Collins 820E-1/F-1 Screen Transformer

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Dale H. Cook
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Collins 820E-1/F-1 Screen Transformer

Post by Dale H. Cook »

I have a client with a Collins 820E-1 with an open winding in the screen transformer modulator secondary. Would any of you have a scrapped-out 820E-1/F-1 screen transformer whose windings all ohm out with continuity? Collins used the same transformer in the 820E-1 (5 kW) and 820F-1 (10 kW).

Failing that can you suggest any good rewinders? It has a 240v Y primary and two 875v Y secondaries so it is not a simple rewind job.
Dale H. Cook, Contract Engineer, Roanoke/Lynchburg, VA
http://plymouthcolony.net/starcityeng/index.html

Jon Book
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Re: Collins 820E-1/F-1 Screen Transformer

Post by Jon Book »

A collins 820-e 1 (removed from service in 2007) is available, in part or whole. 5kw. Not sure if anyone still needs parts
Anyone interested in such unit?

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Dale H. Cook
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Re: Collins 820E-1/F-1 Screen Transformer

Post by Dale H. Cook »

I am definitely interested in the screen transformer. Does it still have any of the 4CX5000A tubes, and if so what condition are they in? We would be interested in one of the 4CX500A chimneys, as the one on the final is home made and does not fit snugly to the tube. Does it have an original manual and schematic? Ours was bought used with a tattered schematic and a photocopied manual (so the photos are poor). We would also be interested in some of the push button switches since we have a few in rough shape. I will see if there is anything else that we might want. I would also like to know where it is - if we can drive there (even if it requires an overnight stay) that would eliminate shipping costs for the screen transformer. PM me if you want to discuss it off-topic.
Dale H. Cook, Contract Engineer, Roanoke/Lynchburg, VA
http://plymouthcolony.net/starcityeng/index.html

Jon Book
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Re: Collins 820E-1/F-1 Screen Transformer

Post by Jon Book »

send pm email for more info.

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Dale H. Cook
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Re: Collins 820E-1/F-1 Screen Transformer

Post by Dale H. Cook »

The Collins transmitter that Jon Book had a lead on is gone, so I am back to square one, looking for a Collins 820E-1/F-1 screen transformer.
Dale H. Cook, Contract Engineer, Roanoke/Lynchburg, VA
http://plymouthcolony.net/starcityeng/index.html

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RGORJANCE
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Re: Collins 820E-1/F-1 Screen Transformer

Post by RGORJANCE »

Try these guys for rewind work on the xfmr....

SNC
101 W. WAUKAU AVE.
OSHKOSH, WI 54902-7200
920-231-7370

They have a good reputation, and have rewound many bcst xmttr xfmrs.
Fossil

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Dale H. Cook
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Re: Collins 820E-1/F-1 Screen Transformer

Post by Dale H. Cook »

Fossil -

Thanks for the reference. Sending it out for rewinding is a last resort, as my 5kW customer will be at 30W daytime power (they run an LPB at night) while the transformer is out. "If I were a rich man" I would spend several hundred dollars to fix my fried 100W LPB as a loaner, but, alas, "I am just a poor boy".
Dale H. Cook, Contract Engineer, Roanoke/Lynchburg, VA
http://plymouthcolony.net/starcityeng/index.html

dd92251
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Re: Collins 820E-1/F-1 Screen Transformer

Post by dd92251 »

Dale.... Did you get in touch with Jeff Konrad from Rock Island, IL ? He is parting out an 820 E/F1....

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Dale H. Cook
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Re: Collins 820E-1/F-1 Screen Transformer

Post by Dale H. Cook »

Yes - I am in the midst of composing a reply to Jeff's email.
Dale H. Cook, Contract Engineer, Roanoke/Lynchburg, VA
http://plymouthcolony.net/starcityeng/index.html

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Dale H. Cook
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Re: Collins 820E-1/F-1 Screen Transformer

Post by Dale H. Cook »

They guy who has the Collins 820E-1 transmitter in Iowa wants too much for the parts, so I would like to ask all of you to keep your eyes and ears peeled for an out of service 820E-1 or 820F-1 from which we might buy some parts. Continental estimates that there are only about six of them still in service, so there are possibly more than six sitting unused in buildings. For you younger engineers who do not have extensive experience with this transmitter, may I point out that the most crucial parts for us, especially the screen transformer, were not used in any other models of transmitter.
Dale H. Cook, Contract Engineer, Roanoke/Lynchburg, VA
http://plymouthcolony.net/starcityeng/index.html

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jthorusen
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Re: Collins 820E-1/F-1 Screen Transformer

Post by jthorusen »

I can't find any detailed info on the Collins 820E series transmitters on line. Does this transmitter use the grounded screen technique where the screen supply is effectively in series with the plate supply and has to supply as much current as the plate supply does, thus necessitating a really hefty screen transformer or is the screen supply more conventional where a smaller transformer may work?

I guess I am also asking whether you require an exact replacement or are willing to use a substitute transformer?

If you are willing to make a substitution, perhaps you could supply us with the required parameters.

Regards,
James K. (Jim) Thorusen
KB6GM
Central Coast Electronics
www.centcoast.com
NW Oregon Consulting Bdcst Eng.

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Dale H. Cook
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Re: Collins 820E-1/F-1 Screen Transformer

Post by Dale H. Cook »

jthorusen wrote:
Thu Nov 14, 2019 9:01 pm
I can't find any detailed info on the Collins 820E series transmitters on line.
I don't find that surprising - online information about the more expensive '70s transmitters can be scarce
jthorusen wrote:
Thu Nov 14, 2019 9:01 pm
Does this transmitter use the grounded screen technique where the screen supply is effectively in series with the plate supply and has to supply as much current as the plate supply does, thus necessitating a really hefty screen transformer or is the screen supply more conventional where a smaller transformer may work?
It is a conventional screen supply. Typical multimeter screen readings at 5 kw (we have an 820E-1) are 850 V @ 0.40 A for the PA, and 875 V @ 0.05 A for the modulators with 1 kHz 100% modulation.
jthorusen wrote:
Thu Nov 14, 2019 9:01 pm
I guess I am also asking whether you require an exact replacement or are willing to use a substitute transformer?
The owner wants an original, as do I. Continental estimates that there are about six 820E-1 / F-1 transmitters still in service. Collins sold enough over several years that there are bound to be some sitting abandoned in shacks where they have been replaced by newer transmitters.
Dale H. Cook, Contract Engineer, Roanoke/Lynchburg, VA
http://plymouthcolony.net/starcityeng/index.html

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