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Old 22nd Jan 2020, 10:15 pm   #1
Nickthedentist
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Default Restoring an unloved Bush VHF90A

HISTORY

I acquired this radio very cheaply years ago in Paul Stenning’s big clearout. I’d wanted one for a long time, after failing to mend (and then taking apart) one that I bought as a child at a jumble sale in the mid-1980s. I seem to remember one being used in a Milk Tray commercial at about the same time. Or am I imagining that?

It sat in a rather forlorn state in my garage until about 2008 when I eventually had time to restore it. It’s taken me just 12 years to find time to post the write-up I put together for the forum!

It seems to be quite a famous example. The set originally came from Jon Evans (Dukenukem), and can be seen on his website here. It then passed to Paul, where it appears towards the bottom of this page.

When I received it, it was almost complete and undamaged, but grimey, dull and generally un-loved. Ideal restoration material.

Last edited by Nickthedentist; 22nd Jan 2020 at 10:27 pm.
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Old 22nd Jan 2020, 10:16 pm   #2
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Default Re: Restoring an unloved Bush VHF90A

CHASSIS

Removal was a bit awkward because of the dreaded fragile plastic tuning knob/dial cover needed to be removed, but this was eventually achieved by pulling it gently and evenly using some thin nylon cord, making sure it was not fouling the dial pointer.

After a quick vacuum and scrub with foam cleaner, the first thing I did was to remove the two extra caps and Belling-Lee co-ax socket that John described as an “aerial socket bodge”, though in fact, they seemed to be isolation components for a tape output. The Sprague one on the tagstrip looked original (or at least professionally done), whereas the “Solar” one bolted to the chassis certainly didn’t. Either way, I decided to do away with both for safety reasons.

The very short mains lead was then replaced (two core, of course), and a 15W SBC pygmy lamp found to replace the original, which was open circuit. I was unable to source one with a small envelope at a reasonable price, but the standard type fitted nicely with a healthy clearance between it and the sensitive tuning scale. Furthermore, this set had been neatly modified with a 1K series resistor to stop the lamp getting quite so hot.

After re-forming the big electrolytics, I applied mains via a lamp limiter. The valves lit and the set picked up a couple of local stations, but the sound was very distorted and quiet, even when the limiter was taken out of circuit.

I then spotted a potentially dodgy SenTerCel rectifer, which I replaced with the usual 1N4007 plus a series resistor. The original was left in-situ as a convenient tie point for the junction of the diode and resistor, after checking that it wasn’t leaky to chassis. I settled on a value of 120R as it gave approximately the correct HT.
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Last edited by Nickthedentist; 22nd Jan 2020 at 10:22 pm.
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Old 22nd Jan 2020, 10:18 pm   #3
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Default Re: Restoring an unloved Bush VHF90A

CHASSIS (continued)

This, and replacement of all the wax/paper capacitors with yellow Vishay/Roderstein polypropylene ones made a huge improvement to the set’s performance. Sensitivity and volume were now excellent, and no alignment was required.

At the time, I didn't replace the little red ceramic caps which isolate the aerial socket, or filter the mains input, but if I were doing this now, I would definitely do so.
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Last edited by Nickthedentist; 22nd Jan 2020 at 10:35 pm.
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Old 22nd Jan 2020, 10:19 pm   #4
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Default Re: Restoring an unloved Bush VHF90A

CABINET

Removing the baffle appeared: It's held in by screws and brackets at the bottom and at the sides, but the top edge is attached by no less than 4 Spire clips which not only touch each other but also rest against the top of the cabinet. So, they can't be rotated, nor can Mike Phelan's sewing machine needle trick be used because of their small dimensions. I found a solution, details here.

The cabinet seems to be made from plain, brown Bakelite, and polished up well using nothing more than Greygate’s Polishing Paste No.6 with no pre-cleaning or wax required. The painted metallic grey/green portion was a little chipped in places, but looked fine after touching-up with a silver metallic paint pen.

As always with these sets, the plastic piping around the baffle was the real let-down. I have simply removed it from the set for the time being. If I ever get time, I will try warming it in hot water and stretching it. I have since been given another VHF90A which has a much lower serial number, and interestingly, this has real brass trim.

The tuning knob was grubby, and responded well to a wash in warm soapy water. Fifty years of sunlight have made it slightly opaque, but it looks fine when illuminated.

I replaced the missing “Chinese hat” bright with something from my scrap pile. It’s silver rather than gold, but beggars can’t be choosers.

The brass ring around the dial, and the inserts on the volume knob were polished and lacquered, and the loose grille cloth was washed and re-stuck to the hardboard baffle with Copydex (I think).
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Last edited by Nickthedentist; 22nd Jan 2020 at 10:36 pm.
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Old 22nd Jan 2020, 10:21 pm   #5
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Default Re: Restoring an unloved Bush VHF90A

CONCLUSION

The set works really well, so much so that it was the main set in my living room for several years, its stylish looks regularly attracting positive comments even from people who don’t share my passion for vintage radios (even my wife!). Several people assumed it was a modern repro.

There is plenty of volume, and the overall tone is very pleasing for a small set, thanks in part to the Celestion speaker (same or similar to those used in the VHF61/2, SRP31, TV22 and so on). Sensitivity is very good for an early VHF set, and it picks up everything well using nothing more than its internal loaded dipole (though we are lucky with the signal in Oxford).

If I had to criticise anything, it would have to be its rather crude tuning arrangements and slight tuning drift. If you tune-in a programme when the set’s cool, the dial needs a slight nudge 15 minutes later. However, the tuning then needs no further adjustment, even when the set’s switched on from cold. I intend to try painting the front-end’s valve’s shield black, as suggested by Leon Crampin in an old thread.
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Last edited by Nickthedentist; 22nd Jan 2020 at 10:37 pm.
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Old 22nd Jan 2020, 10:34 pm   #6
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Default Re: Restoring an unloved Bush VHF90A

I think it (they) look better without the plastic surround, the dial light is much brighter than DAC90A ones, or any other radio.
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Old 22nd Jan 2020, 10:38 pm   #7
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Default Re: Restoring an unloved Bush VHF90A

Yes, but the Ekco U243 (also with a 15W lamp) is a dazzler too though.

And my Philips 371A is also a contender
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Old 23rd Jan 2020, 11:14 am   #8
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Default Re: Restoring an unloved Bush VHF90A

Thanks Nick, this really is most helpful. I noticed the Celestion speaker is the same as the one in my recently restored SRP30C record player, what a good speaker it is too!
Going to take the VHF 90A apart to day........wish me luck!
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Old 24th Jan 2020, 10:51 am   #9
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Default Re: Restoring an unloved Bush VHF90A

What a good write up backed up with some good pictures. I have got one of these that I acquired a few years ago lurking in a corner somewhere.
If it uses the same Celestion speaker as the VHF61 then it will sound good.
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Old 24th Jan 2020, 4:52 pm   #10
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Default Re: Restoring an unloved Bush VHF90A

You could try some T-Cut and a little elbow grease on your opaque tuning knob, I have done this to an E.A.R portable radiogram and it did the trick well. If yours is really bad you could start with some 1000 grade wet and dry and gently remove the oxidation remembering to use plenty of water on the paper. Then dry off and use the T-Cut.

Your restoration is looking really good, all the best with it
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Old 27th Jan 2020, 5:32 pm   #11
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Default Re: Restoring an unloved Bush VHF90A

A nicely executed resto there Nick, and by the sounds of things has proven a reliable set.

The only set I have which has a bright dial, would be my recently revived Philetta, even with extra resistance in the line to run straight from 240V mains, the 'speaker grille looks like a miniature heater!

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Old 27th Jan 2020, 5:37 pm   #12
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Default Re: Restoring an unloved Bush VHF90A

Thanks everyone.

I have since tried cutting compound on another knob, but I think the UV degradation is quite deep.

This set looks like it should run excessively warm, but it doesn't in practice.

Nick.
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Old 30th Jan 2020, 9:32 am   #13
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Default Re: Restoring an unloved Bush VHF90A

Nick, I love that first photo of the set in situ. It looks so nice I called my wife in to take a look. It seemed appropriate to use my favourite 50's phrase 'Hazel, come here at once...'
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Old 3rd Feb 2020, 12:25 am   #14
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Default Re: Restoring an unloved Bush VHF90A

The products made for polishing plastic car headlights might be helpful.
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Old 3rd Feb 2020, 1:00 am   #15
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Default Re: Restoring an unloved Bush VHF90A

Sadly transparent plastics tend to degrade all the way through the material in a manner which is more apparent than with coloured plastics. I assume that this is because UV radiation can penetrate more readily. Usually no amount of polishing will improve things to any great extent. Always worth a try of course.

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Old 3rd Feb 2020, 2:24 am   #16
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Default Re: Restoring an unloved Bush VHF90A

Alan, have you seen the tremendous improvement the headlight polishing kits make in clear plastic headlights which have become opaque? You may find a visit to an auto parts store interesting.
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Old 3rd Feb 2020, 10:49 am   #17
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Default Re: Restoring an unloved Bush VHF90A

I agree with Frank that plastic polishes are very good at removing opacity caused by surface damage as is often the case with vehicles that have been blasting through an abrasive environment for 100,000 miles. However most, if not all, transparent polymers also degrade with age and exposure to radiation (ie, light). Other factors, such as ambient temperature, also have an influence. This degradation takes place thoughout the material and not just at the surface.

The trouble with the transparent radio knobs/dials fitted to sets like the VHF90A is that they are some sixty years old and have had plenty of time to deteriorate. They were also made at a time when polymer technology was in its infancy and they were not manufactured with the additives used these days in an effort to delay degradation.

As I mentioned before, surface polishing is always worth a try but may not be successful in many cases.

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Old 3rd Feb 2020, 11:11 am   #18
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Default Re: Restoring an unloved Bush VHF90A

Yes, sorry to say that the improvement was only marginal here.

My Golf MkV suffered from the opaque headlight problem after about 5 years. A polishing kit worked wonders initially, but subsequent use a year or two later brought little improvement, presumably as the damage was too deep to polish out.

N.
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Old 3rd Feb 2020, 12:12 pm   #19
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Default Re: Restoring an unloved Bush VHF90A

This discussion brings to mind the transparent knobs fitted to Telequipment D83 and D75 oscillocopes in the early 1970s. The same knob was also used on CT71 curve tracers. Not only do they become opaque with age but they eventually become sticky and disintegrate whilst exuding a very unpleasant odour. They definitely were not a triumph of polymer engineering.

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Old 3rd Feb 2020, 12:55 pm   #20
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Default Re: Restoring an unloved Bush VHF90A

That's called "deliquescence" I think.
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