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Malcolm G6ANZ 15th Feb 2020 4:39 pm

Marconi CR300 PSU
3 Attachment(s)
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.


Ed_Dinning 16th Feb 2020 8:23 am

Re: Marconi CR300 PSU
Hi Malcolm, there were full details of the CR series in a comprehensive RB article a few years ago


G3VKM_Roger 16th Feb 2020 9:47 am

Re: Marconi CR300 PSU
This may be the cct you have already but if not:-



Malcolm G6ANZ 16th Feb 2020 11:28 am

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.


G3VKM_Roger 16th Feb 2020 12:51 pm

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.



ms660 16th Feb 2020 1:20 pm

Re: Marconi CR300 PSU
1 Attachment(s)
Never seen that type before, mine was the single fuse on the front panel.


AndyWright 16th Feb 2020 3:40 pm

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

AndyWright 16th Feb 2020 3:46 pm

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.


Malcolm G6ANZ 16th Feb 2020 5:45 pm

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.


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