What rectifier valve for Mullard PM H.T. Unit?

[SurreyNick]

I have one of these Mullard PM H.T. Units which I am planning to sell off, but before doing so I want to see if it'll work. It looks very clean inside and I reckon I may be lucky that it will work straight away if I pop a rectifier valve in the holder.

When I bought it someone had a duff full-wave rectifier valve in it - a Philips 1821. I believe this would be correct because all the literature I have found for this Mullard unit refers to a full wave rectifying valve, but no particular valve is ever specified.

Do you think I can use any B4 base full wave rectifying valve?

A maximum potential of 180 volts is obtained on a load of 10 milliamperes, a reduction of about 2.5 volts occurring for an increase of 1 milliampere load up to the permissible load of 40mA.

Thanks

Nick
           

[pwdrive]

Most rectifiers would supply that current at that voltage but you need to make sure that the transformers heater winding can supply the current needed for the rectifier you use, the Mullard DU3 might be a contender, according to radiomuseum it's a 4 volt 0.6 amp heater job, there's also the Mullard DW3 which is a 4 volt 2 amp heater job, radiomuseum doesn't seem to state whether it's half or full wave for the DU3 but from the picture shown on there it looks like a full wave job, there might be others.

Lawrence.

[pwdrive]

Just had another dig, the Mullard DW2 is the equivalent to the Philips 1821 (see 1st link below):

http://www.g3ynh.info/valves/old/Data-Bo...V-p099.pdf

Here's the directory page for the above:

http://www.g3ynh.info/valves/old/Data-Bo...index.html

Lawrence.

[SurreyNick]

Thanks. I will see if I can track one down on eBay and will also post a wanted here and over on the other forum for either a DW2 or a 1821.

Do you think I could get away with a UU5 though?

I'm sure I have one kicking around somewhere and I'm sure I also read a 1821 can be replaced with a UU5, but not the other way around. However, I'm always a bit dubious about these things.

Oh, I thought you might like to see what the unit looks like nowadays. The pictures at the start of this thread were the only ones I had and was what it looked like when I bought it a couple of years ago. I took some new photos this afternoon. I swear two of the best tools in the toolbox are elbow grease and patience

Nick
                   

[pwdrive]

So far as I know HT wise the UU5 should be ok but heater wise it needs 2 amps or so, if the PSU originally had a DW2 or an 1821 fitted then note that the heater current for those is shown as 1 amp in the data books, I would hate for your transformer to get hot, see what the others think just in case I've got it wrong.

Lawrence.

[Nowhere-Man]

Thanks. I will see if I can track one down on eBay and will also post a wanted here and over on the other forum for either a DW2 or a 1821.

Do you think I could get away with a UU5 though?

I'm sure I have one kicking around somewhere and I'm sure I also read a 1821 can be replaced with a UU5, but not the other way around. However, I'm always a bit dubious about these things.

Oh, I thought you might like to see what the unit looks like nowadays. The pictures at the start of this thread were the only ones I had and was what it looked like when I bought it a couple of years ago. I took some new photos this afternoon. I swear two of the best tools in the toolbox are elbow grease and patience

Nick

There are two suppliers, Billingtons and Langrex. Billingtons tend to do big orders and Langrex will sort you out quite easily and quickly with the exact tube you need. These are based here in the U.K. and post very quickly.