Mullard Tubes looking for information

[marantzgrail]

Morning all!

I have some Mullard UL41 tubes that I'm having no luck finding info on, mine have painted red tips and raised red ring at the bottom edge just before the posts. Has anyone come across these before?

Thanks very kindly!

 

[Dswankey]

I have some Mullard UL41 tubes that I'm having no luck finding info on, mine have painted red tips and raised red ring at the bottom edge just before the posts. Has anyone come across these before?

I found a decent bit of info searching "Mullard UL41 tubes" below is one of the links I found. Type "Mullard UL41 tubes" into whatever search engine you use and you should be able to find info

http://www.r-type.org/exhib/abc0004.htm

 

[Dandy]

Morning all!

I have some Mullard UL41 tubes that I'm having no luck finding info on, mine have painted red tips and raised red ring at the bottom edge just before the posts. Has anyone come across these before?

Thanks very kindly!

The additional red parts sound like later additions. Can you post a picture of them?

 

[Pio1980]

U is series string heater current rated, L for power output pentode, 4# is a short time used obsolete rimlock button base with evenly spaced pins similar to 9 pin mini, #1 is version variant of the series line.

 

[marantzgrail]

 

[marantzgrail]

The additional red parts sound like later additions. Can you post a picture of them?

Pictures posted. Thanks very kindly for the help!

 

[Dswankey]

From what I've read in the past the colored markings denotes that the tube has been designated specialty grade for example to be used in medical test equipment.

I'll let others with more knowledge on the subject clarify.

I've had similar tubes in the sense there was some factory coloration on them. Note these are Amperex not Mullards maybe it was an industry thing? as opposed to manufacturer.

Here's one with a blue tip



Here's a couple that came from the same device with the coloration on the seam

 

[Pio1980]

From what I've read in the past the colored markings denotes that the tube has been designated specialty grade for example to be used in medical test equipment.

I'll let others with more knowledge on the subject clarify.

I've had similar tubes in the sense there was some factory coloration on them. Note these are Amperex not Mullards maybe it was an industry thing? as opposed to manufacturer.

Here's one with a blue tip

View attachment 2289714

Here's a couple that came from the same device with the coloration on the seam

View attachment 2289715

Select sorted seems reasonable.

 

[Pio1980]

The rated heater voltage varies with the 'U' tubes to make wattage draw constant thru a series string heater circuit. The smaller tubes need less heater wattage and can have a lower voltage rating, power tubes need more heater wattage, so their required voltage will be higher at the same current. Series/parallel heaters and ballast resistors may be utilized to achieve even higher, or lower, current if required. Some Sansui models like SM80 and the first series 1000 receivers used four 25 volt heater sweep tubes as outputs, wired in series to match the 100 volt standard.

 

[analog addict]

I have some red tipped Telefunkens that I know came out of late 60's/early 70's EEG amplifiers. I've been led to believe that these markings do denote tubes used in medical or other high grade equipment...

 

[marantzgrail]

Thank you to all for the assistance resolving this query!