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Old 10th Dec 2015, 12:08 pm   #1
David G4EBT
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Default A new lease of life for a tired KB FB10 'Toaster' radio

I’ve just finished restoring a KB FB10 MK1 - one of three sets I bought for a fiver each off the BVWS stall at the Golborne swapmeet recently. It had a chunk out of the cabinet at the rear and was a bit scruffy and tired looking, with a faded speaker cloth. Nevertheless, it was well worth a fiver! It was missing a 6BA6 valve, a 6BE6 when tested had an open circuit heater, and the mains switch on the pot was open circuit.

I’ve restored several of these little sets, which I rather like. I’ve restored two for my son – one with a nice undamaged cabinet which polished up really well, another which had a damaged cabinet, which at my sons request, I sprayed green. I’d also restored another for myself which had a damaged cabinet, and I re-sprayed that one red. My son asked if I came across one in need of TLC, I’d spray it red for him in red, so the one I bought at Golborne was a good candidate.

The others I’d restored had been MK2 sets, which have a different valve line-up (6BE6, 6BJ6, 6AT6, 6BW6 & 6V4), whereas the MK1 has a mixture of B7G valves and Octal. (6BE6, 6BA6, 6AT6, 6V6GT & 6X5. The MK1 has a frame aerial, whereas the MK2 has a ferrite rod. There are other differences – notably in the power supply, and with the trimmers. In the MK1, there appears to be no trimmers – just bits of wire which appear to have been soldered to the tuning cap gangs and snipped off. That’s actually what they are – bits of twisted wire, trimmed to length at the factory as rudimentary trimmers, which are not adjustable. On the MK2 the trimmers as I recall are adjustable ‘postage stamp’ types.

Both the MK1 & MK2 have what appear to be a mains transformer, which it is of course, but they’re auto transformers with only a tapped primary to feed the valve heaters and dial light. Hence, the AC feed to the rectifier comes directly off the mains to the anodes of the rectifier (both strapped together), via a 150R 7 Watt resistor, and one side of the set is connected to the chassis, so polarity is important and the usual ‘live chassis’ precautions are called for. (I use a mains isolating transformer when doing live trusting on AC/DC sets and sets which lack a full mains transformer, and carry out as much testing as I can with the set disconnected from the mains – too young to die – too old for nasty shocks!).

The HT feed is a bit peculiar in that it uses two 8K2 resistors in parallel, making 4K1, then a 1K8 resistor in series, totalling 5K9. Either a single 5k6 or 6k2 preferred value resistor would have been 5% over/under and I’d have thought would have been fine. Seems odd to have used three resistors where one (perhaps of a higher wattage) would do, in such a compact set. No matter - that's how KB designed it.

First off I decided to repair and re-spray the cabinet, which had a chunk out of the rear at the bottom. I bridged the gap with thick gauge paper clip wire to form and armature to support the filler, drilling sideways into the edges of the cabinet. I wrapped thin copper wire over the two pieces of paper clip, and then bridged the gap with Isopon body filler. I cut a template to shape from the undamaged part of the back which has an identical (mirror image) shaped aperture, and used that as a guide to shape the repaired portion. When sanded to shape, primed and finished with gloss, the repair is invisible. The old speaker cloth was badly faded and in any event, not a suitable colour, so I found a piece which went well with red and used that.

Wit the cabinet sorted, I turned to the chassis, and as I always do on any set, the first task was to make a little cradle to support the chassis to do the restoration work and tests – in this case, just a piece of scrap ply and two brackets made of 1” wide flat steel strip.. I can’t for the life of me understand why anyone attempts work on any set without properly supporting it. Not only does it make life difficult, it risks damaging valves etc. When service engineers used to repair sets in customer’s homes, they were up against time pressures and often had the set on the floor, sat crossed-legged, and had perhaps half an hour before they had to be off to the next job. Also, they were only doing one-off repairs to get the set going again – they were not carrying out restorations which may take many hours over a period of several days. We’re not under those time pressures, so why cut corners? I have a chum who used to work for Radio Rentals. He tells me that they were expected to repair 14 – 16 TV sets a day, working into the evening, and often didn’t have time to let his soldering iron warm up, so he just twisted wires together on replacement components when possible, unless it was on a PCB.

Having popped the chassis on a cradle, I checked the resistors to see if any were more than 20% out of spec. Most were still well within that and only two needed changing as they were 60% high. I changed the seven waxy paper caps, though when I tested the old ones out of curiosity at 500V on my Victor VC60B insulation tester, none showed any sign of leakage. The twin 32uF smoothing cap wouldn’t reform, so I stuffed the old can with two new caps, which just fitted. On the pic of the guts of the old one will be seen an elastic band from when it was made. It was still intact!

I was expecting to have to replace the volume control due to the open circuit on/off switch and had a switched 470k log pot to hand. However, a good squirt of Servisol into the switch section did the trick – at least for now. The wires to the dial light, which traverses back and forth along the dial, were brittle so I changed those and another dodgy bit of wire. I had to re-string the dial, which - though not complex is vey fiddly and would test the patience of a saint. They must have had deft fingers on the production line and no doubt did it in a jiffy, day in, day out!

I popped in two replacement valves and switched on the set via a lamp limiter – silence – not a peep. Audio stage was fine, IF too - 422kHz, spot on. Hence, trouble in the front end. Turned the lights off in the workshop - not a glimmer from the NOS 6BE6 frequency changer valve I’d fitted. Lights back on, I removed it and checked the filament, which was fine. Popped the DMM test prods into the valve socket to check for 6V3 AC – nothing there. Took a close look under the chassis at the heater line and noted that the connection to the valve-holder had fractured close the the valve-holder tag. I soldered that back on and the set came to life on MW & LW. Several stations on MW, and R4 and a couple of French stations on LW at good volume - even more so with a short length of wire in the external aerial socket. Checked the Voltages around the set and all were fairly close to spec. Before I put the cabinet on, I checked all the valves on my Taylor 45D valve tester and they tested like new.

Handed the set to my son to add to his small collection, who is very pleased with it.

A few pics of the cabinet repair and finished set are attached.

I'll add some more on the chassis restoration in a second post.

Hope it's of interest to someone out there.
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Old 10th Dec 2015, 12:20 pm   #2
David G4EBT
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Default Re: A new lease of life for a tired KB FB10 'Toaster' radio

A few more pics attached below:

Pic 1) The chassis on a cradle, which makes life much easier.
Pic 2) After restoration - all paper caps replaced, just two resistors out of spec replaced.
Pic 3) The 'scalps' which were taken, including some brittle perished wire.
Pic 4) The opened up twin 32 uF smoothing cap, (complete with its original factory fitted elastic band!).
Pic 5) Two replacement 33uF which just fitted in the can.
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Old 10th Dec 2015, 12:48 pm   #3
Nickthedentist
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Default Re: A new lease of life for a tired KB FB10 'Toaster' radio

Very nice work as always, David. I'm impressed on every level and I'm glad your son likes it.

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Old 10th Dec 2015, 6:49 pm   #4
David G4EBT
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Default Re: A new lease of life for a tired KB FB10 'Toaster' radio

Thanks for reading the thread and for your kind comments Nick!
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Old 11th Dec 2015, 8:14 am   #5
Phil G4SPZ
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Default Re: A new lease of life for a tired KB FB10 'Toaster' radio

A lovely job David, a real bargain and an excellent write-up too. I have one of these sets, resprayed in green, in daily use in the kitchen. Great little sets
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Old 11th Dec 2015, 10:30 am   #6
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Default Re: A new lease of life for a tired KB FB10 'Toaster' radio

Thanks for posting this David - always makes my day to see a restoration / repair like this! I have a pile of these toasters to restore - when I get the time! Your comments on Mk1 and Mk2 are interesting - I always thought that KB just used whatever components were to hand to make them and it wouldn't surprise me to see a Mk3,Mk4,Mk5 etc¬
Thanks again!
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Old 11th Dec 2015, 11:52 am   #7
David G4EBT
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Default Re: A new lease of life for a tired KB FB10 'Toaster' radio

Thanks for your kind comments Phil & Andy.

They're good little performers and thoughtfully designed, with ventilation slots at the top the rear so they don't get too hot inside. Nice the way that the dial bulb traverses back and forth along the dial to illuminate the portion to which the radio is tuned. They often seem to get dropped and have chucks out of them, and as a consequence can be picked up cheaply. One thing to watch for is if the black Bakelite underside is smashed or the dial, which does really render the set only fit for spares, but heck, at a fiver, the speaker and OPT are worth more than that! The dial is held on with those dreadful 'spire clips', but they can be carefully eased off with right angled picks or whatever technique people find works for them.

They sound good, with plenty of volume, and with a couple of Metres of wire into the external aerial socket become even more lively. A nice set to have in the kitchen or wherever. Of course, they hark back to an era when radios were not cheap acquisitions, so one per household was the norm. Small sets such as the toaster, launched in 1950, were often known as ''transportable' or 'occasional' radios, meaning they were suited to any occasion - in the living room, kitchen, bedroom etc. Small in size, light in weight, internal aerial, so sets such as this ticked all the boxes.

The other option for radio listening in more than one room was extension speakers. Even in 1962 when my wife and I married, we only had one domestic radio, (a radiogram actually), in the living room, with extension speakers in the kitchen and dining room. How times change - we can hardly move for them now! (Despite my avowed intention to come home empty-handed, I bought two other sets at Golborne for a fiver each - a cream Bakelite Little Maestro and an Ultra T401!).
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