GEC Radiogram model BC3658. 1935

[Heatercathodeshort]

GEC RADIOGRAM MODEL BC3658. 1935
Part one.
It has been quite a while since I overhauled a pre war radiogram. Since a kid I have always loved records of the 78 variety and the gramophones they were played on. I suppose it's something that begins when your very young that you continue through life.

My first encounter was my parents Columbia cabinet wind up gramophone, a large piece of furniture with record storage at the front with a louvered grill that could be opened and closed acting as a volume control. I believe it dated from 1929 purchased second hand when Mum and Dad were married in Nov 1936. It played with incredible volume.

When Dad was demobbed from the RAF in 1946 he purchased a new HMV 1114 radio from Smith Bros in Merton High Street, South West London. It had switched pick up terminals and the old Columbia was soon fitted with a Bakelite AMPLION pickup. You still had to wind it up but the motor would play three 10" 78's before requiring another crank. I presume it was a double spring unit.

I came along in 1948 and the gramophone soon became a part of my early years, often played by my older sister. The 78 records were a mix of just about everything recorded! Swing music, dance bands, novelty, and a lot of classical of all ages. Some were even acoustic recordings!

By the mid 1950's the old Columbia had become obsolete and was replaced by a Fidelity HF2 record player. It was fitted with the super reliable BSR UA8 changer and sounded great. Years later I was very surprised to discover that it only had single valve amplifier, an EL84 fed with a high output BSR TC8H cartridge.

By 1961 I was working after school at a TV shop in South Wimbledon. I was presented with all manner of obsolete TV and radio receivers and general electrical junk including the odd radiogram. Add to this the quantity I brought home from Jumble sales and you can imagine how my very tolerant Mum had to put up with! [Dad died in 1963]

The piles of 78's seemed to grow without actually adding any to the hoard. I managed to repair most of the grams that usually had minor faults such as dud rectifiers and the odd smoothing caps. I think most were disposed off due to the fact that they had become obsolete rather than breaking down. Eventually I think we had a working pre war gram in every room in the house!

My main interest is television but this fascination with gramophones has continued all my life and I have managed to gather quite a collection of wind ups and mains radiograms.

This 1935 BC3658 GEC has been patiently awaiting attention covered with an old sheet in my workshop for around 18 years. With the present situation I thought it was a good excuse to see what could be done with it.

The BC3658 was produced for the 1935 season. It is a 4 valve + rectifier superhet with a 10" mains energized loudspeaker. The valve line up is MX40 mixer/osc, VMP4B I.F. amplifier, MHD4 detector/AGC rec/L.F. amplifier and a MPT4K catkin output pentode. The rectifier is a directly heated U12/U14.

The cabinet houses the radio chassis secured rather oddly by bolts that pass through bushed holes in the right side of the cabinet. I must admit I find this rather strange as I am sure a more discreet way could easily have been devised that would not have involved defacing the grand cabinet. The Garrard single player motor unit is fitted neatly under a baize lined lid to the left of the radio scale and the 'TUNEON' neon tuning indicator, both surrounded by chrome bezels. It is very smart with a distinctive Art Deco style. The loudspeaker opening has three chromium plated bars together with a decorative motive just below it. Black grooves separate the vertical sides with matching veneers to set off the whole effect. It is very stylish but to appeal to a wide variety of customers tastes, keeps within traditional trends of the day with it's dark varnish and originally highly polished piano finish.

The heavily constructed cabinet is in very good condition but years of storage, thankfully in the warm and dry have resulted in the dirty dark varnish breaking down and becoming flaky and opaque. Some areas are devoid of varnish altogether revealing some very nice veneer underneath all the muck. The refurbishment of the cabinet will be explained in a later part!
The pictures show the cabinet and chassis before the start of restoration.
Regards, John.

[Herald1360]

Someone's been at it before.... Mullard mustards anybody? Blue electrolytics?

[1100 man]

Hi John.

It's always a pleasure to read one of your detailed write- ups and the background stories that go with them- keep them coming!!

I guess cabinet styling from that period was 'distinctive'! I'm not sure what I would have felt about it had I been a prospective purchaser in the '30's!

The Americans seemed to take a completely different route to us with much more fancy styling that the Victorians would have been proud of- lots of embellishment and detail.

Will be interested to see how you get on!

All the best
Nick

[Heatercathodeshort]

Thanks Nick. Art Deco had a very strong following with the 'Bright Young Things' of the 20's and 30's. They wanted to cast aside all the miseries of WW1 and the dark Victorian and not quite so heavy Edwardian era. Granny would not have approved of Art Deco! Outrageous! My dear, have you gone mad?

It also allowed into British homes what was probably their first affordable experience of 'Modern Art' such as a cheap tea service courtesy of Clarice Cliff and Woolworth's that brightened up the tea table. Once again Granny would have needed to have taken to her bed as they used to say if you have served her tea and cakes in such outrageous china.

The Art Deco movement emerged from the Exhibition of Decorative Art held in Paris [where else!] in 1925. It could not have chosen a better launch especially with the arrival of the radio industry, the cinema building and the housing boom that occurred between the wars, the designers of which encompassed it with gusto!

This GEC radiogram manufactured in 1935 is a typical example but being 'The General Electric Company of England' pulled back the reins a bit resulting in a very smart piece of furniture for it's day[it still looks good today] as you will later see into the bargain.
Part two will explain the early checks and assessment. Thanks again Nick. John.

[turretslug]

It's always good to read your write-ups John, there's plenty of sound experience and hands-on wisdom for those of us who came to vintage electronics somewhat after the event. I've come to like the whole philosophy of '30s stuff, when electronics brought what must have seemed almost like magic into many peoples' homes and a radiogram really was an entertainment centre. That chassis top looks in really nice nick, and there's no doubt there that a GEC chassis gets you value for money in steel! I have no objection whatsoever to what some seem to dismiss as "got at" if it's been done competently, it implies that something was felt worth repairing even long after it was superceded in the brochures- seeing Mullard mustards suggests that the work was done a good 30 years on from new. Finding something of that age untouched from new suggests to me that it may well have been a bit unexciting and just faded from interest fairly quickly. I love those old resistors that look like industrial fuses, though they must take a bit of care in positioning.

Originally Posted by 1100 man

The Americans seemed to take a completely different route to us with much more fancy styling that the Victorians would have been proud of- lots of embellishment and detail.

It really is quite marked- many US domestic radios seemed determined to hide their purpose in fussy Victorian-style ornateness and even the early '30s comms receivers, pre-HRO, look as if a bored silversmith was let loose on the front panel.

Colin

[Heatercathodeshort]

Originally Posted by Herald1360

Someone's been at it before.... Mullard mustards anybody? Blue electrolytics?

Yes these are explained in part two. I must admit that the standard of work carried out not long before I obtained this gram would not have guaranteed you a job at Ferguson Radio & Television. They had very high standards at T.E.I.
These were the only components other than the fatty output valve that had been replaced. I guess it just carried on working probably as a radio from 1945 [explained later] till it was laid up may be in the 1960's. I wonder who purchased originally? We will never know. John.

[ekjdm14]

Come on, I want all the juicy details! that is a nice looking piece, good to see RG's getting some love too. Great read so far,

cheers,

[Heatercathodeshort]

Everything comes to those who wait.

[Freya]

I see what you mean about the cabinet style, it is Very Art Deco in its looks.
Cant wait to to read next part, I'm sure your recovered from your winding..

[peter_scott]

One of those used to sit in my parents' house and its chassis had been stripped out and hidden under the floor.

My father had gutted it as a free standing cupboard and put a couple of doors on the front. I, aged 13 subsequently removed the doors and installed a new front panel with the speaker aperture adorned with the original chrome strips. I mounted a BSR autochanger in where the original 78 rpm turntable had lived and an FM tuner above the speaker.

Seeing the chassis again certainly brings back memories. I stupidly blew up the tuneon on our one!
If memory serves me correctly the tuneon had a nice little bevelled chrome surround and the tuning dial a separate one with similar profile.

Was the turntable motor a circular thing about 10" in diameter but only about 1.5" deep?

Peter

[Heatercathodeshort]

We all destroyed things Peter. They were just obsolete old fashioned looking items that did not fit into the G Plan living room of the 60's. Neither would it play your Rolling Stones 45's, just dad's old 78's and can you tell me, who was Roy Fox dad?
Mind you the thought of playing them in the living room was not very hip, much better as a teenager in your 'knock to enter' bedroom.
They ended up as ornament stands covered with a linen cloth or a TV table. I saw many during my early days in the trade. That's why so many survived. Happy Days. John.

[Heatercathodeshort]

Part two.
The chassis was disconnected together with it's tangle of speaker leads and placed on the bench for inspection. The first thing do do was to remove the square glass scale and put it aside in a safe place. If this was accidentally broken the whole project would be in jeopardy. A replacement glass would be almost impossible to obtain being an important part of the presentation.

A visual inspection showed nothing nasty other than a few modern Philips 'musties' rather badly fitted and entirely the wrong values. At first sight the 3 x 8uf 500V smoothing capacitors appeared to be original but delving into the can at a later stage discovered the B.I. 'condensers' were three individual units in wax paper oblong cases date stamped 'DEC 1945' I guess it went in for an overhaul soon after the end of WW2. That was still three years before I was born! They were actually OK but 75 year old paper electrolytics could not be trusted. It's odd that they were still producing these old card case types when the aluminium can had universally replaced these some years earlier.

The front mounted 500K volume control complete with single pole switch was possibly a later replacement but was falling to bits and looked as if it had been fitted by a boiler maker using a soldering iron borrowed from the foundry. A suitable period replacement was sorted after tipping many boxes of pots out onto an old sheet. You guessed it...The one required was in the last but one box. Spindle length was checked and the pot was secured to it's special remote bracket and soldered into service. It was time to arrange some power and see if the chassis was willing to give up it's secrets.

That completed, the H.T. line was checked for shorts and a temporary ex TV chassis smoothing choke was fitted in place of the speaker field. This was to cause some odd faults the reason of which should have dawned on me in a lot less time than it did. I'm so used to dealing with auto bias in television receivers that my mind has to readjust back to the 1930's! It's a bit like reversing an articulated lorry. You have to turn the steering wheel the other way when reversing.

With the bench test output transformer and speaker connected, around 120V was supplied resulting in a very dim glow from the U12/14 rectifier. At least it wasn't glowing blue! The two scale lamps 3.5v .3A were both U/S. Each lamp is connected between the center tap and outer of the 4V winding on the mains transformer providing 2v per lamp. These were soon replaced if nothing else other than to prove that power was applied. After a couple of minutes their was a faint hum from the speaker and crackles when operating the muting and waveband switches. Life stirred.

Everything was cool and the H.T. remained stable. Advancing the mains input livened up the general hum and crackles but with my 50ft aerial applied there was absolutely no sign of any signals.

It was time to carry out some very basic tests in an attempt to get a signal from the aerial socket to the loudspeaker. A quick check of vital voltages was made. The audio preamp MHD4 and output stages seemed lively enough. The output valve should have been a Catkin MJP4K. The one fitted was a massive MKT4 of glass construction. The valve is so fat that it fouled on the front tuning gang. A hunt through the Catkin box produced a clean looking example. This was tested on the AVO Mk3 and gave excellent readings as Catkin's always do. Checking voltages on the VMP4G I.F. amplifier revealed zero on it's screen grid pin. The cause of this was a clumsily broken odd value 77K feed resistor. An 82K was fitted and the chassis powered up. [This was manufactured prior to the introduction of preferred values in 1941]

This time I had signs of weak signals on both MW and LW and these were being blasted out with interference. An examination of the 125kc/s I.F. transformers and all ceramic trimmers including the ones on the three gang capacitor had been well fiddled, mostly completely unscrewed.

The waveband switch was carefully cleaned with DeOxit together with the I.F. selectivity and muting switches plus valve pins. With the Advance E2 set to 125kc/s the little circular I.F. transformers were soon brought into line. They were a l o n g way out of alignment.They transformers are very small, only a little larger than the gray painted circular microphone transformers that were popular in the 40's and 50's.

The Oscillator trimmers and padders were roughly set at mid point and again power was supplied. This time stations were received at a fair volume but the bandwidth and muting switches had some very odd effects and clearly something was out of tolerance to say the least!

I had gone about as far as I could with the satisfying knowledge that I was likely to get a worthwhile result. The chassis had the usual number of waxie caps together with a tin box called in the manual the 'paper capacitor box' These would have to be dealt with before proceeding any further.

It contained a block of pitch engulfing four capacitors, and some cotton covered leads. Not a nice job to get the tar baby out of the can, or so I thought but the heat gun carefully applied soon had the contents slipping out of the tin box.

This was soon repacked with good quality BVWS capacitors. C6 .1uf MX40 osc anode decoupler, C11 .5uf MHD4 cathode bypass, C19 .2uf EXT speaker coupling and C12 .5uf part of [14] Amplified AGC circuit.

Next to tackle was the much larger tin box containing the three 8uf 500v reservoir and smoothing capacitors. These were small rectangular waxed cardboard boxes manufactured by British Insulated. They only needed a tap to extract them and to my surprise they were dated Dec 1945, probably part of a general overhaul after the dark days of WW2.

Again the tin box was repacked with quality BVWS components and the box complete with six fiddly leads, refitted on the chassis.

Powering up produced greatly improved reception with even the TUNEON neon tube tuning indicator working to some extent on a strong signal. It was far from correct with distortion on strong signals and the muting circuit cutting all signals dead when it was switched into circuit.

The delayed AGC circuit was obviously not working and it was time to look at the negative bias supply for the delayed AGC circuit or more correctly, where did it come from? This voltage is derived from the negative H.T. supply developed across the field winding of the 10" energized speaker feeding a series resistor network and finally returning to chassis earth. The field coil has a resistance of 1400 ohms and my temporary smoothing choke measured just under 50 ohms. Their was very little voltage being developed across the choke and this was upsetting the operation of the valves controlled by the negative line. What side tracked me a bit [excuse] was the complete absence of mains hum. The background was completely silent. I really should have known better but you learn something every day. It's all part of the fun.

I feel a bit guilty about this because my pet Orangutan 'Interlace' kept prodding the choke but to get rid of him I just produced a banana from his treats box that resulted in a rapid exit to the tool shed to consume it..I really should have noticed what he was trying to tell me.

With a temporary 1.5K wire wound resistor was wired in place of the choke, reproduction cleaned up dramatically. A full alignment was carried out and everything peaked exactly as the directions in the GEC service data obtained from this Forum's link at the top of the page. [£1.99! What an absolute bargain!] The chassis was now very lively and time had come to repack the waxies I had replaced earlier. The under chassis views are now much more in keeping with 1935. To be honest, if they had been fitted nicely and of the correct values I would probably have left them in place but they were horribly fitted and incorrect values.

After this exploit I fancied a change of scene and decided to see if the Garrard single player 78 deck was capable of playing a record. Some hope!

To put it in a nutshell, the motor was seized, the autostop had been vandalized and the speed controller botched up with a bent nail. To add insult to injury the 1.8k pick up coil was O/C and oh, of course I must not forget the armature damping material that had turned into concrete.

What to tackle first? I'll let you know in the third part..

[Heatercathodeshort]

A few more pictures of the entrails.

[Andrewausfa]

Hi John,

I'm especially interested in watching you work on yours as I have a Fidelity AC5 (BC 3650) up in the loft. The last time I worked in it I had power, Tuneon action and lights but otherwise no-one at home. One of those sets I keep meaning to look over again.

Andrew

[Heatercathodeshort]

Hello Andrew. Yes it's the same chassis. Straightforward to work on but with a few buried components. A typical high quality British GEC product. Good luck with it but study that bias line! Regards, John.

[Heatercathodeshort]

Part 3.
The Garrard motor unit and pickup looked to be in good condition but as always, appearances can be deceptive.

Upon removal of the turntable the first thing that came into vision was a bent nail that was fitted to the base of the speed control spindle in place of the correct split pin. The spindle was also flopping about due to the lack of tension between what should have been the split pin and the motor base plate due to the lack of the correct spring washer. Fortunately I had a spring washer in the gramophone weird bits box and the correct parts were soon assembled resulting in the correct operation of the speed control spindle.

Before I go any further I would like to add a word of caution. The motor housing and the pick up arm are constructed of a light weight metal material known as 'Mazak' It's manufacturing advantages are that it can be easily cast, is rustproof and light weight. All good so far but it's biggest let down is that it is extremely brittle. Great care has to be taken when handling it or reassembling items manufactured from this material. When servicing record decks extreme care has to be exercised when handling to prevent the deck from falling back onto the arm. A fracture will surely occur.

The whole assembly was stripped and the motor unit removed from the plate. Removing the cover [wrong screws fitted] revealed the speed control bob weights that were fortunately undamaged and the worm drive via the gear from the motor.

Everything was coated in hard, thick, dark brown grease that had to be removed. The drive unit including the bob weights were soaked in diesel for an hour then very carefully dismantled, cleaned, then reassembled checking that a tiny steel ball at each end of the drive shaft were in place. The felts on the speed adjuster were lubricated with 3 in 1 thin oil and were in remarkably good condition. The bob weight assembly was now a smooth fit on the drive spindle and after testing manually decided to apply power to the motor. [I did check the windings were not O/C during my initial tests..

To my relief it ran as they say, like a sewing machine. It is very quiet and after 85 years must be a tribute to Garrard Engineering.

Attention was then directed towards the rubber mounts that isolated the motor proper from the steel deck plate. As always these had turned into Bakelite door knobs in urgent need of replacement. I have a large grommet box containing all sorts of strange rubber devices most of which I have absolutely no idea of their purpose. [please don't ask for pictures] Time and again the box comes up trumps as it did this time with four nice black rubber grommets of a similar size but not shape as the originals. These together with some spacing washers made excellent replacements. Replacement of some horrendously bodged auto switch wiring [why do guys do this?] completing the rebuild of the main motor assembly and deck.

The auto-stop mechanism was a mess. Trip lever assembled at far too lower point on the spindle. Incredibly strong springs fitted on the mains switch operating lever and the auto trip friction arm. The small rubber roller on the trip arm was also hardened and useless. Sounds bad but it was soon sorted out with help again from the rubber box. [I'm sure some of those weird rubber things have nothing to do with the radio trade] The correct springs were fitted and after adjustment, all was nice and smooth if a little noisy in operation. Sleeving slipped over the springs got rid of the twang on switch off.

The final item was the pick up..............Oh that pick up!

As mentioned earlier the high resistance coil was O/C. A check revealed it was at the start of the winding buried in the tiny bobbin and there was nothing to do other than have a crack at rewinding it.

I dismantled the pick up assembly and removed the tiny delicate bobbin Gently cutting away the tiny piece of tape insulating the lead out wire from the coil itself revealed the coil. I have never seen such fine wire. I can only compare it to a cat hair and when unwound can only be seen with a white card and a bright light behind it. How did they draw this wire? It seems an impossible task and not only that but manufacture it in mile long lengths!

The wire could not be salvaged and had to be removed from the delicate bobbin. Luckily I had a single reel of very similar wire. It was given to me with some transmitting valves by one of Britains first radio amateurs. He was around 90 odd years old at the time and lived in sheltered housing just along the road fom my shop. [Thanks Reg.]

To cut a long and tedious story I had several goes at hand winding it but just the tension of my fingers was enough to break the wire usually when half way through.

The answer was a surprising one. Some years ago I replaced my old power drill with a 14.4v Black & Decker drill. I must say it far exceeded it's expectations and has proved to be one of the best tools I have ever purchased. It's small and very light but incredibly powerful but it's best act is that it has a very smooth consistant trigger. You can start it gently with less than one revolution per second. I have used it before but not with such a ridiculously fine wire gauge.

There was nothing to loose and I rigged up a feed stand for the wire supply reel that was simply a miniature vice set and a screwdriver sleeved in heat shrink and oiled to reduce tension. It was pure luck but the weight of the reel against the oiled screwdriver spindle was exactly correct for the job. The bobbin was placed onto the shaft end of a drill and all was set..

A short length of lead in wire was soldered to the fine wire and assembled through a tiny hole at the start of the bobbin. With my breath held and the first few turns of wire brought under tension I gently pulled the trigger on the drill. Slowly it started and with my left eye could see the supply reel begin to turn as the first 30 or so turns wound nicely onto the bobbin.

I could hardly believe it was winding but for how long? With a very slight side to side movement of the drill the winding continued forming layers of this hair like wire onto the bobbin. Even with the white card behind the wire I often lost sight of it and it was only the supply reel turning that proved it hadn't snapped!

Unbelievably the winding continued building up without a break finishing off just a short distance from the outer edge of the bobbin. To be honest I had run out of concentration and at this point decided to call it a day before the wire snapped and irretrievably became lost somewhere in the winding.


With great care and frustration a second lead out wire was soldered to the fine finishing wire This was fixed securely with a minute dab of resin glue and allowed to dry. It reads 1.4K on the meter and I am quite happy with that.

The whole unit was reassembled with new damping rubbers for the needle armature and centering device and reassembled into the pick up assembly. I only have a small quantity of bicycle tyre valve rubber left but only a very small amount is required for a single pick up so I expect it will 'see me out!' I use Butal pond liner for the top armature centering clamp.

Well, the radio chassis gives a tune and with a bit of luck, so will the gramophone but that cabinet looks as if it housed chickens during WW2 and radiogram cabinets have to be in tip top condition to be acceptable in any home.

Pictures show Motor assembly stripped down with remains of rubber suspension on the left together with the horse shoe shaped oil soaked pads to control the bob weights slip ring. Internal view of motor box showing bob weights and slip ring. Top plate now with correct spring washer and split pin and finally ready for reassembly.

I will reveal the tale of the restoration of what had originally been a rather nicely finished cabinet. John.

[Heatercathodeshort]

The Pick-up head rebuild pictures showing the mass of fine wire that was removed from the bobbin. The drill complete with drill spindle [drill reversed in chuck] The wire 'tensioner' stand and the finished coil.

[MurphyNut]

A most enjoyable and interesting thread, for me anyway the 1930's was the golden age of radio and equipment like this with it's style and quality of manufacture is pure magic.
If I had the space I'd fill my house up with pre-war radios and radiograms such as this.

[peter_scott]

I am very much is awe of people that can restore these old chassis so well but that is totally eclipsed by those who can also rebuild a magnetic pick-up. Just amazing!

Peter

[Heatercathodeshort]

A fiddle to wind Peter but how to you manufacture the wire in the first place?
Can you imagine making the wire drawing die to do the job. It would appear to be an impossible task.
I have attempted to measure the gauge but my electronic calipers just show zero! Even attempting to photograph the wire presents it's difficulties.
The best I can do is to compare it to fine sewing thread as I have attempted to do in the pic.
Cabinet next. What fun! John.