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Author Topic: HV power supply NOS parts bargain(?)  (Read 5124 times)
K8BYP
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Posts: 256




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« on: December 18, 2017, 03:00:06 PM »

Bargain? You decide.

http://www.surplussales.com/item/_ps/ar-150a.html

PS schematic:

http://www.surplussales.com/PowerSupplies/pdf/eqp-ar-150a.pdf

My pictures:

https://ibb.co/mfSEQR
https://ibb.co/ipPps6
https://ibb.co/jDV7em

2500V, 1A PS from a HF amp. combo (this didn't have the amp, it was the PS). One of the tags marked "in process" hints that this was a new unit but not fully assembled. The wires with connectors that are hanging loose all show signs of the terminals having been connected, but it's advertised as "diodes and capacitors" removed. That doesn't mean its a used unit.

There are two large wire-wound resistors under the board marked "Danger High Voltage" but the board has not changed color, indicating the resistors ever got hot.

Basler XFMR, 110813, marked "28 Jan 85" - back when this classic shredder was released:

https://www.youtube.com/watch?v=fZmHu1t_5X0&list=PLyNpL8jGjCtYh7NySBs8heXeuQsQmT7rl&index=7

NOTICE THE POTENTIALLY FATAL FLAW in the transformer assembly - screws with (in operation) have DEADLY voltages pointing UP. Hammond = same problem. This is what goes wrong when Designers don't fully grasp the problems they are dealing with.

Those screws are relatively sharp, especially with external threads and a hand or arm falling one of them equals "dead before the body hits the floor"

They couldn't mount the screws pointing DOWN?  I once re-designed a 600V bench test fixture in which some moron put needle- sharp PC board piercing test points for the incoming 3 phase line WITH NO SHIELDING OR ISOLATION. One touch across two points= DEAD. it only takes microampere level current applied internally to kill a human. The Technician said "Ill just be careful to not touch them" to wit I replied.. "you only get one chance to be wrong..." Unlikely to survive such a contact-it's dangerous enough on relatively dry, calloused skin.

112 lbs. UPS Delivery Man was not happy about lugging this monster up the driveway and steps, especially marked "FRAGILE ELECTRONIC EQUIPMENT"

HI

Other included parts and guesstimates on new prices:

19" cabinet, about 8" high front panel, $100
Humongous  choke. $100
filament transformer $75
240V, 2 pole, 25A /pole  high current contactor for remote control $100
smaller power resistors, two large wire wounds under the circuit board, $30
two HV jacks
two Jennings 1000 pF 5Kv doorknob capacitors $75

 Planning to remove the iron and mount the tubes and DC filament PS in the cabinet, and put the XFMRs on the floor.
That will make a rack amp unit maybe 30 lbs, a LOT easier to deal with than 130 lbs, and all that heat isn't in the same compartment. I don't want the huge 60 Hz fields in the cabinet...

This is probably a bargain just for the HV transformer.

« Last Edit: December 18, 2017, 03:18:52 PM by K8BYP » Logged
KM1H
Member

Posts: 5078




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« Reply #1 on: December 18, 2017, 06:10:19 PM »

You could buy two of the big Ameritron transformers for $800.

If that transformer is the bulk of the 112# then it HAS to be more than 2500VA.

What is the DC resistance of the secondary? With a choke input it could be fairly  high making it fairly useless with a constantly varying load. The 100K bleeder says it is a constant load design.  Personally I would pass.

I have no problem with top terminals with users that have half a brain. Most of my homebrew are top terminals including the big GE Pyranol filter caps in the up to 4000V at 1.5A CCS  transformer in the general purpose supply I built around 35 years ago. Most amp manufacturers used exposed filter cap terminals until the Snap In types came along. Even then I wouldnt trust the thin plastic covering even at 450V.

Ameritron still uses the 70's era case design along with multiple other places to get zapped as does any amp from PS to that big tube all bare assed exposed... Shocked

I grew up with all HV very exposed by the age of 16, 2200 VDC in a scrapped PP HF- 200 diathermy amp I converted to 20 and 40M Class C for CW and AM and learned to live with it. By 17 I had PP 250TH's at 2500V with PP 810 modulators, all thanks to MARS. The power supplies and modulator were built on wood and a wide open relay rack.  I wont go into the RF deck but that was limited to 80-40-20 by my parents who were amazed at the phone calls when I put it on 10 and 15 Roll Eyes Grin  But with Cycle 19 approaching the peak I did well enough with 100W from a Viking I that I did install the TVI kit and bought a Johnson LPF.

But the modern 12VDC no clue ham these days may not be so lucky and should stick to SS up to 50V....so far.

Carl

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N3QE
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Posts: 5575




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« Reply #2 on: December 19, 2017, 04:45:53 AM »

Even then I wouldnt trust the thin plastic covering even at 450V.

Never mind 3600V or 4500V or whatever is on the entire bank! I don't think the plastic covering is there for touch-safeness because rarely (never?) is the top of the can covered, it's just the sides. I think the covering is there only for PCB density.

Quote
But the modern 12VDC no clue ham these days may not be so lucky and should stick to SS up to 50V....so far.

Some of us had interesting experiences after the shift to low voltage high currents, where we had to educate ourselves about what a current of a few hundred amps would do. The rules become more like working under the hood of the car - disconnect the battery negative first!
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K8BYP
Member

Posts: 256




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« Reply #3 on: December 19, 2017, 08:26:03 AM »

"You could buy two of the big Ameritron transformers for $800."

Link? Take a look at the Dahl website, see the prices for top flight transformers. The one(S) for the ALphas are $1400.

"If that transformer is the bulk of the 112# then it HAS to be more than 2500VA."

It is, and it was "suggested" that it is, although NS wouldn't "guarantee" it. Yes, its a brute. The ad for the XFMR by itself says 67# but I think its more.

Theres a big difference in ICAS and CCS services. Full power continuous duty without thermal runaway takes more meat.

It was built for a company that made scientific equipment, so it might have a lot of "overhead" built in.


"I have no problem with top terminals with users that have half a brain. "

Its not about "users" its about engineering and technicians who spend a lot of time working around such thing. Users may never see the problem.

Its inexcusably bad design because it costs nothing to correct.

"interesting experiences after the shift to low voltage high currents"

YEs, especially about contact pressures, cleanliness, sound solder joints... Its a much different world than HV!

Wait till that problem hits the Electric Vehicles, wait till Mechanics slop "dielectric grease" all over terminals in an EV and the FIRE that results will be epic!
« Last Edit: December 19, 2017, 08:33:36 AM by K8BYP » Logged
N3QE
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Posts: 5575




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« Reply #4 on: December 19, 2017, 08:35:00 AM »

"You could buy two of the big Ameritron transformers for $800."

Link?

AL-80B transformer (including filament), $199: http://www.mfjenterprises.com/Product.php?productid=406-1109-2C

AL-1200/1500/AL-82 plate transformer, $403: http://www.ameritron.com/Product.php?productid=406-1418-1D

Ameritron/MFJ is my go-to source for many RF and HV parts because they have them in stock and know what they are.
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KM1H
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Posts: 5078




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« Reply #5 on: December 19, 2017, 08:42:09 AM »

Quote
AL-80B transformer (including filament), $199: http://www.mfjenterprises.com/Product.php?productid=406-1109-2C

AL-1200/1500/AL-82 plate transformer, $403: http://www.ameritron.com/Product.php?productid=406-1418-1D

Ameritron/MFJ is my go-to source for spare parts for several brands of amp because they have them in stock and know what they are.

The MFJ catalog has a whole section dedicated to various repairs and home brewers. The AL-811/811H transformer (same part) is an absolute bargain for all sorts of medium power HB amps starting on Pg 85 in the 2017 version on line.
http://www.mfjenterprises.com/catalog/mfj/MFJ_2017_Ham_Radio_Catalog.pdf
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K8AXW
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Posts: 7036




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« Reply #6 on: December 19, 2017, 09:28:04 AM »

BYP:  Engineers bring us life as we know it.  God bless 'em.  However, I have always said that in many cases engineers NEVER use the stuff they design!

In your exposed HV terminals on a PS. it is necessary to re-engineer out these stupid designs...... almost without thinking.  Clean up the sharp points and put a good cover over the terminals.  Good deal: Simple fix.  This is homebrew at it's best!   Cheesy
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A Pessimist is Never Disappointed!
W1ITT
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Posts: 199




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« Reply #7 on: December 20, 2017, 03:02:00 PM »

I paid my college bills running broadcast transmitters, TV, FM and AM.  They had exposed HV terminals if you opened the access doors, most of them pointing"up".  Occasionally, with great care, we had to bypass interlocks and run the transmitters with doors open for troubleshooting purposes.  For most of my working career, which isn't over yet, I've put food on the table with high power RF and HV, and never a close call. This has been going on for decades and, although a few have been weeded out, I never knew anyone, in close to 50 years, who got zapped. 
Perhaps for some of the new kids in amateur radio who don't take things seriously, this would be ill advised.  In fact, many today should probably stick with 12 volts DC.  Among these people are those who should avoid chain saws, firearms, and tractors.  The safety naggers need to realize that nothing will ever be foolproof, because fools are so ingenious.
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K6AER
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Posts: 5689




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« Reply #8 on: December 20, 2017, 03:13:18 PM »

Have you bought a pistol lately? Stamped on the slide is a disclaimer to keep the hole end pointed away from you. I have been thrown to the ground from HV shock from an amplifier. I was not the manufacture's fault, just my bad. We can not snow flak proof the world for safety. At some point you have to know your limitations.
« Last Edit: December 20, 2017, 03:16:50 PM by K6AER » Logged
K8AXW
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Posts: 7036




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« Reply #9 on: December 20, 2017, 05:39:26 PM »

AER:  You nailed it!  In every case when one reads the manual on a power tool the first 3 or 4 pages are disclaimers to protect the manufacturer. 

TTT: While I never had to pay bills with the "beer money" is was paid at the local AM/FM station I had sense enough to watch what I was doing when the "back door had to be opened!" 

I don't think that the people are getting dumber but I think it's the bottom feeding lawyers that are causing the problem.
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A Pessimist is Never Disappointed!
KB2WIG
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Posts: 625




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« Reply #10 on: December 21, 2017, 08:16:48 AM »



Who hires the Lawyers?

KLC


If all the lawyers in the US were placed end to end, how far would they reach?
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EXTRALight  1/3 less WPM than a Real EXTRA
N8FVJ
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Posts: 866




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« Reply #11 on: December 21, 2017, 09:35:11 PM »

$795 is too expensive. 3000 volts at 1 amp ICAS could be built for $300 with careful shopping for the transformer.
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WA7PRC
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Posts: 2319


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« Reply #12 on: December 22, 2017, 08:44:44 PM »

3000 volts at 1 amp ICAS could be built for $300 with careful shopping for the transformer.
I found a scrapped medical equipment PS w/ a nice transformer and rewound it to get close to 4100V @ 1.5A continuous:



It came w/ a split Nylon bobbin that made for easy rewinding AND gave me excellent primary-secondary isolation. I replaced several LV secondaries w/ a single tapped HV secondary (DCR = 6Ω). The two tapped primaries are good for 100/120/200/240V @ 50/60 Hz.

A fullwave doubler rectifier gives 3338, 3581, 3827 or 4073 VDC. Cost was about $100 for 10# of 18AWG polyimide (Kapton™) coated wire + a bigly amount of NMN333 "paper". A local transformer shoppe graciously vacuum-pressure impregnated it w/ polyester resin.  Ten 6A10 rectifiers (6A/1KV) and ten CDE 381LR 470uF/450V capacitors were also cheap. I screwed together an aluminum box for it:


Bryan WA7PRC
http://www.tinyurl.com/wa7prc-transformer
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KM1H
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Posts: 5078




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« Reply #13 on: December 23, 2017, 10:44:15 AM »

Quote
$795 is too expensive. 3000 volts at 1 amp ICAS could be built for $300 with careful shopping for the transformer.

Some years ago I bought a transformer from an industrial amp for all of $30 plus UPS from CT that ran a pair of 3-500Z's CCS for hours at a time. With a 3450VAC secondary and choke input it ran at ~ 3100VDC. I also bought the dark brown tubes, plus sockets and chimneys, and surprised to find the tubes still ran 1200W in my LK-500ZC Shocked

The design is modern with a low DC resistance/impedance secondary so it runs cool at a nice ~4850V unloaded with 11 330 uH 500 V 'lytics. At 40.9# it is just the ticket for an efficient and loafing 4-1000A or some of the Russian and other EU tubes.
Or wire to switch between 120 and 240V for many other lower voltage tube choices.

Life is too short to get into rewinding when there are plenty of bargains once you are weaned off Fleabay. Grin

Carl

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WA7PRC
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« Reply #14 on: December 23, 2017, 11:03:51 AM »

Quote
Life is too short to get into rewinding when there are plenty of bargains once you are weaned off Fleabay.
Rewinding = always fast, easy, and inexpensive.  Grin
Searching for a bargain = not guaranteed to be fast, easy, nor inexpensive.  Grin
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