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Vintage Amateur and Military Radio Amateur/military receivers and transmitters, morse, and any other related vintage comms equipment. |
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15th Feb 2020, 4:39 pm | #1 |
Octode
Join Date: Feb 2006
Location: Bristol, UK.
Posts: 1,042
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Marconi CR300 PSU
I have been given a tatty CR300 with power supply. It was stored in a garage for many years so is need of a rebuild!
I thought I'd start with the PSU. The receiver came with whet appears to be the original manual however the PSU section is totally different to the actual object. The manual, all other information on the net shows the PSU as having one fuse and one switch on the front and another switch inside. Mine has two fuses and no internal switch. Also the tappings/links for the various supply voltages are labelled differently. The manual indicates them as numbered links and mine has them as voltage links coupled with letters. So does anyone have a correct circuit? I probably wont use the receiver on DC of any voltage as the vibrator is missing, but I will change the caps so in the future DC operation might be possible. Malcolm |
16th Feb 2020, 8:23 am | #2 |
Dekatron
Join Date: Jan 2004
Location: Newcastle upon Tyne, Tyne & Wear, UK.
Posts: 8,194
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Re: Marconi CR300 PSU
Hi Malcolm, there were full details of the CR series in a comprehensive RB article a few years ago
Ed` |
16th Feb 2020, 9:47 am | #3 |
Heptode
Join Date: Jun 2012
Location: Southeast Norfolk, UK.
Posts: 773
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Re: Marconi CR300 PSU
This may be the cct you have already but if not:-
http://www.vmarsmanuals.co.uk/archiv...300_Manual.pdf 73 Roger/G3VKM |
16th Feb 2020, 11:28 am | #4 |
Octode
Join Date: Feb 2006
Location: Bristol, UK.
Posts: 1,042
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Re: Marconi CR300 PSU
Roger, yes that is the circuit I already have. For my PSU it is incorrect. Thanks anyway.
From what I can find on the net all the PSU's are for the single fuse and numbered tappings. Ed, I presume RB is Radio Bygones? If so their search engine doesn't come up with any results for Marconi or CR300. If you can let me have the issue date I'd be willing to buy the download to get the information. Malcolm |
16th Feb 2020, 12:51 pm | #5 |
Heptode
Join Date: Jun 2012
Location: Southeast Norfolk, UK.
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Re: Marconi CR300 PSU
OK Malcolm,
I have a hard copy of that Radio Bygones and it does have several pages on the Marconi CR-series. It's Issue no 31 , dated Oct/Nov 1994. P/M me for more info. The article says the manual for the CR300 is T1864/2 but seems to be the same as the VMARS link. 73 Roger/G3VKM Last edited by G3VKM_Roger; 16th Feb 2020 at 1:11 pm. Reason: Add |
16th Feb 2020, 1:20 pm | #6 |
Dekatron
Join Date: Apr 2011
Location: Cornwall, UK.
Posts: 13,454
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Re: Marconi CR300 PSU
Never seen that type before, mine was the single fuse on the front panel.
Lawrence. |
16th Feb 2020, 3:40 pm | #7 |
Tetrode
Join Date: Feb 2012
Location: Bishop Auckland, County Durham, UK.
Posts: 92
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Re: Marconi CR300 PSU
This style of PSU was also used with the Marconi Mercury receiver. You may want to download the manual and have a look at the psu schematics. Let me know if you cant find it on the web.
Andy G4OJY |
16th Feb 2020, 3:46 pm | #8 |
Tetrode
Join Date: Feb 2012
Location: Bishop Auckland, County Durham, UK.
Posts: 92
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Re: Marconi CR300 PSU
I've just had a look at my Marconi Mercury manual, and the schematic for the type 889A PSU clearly shows 2 fuses on the AC input to the transformer.
Andy |
16th Feb 2020, 5:45 pm | #9 |
Octode
Join Date: Feb 2006
Location: Bristol, UK.
Posts: 1,042
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Re: Marconi CR300 PSU
Eureka! Thanks Andy that's the PSU I need.The mains and low voltage input look the same as mine and the layout diagrams are the same.
Many thanks. Malcolm |
27th Oct 2022, 12:53 pm | #10 |
Moderator
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Re: Marconi CR300 PSU
Thread reopened at Julesomega's request.
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Graham. Forum Moderator Reach for your meter before you reach for your soldering iron. |
27th Oct 2022, 1:11 pm | #11 |
Nonode
Join Date: Dec 2012
Location: Stockport, Greater Manchester, UK.
Posts: 2,102
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Re: Marconi CR300 PSU
I have just got hold of a Type 889 PSU which I intend to use for an Electra rx but I cannot find a circuit diagram for this. The Mercury & Electra require a Type 889A, and the schematic is included in the receiver manual which is widely available.
The differences must be minor, but an original diagram is always helpful, especially when dealing with something that has been 'got at' as in this case - can anyone help?
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27th Oct 2022, 1:26 pm | #12 | |
Dekatron
Join Date: Apr 2011
Location: Cornwall, UK.
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Re: Marconi CR300 PSU
Quote:
Lawrence. |
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27th Oct 2022, 1:31 pm | #13 |
Dekatron
Join Date: Apr 2011
Location: Cornwall, UK.
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Re: Marconi CR300 PSU
I found it sooner than I thought (Manual page 36 and onward for the 889 PSU details)
Lawrence. |
27th Oct 2022, 1:58 pm | #14 |
Nonode
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Re: Marconi CR300 PSU
Thanks so much Lawrence, that's perfect!
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27th Oct 2022, 4:54 pm | #15 |
Dekatron
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Re: Marconi CR300 PSU
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28th Oct 2022, 11:59 am | #16 |
Nonode
Join Date: Dec 2012
Location: Stockport, Greater Manchester, UK.
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Re: Marconi CR300 PSU
Whatever it was has been replaced by three silicon diodes, don't ask why three, one is in series with the junction of the others - maybe it was a convenient anchoring point for the two cathodes
This one has the usual mains voltage selection switch with the rather cute arrangement of a rotary switch operated by a lever arm which is accessible with the cover off
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28th Oct 2022, 12:33 pm | #17 |
Dekatron
Join Date: Apr 2011
Location: Cornwall, UK.
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Re: Marconi CR300 PSU
Thanks, I can't remember for sure what was in mine but I don't think it was an OZ4, possibly a 6X5.
Lawrence. |