Help identifying a 1930s Decca

[Phil G4SPZ]

I posted this request https://www.vintage-radio.net/forum/...ad.php?t=28430 last year and have just started work on restoring this set.

I'm convinced it's a Decca because the dial escutcheon and the knobs are the same as the Decca model 66 (RR, page 148, fig 155) but the chassis on my set is completely different to that shown on the Trader sheet for the model 66.

The set has had minor repairs in the past and it works, although the main smoothing block and many waxies are overdue for replacement. The valve line-up is AC/TH1, VP4B, 2D4A, an unmarked output valve, and IW4/350 rectifier. The speaker is a Rola energised type. The dial illumination comprises no fewer than six bulbs, switched to indicate waveband in use.

Thanks for any help,

[Paul_RK]

Hello Phil,

I'd guess the 77, an AC-only radio whereas the 66 is AC/DC. Valve complement for the 77 is AC/TH1, VP4B, 2D4A, 7A3 and R2. Nothing else in the Decca range seems very similar - the contemporary model 99 added an RF stage, and the following year's releases were almost all push-button sets.

Regards,
Paul

[McMurdo]

I agree, I have a Decca cataogue from 1937 which has the 44/88/110/120/33/55/66 and 99...the 99 has the same dial and knobs but a different cabinet.

Scans for anyone who wants them.

[Phil G4SPZ]

Paul, McMurdo,

Thank you both very much for your advice, and for completing the valve line-up. The rectifier valve is probably not the original as the smoothing block has also been replaced at some time in the past.

I'll look up the Trader service sheet tonight and report back. Thanks again,

[Phil G4SPZ]

Well, it's definitely NOT a model 77 (as I found out after paying Paul £1.99 for the circuit ) and it's not a model 99 either, but it's nearer the 99 than the 77. My set is badged "Property of London Rentals" and it appears to be a model 99 without the RF stage and with a single short-wave band, not two. The frequency changer is where V1 would have been, and there is even a properly-fabricated metal blanking plate covering the hole that V2's valveholder would have fitted in. The valve line-up in my set is identical to the 99's with the omission of V1, i.e. AC/TH1, VP4B, 2D4A, AC4/Pen and IW4/350.

There is another major difference in that the model 99 has its RF and oscillator coils below the chassis, whereas on my set they are housed in three large rectangular cans above the chassis, as you'll see from the picture.

I now think I have sufficient service data to work on it with slightly more confidence! Thanks again for everyone's help and interest.

[Mark the Mender]

I have seen a chassis like this before! spent enough time looking at it
I have a feeling this is one of the Decca 520,530 or 540 sets very similar to the Decca 400 I have recently restored (the 400 only has LW and MW whereas the 500 series has SW) the clue is in the blanked off valve.
the 400 series is a monoknob design but the 500 series have the knob design on the cabinet you have....I think!

Nice sets when you get them going.

cheers Mark

[Paul_RK]

The 500, 520 etc. models, though, use valves with 13 volt heaters according to 'Receiver Specifications and Prices':9D2, 10D1, 15D1, 7D8 etc. I'm sorry to have given an imperfect steer toward the model 77: this set seems now to be a 'special' produced by Decca for the rental market and hence one whose exact service details aren't very likely to turn up.

Paul

[Phil G4SPZ]

Thanks Mark, that's been very helpful. I've now obtained the service data from Paul which covers both the 400 and 500 series. The physical layout of my set most closely resembles the model 500, 510 or 550, although there are significant differences. My set has three bands and switched dial lamps like the model 99, whereas the 500, 510 & 550 are LW/MW only. The valves are also different.

I'll check the IF frequency next, because Decca used both 130kHz and 456kHz and it will help with identification.

I still think the model 99 is the nearest. Decca obviously used the same chassis for a number of models, and my set being made for the rental market could have been a hybrid, as Paul says, put together from what they had left over from normal production!

Thanks again for everyone's input. I'll probably end up tracing the circuit out.

[Phil G4SPZ]

After tracing out the circuit, this ex-rental set appears to be a Decca Model 99 chassis minus its RF amplifier stage and with a single short wave band instead of two. There are a few other design differences, but it's close enough to a Model 99 to enable me to identify most of the likely suspect components.

Thanks to everyone for their inputs, I now have sufficient service information to restore this set.