Philips B2X67U/65

[G6Tanuki]

I've already factored them in for pre-emptive replacement with modern 600V-DC-rated MKT yellows.

Thankfully apart from them pretty much all the other coupling/decoupling caps are 'stick' tubular-ceramics which in my experience tend to retain both their capacitance and DC-resistance qualities even after 60 years.

[ms660]

There were two different SW bands for at least two versions of the B2X67U receiver, the parts list for the scales indicate:

(South)
(Oversea)

http://www.philipsradios.nl/Schemas/B2X67U.pdf

Lawrence.

[G6Tanuki]

Yes, mine's the '65' variant.

I still wonder how it came to be for sale at a car-boot in a rural Wiltshire town: one possibility I guess is that it could have been brought back to the UK by someone in the services (there having been loads of military bases - Tidworth, Sarum, Amesbury, Andover, the Wallops) round here.

Now that I've managed to work out how to remove the PCB from the case without destroying the dial-pointer, this weekend will see me start work in earnest. The tar-bombs [c18 c21 c25] will be first for attention.

[ukcol]

I've not seen a UY42 before but according to both Philips data sheets for it on Frank's site the UY42 is designed for 110 volts mains, which explains why I've not seen one.

Interestingly the radiomuseum entry for the B2X67U/65 states that it is a 110/220v AC/DC set which doesn't ring true for a UY42. There is a picture of the rating plate on the set but not being a member I haven't got access to the high definition picture.

There's not a valve list given either so I can't say if it is supposed to have a UY42 or UY41.

EDIT:

I've just downloaded the schematic from radiomuseum and the set does indeed use a UY42. The mains input is marked 220volts and the anode of the UY42 is marked 110 - 127v. It looks like it relies on the volts drop in the feed resistors to bring the anode voltage down to the UY42's rating. Not particularly elegant IMHO.

[G6Tanuki]

Originally Posted by ukcol

Interestingly the radiomuseum entry for the B2X67U/65 states that it is a 110/220v AC/DC set which doesn't ring true for a UY42. There is a picture of the rating plate on the set but not being a member I haven't got access to the high definition picture.

There's not a valve list given either so I can't say if it is supposed to have a UY42 or UY41.

The schematic/service-instructions I've got here specify an UY42.

And it seems other Philips radios of the era used the UY42 in 220V-supply situations too.

https://www.vintage-radio.com/recent...ilips-95u.html

[ms660]

The UY42 was uprated at some point according to what's in here:

https://www.vintage-radio.com/recent...ilips-95u.html

Lawrence.

[ukcol]

That makes it all clear. A good point is made there too, namely don't fit an early UY42 in anything but a 110 volt mains set.

[G6Tanuki]

Having 'sprung' the PCB from the case and given it a good dust-down with an airjet and a soft-bristle paintbrush, it all looks good.

The only 'issue' is a sign of rework round the cathode-resistor of the UL84: there's a clearly-lifted PCB track that's been replaced by a length of orange PVC-covered 25-gauge wire, and the 180-Ohm cathode resistor for the UL84 has been replaced by a somewhat-fatter Welwyn 270-Ohm resistor lifted clear of the PCB by a couple of porcelain 'fishbone' beads.

Signs of a previous burnup? The UL84 is the only valve in this radio that's not marked "Made in Holland".

Apart from that, everything seems to be just as I'd expect it to have come from Eindhoven. I'm particularly intrigued by the bell-crank pushrod arrangement [looks like it could have been made from a repurposed bicycle-spoke] linking the wavechange-kinob to the actual wavechange-switch, and the crude-but-effective high/low tone-control switch which is a sort-of W-profile metal/paxolin thing which in the 'low' position shorts the tone-capacitor to the metal rail that also supports the volume/wavechange/tuning controls.

Cheaper than a traditional 1-pole 2-way rotary switch.

Clearly there's been detailed 'value-engineering' in this radio, something of which I wholeheartedly approve! Saving a "Dubbeltje" -

https://en.wikipedia.org/wiki/Dubbeltje

on each radio by such tricks could have turned a cost-centre into a profit-centre.

[G6Tanuki]

More work on this@ Much of the dust and a couple of dead wasps have been ousted from the circuitry: I decided to see what would happen when I applied power.

Valves lit pretty much to the expected brightness; no dial-light, and - total silence - not even a crackle when turning the bandchange switch. Some swift probing revealed no HT and an open-circuit dial light bulb. Without consulting the schematic I had a vain hope that replacing the bulb would get me HT again [this is sometimes the case with US series-valve sets] but though a new 6.3V 0.3A bulb lit to the expected brilliance, still no HT.

A quick substitution of the UY42 made no difference; the culprit, it turns out, is the part of the dropper-resistor in series with the UY42 anode [R12, 130 Ohms] which has gone open-circuit.

I suspect the dropper-resistor assembly of having been replaced in the past: the one in this radio has four tags whereas the one shown in the schematic and drawings has but three, and one of the leads has clearly been extended.

Now, where do I get a replacement? In the past I'm sure that a serviceman unable/unwilling to source a new dropper would simply have soldered a 130-Ohm wirewound resistor or a couple of Watts across the tags of the failed part of the dropper and sent the set back out to the customer. While I could do that, it's not really my style - and to be honest the resistor as-fitted looks crumbly - I'd be worried that if I waved a soldering-iron near its tags the remaining non-open-circuit bit might decide to die too.

The other part of the resistor (which feeds just the heaters) is 950 Ohms: given that the radio is intended for 220V use according to the selector-switch I'd have no issues upping the heater resistor to 1K to help hold the heater-current down, considering that my mains here generally sits between 240 and 250V.

A plate to act as a bracket-and-heatsink, fitted with a couple of the nice big gold-cased power resistors seems the way to go.

[turretslug]

It won't be quite the same without the smell of hot, dusty dropper slowly purging years of gently-acquired moisture, though....

[G6Tanuki]

Originally Posted by turretslug

It won't be quite the same without the smell of hot, dusty dropper slowly purging years of gently-acquired moisture, though....

True - but at least it will work, without the risk of suddenly degenerating into a shower of sparks and flames!

Must admit, if they could bottle the smell of warming-up-dropper - or the smell of the insides of 1940s/1950s tropicalised Military gear - they'd make great air-fresheners!