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Old 25th Apr 2018, 2:58 pm   #1
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Join Date: Jul 2010
Location: Royal Berkshire, UK.
Posts: 339
Default Philco 333 'Haunted Radio' Battery to Mains Restoration

Named ‘The Haunted Radio’ in our house, after my daughter came home from school & saw the set sitting on the patio table, with its ragged speaker cloth gently fluttering in the open-air breeze. The set had an almost sombre ‘expression’, if inanimate objects have such things. She wasn’t so keen on this radio to begin with, ‘looks eerie’ …

It certainly had a spooky look to it, the classic lines of its heyday fading, with a ripped speaker cone, damaged beyond repair speaker cloth & battery obsolescence … what to do with such a wireless … why, turn it into a fully working set, surely(!)

It was clear from the off someone had reworked parts of the circuit previous to my custodianship. Now, this could be a good sign & an indication that the set was up until fairly recent times, a worker … or, it could be someones’ gone in there & ruined an otherwise viable project! Thankfully, it was not the latter …
As is my way with such things, I checked for filament continuity on the 3 valves, checked the loudspeaker & transformer for continuity, plus the various coils, looking for all the usual signs of attempted repair, bits missing or broken. Mercifully, the set was remarkably complete & largely original. The previous repairer has left the original bakelite ‘blocks’ in place, having moved the original wires from said blocks & suspending replacement parts from the now ‘free’ wires.

The battery connections were a real mixed bag, one can only surmise as to how the previous owner(s) powered the set, my intention was to run the set from the mains & you’re about to see how it went.
Having checked coils/transformers/switches previously, the next task was to strip the cabinet of its hardware. Chassis safely to one side for now, along with the loudspeaker & baffle board.

The cabinet plus the 3 knobs, save for a few light scratches, came up really well with little to no effort. The original Perspex dial cover was beyond redemption; however, it came out along with its retaining pins, with no drama. The original dial cover was placed over the top of new Perspex; this was then marked up, cut, drilled, deburred & reinstalled using the original retaining pins.

Attention was then paid to replacing the original speaker cloth. The remains of the old cloth put up a bit of a fight; the old glue was certainly tuff stuff. Once the baffle board had been cleared of the old speaker cloth & glue remains, the new material was soon pressed (stretched more like) into action, having previously applied the glue.

Whilst this was curing, I centralised the loudspeaker cone with suitable spacers, then repaired the damaged loudspeaker cone with coffee percolator conical filters & water based glue. Trimming these coffee filters to an approximate shape, the water based glue allowed for shaping, & adhesion! Happy with my efforts thus far, once the loudspeaker glue had cured, I removed the speaker magnet, removed all visible remains of debris from the inner part of the voice coil & central magnet ‘stem’, then reassembled the loudspeaker, centralising as I went … with the dial cover in place, the baffle & loudspeaker were reinstalled into the cabinet. The cosmetics were coming along nicely.

Attention was then paid to the electronics, making a terribly crude power supply for the 120 volt, 67.5 volt & 2 volt supplies, just to prove the chassis was largely ok, & it was, sort of. The ‘new’ parts fitted by a previous repairer, were out of spec, with a couple of the caps acting as high value resistors. The original bakelite blocks were removed, filleted & re-stuffed with modern parts, then reinstalled back to how they were in the 1930’s. The other modern capacitors I fitted were bright yellow & stood out a little, so I printed some labels with ‘Philco’ & the part value/part number under the brand name, adding a brown background to try & make the new parts blend in. The labels were then glued onto the bright yellow capacitors. Had the original capacitors been in situ, these would have been re-stuffed too. One or two resistors were wildly out of spec, & were replaced accordingly.

Since the set was to be powered from the mains, I wanted to revise the power switching arrangement. Originally the power switch controlled the heater supply, nothing wrong with that, but I wanted the switch to control the mains, so the original wiring was left in place, the original switch having a discrete link placed across it. The new switch was fitted to the volume control via my homemade bracket, & having fitted a collar to the volume control shaft with a slightly longer retaining grub screw, which operates the lever. The new switch has a clear plastic cover along with heatshrink sleeving on the wires (belt & braces).

The dial now has a backlight. Having scrapped a printer/scanner, inside the lid of the scanner was an A4 sized piece of white sheet, which is the right width for a Philco 333 dial. This white sheet was fashioned into a dial ‘lightbox’ & furnished with LEDs. This gives pretty even spread of light across the dial, amazing given the directness of light from LED’s.

The main power supply took some work & a lot of thought to make it fit into the space the batteries once occupied. The metalwork for the new power supply being leftovers from my Bush DAB90A project, most of the electronic parts were from previous orders. You know, you only want one part but they come in a bag of 5 … & the transformer salvaged from a previous project. The power supply sits on runners, along with the original chassis, the original screw passing through the new runners holding everything in place.

The whole set is protected by three fuses & three triac-fired crowbars. The heater supply is regulated with a trip point tolerance of +0.3 volts. Even at this trip point, by the time the valves see it, the supply at the valve base is 2.1 volts. The other supplies have a +10 volts trip point, the triacs on the 67.5 volt & 120 volt HT rail pulling in a 30K 50W resistor strapped across the main HT, which draws more current than the fuses can supply, thereby, protecting my set. I’ve removed (but retained) the battery connections & fitted a 6-way, keyed, Molex connector.

A back cover has been made for the set; it’s nothing more that thin marine-ply. I’m in two minds as to whether I should vent it, just like the Philco 444, but in all honesty, my power supply runs tepid, & the valves themselves barley get warm.

How does the set perform? Once you get to grips with a TRF, it’s a joy to listen to. Last night on LW it pulled in Radio 4 plus a couple of foreign stations, & on MW we had Smooth, possibly Absolute (?), 5-Live & a number of foreign stations. No alignment has been adjusted, seems a very happy radio so this side of things has been left well alone.

Sound quality was a real surprise, so long as the reaction control is set right, you have a wonderful mix of warmth & clarity, with the ability to chop out unwanted noise.

I’ve done my best to keep this repair as sympathetic as possible, all my modifications are completely reversible, should it be desirable to do so in the future.

Has taken a while to orchestrate this project, but I think it went ok …

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