Salford Electrical Instruments component(s) ID

[Goodizzy]

Good afternoon,

I am restoring a pair of rather rare EMI DLS-1 column speakers. These have the EMI STD "Orthtone" 373 amps fitted. I am slowly working my way diagraming the circuit and these three components came up. I'm hoping someone might recognize them:

The left component is labeled-

Salford Electrical Instruments Ltd.
Gecolite

With the words 'Type MM103' in the center. It has four taps on it.

The component on the right looks to be some sort of trim pot on top, but has six pins on the bottom. The only identifier is the number 12304. There is an identical component, (cut off in picture) to the right, with the number 12307. Both numbers are hand written in pen.

There are three additional, smaller, carbon track trim pots atop with tie points and various resistors/coupling caps. The entire plate is mounted above the output transformer. (Picture is upside down) I believe it to be the three freq tone correction network or something similar. I believe this is described vaguely as part of the marketing literature but I'd have to go back any check.

Is anyone familiar with this company and maybe could identify the components? Some sort of transformer/inductor.

I appreciate any help.

[dseymo1]

The Gecolite component is a ferrite core, on which is wound either a transformer or an inductor. The other also looks like some sort of audio transformer or inductor, but that doesn't explain the trimpot. Are you sure it's not an adjustable core?
SEI is GEC by another name (more or less).

[ms660]

So far as I can make out Salford Electrical Instruments used to do ferrite pot core inductors, Gecolite was a type of ferrite.

If that's any help.

EDIT: Post crossed.

Lawrence.

[Radio Wrangler]

SEI made ferrite cores and all the associated accessories. GECALLOY was their brand name on powdered mrtal cores... metals like mumetal. They also made their own carbonyl iron dust for RF cores... there was a large gasometer full of hydrogen at the side of Times Mill for reducing iron powder.

They made polystyrene capacitors and various other film types. They made quartz crystals and complete oscillators and filters. I remember them rather proudly showing me the car radio aerial adaptor box for using heater rear window elements as car aerials.

They did test equipment like the GEC Selectest multimeter, and I once had a sig gen they'd made.

Quite a comprehensive company and they still retained a faiir bit of individuality under GEC. About 30 years ago I designed a dual directional wattmeter for the G-QRP club which became fairly well known. I thought it funny to design the transformers around ferrite cores made about a mile away from George Dobb's vicarage

Keep it local!

David

[Goodizzy]

Thank you for all the replies! I would be lost without you guys!

The only reason I alluded to trimpots is because they appear to be adjustable with a flathead on the topside of the mounting plate. Here is (hopefully) a better picture. I apologise as my camera skills are not the best.

[KeithsTV]

Originally Posted by Radio Wrangler

I remember them rather proudly showing me the car radio aerial adaptor box for using heater rear window elements as car aerials.

I remember that adaptor box as I fitted one on my fathers Fiesta. I also knew the people that developed the heated rear window aerials for Ford. There was an article in WW in the 80s written by one of them where the impedances of various heated rear windows were measured. Curiously the Ford Orion rear window came out as 50 ohms. The system separated LW/MW and VHF signals, amplified the VHF signals then recombined them before passing them to the radio. Ingenious system but expensive as later vehicles resorted to a conventional roof aerial.

Keith

[Radio Wrangler]

The screw adjuster moves a small ferrite slug into the pot core's gapped centre post to adjust the inductance You get about 7% adjustment range.

David

[turretslug]

Originally Posted by KeithsTV

The system separated LW/MW and VHF signals, amplified the VHF signals then recombined them before passing them to the radio. Ingenious system but expensive as later vehicles resorted to a conventional roof aerial.

I rather liked the concept and found that it gave good results on all bands, though the motoring press could be sniffy about it- not that I've ever placed that much faith in any area of journalism whose motivation is telling you that this year's product is wonderful and last year's is rubbish.

I hung onto a couple from my Sierras when tin-worm doomed them and they are quite sophisticated, with several Toko coils to band-split, several transistors, and hefty chokes and pot-cores to separate DC element current and RF- I can certainly see that the bean-counters would jib in an industry where costing is famously ferocious. Trouble is, thoughts of retro-fitting to later cars are dissuaded by thoughts of head-lining air-bags and general faff....

[Goodizzy]

Very interesting stuff!

I've since determined the three inductors/coils are part of a complicated feedback network. Some sort of three band frequency control I'm positing. I will hopefully have a completed schematic at some point in the near future....before Christmas I hope!

Is there a catalogue for the company from the amp's era? (Mid 1950s-1960s). Or maybe any ads/magazines I could sift thru online. I'd like to identify the inductance and maybe DCR for the schematic. You