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Author Topic: Question on 866/Hg Rectifiers.  (Read 9777 times)
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Ed/KB1HYS
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« on: December 21, 2008, 09:56:20 PM »

been doing some readin'  there've been some references to putting resistors in lines on 866 and other type Mercury tubes to prevent ocsillations being setup.  Anyone actually experience this?  Is this a likely enough problem to worry about?

The 866's in question will be in a ~3000V at 250mA supply with 7Hy and 12Uf filter(cap may grow as I get more parts) to power a class C final.
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73 de Ed/KB1HYS
Happiness is Hot Tubes, Cold 807's, and warm room filling AM Sound.
 "I've spent three quarters of my life trying to figure out how to do a $50 job for $.50, the rest I spent trying to come up with the $0.50" - D. Gingery
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« Reply #1 on: December 21, 2008, 10:14:11 PM »

I've heard of putting resistors in series with MV tubes to equalize current when you are putting multiple MV tubes in parallel. At only 250ma you wouldn't need to parallel 866a tubes so that's not a consideration.

Designers also put RF chokes in series with the plate to prevent oscillations.

I've attached the MV tube chapter from an RCA transmitting tube quide. It talks about these issues and shows the RF choke/cap filter circuit..

Dave

* RCA-MV-Stuff.pdf (445.13 KB - downloaded 448 times.)
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Ed/KB1HYS
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« Reply #2 on: December 22, 2008, 06:44:06 AM »

Thanks Dave!
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73 de Ed/KB1HYS
Happiness is Hot Tubes, Cold 807's, and warm room filling AM Sound.
 "I've spent three quarters of my life trying to figure out how to do a $50 job for $.50, the rest I spent trying to come up with the $0.50" - D. Gingery
N3DRB The Derb
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« Reply #3 on: December 22, 2008, 08:14:12 AM »

ed,

my 2 cents....except for the awesome blue glow, 866's are teh pass. Use 3B28's instead. no arc-backs, almost no warm up time. pin for pin replacement. used em on my HB rig for both suck plys.... never a problem.
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W7XXX
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« Reply #4 on: December 22, 2008, 09:35:04 AM »

I agree ... use 3B28's. If you want the glow use the Cetron 3B28's. More of a blue (masculine) glow rather than the lavender 866 (feminine) glow.


* w7xxx 005.jpg (1546.28 KB, 1441x2468 - viewed 576 times.)
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w1vtp
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« Reply #5 on: December 22, 2008, 07:10:30 PM »

I agree ... use 3B28's. If you want the glow use the Cetron 3B28's. More of a blue (masculine) glow rather than the lavender 866 (feminine) glow.

What a cool idea -- using a base for a shorter than needed rack.  I love it.  I'm going to do the same thing.  I have a 4 foot rack that I like a lot but need extra space for my PS.

Sure, I like the blue over the lavender glow -- but the support for the rack caught my attention

73, Al VTP
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W7XXX
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« Reply #6 on: December 23, 2008, 10:34:44 AM »

Al, It is an angle iron welded frame with aluminum panels and heavy plywood bottom. The frame was tapped for 8 x 32 screws for easy removal of the individual panels. I use to have photos of this but can't find them now. ADVICE: Use the largest roller you can find and use all 4 swivel rollers. My front rollers are swivel and the rear fixed. They are also too small and bent a little from having to pull xmtr out for maintenance. Built in 1999.
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k4kyv
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Don
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« Reply #7 on: December 23, 2008, 12:35:55 PM »

3B28's are xenon gas equivalents to 866A's.  4B32's are xenon equivalents to 872A's.  I have used both, and while MV rectifiers are indeed more trouble prone, I have had the xenon rectifiers to arc over as well.  Since I have a large number of MV tubes, I plan to keep using them until my supply of good ones is depleted. New old stock MV tubes are  getting harder and harder to come by at hamfests, but they occasionally show up in estate sales.  I also have plenty of spare xenon rectifiers as well.  The Gates BC1-T has been converted to all solid state rectifiers and remained  trouble free, but I never have had much luck with homebrew strings of diode rectifiers.
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Don, K4KYV                                       AMI#5
Licensed since 1959 and not happy to be back on AM...    Never got off AM in the first place.

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w1vtp
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« Reply #8 on: December 23, 2008, 09:36:43 PM »

Al, It is an angle iron welded frame with aluminum panels and heavy plywood bottom. The frame was tapped for 8 x 32 screws for easy removal of the individual panels. I use to have photos of this but can't find them now. ADVICE: Use the largest roller you can find and use all 4 swivel rollers. My front rollers are swivel and the rear fixed. They are also too small and bent a little from having to pull xmtr out for maintenance. Built in 1999.
Sam -- visited your bio on QRZ.  Thanks for the great idea.  I have two bases one super heavy duty with 4" wheels and another smaller duty.  This is the idea that will get me going.  I think I have a modulator lined up that I used to own (may be getting it back) that will modulate a single 813.  My only need now is the parts for a 2KV PS for the single 813 I want to use in the RF deck.  I may even have a 4D32 xmtr lined up that a good friend of mine's (now SK) XYL may sell me.  Think I'll be putting that on 160.

I'm getting there.  Any other ideas would be appreciated.  My email is

al@w1vtp.com

Cheers, Al VTP
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Patrick J. / KD5OEI
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« Reply #9 on: December 24, 2008, 12:50:33 AM »

I love the 4D32. And I'll take Hg rectifiers any day, even trading 3B28's for them. I have at least 24 3B28's stocked up, but only about 10-12 866's.

If you really like the glow maybe you will find the older style 866 (non-A) more attractive -that has the filament visible, no shield. It is not as robust however.

BTW I am looking for 575A's (the 575 plain pear bulb won't fit) and 673's.
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k4kyv
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Don
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« Reply #10 on: December 24, 2008, 05:24:27 AM »

I love the 4D32.

Don't confuse the 4D32 with the 4B32.
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Don, K4KYV                                       AMI#5
Licensed since 1959 and not happy to be back on AM...    Never got off AM in the first place.

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W7XXX
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« Reply #11 on: December 24, 2008, 08:31:35 AM »

Don, I never had much luck with the diode strings either and I never had a failure using the K2AW diodes. I have enough Cetron 3B28's to last longer than I will.

Al, Glad to help. My PS is a Stancor 2000/2500 v 500 ma from BC 610, Stancor 8 hy swg 500 ma choke, Cetron 3B28's with 8 mfd capacitance and 75k 200 watt bleeder. I use a simple 2 second in rush current circuit that if my health allows I will change to 1 sec, Matter of lowering capacitance. I covered the plywood bottom with aluminum (grounded) and used 1/2" 18 gauge copper strips for connections. Had to break out the old large tinsmith soldering iron. If you need a large 30k-100k 100-200 watt bleeder let me know. I have several values some NIB and I will sell for what I paid many years ago plus shipping. The shipping is the bad part and isn't coming down with gas prices either. I have no plans to build anymore high power xmtrs. I will just keep spare parts for my current homebrew junk and sell off the rest.

 I have a new in the box JAN 4B32 if anyone needs one very reasonable. I also have 4 NIB GE (only used to test) 866A's extremely reasonable if anyone is interested. Can't give them away around here. Also NIB 5557 Westinghouse, and lots of good used Jan 3B28's. Anyone interested PM me and make a reasonable offer on one or more plus priority mail shipping and they are yours. Also several good used 5U4's, 5R4's, 5Y3's, 83v, 6X4, etc., several styles that I will part with reasonable. I hate to EBay anything anymore.

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Mike/W8BAC
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« Reply #12 on: December 24, 2008, 09:23:07 AM »

Quote
BTW I am looking for 575A's

575A's are not easy to find, nos or used. I looked for 2 years until I found a few nos on eBay. Not cheap either.

Having said that, I bet a few here have a stock. Here is a picture of a pair of 575A's in use.



* BPL6.jpg (155.45 KB, 777x843 - viewed 569 times.)
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flintstone mop
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« Reply #13 on: December 24, 2008, 10:10:30 AM »

Nice pic of the 575A's. I hope that with the exposure set for the nice glow that those 4-400's aren't running excessive fil voltage. They look almost white.

Fred
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Fred KC4MOP
Ed/KB1HYS
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« Reply #14 on: December 24, 2008, 10:37:59 AM »

I'm using the MV tubes because I have them. I also have some 3B28's  I like the look of those tubes and have wanted to build something using them for a while.
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73 de Ed/KB1HYS
Happiness is Hot Tubes, Cold 807's, and warm room filling AM Sound.
 "I've spent three quarters of my life trying to figure out how to do a $50 job for $.50, the rest I spent trying to come up with the $0.50" - D. Gingery
Mike/W8BAC
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« Reply #15 on: December 24, 2008, 11:37:12 AM »

Thanks for the concern Fred. The filaments are separately metered and watched closely. I think they look so bright because of the exposure setting. That was taken with no lighting other than filaments.

Mike
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Patrick J. / KD5OEI
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« Reply #16 on: December 25, 2008, 02:26:03 AM »

I love the 4D32.

Don't confuse the 4D32 with the 4B32.

oh yeah you are right.. In that case I'll take the Hg tube. I stil like the 4D32 very much. It says "Raytheon" on it. My liking for the 4D32 must have clouded my vision for a moment. we see what we wish to see..

Quote
BTW I am looking for 575A's

575A's are not easy to find, nos or used. I looked for 2 years until I found a few nos on eBay. Not cheap either.

Having said that, I bet a few here have a stock. Here is a picture of a pair of 575A's in use.



The 575A is better for glow than the 673 because of the open area above the shield. 673's are electrically alike but have more shielding and a less-curved top.

Is there a datasheet and website for the K2AW rectifiers? I might have to use a couple SS rectifiers in the "JAWS II".
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W7XXX
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« Reply #17 on: December 25, 2008, 08:30:27 AM »




[/quote]


Is there a datasheet and website for the K2AW rectifiers? I might have to use a couple SS rectifiers in the "JAWS II".

[/quote]

Good question. I purchased several many years ago after seeing his ad in some ham magazine. I have never seen a website. I purchased both his 6KV 1A large shell radial lead and 12KV 500ma small tubular axial lead. I don't have anymore info.
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