's why the conversion to the 5AR4 is so simple.
 
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