Help With setting up a 1932 ish bandpass receiver

[lloydwells]

I Bought this British Brunswick a few weeks ago for £28 it's in staggeringly good condition I can't for the life of me find service data for it when bought it contained an AC/SG two VMS4B a pen4va and an IW3 firstly I'm wondering if the two VMS4B valves are correct anyway after replacing the caps and some stray resistors it'll pick up Talksport which to be honest where we live you can receive on your fillings! Anyway I'm assuming this is a Bandpass receiver it obviously needs some sort of aligning but I'm not sure how to do it on one of these. I have two trimmers accessible through the side of the chassis another two under the chassis three trimmers on the tuning condenser gangs and two on the rear can any ideas how to get it in wiggle ??

[Silicon]

I don't recall seeing the term 'Bandpass receiver' before.

Is this another name for a 'Tuned Radio Frequency' receiver?

[Herald1360]

It's normally used for a basic 4+R superhet that has two coupled tuned circuits in front of the mixer but no RF amplifying stage between them. Hence a three gang tuning capacitor but no extra valve.

[Mr 1936]

Hi

Firstly, congratulations on your purchase. That looks to be an extremely well made chassis, more Eddstone type quality than the usual domestic offerings. The cabinet style is more typical of the USA than the UK, so were "British Brunswick" an offshoot of an American firm using imported cabinets with british valves ?

At first glance (assuming it is an early superhet) it looks like the RF and LO coils are in the large cans on the right, and a single IFT is in the can at the back of the chassis. The IF may be quite low, e.g. 127 kHz which means a lone IFT is quite selective but the image rejection is poor unless 2 RF tuned circuits are used.

I suspect your best option is to trace out the schematic (or at least the signal flow) to determine what each trimmer does, i.e. Long or Medium Wave, RF, LO or IF etc. Then (as you already know), peak the IF first, then set tuning ranges with the LO trimmers, then peak RF alignment at the HF end of each band with the RF trimmers.

[PJL]

There are a couple of open coils under the chassis, one of which could be an IF transformer. 3 RF valves and no oscillator/mixer sounds a bit odd, the Marconi 256 has 6 valves and a dedicated triode oscillator. I agree you need to draw the circuit out.

[PJL]

The Ultra Tiger AC Superhet has similar valves and bandpass aerial coils so could be a good place to start.

[stevehertz]

Once in a while sets of such amazingly good condition turn up. Incredible. The homes they came from must have been equally clean and pristine.

[McMurdo]

That's nice, and no chance of a plant pot stain on the top! Be interesting to learn about Brunswick's UK history, where they were made etc, how the designs for the UK differed, that sort of thing. I know nothing about them (apart from the record label).

[lloydwells]

I think superhet is barking up the wrong tree isn't it. " Bandpass receivers were the thing at the cheaper end of the market 1931-33 ish generally they're a selective TRF with a Droitwich coil to stop it spreading all over the dial the problem I'm having is Talk Sport seems to be all it wants to receive at the moment.

[PJL]

Bandpass aerial coils added cost and were used on more expensive radios in the 30's like HMV/Marconi. 'Rejector' was the term used to describe a separately tuned circuit in series with the aerial to filter out powerful local stations (or 'IF Rejector' to filter out IF frequency from the input).

Not sure if it is a superhet but the coil with 2 adjusters on the top looks like an IF coil.

[kalee20]

Originally Posted by Herald1360

It's normally used for a basic 4+R superhet that has two coupled tuned circuits in front of the mixer but no RF amplifying stage between them. Hence a three gang tuning capacitor but no extra valve.

Absolutely - the Ever Ready 5033 is an example.

[Mr 1936]

Hi

I don't know if this is a related model:

https://www.radiomuseum.org/r/brunsw...radiogram.html

A 6 valve radiogram from about 1933 by British Brunswick which was a Superhet with 183 kHz IF on Medium Wave but operated as a TRF on Longwave. Maybe an adaption of a Medium Wave only design ?

Service Data here: https://www.service-data.com/product...132/791/b11132

[lloydwells]

Right I think we've got a Decca version of it the Decca 222 of 1932 right number of valves right width and depth on the radiomuseum measurements same escutcheon and knobs now I just need some service data for it.

[PJL]

It confirms it is a superhet but appears there is no service data for that either. You need to get your pen & paper out!

[lloydwells]

It's always the one I've got that doesn't have service data the joys. Anyways I had a crack at setting the IF to 183khz this was the frequency of a 1934 Decca so I guessed worth a pop what I've noticed is the trimmer on the can nearest the valve makes it obvious when you're on frequency the one behind it doesn't seem to make much if any difference. It appears to be the oscillator that's giving me grief and I think I may have bother around there.

[lloydwells]

I've had it out of the case again and poked to no avail the can is likely an IFT so I attempted to set it to 183 this seemed logical as the next year's Decca used that frequency it didn't care for it my Signal generator an advance SG62 only goes down to 150khz however with the trimmers screwed right in the sets still just above 150khz I can get it set up so I get talk sport MW at its usually ridiculous volume and just about get radio 5 not at any sort I listenable volume and the same with radio Cumbria what I have noticed is it doesn't like the signal generator turned up to high which made me think this was an AGC problem BUT the set doesn't have a valve with a diode jn it so I suspect the bother us somewhere around the first or second stage. Now this thing had the volume lot directly attached at the aerial socket turning that up to max cuts the signal and it's not the control I've tried a brand new one.