UL41 valve.

[rockinmark]

Hi would anyone have a UL41 valve?

[Pamphonica]

Quite a few will have spare UL41s but the usual caveat is that UL41s tend to end up with a heater-cathode leak, often producing an incurable hum. Quite a few of my used spares sadly turned out to have that problem. NOS may be OK, as would tested spares, or look out for UL46 - a better made equivalent, used I think as a video amp for TV.

[David G4EBT]

New/Old Stock UL41 (and UL46) valves are becoming quite rare now. Consequently that reflects in their prices, now typically in the £27.00 - £30.00+ range. As Jeremy says, used 'tested' ones which might have reasonable emission may well produce hum, which the UL41 is noted for.

Most NOS UL41s on sale now are either CV1977 MIL Spec, or 'Miniwatt' French ones. EG:

CV1977 MIL Spec £30.00:

https://www.langrex.co.uk/products/u...alve-tube-lb8/

Langrex - a major UK supplier - now only have 9 CV1977 (UL41) left in stock, and 3 UL46.

Miniwatt French NOS £27.00:

https://www.vintage-electronics.co.u...alve-tube-nos/

An EU supplier has NOS UL46 at €44 (£38 GBP) plus post.

It makes radios such as the ubiquitous Bush DAC91 an expensive restoration proposition, especially if the UY41 rectifier is past its best, then waxy cap replacement, and heaven forfend, an open circuit output transformer, and a pair of 3.5V 0.15A bulbs if you can find them).

Sorry to be so downbeat, but these are the facts of life.

Good luck in your quest.

[G6Tanuki]

I converted my Eddystone 840A to use a UL84 instead of the distinctly-problematic hummy and expensive-even-a-decade-ago UL41; after half a decade of using it for regular night-time HF listening the UL84 is still going strong.

The swapping of the B8A base to a B9A is not difficult; if you get the right brand of base there's no need to do any non-reversible metalworking.

[David G4EBT]

Originally Posted by G6Tanuki

The swapping of the B8A base to a B9A is not difficult; if you get the right brand of base there's no need to do any non-reversible metalworking.

That's a good tip - lots of UL84 NOS available at half the price of NOS UL41s.

Gold plated B9A bases from Cricklewood £2.40 in VAT!

https://www.cricklewoodelectronics.c...BoCq6UQAvD_BwE

(The hole diameter for B8A and B9A valve sockets are both 3/4")

[gallowfields]

you can also find 30p15 equivs at a reasonable price
brian

[G6Tanuki]

Originally Posted by David G4EBT

(The hole diameter for B8A and B9A valve sockets are both 3/4")

The spacing of the holes in the two mounting-tabs can vary though, hence my suggestion that you may need to investigate different styles/brands of replacement socket if you want to avoid the need for any irreversible mechanical rework.

[Valvepower]

I unearthed a UL41 earlier in the year for someone on the forum, but the chap had already located one so it went back into the toy box. Like most things at the moment, I’m not sure where it is, also it may have already found a new home… I’ll have look in the next few days when I’m in next in the workshop.

This was tested in a DAC90, and from memory was OK. If I do find it, I could check the heater cathode insulation, however, to save me hunting for data - what would be typical test voltage and the expected insulation resistance?

Terry

[Leon Crampin]

In the DAC90A and DAC10 which both operate the output valve at a low screen voltage and hence low anode current, a Mazda 10P13 is a good direct plug in replacement for the UL41. There is a slight loss of gain due to its lower gm.

This substitution is not valid in a set where the UL41 operates near its maximum ratings. Within its published ratings, the 10P13 is much the more reliable valve.

Leon.

[Joe_Lorenz]

Just spotted that Siemens UL 41 at 10.50€:

https://www.meggys-shop.de/UL-41

I do not know that seller, just a google result.

Joe

[paulsherwin]

Oddly enough, one of the last users of the UL41 seems to have been the German navy (GDR maybe?). I think they came from Tungsram in Hungary. Late production UL41s seem much more robust than earlier ones, but take ages to warm up. You can identify them by the lack of a raised collar around the base.

UL41->UL84 substitution was a standard repair in the 60s and 70s, and recommended in several valve data books. You need to bump up the cathode resistor to reduce the anode current.

[Joe_Lorenz]

GDR East German manufacturers did use U-Type valves much longer than West German manufacturers.
West German Bundeswehr (military) would never buy any component of Warshaw Treaty states origin those days. Most but all western mil-gear valves were Telefunken, Valvo, Lorenz, Hoges or maybe RCA then.

Joe

[turretslug]

Originally Posted by paulsherwin

Oddly enough, one of the last users of the UL41 seems to have been the German navy (GDR maybe?).

Maybe not quite so odd? The Germans seemed to take Rimlock more to heart than in the UK, and navies tend to have kit in service for decades by the nature of things- look how long the Murphy B40 was used by the RN and others. I'm sure that there was a DC-mains, series-heater version of the Telefunken E103 (admittedly with a UCL11 output valve in an otherwise Rimlock line-up), and there would have been a similar, if peripheral, requirement with other marine electronics so I wouldn't be so surprised if there was in-depth stock of the UL41 for something or other. I'm sure that there would have been many more British and US '40s and '50s valves on the surplus market if it hadn't been for the likes of the 1983 Donnington fire....

[gallowfields]

Originally Posted by gallowfields

you can also find 30p15 equivs at a reasonable price
brian

ooops my error , meant a 10p13
brian

[Sideband]

Originally Posted by gallowfields

ooops my error , meant a 10p13
brian

I thought that didn't sound right....I think the 30P15 is a TV frame output valve.....

Yes 10P13's are a plug-in replacement for the UL41 but they are NOT equivalent. You need to increase the cathode resistor when using the 10P13 to bring the anode current down within the limit of the valve. Something like 470 ohms or 560 ohms should do.

[Leon Crampin]

In the DAC90A and 10, the 10P13 is a straight swap. The low screen voltage limits the anode current.

Leon.

[David G4EBT]

Originally Posted by Leon Crampin

In the DAC90A and 10, the 10P13 is a straight swap. The low screen voltage limits the anode current.

Leon.

That's more like it!

Several NOS ones on eBay in original box at £7.00 plus P&P.

What's not to like?

[Valvepower]

Hi,

I did look for the UL41…, but, sadly I can’t find it…, something at the back of my mind says I gave it to one of the chaps at the factory to restore a Bush 50s woodie…

Terry

[rockinmark]

Thanks everyone for the great advice might have to see about getting my own tested.