Microwave Oven HV Rectifier Diodes

[k4kyv]

I found a handful of apparently unused microwave oven HV rectifiers in a box of misc junk that was given to me.  They are all marked HVR-1X, and some follow that type number with a 3, 4 or 6.  I looked for the specs, and from the best I can tell, they are all rated at approximately 350 ma, 10 kv PIV.  I tested them, and they all check good (an ordinary ohmmeter is useless for testing them, since the forward voltage seems to exceed the battery voltage in the meter).  I hooked up a low-wattage 110v lamp, with the diode in series to check for rectification.

One thing I noticed was that with these diodes, there appears to be about a 10v drop in the forward conducting direction.  Measured DC voltage to the lamp is between 49 and 50 volts, whereas with a normal silicon diode, I measured 60v.  The charts also mention 10 to 11 forward voltage drop.  Each unit must actually be a series string of diodes encapsulated in epoxy, and what you see is the cumulative forward voltage drop.

I am thinking of using four of those in a full wave bridge, to obtain about +1500 volts at a little over 150 milliamps, using a single-section choke input filter.  Wonder if anyone has already tried using these type diodes with choke input, and if so, did they blow up?  I know that SS diodes are sometimes picky about working into a choke input filter, since transient spikes see an open circuit rather than a dead short as they would with a capacitor input filter. Perhaps I should bypass with something like a 0.05 mfd HV cap at the output of the bridge, enough to take care of short-duration HV spikes, but not enough to make it act like a capacitor input filter.

If these don't work, I can still use a quad of 866-A SS plug-in replacements I also have on hand, but that would seem a waste, if I can safely get by with these microwave oven diodes.

[Ed/KB1HYS]

I tried to replace the MV rectifiers in my Valiant with MW diodes.  It should have worked great, but I ended up having to swap out the MW diodes for a string of 1N4007s when the MW Diodes failed.  They were used/salvage (and free) so may have been less reliable than new unused ones.

[WA2IXP]

Don,
   I've used oven diodes in full wave and bridge circuits without problems. One in each leg. Output voltage 2kv or less. Some choke input and some without. Always included a step start relay/resistor. These were used with modified oven transformers with secondary lifted from ground or two transformers in a ct configuration. One supply with 2 transformers yields 1940 v @250 Ma for 2 4cx250b's. Maybe I've just been lucky as the current ratings aren't real high and in thier original use the inrush current is low as the cap is small. Some of mine had the same # as yours. I have used without step start in testing but not in finished project.
                                                                                                Jay-

[The Slab Bacon]

Don,
      all of them are definately a string of diodes encapsulated in one epoxy block. Reading the total voltage drop across a good unit will give you a pretty good feel for how many are in there. (at + .5v per diode) that can also be used for calculating (guestimating) the voltage of an unknown unit.

I have purchased a boatload of "microwave oven" diodes marked "VARO VC60X" and VC80X. With a little research I found them to be 1.5A @ 6 and 8kV. I have used them for everything I have that operates over 1500v with no problems. They have also survived numerous shorts, transformer and choke failures, etc, and seem to be just about indestructable.

[W3GMS]

Speaking about HV diodes, it looks like Frank-K2AW of Silicon Alley fame is no longer selling his HV diode blocks.  I know he was up in years and may be an SK, not sure.  He provided a good product for many years and was a heck of a nice guy to deal with.

Does anyone know what his status is? 
 
Joe, W3GMS 

[K6IC]

Hi Joe,

YES,  Frank was a great guy to deal with.

Have read,  perhaps here,  that he was an SK.  QRZ says he was born in 1914.  He would need to be one tough bird to still be going at 97 - 98 years of age ...   but.

He was a very honest and trusting guy.  You'd order items on the phone,  he'd ship them to you,  and then you'd pay him from the enclosed invoice -- if you were a licensed Ham.  A great guy.

Had heard/read,  that this daughter ran the biz for a while,  but this is from distant memory.  Will try searching here for some info.  Vc

[K6IC]

In searching here found this:

>>Detroit47:
Quote from: K1JJ on September 29, 2010, 05:52:53 PM

Quote from: Pete, WA2CWA on September 29, 2010, 05:05:35 PM

3. Although the diodes are rated at 3 amps, Frank derates the module to 1 amp to make them "idiot proof".

Yep, Frank's a good guy. He always sent me the goods before a check arrived too.

Too bad he may be retiring, but at his age, God bless him... Maybe someone will take over the biz.

T

I just talked to Frank’s daughter a few days ago. Frank is suffering from Dementia. For the time being she is handling the business Frank hasn’t made the diodes for some time. He was unable to get the cases that he built them in. They are just off the shelf block diodes that they rebrand. I’ve bought diodes off of Frank for years. I liked them for three phase mobile work but they are too wimpy for base stuff.

John N8QPC
<<>

He MAY still be going,  his License has not been cancelled ...  Vic

[W3GMS]

Hi Vic,
Thanks for the information about Frank.  

I first met him in the late 70's at the Dayton Hamvention.  His booth inside was right behind mine in the next isle.  We always came in early to set up our booth and I saw this man that was very upset.  I went over to see what the problem was and he said some of his things had been stolen sometime between when he left the arena the night before and when he arrived in the morning.  We talked a little and he found out I was interested in old time radio gear.  He had a National NC-101X at home and said he would like to give it to me.  Well several months had passed and I got a phone call from Frank.  He was going to be traveling south on RT 95 and wanted to know if I could meet him in Delaware.  I said sure and he gave me his very nice NC-101X.  What a great guy and his wife was a very nice lady as well.  She was always with him when I saw him at Dayton.  

Lots of very fond memories of Frank, K2AW for sure.  

73,
Joe, W3GMS

[K6IC]

Yea Joe,  Frank (hopefully) IS a great guy!  Have never met him,  but he knew his stuff and built great diode stacks.

Believe he had said on the phone that he had worked for General Instrument Semiconductor,  in New York IIRC.  Hope that he is still going.
Vic

[W3GMS]

Yes Vic, that is where I remember him working.  In the old days and maybe when the business was shut down, he was still buying diode stacks from them.  I remember back in the late 70's when I met him he said the diode stacks had small cosmetic flaws in the housing of the diodes.  Still electrically fine, but with the cosmetic flaws G.I. would not sell them.   I have used many of his stacks and never had a problem with them. 

When you meet people like Frank, those are the ones you never forget.   

I am not sure how his prices compared to other sources, but he appeared to keep real busy with the small cottage business he and his wife had going.  To the best of my knowledge no one has continued doing it.  Maybe G.I. just cut of the stream of those diodes he was buying. 

Joe, W3GMS   

[Opcom]

His diode blocks are the best, and there are two in the 3CX3000 amp here. But no longer available, a pity and a shame when these 'good guys' pass away. What would one need to make blocks like them today? A string of high-rated diodes and some potting epoxy compound, a silicon mold and jig, drill press and a jig. My worry would be the potting would not let the diodes cool well unless it had good thermal characteristics.

[Pete, WA2CWA]

Here's a 16KV 750A diode for $5.79.



Here's the site: http://www.sourcingmap.com/hvp16-high-voltage-16000v-750a-single-phase-half-waverectifier-diode-p-168384.html
There's probably others out there too.

[Opcom]

a 750A fuse, maybe.. 750mA in the details. free shipping via subsidized air transport. it's almost enough to tempt one into going solid state.


20KV 2A:
http://www.sourcingmap.com/hvp2a20-20kv-high-votlage-single-phase-half-wave-rectifier-diode-p-168311.html

25KV 2A
http://www.sourcingmap.com/25kv-high-voltage-rectifier-silicon-stack-diode-2dl-green-p-191076.html

[W3GMS]

His diode blocks are the best, and there are two in the 3CX3000 amp here. But no longer available, a pity and a shame when these 'good guys' pass away. What would one need to make blocks like them today? A string of high-rated diodes and some potting epoxy compound, a silicon mold and jig, drill press and a jig. My worry would be the potting would not let the diodes cool well unless it had good thermal characteristics.

The extra mass of the epoxy and they do have thermal epoxies can actually lower the thermal junction temperature of the diode in some environments.  Think of it as just a bigger mass for the heat to spread out to.  Then again if the diode by itself has some decent air flow around it, the thermal resistance from the junction to air will be lower than the added thermal resistance factor of the  epoxy.  In that case it can be better. 

Joe, W3GMS   

[W3GMS]

Here's a 16KV 750A diode for $5.79.



Here's the site: http://www.sourcingmap.com/hvp16-high-voltage-16000v-750a-single-phase-half-waverectifier-diode-p-168384.html
There's probably others out there too.

Before people start believing in magic, that diode has an average forward current of 750 MA.....Bantering the non repetitive peak current like done in the ad reminds me of the inflated power rating on power transistors.  Once you do the math, it will be easily seen that the junction temperature will be in a meltdown condition.  Taking it a bit further you then find out what the rating really is with a doable heat sink. 

Joe, W3GMS

[Pete, WA2CWA]

In the October 2012 QST, K2AW, Frank P. Fix, Westbury, NY, is listed as a Silent Key.

[WB2CAU]

In the October 2012 QST, K2AW, Frank P. Fix, Westbury, NY, is listed as a Silent Key.

Sorry to hear about this.  Frank was such a nice guy.  But he lived a long life and the last time I saw him at a hamfest selling his silicon was a few years back and he was already in his early 90s at the time.  One can only hope to be in as good shape in their 90s as Frank was.  Sorry that he's gone but glad he lived as long as he did.  RIP, Frank. 

[KM1H]

Sorry to hear that he went SK.

Ive a pair of the stacks in the 2M amp and running 3900V standby and 1A full bore for 25+ years with never a hickup.