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Author Topic: It Pays to Look in Dark Corners; the rest of the story.  (Read 6590 times)
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KD1SH
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« on: December 07, 2019, 02:41:13 PM »

   Went to the small hamfest/fleamarket at the Vintage Radio and Communications Museum of Connecticut this morning. Small event, but it's always fun; great for socializing with fellow hams and finding the occasional small treasure. Met Carl, WA1KPD, and Ron, K1VYU for the first time, which was great, and a handful of regulars, including Larry, WA1LGQ.
   Found a few small items of interest, and then starting poking around in the dark corners (glad I always carry a flashlight) where the museum stashes their old surplus items that they're looking to get rid of. Burried in a corner was a big black box with caster-wheels, roughly 3 feet high by 2 feet square, and very heavy. Didn't think too much of it until I started looking closer: big power cord with a 240V kitchen-range type plug; big breaker switch on the front (starting to look like a big power supply); and on the back, some big white porcelain insulators (starting to look like a big high voltage power supply).
   I asked a couple of the museum guys, and they didn't seem to know a whole lot about it other than that they'd be happy to be rid of it. We discovered that the front panel hinged open, and there inside was a huge-normous Peter Dahl transformer, two big 32uf 4500 volt oil-filled capacitors, and a bridge rectifier consisting of big epoxy encapsulated diodes, each mounted to its own huge heat sink. Obviously home-brewed, but extremely well built and professional looking. Clean, no rust or corrosion, and I don't think it's all that old, really. The oil-filled caps even say "No PCB's" on them.
   Needless to say that it came home with me - after four of the museum guys helped get it into my truck - and for a price probably less than its scrap value. I looked up the Peter Dahl transformer: it was originally made as an external plate transformer for the Alpha 77SX, the "two hole" model, with two 3CX-1500's. That transformer is rated 3KV at 3 Amps!  The Dahl website doesn't list the price - it says "call or e-mail" - but the next model below it, rated at "only" 2 amps, goes for $1500.
   Well, I've been wanting to build myself an amp capable of a comfortable Full Monty on AM; now I've got no excuse. And I don't have to replace old electrolytics - it's all oil-filled (a big selling point). Those ceramic insulators and terminals on the back gotta go, though; probably replace them with something like SHV's, for safety.
   The moral is, never forget to look in the dark corners, or under tables and in old cardboard boxes at hamfests and such; you never know what treasures may lurk there!
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« Reply #1 on: December 07, 2019, 04:03:21 PM »

Great catch!  Now to find some nice big glass or ceramic bottles with that magic flashlight! 

Time to start quoting "Life is much too short for QRP"!
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Rick / W8KHK  ex WB2HKX, WB4GNR
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KD1SH
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« Reply #2 on: December 07, 2019, 06:23:10 PM »

The Peter Dahl specs for the transformer:

ALPHA A77S-X2 OUTBOARD PLATE
3 AMP OUTBOARD PLATE TRANSFORMER
CORE) A-0530/ C-CORE         STYLE #) 10  HIPERSIL C-CORE

PR) 230 VAC 60 HZ 1 PH

S1) 0-1800-3000 VAC @ 3.0 AMP CCS

DM) HT = 12.375 WT = 10.700 DT =  9.813 MD =  5.625 MW =  6.500
PRICE)    CALL or e-mail Plus S&H FOB Buffalo, NY   WEIGHT)  127  LBS


  Curious what it cost new - which I don't think was all that long ago by the look of it. I'll bet it was at least $2000. 9000 Watts CCS - key-down until 'til the cows come home.
  I'm thinking a Russian GS-35B. Very conservatively rated at 1500 watts plate dissipation and a lot cheaper than three 3-500Z's. I love the 3-500Z, but more expensive at $659 for a set of three (RF Parts) as opposed to $170 for a single GS-35B, which probably gives somewhat more plate dissipation in the end.  And with the 3-500Z you need to add chimneys - which are pricey - and air-system sockets for full cooling, not to mention 45 amps for the filaments.
   With the GS-35B, though, manufactured sockets are unobtanium, but I've got a milling machine and a lathe, and the plans and specs are out there.
   And, this supply might just wind up feeding more than an amplifier one day: I've got some 4-400's, 810's, 813's, and some heavy Thordarson and UTC mod. iron hanging around in the shop. Retirement's only three years away - I think I'm going to stay busy.
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Patrick J. / KD5OEI
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« Reply #3 on: December 07, 2019, 11:03:04 PM »

Congratulations on your great find!

I like the trio of 3-500Z idea but sure appreciate the cost and durability of the Russian tube.  hey why not use two?
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« Reply #4 on: December 08, 2019, 12:15:23 AM »

Peter Dahl 2004 Amateur catalog:

ALPHA A77S-X2 OUTBOARD PLATE
3 AMP OUTBOARD PLATE TRANSFORMER
CORE) A-0530/ C-CORE STYLE #) 10 HIPERSIL C-CORE
PR) 230 VAC 60 HZ 1 PH
S1) 0-1800-3000 VAC @ 3.0 AMP CCS
DM) HT = 12.375 WT = 10.700 DT = 9.813 MD = 5.625 MW = 6.500
PRICE) $810.00 Plus S&H FOB El Paso, TX WEIGHT) 127 LBS

------------------------

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KD1SH
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« Reply #5 on: December 08, 2019, 08:36:32 AM »

  The current catalog says it's effective 2018, so in 14 years I imagine the price has gone up.  I based my $2000 assumption on the smaller model being listed for $1500, but that's certainly not proof.
  In any event, it's a keeper, so the original price isn't relevant other than as a matter of curiosity. In fact, I suppose a lower original price makes me feel less guilty for getting the whole supply for $100.


Peter Dahl 2004 Amateur catalog:

ALPHA A77S-X2 OUTBOARD PLATE
3 AMP OUTBOARD PLATE TRANSFORMER
CORE) A-0530/ C-CORE STYLE #) 10 HIPERSIL C-CORE
PR) 230 VAC 60 HZ 1 PH
S1) 0-1800-3000 VAC @ 3.0 AMP CCS
DM) HT = 12.375 WT = 10.700 DT = 9.813 MD = 5.625 MW = 6.500
PRICE) $810.00 Plus S&H FOB El Paso, TX WEIGHT) 127 LBS

------------------------


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« Reply #6 on: December 08, 2019, 08:48:50 AM »

  I've thought of using two - for $340 you get a minimum of 3000 watts dissipation. It'll need more drive, but I'm attenuating my Ranger down to 15 watts to drive my SB-221, anyway. Having that sort of dissipation headroom would be very comforting.

Congratulations on your great find!

I like the trio of 3-500Z idea but sure appreciate the cost and durability of the Russian tube.  hey why not use two?
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« Reply #7 on: December 08, 2019, 11:34:02 AM »

The GS35b in ICAS use is more like 2.5kw PDiss.

It's not hard to see 3.5 plus grand out of them.

I run them at 4 kv to 5kv.  I've seen guys run them at 6, but that takes some real conditioning of the tube.

--Shane
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WA1LGQ
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« Reply #8 on: December 08, 2019, 03:21:22 PM »

So I am meandering around at the little swap fest that is in the newly cleaned out multi-purpose room as they call it. Oh it was SRO in there, good turnout. Bill pushes his way through the crowd over to me wearing his usual bright orange jacket and tells me that he must show me something in his truck all excited. We go out to his truck, I spy this huge black box in there. I see casters and a big breaker switch on one side. I say "Holy crap, what the hell is that?" He flips down the gate and opens the cabinet door.....Oh yeah, baby, I almost fell over when I saw the guts. Nice find indeed. I rummage around the museum stash occasionally when I make a visit to see the guys over there but I never saw that thing. What a find. I asked Dan, NC1J, a regular volunteer over there where that came from. He had no idea. They get donations of stuff sometimes by the pickup truck load, and have a vast amount of buried treasure in the back. Good one Bill! Now you MUST build something to melt your antenna.
   Bob, WB1GCM was manning another table full of donations, and I saw a HQ-140 black crinkle on the floor, I checked it out and looked pretty good inside and out, it had an original manual,  though was missing an original knob. Almost bought it, but changed my mind. A guy offered 20 bucks and they sold it! They really need the room and even small donations help them out. I think their next fest is in Feb. They do at least 4 a year.
Larry
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KD1SH
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« Reply #9 on: September 18, 2022, 09:37:08 AM »

   The rest of the story, as Paul Harvey used to say: I went to the Vintage Radio and Communications Museum's swap-meet/hamfest on Saturday, and came home with the long lost companion to this awesome power supply. It's an 8877/YU158 two-holer! They were very obviously home-built as a pair; the paint on top of the power supply even shows clear imprints made by the amp's unique footprint.
   It appears to be in fine shape; the tubes, chimneys, plate choke and associated components all look perfect, and the Jennings vacuum variables show brilliant copper inside, so the vacuum is still good. Nice turns counting cranks, too, and an absolutely pristine B&W 852 switching inductor.
   The outside is fine, but might benefit from a little paint. (Anyone have any recommendation for good black crinkle?) One thing I'll be changing is the high voltage connectivity on both the amp and the supply: in its current form it's nothing more than a couple of dangerously exposed threaded studs sticking out the back of each (B+ and B- are both floating, for grounded-grid metering) with no sign that there was ever a protective enclosure. Even at 115vac I wouldn't live with this, but at 4kv/3 Amps it's insanity. Maybe the original builder also enjoyed running blindfolded across busy highways while juggling running chainsaws.
   The first step is to go through everything and make up a schematic and wiring diagram (the panel meters are unlabeled, for example), and I've got no idea at this point what sort of control/switching circuitry exists and if there's any grid current protection included. Likewise for the input tuning circuit. Most of this stuff would be concealed inside a part of the cabinet that I haven't accessed yet.
   I will post pictures as I get more into it. It's going to be a fun project!
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« Reply #10 on: September 18, 2022, 10:32:49 AM »

Good stuff Bill. It was really great to be able to help reunite the pieces of this creation. Just wish we knew who built it. What a great day for a tailgate it was. Big turnout. The vehicles were parked in every crevasse and in the street all the way down to the train tracks. We moved out almost all of the excess gear and parts etc that we dug out. The funds will help pay for the antenna installations that we need. Thanks! to all. Yes there is a 75M antenna but its far from ideal for getting the BC1T on the air with.
Larry


* IMG_0395.JPG (4010.79 KB, 4372x3279 - viewed 220 times.)
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KD1SH
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« Reply #11 on: September 18, 2022, 11:35:13 AM »

Yes indeed, a wonderful day. That bald guy in the orange looks like someone who'd bring home some radio gear, doesn't he?
I do keep hoping that maybe I'll find the builder's call sign or something inside one of those units.
Hope you guys can get a good 75M antenna up in time for the Rally - I want to hear that Gates on the air again!

Good stuff Bill. It was really great to be able to help reunite the pieces of this creation. Just wish we knew who built it. What a great day for a tailgate it was. Big turnout. The vehicles were parked in every crevasse and in the street all the way down to the train tracks. We moved out almost all of the excess gear and parts etc that we dug out. The funds will help pay for the antenna installations that we need. Thanks! to all. Yes there is a 75M antenna but its far from ideal for getting the BC1T on the air with.
Larry
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"Gosh, Batman, I never knew there were no punctuation marks in alphabet soup!"
—Robin, in the 1960's Batman TV series.
KD1SH
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« Reply #12 on: September 19, 2022, 12:01:32 PM »

Some pictures:
  Not a single switch, panel meter, or connection is labeled. Maybe there were labels at one time and they've since fallen off, but I see no evidence of glue residue or paint discoloration.
  Get a load of those huge heat-dissipating anode caps! Seems a bit of overkill on external anode tubes. Those nice glass chimneys are Coleman lantern globes!
  That rectangular box on the bottom is just an air plenum. Creative use of those ceramic insulators!
  Very interesting steel enclosure. The separate rear compartment is integral with the rest of it; not an add-on. Note the captive/retractable handles. Could this enclosure be ex military?
  The big transformer in the rear compartment would appear to be the filament transformer; the smaller one probably for control voltages.


* Front.JPG (109.88 KB, 1024x768 - viewed 239 times.)

* Rear Inside.JPG (114.09 KB, 1024x768 - viewed 236 times.)

* Inside.JPG (109.64 KB, 1024x768 - viewed 249 times.)
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« Reply #13 on: September 19, 2022, 12:26:50 PM »

Those plate caps are impressive.

And useless as heat dissipators.  Those work for air blowing across the tube (SB220 style).

They make them with the foils going vertically.  Those work with pressurized tubes.

Great find.

Also, I bought one of those Dahls years ago.  350 bucks in the late 80s.  When I went to buy another it was almost 800, albeit a decade later.

You made your money back, easily....!


--Shane
WP2ASS / ex KD6VXI
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KD1SH
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« Reply #14 on: September 20, 2022, 04:21:31 PM »

Power supply seems to work fine: 3800vdc out with 240vac in. And with the tap-selector in the "low" position: 2100vdc out, which will be handy if I ever want to use it with lower voltage tubes like 4CX-250's and the like, or 813's and such.


* Power Supply Output.JPG (68.66 KB, 1024x768 - viewed 204 times.)
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« Reply #15 on: September 20, 2022, 10:45:20 PM »

Some pictures:
  Not a single switch, panel meter, or connection is labeled. Maybe there were labels at one time and they've since fallen off, but I see no evidence of glue residue or paint discoloration.


--I really like the looks of that amplifier! The plate heat dissipation caps don't bother me a bit.
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« Reply #16 on: September 23, 2022, 12:38:41 PM »

  It is indeed quite an impressive beast. The builder did a nice job of shoehorning all the RF components into a relatively small enclosure, although the enclosure isn't exactly the epitome of RF tightness. I would have preferred, for example, a "double-wall" front panel assembly, to better isolate the meters and indicators from the RF. As it is, the enclosure, which is massively heavy steel (copper plated to boot) has many unused holes and gaps; the chart-holder frame on the front covers a number of good sized holes, for example. It was obviously repurposed from something previously built. No fancy EMI finger-stock or braid here.
  The low voltage and control wiring in the rear compartment is a rat's nest of zip-cord, wire nuts, and marginal soldering. I will probably install a nice double-row barrier strip back there to tidy it all up, and of course get rid of all the zip-cord. All the RF wiring was done with thick RG-8; the old Radio Shack stuff with the jacket that's as stiff as re-bar. I'll replace all that with LMR-240 Ultraflex. There are no RF chokes in the heater leads; probably not a problem since the cathodes aren't tied to the heater, but it's probably not a bad idea.
  An amplifier of this power (and expensive to replace tubes) deserves some sort of grid protection circuit, too. There is currently no sequencing, either. All of the switching is done by a single relay, so in order to apply sequencing I'll need to change that. It also completely lacks any sort of input tuning.
  The meters, as tested with external sources, are largely inaccurate; the plate current meter, for example, is off by 150 ma, and the filament voltage by half a volt. The plate current meter has an internal shunt so there's not much I can do about that. I'm wondering if the steel panel is affecting the meters.
  Those heat-dissipating anode caps are even bigger, I think, than the ones used with 4-1000's. Like Shane said, they're more effective when placed in crosswise airflow, but I suspect that airflow around them would be pretty turbulent, so some air should flow through them. I've got plenty of aluminum stock; maybe I'll machine up some vertical finned ones of my own, but the tubes probably wouldn't benefit from any additional heat dissipation. I'll need to maintain the anode cap's height, though, unless I want to modify the anode straps going to the plate choke.
  I'll probably replace that off-center lower box - which is just an air plenum - with a full-width chassis/box, giving me more room for additional circuitry like grid protection and a sequencer. Otherwise than that, I'll pretty much leave the amp as it is. I had originally considered transplanting all the guts into a better enclosure, but that would be enough work so that at that point I might as well just build a whole new amp from scratch.


Some pictures:
  Not a single switch, panel meter, or connection is labeled. Maybe there were labels at one time and they've since fallen off, but I see no evidence of glue residue or paint discoloration.


--I really like the looks of that amplifier! The plate heat dissipation caps don't bother me a bit.
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"Gosh, Batman, I never knew there were no punctuation marks in alphabet soup!"
—Robin, in the 1960's Batman TV series.
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