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Keith 24th Oct 2020 3:45 pm

Philips 274A - ugly duckling!
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Some of you may remember seeing this set at the Wooton Bassett auction in February 2019. I daresay a number of members had a good chuckle at the indignity that someone had inflicted on an otherwise potentially sought-after receiver. Not so much a minor blemish - more a "monstrous carbuncle", as Prince Charles would have put it! Actually, I thought of it as a possible blessing - maybe the bidding would be correspondingly impacted and I might walk away with it for a song. It almost worked.

I had always liked the understated lines of the 274. Presumably Jonathan Hill must have agreed when he featured it on the cover of Radio Radio being held aloft by a silvery goddess! Furthermore, apathy had once let one pass me by when I failed to follow up an advert in our local paper.

Having got it home it became clear that things were worse than I thought (we've all been there, haven't we). I had assumed that I would have three holes in the side of the case to deal with which might not have been too difficult to conceal. However, in order to make the switch sit flush on the surface, the perpetrator had also carved two channels through the veneer for the wires to lay in. I didn't take a photo of this as it was too depressing. The set sat on a shelf for a long time....

To take my mind of the conundrum of the case, work commenced on the chassis. The first items to be tackled were the electrolytic capacitors. These were of the wet electrolyte type and, being a prominent feature, I decided on the re-stuffing process. Careful hacksawing allowed the can to be removed, along with a dribble of electrolyte, and revealed a wavy star shaped stucture - presumably a way of maximising surface area and hence capacitance. The metal surface had a sintered appearance. Modern components were substituted and the can re-assembled.

Next the multiple capacitor can was dismantled and re-stuffed - nice to see the precise date of manufacture (24th April 1934). Very few other components needed to be replaced - all the resistors were deemed to be near enough for valves! Of course, it no longer has an on-off switch. The original has lots of missing bits. An in-line switch has been fitted - not ideal but far better than what preceeded it!

Eventually the cabinet had to be tackled. A complete strip of veneer was removed as shown and car body filler used to fill up the holes and other excavations. After rubbing down to a flat surface a new piece of veneer was applied. I was lucky enough to find a reasonable match for the grain. Getting the toning right took a number of attempts, however, using a mix of propietary wood stains. In the end I decided enough was enough and the whole case was sprayed with matt polyurethane. This was flatted down on subsequent coats to remove any hint of glossiness.

Cabinet and chassis finally came back together, but the odd mounting of the speaker baffle caused some puzzlement. A significant gap between this and the case made me suspect that something had been mislaid during the long period on the "shelf of shame". Thankfully a helpful fellow member pointed out that this was a design feature and suggested a source of suitable felt to replace the tatty bits that I had presuably discarded. Thanks Sideband.

So there we have it. An ugly duckling restored to a half way decent swan! The performance is remarkable for a TRF with no apparent reaction. The "tone" is only OK but I suspect that the substitution of a 354V for the apparently unobtanium 994V may be the culprit here. The really good news is that my wife likes it so it has taken its place in the lounge, no less. The only downside is the lack of the shiny red "waves and stars" Philips badge in the dial escutcheon. If I could find one of those I'm sure my wife would love it even more!

Sideband 24th Oct 2020 4:37 pm

Re: Philips 274A - ugly duckling!
I also tried a 354V in works but with less volume (it is a very good valve). The 994V was apparently designed as an anode bend detector. The 994V in mine measures very low but oddly works better than the 354V with more volume.

Keith 25th Oct 2020 2:37 pm

Re: Philips 274A - ugly duckling!
1 Attachment(s)
Hi again Sideband,
Thanks for the response. I would describe the audio as lacking in brightness. Perhaps the inherent regeneration (presumably there must be some to give so much gain) reduces the bandwidth a bit too much. There is no adjustment so it's impossible to say. I did wonder whether the PM24A was a bit weak but it tests out OK on the AVO VCM. I wonder if you explored the inards of the wet electrolytics. Interesting construction!

Sideband 25th Oct 2020 2:53 pm

Re: Philips 274A - ugly duckling!
Hi Keith. Yes I rebuilt the wet electrolytics and in fact restuffed all the others including the big can. Mine has May 1934 stamped on the side so they are of similar age.

Interesting that you have a PM24A in yours. Mine has a PM24M (which ties in with the valve diagram on the back cover) which in fact I have recently replaced due to failure of part of the filament in the original. I was lucky to find a very good replacement on eBay which gives a huge improvement over the original. As an experiment some time ago I tried a PM24A since I already had a good one of those. Less volume although the quality seemed about the same. One thing that does notice on these....the anode bend detector doesn't like the high modulation levels of some of the local MW stations, (in this area, Gold) which shows noticeable distortion whereas R4 is clear and clean as is Talk Sport. Not sure about the regen. I was told by an older engineer (no longer with us) that the gain and selectivity was purely down to the design of the coils, hence Superinductance. These are apparently wound in a special way on glass formers but I haven't dared open one to have a look.

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