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Last updated 13th March 2003

Restoration - You Choose How


SAFETY FIRST!

Here's the mandatory safety warning (which you all should know and heed). Valve ('tube') equipment contains LETHAL voltages so if you have to work with the set powered up then make sure you keep one hand out of the way and watch what is touching where. If you are working with the set off make sure the power is fully disconnected and the mains smoothing capacitors have been properly discharged. BE CAREFUL when powering a valve radio up for the first time and either use a variac or a light bulb in series with the live feed - check for burning smells, smoke, bubbling capacitors etc. before subjecting the set to full line voltage. So, the voltages on battery sets are lower but the warnings still apply.

Right - that's my back covered! And remember, if you don't really know what you are doing then STOP and learn, or get someone to do it for you!


How to Restore A Valve Battery Portable Radio

'Step 1 - acquire a valve battery portable radio'. From whence? Well, lots of these sets seem to be in the hands of people who don't know (or don't care) about putting them back into working order. They turn up in charity shops, jumble sales, one-off car boot sales and, of course, on E-Bay. Another good source is from fellow enthusiasts contacted via privately maintained bulletin boards or places like the Usenet group rec.antiques.radio+phono. Prices? Anywhere from 5 to 50 depending upon what it is and what sort of state it's in. Of course, an old radio (like anything old) is only worth as much as someone is willing to pay. Although valve portables were produced in numbers they were of very basic design, not particularly robust, exposed to the outdoors (probably), had batteries leaked in them (maybe) and many were dumped/smashed/destroyed when the transistor portable came along.

The fashion at the moment seems to be for Roberts and Bush portables - maybe because these are fashionable names anyway (especially given the Roberts revival line of retro trannie sets).

A basic battery-only set would be a good place to start as there is no power supply to go BANG! The casing and electronics MUST be complete - scratches and dings are OK but no broken handles, smashed cases or frosty valves (no vacuum - although many 1.5v filament valves are easily available).

There are several opinions on the thorny issue of restoration and although the analogy of the classic car is often used it does not compare to vintage electronics. A classic car can often have components re-machined or re-manufactured from the existing units whereas a radio cannot - well, not easily.

These are, briefly, the three leading views on restoration of old radios, generally:

1. Leave it as it is, dust, warts and all whether working or not (like keeping an old car full of rust and dents)

2. Clean and restore the appearance and replace 'hidden' bad components with modern equivalents - this way it looks like it should and it works properly.

3. As above but hide the modern components in older 'packaging' - extreme but the most authentic.

Of these, I prefer Option 2 as it maintains a pleasing original appearance and lets you use the set as it should be used - free of wires! There is also an Option 2A which is retain original as much as reasonably practical (ie: no leaky capacitors or corroded hinges)

Appearances - The Outside

Case fittings, like hinges, stays, catches, knurled head screws, handle anchors etc. are best replaced with new for the sake of appearances and any large hardware stockist should be able to assist - although the style of such things as toggle catches has changed somewhat. In fact, the style of knobs, handles and much else has changed and one has to decide on the compromise between useable/good-looking and authentic/original.For example, in place of original knobs, RS Components have a line of black skirted control knobs (some with wings) that have enough of an 'old-style' look about them to be effective - stay away from any brushed metal knobs or anything with coloured inserts!

The original covering is best kept unless damaged or torn in any large way - minor scuffs and nicks are OK and may be hidden otherwise it may be best to re-cover. Who knows? The use of plastic covered fabrics in bright colours and patterns may not be original but could be a whole lot more interesting to look at. Also, PVC 'leatherette' can be found in a variety of bright colours (not just black & brown). I have come across the same greens as used by Roberts and blues by Pye - if authenticity is not your ideal then this could be a good thing for you! The only difficulty in re-covering is the thickness of the material used ('Rexine' being, literally, paper thin) can often lead to unsightly seams unless one is highly proficient in this area.

Firstly, the casing needs to be stripped of radio and fittings - the better to prevent damage to anything one might regret damaging. Any paper schematics that can come away in one piece should be recovered for copying (although this is contentious I think it's better to replace the paper labels with plastic encapsulated copies) - otherwise, coat them with some diluted PVA glue - which dries clear to protect them. Using a small brush (a nail brush for large areas and an old toothbrush for detail areas), apply a cream cleaner - Cif works very well but be careful if it's the bleach variety. Cream cleaners are slightly abrasive and remove the ground-in dirt very well but be careful not to over-wet the case. Remove the residue with a damp cloth and wipe again with a clean damp cloth. The rexine covering, once dry, can be re-coloured and made to shine a little, if necessary with 'Meltonian' cream mixed to the closest match (Meltonian is a cream dye/cleaner for leather shoes and mixes easily from a wide variety of colours - it is made by the Sara Lee Corp.).

Secondly, one needs to ensure the correct knobs are fitted (and that they are clean - liquid 'Brasso' is an excellent bakelite cleaner - other wise Cif With Bleach used with a toothbrush is excellent) and that the top deck is free from dirt and grime. Paintwork responds well to just a wipe with a damp-soapy cloth (glass cleaner is also good), followed by a buff polish. Minor chips and scratches could be filled with auto-paint touch up sticks from car accessory stores - again mix paints to suit. I have heard that smooth white Hammerite can be coloured for such a use and even pots of model-makers enamel (which should be available in a good range of colours from places like Beatties).

Appearances - The Inside

The inside of the case should be cleaned with a damp cloth and evidence of battery leakage may require treatment with a baking-soda solution to neutralise any acids present. There isn't much more that can be done. Paper schematics may be carefully removed and photocopied or, if being left in-situ coated with a dilute PVA glue.

The Electrics

I always start, if it's a mains set, by replacing the old mains smoothing capacitors before even switching on - they are cheap and it's cheap insurance from any nastiness occurring. The best way to do this is with a schematic for the set (Paul Stenning has a comprehensive collection on CD-ROM) as old paper/wax capacitors are often difficult to read for the correct value. Ideally, one should replace the HT & LT smoothing electrolyticsand any paper/wax coupling capacitors - the latter with a decent grade polyester item rated at at least 100V.

The battery leads usually require replacing and since the power supply is to be changed anyway it makes sense to put on the right kind of plug (whatever that may be). If the set is a mains set then a new mains lead - 3 core with toughened rubber sheath (TRS) preferably or cotton-covered for the 'vintage look' - should be fitted, making sure that the chassis is properly earthed and the live supply is switched.

Last, but not least, there are two things that are a VERY good idea:

  1. Install an in-line fuse holder at a low value like 1 amp
  2. Ensure the chassis is grounded - hum problems can be dealt with later.

Troubleshooting

Sometimes, although not often, the application of the correct HT & LT voltages will bring a radio bursting into life - usually very loudly as many stations apparently use transmitter powers significantly higher than before and even a slight efficiency drop in the AVC/AGC circuit caused by components being out of spec may result in very high volume levels indeed.

Usually, the set is a dud and may only crackle intermittently. In order for any repair attempt to be anything other than stressful, one MUST secure the correct circuit diagram (schematic) and, if possible, a chassis layout diagram. There are two principal schools of thought on fault tracing - 1.work backwards from the output stage (the preferred English method) or 2.work forwards from the antenna (the preferred American method). Either method will require a signal generator and a multimeter to be effective (although a sig gen is not mandatory it can make diagnosis much faster).

Assuming there is correct HT present on the anodes of the output valves and that the output transformer is not open circuit...

At this point I refer you to Bill Harris...an excellent series of articles on the stages of troubleshooting. These notes apply to American AC table radios generally but the style is clear and easy to follow and offers lots of practical advice (use the 'BACK' link in the top-right corner of each page to return here).

1.AC Power Supply

2.The Audio Output Stage

3.The Detector/AGC Stage

4.The Converter Stage

5.The IF Amplifier Stage

6.The RF Amplifier Stage