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Old 8th Nov 2023, 3:31 am   #1
Doctordigital
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Default Need a little help with a PCR radio

Greetings ,

I purchased a PCR radio from Ebay seller in the U.K. and had it shipped to me in the United States. This is my first time dealing with a radio of this type.
Needless to say, I am having trouble finding much technical information on this set. When I got the radio, apparently, I am lacking a power supply. It has a cord with three connections, a sort of rubber motor plug.

I have no hope of locating a power supply on this side of the pond, so yes I am going to commit a bit of antique radio sacrilege and make an internal power supply. After all we use 120 volts over here, so even if I found a line powered power supply unit, it most likely would be 220 volts.

I understand the filiment circut and bulbs are a 12 volt circuit. But what is the B+ voltage ?? is it 90 volts or higher ?? I have looked all over the place but cannot find a clear answer to the high voltage B+ side of this radio.
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Old 8th Nov 2023, 8:40 am   #2
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Default Re: Need a little help with a PCR radio

Hello and welcome to the forums.

That looks like a PCR1 which differs from the PCR2 in having an internal speaker.

Connection to the Power Supply Unit (PSU) was via a five pin connector. LT 12V 0.7A, HT 250V 55-65mA.

Do you have the circuit for the receiver and PSU? These can be found in "Wireless For The Warrior Volume 3 Reception Sets". I could scan them, but it would take a few days.
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Old 8th Nov 2023, 9:14 am   #3
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Default Re: Need a little help with a PCR radio

Turns out I scanned it some time ago. PM me your email address and I'll email it to you.
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Old 8th Nov 2023, 9:18 am   #4
M0SOE_Bruce
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Default Re: Need a little help with a PCR radio

There is a manual for the set here:

https://www.cryptomuseum.com/spy/pcr/files/pcr_tech.pdf
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Old 8th Nov 2023, 10:25 am   #5
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Default Re: Need a little help with a PCR radio

Lots of people fitted internal PSUs to these in the 60s and 70s along with even less sympathetic modifications - there was a lot of military surplus equipment around then. That would certainly be frowned on today, but it's your radio to modify as you want, and you could take more care to make your mods reversible than was typically done in the 60s. The original cabling is hard to find, and often in poor condition after 80 years.

PCRs were mostly intended for use with external vibrator power supplies in the back of trucks, though many were unissued or pressed into postwar service as recreational sets. The original idea was that invading allied troops could keep in touch with general news about war progress from broadcasters like the BBC and AFN, rather than having to learn everything through military command channels.
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Old 8th Nov 2023, 10:31 am   #6
Mr 1936
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Default Re: Need a little help with a PCR radio

Hi Doctordigital

There was a recent article in the long established UK magazine "Practical Wireless" which gives some useful background: http://www.radiomanual.info/schemi/S...eview_2022.pdf

I used to get this magazine in the 1960's when I was about ten. There were often adverts for these receivers as "army surplus", and they were popular with radio amateurs after a bit of modification like adding a BFO and Power Supply. Practical Wireless published a few modification articles around that time, but I can't find these yet.

I suspect that the original power supply was outboard so that it could be changed depending on the conditions of use, e.g. AC mains or 12 volt lead-acid batteries with a rotary transformer or vibrator for the HT.

I suggest you make up an external power supply first, as adjusting the values will be easier. With modern silicon rectifiers and high value smoothing electrolytic capacitors this can be relatively simple. The transformer can be 110 V primary and say 220 V secondary, followed by a bridge rectifier, shunt reservoir capacitor, series resistor (say about 220 ohms 2 watts) and finally a shunt smoothing capacitor. The HT current drain is more or less constant, so the HT voltage can be trimmed by changing the smoother resistor. This should be rated at about 1 watt for every 100 ohms of value. The simplest thing for the LT/heaters would be a separate 110 to 12 volt transformer, but do check the output voltage under load.
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Old 8th Nov 2023, 1:54 pm   #7
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Default Re: Need a little help with a PCR radio

There's a thread about the PCR variants on the forum here: https://www.vintage-radio.net/forum/...ad.php?t=22896


And the Pye Telecom History site has a few more details about their manufacture: http://www.pyetelecomhistory.org/pro...Type_PCR_PCR2_

As well as: https://www.electronics-notes.com/ar...ions-radio.php - where the one shown has a retro-fitted Magic Eye - just like one of mine does, and fitted in exactly the same place. I suspect there was some sort of semi-official [or small-business] operation doing these mods before sending the radios back out.

and http://www.radiomanual.info/schemi/S...eview_2022.pdf as noted upthread.

along with links to the "EMER" technical manual, alignment procedures, schematics etc at https://www.cryptomuseum.com/spy/pcr/index.htm


I've got a couple of PCRs here, alas they are both the version with only a single SW band so they are not that useful given the rapid closedown of broadcasting on MW and LW.

In times past I used one as an 'intermediate frequency' stage at 7.5MHz with an old WWII-era "Gee" RF-unit in front of it as a VHF converter, which worked surprisingly well.
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Old 8th Nov 2023, 6:31 pm   #8
M0FYA Andy
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Default Re: Need a little help with a PCR radio

I confess I can't understand why you would want to build a power supply into the radio, thereby significantly reducing its value.
Simply build your psu into a separate box to sit alongside it, in the manner of the original.

Andy
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Old 8th Nov 2023, 6:40 pm   #9
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Default Re: Need a little help with a PCR radio

Quote:
Originally Posted by M0FYA Andy View Post
I confess I can't understand why you would want to build a power supply into the radio, thereby significantly reducing its value.
Simply build your psu into a separate box to sit alongside it, in the manner of the original.

Andy
Convenience? Practicality? Domestic acceptibility?

Remember that in the 50s 60s and 70s when these things were being sold off to us SWL/Ham types as cheap and cheerful government surplus the idea that they might subsequently have any lasting 'value' never occurred to us. We bought them cheap and reworked them to do what we wanted them to do.

I have no problems at all with "Period" reworkings/updates/modifications of such radios.
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Old 8th Nov 2023, 6:50 pm   #10
M0FYA Andy
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Default Re: Need a little help with a PCR radio

I don't think convenience and practicality are materially affected, and if the basic radio is accepted domestically then why not with a psu? If it is an issue put it behind the main unit!
What was commonplace in the 50s, 60s and 70s is irrelevant, PCRs have now become 'vintage', why destroy their authenticity.

We'll have to agree to differ.

Andy
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Old 8th Nov 2023, 6:59 pm   #11
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Default Re: Need a little help with a PCR radio

One of the common mods was to replace the LW coils with the SW tropical bands.

It isn't clear why the PCR spec included LW - there weren't any Allied LW transmitters operating in 1944.
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Old 8th Nov 2023, 7:10 pm   #12
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Default Re: Need a little help with a PCR radio

Quote:
Originally Posted by paulsherwin View Post
One of the common mods was to replace the LW coils with the SW tropical bands.

It isn't clear why the PCR spec included LW - there weren't any Allied LW transmitters operating in 1944.
That aspect intrigued me. The PCR-series of radios always seemed to be a strange amalgam of civilian and military design. The radio itself, and the various-voltage power-units, fitted the same case-profile as the WS19 which would have made sense from a production perspective, and it meant that the PCR-series radios could occupy the same mounting-slots in 'fitted for wireless' vehicles that might otherwise have taken a WS19.

The RF/IF stages of the PCR radios also share a lot of commonality with the WS19.

But why include LW? It seems odd.
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Old 8th Nov 2023, 8:59 pm   #13
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Default Re: Need a little help with a PCR radio

Hi, I've done a few of these sets for people, note that some were modified for 6.3V heaters with all valves in parallel, instead of the series/ parallel standard configuration, which cam lead to confusion if one valve heater goes.
It should be quite possible to add a small internal subchassis with the transformer etc for the psu. This could then be later removed to revert to original vibrator condition if wanted

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Old 8th Nov 2023, 9:14 pm   #14
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Default Re: Need a little help with a PCR radio

There's certainly lots of room inside for a PSU.
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Old 8th Nov 2023, 11:01 pm   #15
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Default Re: Need a little help with a PCR radio

I think that you Tanuki et al and the article Mr 1936 posted, have put the background of the PCR series together Paul. I remember quite a long thread at one point, simply trying to establish whether they were intended as a NAAF set or not and the wavebands etc but nobody really seemed to know very much more about the background then.

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Old 9th Nov 2023, 1:54 am   #16
Doctordigital
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Default Re: Need a little help with a PCR radio

Quote:
Originally Posted by M0FYA Andy View Post
I confess I can't understand why you would want to build a power supply into the radio, thereby significantly reducing its value.
Simply build your psu into a separate box to sit alongside it, in the manner of the original.

Andy
I must admit I did not want to, but as these Radios are not as common over here in the States, I would love to have found an original power supply for it, but after calling every source over here, they are nowhere to be found. Also given the " Plug " it has cannot be original and reminds me of a Bakelite version of a plug used on Goulds well pumps, I do not think it is original as is.

I have nearly 100 radios in my collection, the majority being military sets used by the United States Military from 1932 through Desert Storm, I like to keep them original. There just are times I have no choice.

I will post a picture of the plug, I do not think it was original.
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Old 9th Nov 2023, 1:57 am   #17
Doctordigital
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Default Re: Need a little help with a PCR radio

I do not know if this was the original plug, I believe some one said it was a five pin plug.
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Old 9th Nov 2023, 9:56 am   #18
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Default Re: Need a little help with a PCR radio

The original plug definitely had five pins. However two pairs of pins were paralleled to carry the LT current, so a three pin connector will do the job so long as it can carry the current.
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Old 9th Nov 2023, 11:12 am   #19
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Default Re: Need a little help with a PCR radio

When these radios were being sold off in the 60s, they almost always came without a mains PSU. This is because they were intended for mobile use as Allied forces fought their way across Europe, as mentioned upthread. Original mains PSUs are rarely seen apart from in a few specialist collections.

In the event they weren't widely deployed and many thousands were sold off in unused condition.
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Old 9th Nov 2023, 11:42 am   #20
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Default Re: Need a little help with a PCR radio

The 3-pin connector on that cable looks very much like the popular Bulgin 5A mains connector, frequently found on guitar amplifiers and very much in demand. It doesn't meet today's safety standards and certainly isn't original to the PCR set. Unless you need it for something else, I'd suggest selling the connector and using the proceeds to fund construction of a suitable power supply with a more appropriate connector. Jones connectors are still available and work quite well for such things.

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