Radios with motor tuning units

[andrewferguson]

I was reading the (very interesting) thread on "Vintage radio prices - trends and observations" and I came across the post by Steve (Panrock) about his Defiant MSH938. Curious about the looks of a radio, which, in Steve's words "has such a commanding presence it cannot be missed", I looked it up on Radiomuseum.org. In the description, I spotted this gem:

An exceptionally large pre-war AC mains 5 band table radio housed in a wooden case. With a magic eye tuning indicator, a Motor Tuning Unit controlled by 12 station selector buttons operative on all 5 wavebands permitting easy adaption to individual radio station requirements except for television sound which remains permanently set.

Am I correct in thinking that this "motor tuning unit" means you press a button and the tuning dial automatically moves to the desired station? If true, this would absolutely blow my mind (and my budget - as I would need to acquire a radio with this capability at once! ).

A few months ago I bought a Sony ST-333, a lovely late 70s tuner that has an unusual tuning system based upon variable capacitance diodes whereby you can tune it manually or jump to pre-sets using buttons, but that doesn't automatically move the tuning dial to the desired station (instead, it essentially has many tuning dials, one for each pre-set, and selecting the pre-set selects the desired tuning dial).

[Techman]

Originally Posted by andrewferguson

Am I correct in thinking that this "motor tuning unit" means you press a button and the tuning dial automatically moves to the desired station?

Absolutely!

I've got an old RGD up in the loft with motorised push button tuning and years ago I used to have a Philips radio that had the same. Unfortunately the Philips contracted bad woodworm and was dumped during a house move several decades ago - today I would have treated the woodworm and kept the radio. The Philips radio was working perfectly back then, but the RGD packed up about 20 years ago and I never bothered with it. The motorised tuning part had long been disconnected by its previous owner on this RGD, who was the son of the person that bought it new in around 1936, 7 or 8 - I can't remember exactly now without looking it up.

As the RGD was a 'one owner from new' type job, it still had it's original paperwork/instruction book, which I've got filed away somewhere - if I can find it I'll post the part that describes the motor tuning. Unfortunately, the radio itself isn't in the best of condition, as the previous owner bought it into the place where I used to work and it was used as the workshop 'music and news' entertainment source for many years and got knocked about a bit. It would have been dumped in the end when he left if I hadn't saved it and taken it home.

[Panrock]

Originally Posted by andrewferguson

Am I correct in thinking that this "motor tuning unit" means you press a button and the tuning dial automatically moves to the desired station?

Yes. The Long Wave, Medium Wave, Short Wave, and Television Sound bands are automatically selected as appropriate and the final bit of tuning-in is done by AFC (automatic frequency control). My Defiant is seen here.

Steve

[Vintage Engr]

Yes, there are quite a number of radios with motorised tuning.
The Bush PB189 springs to mind, as I have a couple of these.

Many years ago, when I lived in London, we had a break-in & most things of value were taken.
The police officer who came to take details, was very fascinated with the PB189, which we used every day. He just couldn't believe that something that ingenious was made in the 1930's. His enquiry took second place!

There were also a few TV receivers in the 1960's that use the same technology. The Philco Selectaflash, for example. That was remote controlled by a torch, & the motor drove the usual VHF turret tuner.

All clever stuff.

David.

[vintage_8bit]

I also have an Ekco PB189. Which has motorised tuning. It performs well & sounds good. You also have extra electronics to keep the set on tune, this alleviates any backlash in the mechanics. This extra circuitry also works very well, & adds to the interest in this set. The attached image is prior to restoration. The BB189 is one of my favourites.

[Panrock]

This looks quite similar to the Defiant. Was the motor tuning a standard unit, I wonder, made by Plessey?

Steve

[Paul_RK]

My Ekco PB189 found another home some time ago, but I'm still harbouring three motor-tuned sets - a Defiant MSH957 (console version of the 938, but with push-pull AC4/PENs), a home-built radiogram cabinet incorporating an RGD 1175 chassis, and a Truphonic MA7.

Paul

[Aub]

The Rigonda Symphony radiogram I had, back in the seventies, had a motorised system which kept it locked on an FM station. Not quite the same as what the OP was asking about though.

Cheers

Aub

[Mr 1936]

Hi

I have a mere one motor tuned set (PB189) in my collection, but remember being fascinated by the description of them in a book my father gave me when I was about 8 or 9.

Whether it was magic eyes, shortwave bands, preset stations or motorised tuning the industry was always on the lookout for features that could out-do the competition. The motorised sets seem to come mostly from the 1937 to 1939 period until WW2 got in the way.

Postwar austerity, then the lure of television meant that motor tuning never really made a comeback.

[Techman]

Looking back on the PC, I found some old photos of the RGD that I took over 12 years ago and it shows the motorised tuning. This was when the set packed up and I've just remembered that it failed spectacularly with a flash and some sparking from inside. I seem to remember that the wiring was quite rotten and was shorting out the HT. I decided not to bother with a major fault finding and rewiring job at the time and shoved it up into the loft to be looked at again sometime in the distant future - and it's still there!

I did work on a Rigonda radiogram for someone a couple or three years ago that had motorised tuning - driven by an EL84 type valve, I seem to remember.

RGD pictures below - probably I should have another look at it sometime this winter...if I can work up the enthusiasm - and if I can find it!

[Panrock]

Another fad to make tuning seem effortless would have been 'flywheel tuning'. I believe this was popular in the UK between about 1947 and 1950, and later it was also a feature of the 'piano-key' continental sets.

Steve

[Techman]

Just looking at those pictures of the RGD reminded me that it really needed a complete going over after being in storage for many years. I seem to think I'd started on it when there was a major wiring short and I decided that it was an all or nothing job, so put it aside for another day. The previous owner had replaced the original IF transformers with physically smaller ones. I don't know the history or reason for this, as the radio was already at the place of work when I first started there. I remember that reception in the city where this was being awful, with a lot of noise and crackle. I went up onto the roof of the building and strung a long wire antenna up there which improved things a bit. When the chap left and I inherited the radio and took it away, I remember a big cheer went up from all the staff that worked there, as they'd all had enough of him keep having it turned on with all the interference and noise and everybody having to suffer it. We go on about all the interference on AM radio now, but it was certainly bad in that building back then in the 70s - certainly on that particular radio, anyway.

[andrewferguson]

Oh dear, I think I may have found my latest obsession.

I've always wanted to get a pre-war set. I only have one other "antique" radio - the Vidor CN359 I repaired a few years ago, and getting a pre-war set has always been a goal. I wasn't quite sure what type of pre-war set I wanted, but now I know! I will have to keep a good eye out for one to come up in reasonable condition, given my limited expertise on repairing valve equipment.

Of course, I don't really have space for another "thing", but that's never stopped me before!

Aside from the few models listed in this thread, is there a comprehensive list anywhere of models with the motor tuning unit? (Rather unlikely I know.... I suspect a better approach is to keep an eye on the 'for sale' section of the forum and see what comes up).

[Lloyd 1985]

I’ve never had a motor tuned set, but I have the next best thing! A GEC BC4050, it’s a push button tuned set, but instead of having lots of fiddly little tuning controls for each preset, it moves the whole tuning gang and pointer when each button is pressed. Not quite as much fun as a motorised one…

Regards
Lloyd

[DavidEsp]

Superb sets - I acquired one around age 10, from a friendly neighbour. The magic eye seemed indeed magical (or sci-fi) to me. I used to mess its beam around with TV ring magnets (probably blasting myself with X-rays...). I impressed my school friends with it, especially the power of the motor - many could not hold the tuning knob still against it.

On SW, at night, it introduced me to the likes of "Cemetary 347, Radio Check", which I imagined were secret US-NATO forces lurking in shadowy German churchyards...

[Techman]

One thing I forgot to mention is that if you look at the first picture of the RGD in post #10, that you'll notice a multi-pin socket in the centre rear of the chassis. This socket was for the 'optional' remote control so that you could sit in your armchair and work the tuning controls from a distance. I don't have this unit and I don't remember the previous owner ever mentioning having it. So if you're going to go for a set with motorised tuning then you may as well go the whole hog and get one with remote control too...it would be on the end of a hefty cable which you'd end up tripping over and pulling the set off its table and onto the floor. If I can find that instruction book for the RGD, I'm going to have to have a read of it to remind me about this control - I'm sure it didn't come with the set, but could be purchased as an optional extra at the time.

[Freya]

Have a bought a few motor tuned sets in the last few years, the 1938 HMV 1200 (below) and Ekco PB199 are my favourites, the Grundig 5050W3D doesn't quite do it for me now.
The HMV provided many hours of enjoyment with re stuffing capacitors and cleaning decades of dirt of the chassis... my kind of fun !

[cathoderay57]

Hi Andrew. If you want a pre-war motor-tuned set, then my advice is to go for one in the best condition you can find or afford. The Achilles heel of these sets tends to be the brass contacts that provide the station setting on a metal rotor disk that is rotated by the motor. The disk has insulated segments and once the selected contact passes over the insulated strip the motor supply is interrupted, and it stops at the station setting. The brass contacts get brittle through age and heat and tend to be found broken or cracked. Exact replacements are unobtanium but if you are extremely handy you can make them, but not easily. Also, the rotor disk suffers wear and corrosion and can result in bad contact. I don't want to put you off, but just to make you aware of potential pitfalls. Because the mechanical process of setting the contact position using a thumbwheel to tighten down the contact is somewhat imprecise there would be an element of off-tuning. For that reason, these sets use automatic frequency control (AFC) using an extra reactance valve and discriminator that feeds back a tuning correction to the local oscillator circuit. Jerry

[G6fylneil]

I had a US "town&country" radio in my car in the early 70's with motorised tuning.It had the normal push button permeability tuner, with an additional motor and clutch to tune to the next station with a high enough agc signal. The output valves were driven with a centre tapped choke, and didn't have a cathode bypass capacitor, which rather impressed me too.

[andrewferguson]

Originally Posted by cathoderay57

Because the mechanical process of setting the contact position using a thumbwheel to tighten down the contact is somewhat imprecise...

Actually, that's one thing I was wondering about - are the pre-sets on these sets changeable, or hard-coded. From this description it seems they are changeable (although may(?) involve opening the set up).

Thanks all for the information and advice so far!