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Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets.

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Old 21st Oct 2019, 10:28 pm   #1
Dick Glennon
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Default UY41 Valve.

Hi again, Is a uy41 a direct replacement for a uy42. Thanks again Dick.
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Old 21st Oct 2019, 10:43 pm   #2
paulsherwin
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Default Re: UY41 Valve.

The UY42 was supposedly designed to half wave rectify 110V mains, but looks suspiciously like a remarked UY41 to me. It may even have been a way for Philips to dispose of substandard UY41s.

I can't see why a UY41 wouldn't work perfectly well as a UY42 substitute, though subbing a UY42 for a UY41 would exceed the UY42's voltage rating (if that's to be believed).
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Old 22nd Oct 2019, 10:10 am   #3
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Default Re: UY41 Valve.

Could it be that the UY42 genuinely is a developed UY41 with, say, smoother cathode coating (as later distinguished the lower forward voltage-drop PY33 from the PY32) and perhaps more precisely defined anode cylinder and positioning in order to produce a lower forward voltage drop but still good PIV? With mains supplies of 200VAC+, one can be fairly lenient with rectifier drop, also with smoothing and filtering resistors as many series-heater valve types were specified for 170V or so operation but 110VAC operation is a different matter with designs straining for every volt they can get. As a pan-European operation, Philips would have been aware that there was still substantial 110VAC supply presence at the time, so there might have been considerable interest from set-makers as regards a lower forward voltage rectifier.

This Philips pdf (courtesy of the Valve Museum) implies that the two valves were generally similar (including PIV) but that the "UY41/42" exhibited lower forward voltage drop than the UY41. Perhaps later production was simply interchangeable as regards PIV but the UY42 description was used to signify the better choice for 110VAC regions.

http://www.r-type.org/pdfs/uy41-1.pdf
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Old 22nd Oct 2019, 10:17 am   #4
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Default Re: UY41 Valve.

You may be right about the voltage drop issue. I don't have much familiarity with the UY42 as it was never used in radios for the UK market to the best of my knowledge. Even documentation is thin on the ground, so it must have been pretty niche even globally.
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Old 22nd Oct 2019, 12:43 pm   #5
Maarten
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Default Re: UY41 Valve.

According to the code list they always remained separate types (2 main versions of each, possibly one with a fritted construction and one with a melted construction). I seem to remember having heard that one or both tubes were at some point in time improved to have the best of both worlds. Since this isn't confirmed by the codes I would take it as just a rumour. If for example the valve books give higher voltage specs for later date UY42, that would confirm it.
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Old 22nd Oct 2019, 12:58 pm   #6
kalee20
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Default Re: UY41 Valve.

It's been discussed before but not with any conclusion.

Needs someone like Synchrodyne to start digging!
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Old 22nd Oct 2019, 1:05 pm   #7
Maarten
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Default Re: UY41 Valve.

Apparently from that thread, the UY42 was from some point in time deemed suitable for higher voltages. This is the same as I remember from the rumours, there might even be a Dutch service bulletin on it regarding valve replacement in certain sets. If they had relabeled UY41 production as UY42, this would have shown up in the code lists. A bit to my surprise it doesn't, so it's likely just some improvements to the UY42 specs.
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Old 22nd Oct 2019, 1:10 pm   #8
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Default Re: UY41 Valve.

http://www.r-type.org/pdfs/uy41.pdf

http://www.mif.pg.gda.pl/homepages/f...046/u/UY42.pdf

Lawrence.
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Old 22nd Oct 2019, 1:18 pm   #9
Stylo N M
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Default Re: UY41 Valve.

Hi,

I was imformed many years ago, that a UY42 would directly replace a UY41 in my Bush DAC90A radio and it seemed to be perfectly OK.

Having said that, at the time I had no way of proving it or dissproving it, and I've never really soak tested anything for any long periods of time so it's hard to say, anyway nothing went bang

Paul
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Old 22nd Oct 2019, 9:22 pm   #10
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Default Re: UY41 Valve.

I think that the information provided at this pair of sites shows (and explains why) that as originally designed, the UY41 and UY42 were significantly different, with the UY42 having much lower internal resistance.

Reconciling the different characteristics of the UY41 and UY42 in a single valve if indeed it were done - does not look as if it would have been at all an easy task. Id say that absent hard evidence that the combination was done, the safest assumption is that the UY41 and UY42 remained different until the end. That does not preclude interchangeability for some applications, but that was probably situation-specific.



Cheers,
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Old 22nd Oct 2019, 9:47 pm   #11
Dick Glennon
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Default Re: UY41 Valve.

Hi again, The valve lineup for this set is uch 81. Uf 89. Ubc 81. Ul 84. Uy 42. It is a Philips set no. B31F80U made in Dublin. Why I asked the question is that I have a few uy41 valves but nothing in uy 42 . What is the worst that could happen?. Regards Dick.
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Old 22nd Oct 2019, 10:50 pm   #12
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Default Re: UY41 Valve.

As I understand it, Dick (Other members please feel free to correct me if I'm wrong) it would be O.K. to replace a UY42 with a 41, but not the other way round. Having looked at thedata on the two valves, I'm surprised that Paul (Stylo N M) was able to use a UY42 in a DAC90A, where it would surely have been overvoltaged.
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Old 23rd Oct 2019, 12:40 am   #13
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Default Re: UY41 Valve.

Hi 'LIVEWIRE?'

Yes I do remember at the time i was a little worried and it was only a short test say maybe no more than about six minuites so I must have been lucky. It was really to establish that the radio was still working after a few small repairs, and also whilst I was waiting to obtain a decent UY41 raplacement valve, as the original had cracked at the base where the glass pip is on the side.

The radio was not used again until the replacement UY41valve arrived. I wouldn't have passed the radio on to anyone else with an incorrect part fitted anyway and I still have the radio now in working order.

I hope I haven't given any misleading impressions in relation to the two different types of valve, that was not my intention, I can see now that the UY42 is the lower rated valve, thank you for pointing it out

Paul
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Old 23rd Oct 2019, 12:47 pm   #14
Maarten
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Default Re: UY41 Valve.

John Hupse's site confirms the rumours on the Philips UY42 having been uprated to take 250V mains. Since he mentions no source, it's still rumours and he made some kind of a mistake in the codes or years mentioned, but his site is generally well informed so I think there must be some truth to it.

According to http://www.hupse.eu/radio/tubes/UY42.htm the UY42 was manufactured under 3 codes, which is indeed very likely. The 2 codes N7 and TM that I had already found, and a 3 digit code that Philips used up to roughly 1948-1950. On this site, the 3 digit code is erroneously mentioned as 71 with likely the last digit missing (the UY41 has old code 691 so the code for the UY42 starting with 71 is plausible).

It's also stated that all valves carrying one of the other 2 codes are good for 250V and that all Philips UY valves from 1954 on are good for 250V. This leaves a 5 year gap of uncertainty, but suggests that only the very first production of UY42 was for 110V only.

I still have to find the Service Bulletin I was thinking of.

Last edited by Maarten; 23rd Oct 2019 at 1:05 pm.
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Old 23rd Oct 2019, 12:59 pm   #15
turretslug
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Default Re: UY41 Valve.

Quote:
Originally Posted by Dick Glennon View Post
Hi again, The valve lineup for this set is uch 81. Uf 89. Ubc 81. Ul 84. Uy 42. It is a Philips set no. B31F80U made in Dublin. Why I asked the question is that I have a few uy41 valves but nothing in uy 42 . What is the worst that could happen?. Regards Dick.
I don't think anything really bad would happen- it's possible that HT would be a few volts low compared to a good UY42, resulting in the set running a little cooler! If the UCH81 was really tired, the LO might stop on some bands or sections of bands but it would have to be well knackered and on its way out anyway to be affected by a small percentage HT drop. If you were really pedantic, you might be able to measure a slight drop in maximum audio output capability but in subjective aural terms it would be unlikely to bother you,

Colin
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Old 23rd Oct 2019, 2:17 pm   #16
paulsherwin
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Default Re: UY41 Valve.

I don't really see what a UY42 is doing in an Irish radio anyway. I'm pretty sure Ireland has always had 240V mains supplies, like the UK. I wonder if Philips were using up some old UY42 stocks, given that the rest of the valves are B9A Novals. If it was a late production UY42 then it would have been 250V rated.

By the way, the model number will be B3IF80U. IF is the Philips country code for Ireland (Irish Freestate).
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Old 23rd Oct 2019, 4:50 pm   #17
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Default Re: UY41 Valve.

I've got a Philips B2X67U/65 here which has the 'expected' mid-1950s B9A lineup of UCH81 UF89 UBC81 UL84 - but also an old-style 8-pin UY42!

And yes it's specified to run on 110-240V, with the rectifier getting full line-voltage in the "240V" series-dropper setting.

I can only think that there must have been some financial benefits to using an old-style B8 valve in the lineup with the more-modern B9A bottles.

Using-up old stock? A Tax-writeoff of 'remaindered' parts?? Methinks we will never know.
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Old 23rd Oct 2019, 5:11 pm   #18
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Default Re: UY41 Valve.

Quite possibly. The PCL83 employed in the Pye 'Black Box' may also come into that category. John.
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Old 23rd Oct 2019, 5:16 pm   #19
Maarten
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Default Re: UY41 Valve.

In the "Philips Service Maandblad" October 1949, Philips warns against using a UY42 at 220V in BX180U and BX182U sets. They also state that using a UY41 at 127V isn't a problem but will cause slightly less performance.

1949 is sufficiently close to the end of the old code usage that most or all UY42 on the market would have been of the 71x variety, so this is in line with what's mentioned on hupse.eu, even though I haven't found any mention yet in later documentation, of the UY42 from then on being suitable for 220V mains, but I've found numerous later sets that both have a UY42 and a 220V setting.

Though the exact year is as of yet unknown and the codes unconfirmed, it seems plausible to me that Philips at some point in time, made the UY42 suitable for use on 220V mains.

Also, the successor valve UY85 requires a series resistor when used on 220V mains, but it may be omitted at 127V. Maybe it isn't (only) the voltage but also the low internal resistance and resulting higher surge current that made the UY42 unsuitable for use on 220V mains.

Last edited by Maarten; 23rd Oct 2019 at 5:34 pm.
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Old 23rd Oct 2019, 11:11 pm   #20
Dick Glennon
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Default Re: UY41 Valve.

Hi again, Thanks for all your advice, very much appreciated, just one more questions? What is the dial bulb spec. All I can make is Philips Holland. 2 bulbs. Regards Dick.
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