PCR Type differences

[Mark James]

While we are talking about PCR's ... I have a PCR (with integral speaker) made by Philips. Someone told me that the Philips made ones may have an IF of 470 rather than 465. Is this correct?

Mark

[rjm2013]

Hello,

Not sure on IF's. I've got limited information on the PCR. I've managed to get some REME documents from 1950 regarding alignment, but this is missing component values and voltage test points.

May be I've been spoilt with Murphy circuit schematics.

Still, they are interesting sets.

[G6Tanuki]

Originally Posted by Mark James

While we are talking about PCR's ... I have a PCR (with integral speaker) made by Philips. Someone told me that the Philips made ones may have an IF of 470 rather than 465. Is this correct?

The IFTs in a PCR have adjusters that let them be 'peaked up' correctly over quite a range of frequencies. Given the exigencies of WWII manufacture and the likely accuracy of the signal-generators used on a typical production/alignment line, I'm inclined to say that a 5KHz error either way is quite likely - indeed, an IF signal generator in a poorly-heated factory and fed by wartime-regulation-grade mains (or possibly even an on-site steam/gas-powered generator: such things were commonplace in large factories well into the latter half of the 20th century), could easily drift by 5KHz during a day's production as it warmed up.

In other words - whatever the 'official' IF was, expect to find variations!

[Racal Zonal]

Evening All

Interesting discussion and to think that in the 60s and 70s these sets would hardly be given a second glance.
I may have missed it in the thread but reading the link to the Pye site shows this.....

"A communications receiver similar to the original PCR receiver, which was fitted with a BFO valve stage and other circuit features making it suitable for both speech and CW (Morse code) reception.

The existence of this equipment version explains why the chassis of every PCR series receiver (which was common to all models) has a hole cut for an extra valve holder near the IF strip."

Doesn't this explain the extra valve base ? or is the reference to yet another space.

[G6Tanuki]

I have a suspicion that the answer to that one is lost in the dim, distant memories of wartime exigency. I've seen a couple of amateur-modified PCRs where another IFT [from an 18-set?] has been grafted into one of the unused holes and configured so the mixer-1st-IF transformer had 4 tuned-circuits with a very small [5pF or so] coupling between the second and third windings.
Another mod popular in the 1960s was to replace the EBC33 with an ECH35 and a couple of OA81-type semiconductor diodes. The diodes operated as detector/AGC on AM, the ECH35 was BFO and product-detector.

Even with a homemade mains PSU including a VR150/30 stabiliser for the oscillator, and a transistor BFO, I could never get decent amateur SSB reception on a PCR. The tuning-rate was too high and when you let go of the tuning knob it would usually 'creep' a few hundred Hz one way or the other.

[DoctorWu]

I had exactly that problem. I built a BFO in, I think the design was from Practical Wireless, and had a similarly stabilised PSU, but SSB required constant twiddling.
John

[G6Tanuki]

Here are a few pics of my current PCR "Kitchen Radio": ZA26707, S/N 10727 if you're interested.

It's been rather professionally retro-fitted with a 240V mains PSU and a 'Magic Eye' tuning indicator [VI103, ex-RAF]. The rectifier's a 5Z4G. It's got a 6V6GT/CV511 as the output valve.

The front-panel handles have been removed - and both the jack-sockets you'd expect to find on the front panel have similarly been removed to make room for the "Goodmans" output-transformer you can see in the bottom right corner of the last photo.

I've been able to source a couple of the original 'Igranic' jack-sockets so I can partially return the front-panel appearance to the-way-it-should-be assuming I can move the OPT back an inch or so.

The only mods I have done on this particular PCR have been replacing the old waxie-decouplers with modern WIMA 400V-rated polyester jobbies, replacing "that capacitor", and fitting a modern electrolytic to bypass the 6V6's cathode-resistor.

As regards the eternal argument about what the output-valve should be: on this one there's a hole next to the output-valve which has a smooth-edged bushing clearly designed to take a cable to feed a top-cap-equipped valve, in the same way that there's an identical bushing for the grid-feed to the EBC33 1st-audio valve. So I'm minded to say that the original design was EL32-capable but subsequent production switched to the 6V6 and the smooth-edged EL32 grid-connector hole just never got deleted....

[Station X]

Two posts moved to a new thread here:-

https://www.vintage-radio.net/forum/...d.php?t=119495