H.T. 120 volts; L.T. 2 volts (accumulator) batteries?

[SurreyNick]

Hi All

I have (what I believe is) an Etronic model WB430 battery operated (H.T. 120 volts; L.T. 2 volts (accumulator)) superhet that I am restoring. I am new to restoration and could do with a little advice regarding replacement batteries. I might consider building a simple mains-powered battery eliminator for the longer term, but initially (as far as is practical) I’d like to restore the radio to its original ‘as new’ condition and that includes running it on batteries. Although I will rule out the possibility of using a rechargeable wet battery, unless of course someone can show me a feasible solution.

The Trader Service Sheet states the four valves are: (V1) TP25; (V2) VP23; (V3) HL23DD; (V4) Pen25. Given the state of the radio when I got it I doubt any of the existing valves work. So my question is as follows: If I replace the valves, with more efficient ones, rather than early bright emitter tubes, can I power the radio with 90v H.T. and 1.5v L.T. replacement dry batteries and get good performance, or would I be better sticking to 120v and 2v (dry)? If I can go for 90v/1.5v, what easily obtainable valves (makes/models) would you recommend for best performance? Your advice would be most helpful and welcome.

[Note: I have attached images of the valves that are currently in the set.]

Thanks

Nick

[julie_m]

There was definitely a D_3_ range of directly-heated dry-battery valves on octal bases.

[Heatercathodeshort]

These are not 'bright emitter' valves. [These early types had all gone O/C by the late 1920's.]They are from the Mazda octal range and were still employed in some receivers post war. The bases are completely different from the International octal range having a larger spigot, wider pin spacing and differing base connections. Unless someone has accidentally mixed up the battery connections and put H.T. across the filaments, my guess is that they will all be ok.
If it were my project I would probably use a 2v Cyclon cell or use an old accumulator case to hide one. The valves perform very well generally slightly better than their 1.4v 'Alldry' equivalents. Regards, John.

[SurreyNick]

Thank you John and AJS.
Sadly, a couple of the valve bases are loose, but now I understand what I'm dealing with I will try and test them and find Mazda replacements for any that don't work. I like the idea of the 2v Cyclon cell so will get one of those. Any advice on the 90v / 120v question? Easy enough to connect ten 9v PP3 cells in series, however I could try ten 12v A23 cells in a makeshift battery clip or just opt for thirteen or fourteen 9v PP3 to get close.
Nick

[jonnybear]

A23 12 volt battery, would not last very long, if you were very lucky 1 hour,
PP3 if you are going that route I would use Ni-Mh rechargeable, or alkaline.
Just because the base is loose on the valves, it does not mean they are faulty, a little shellac around the rim will usually firm them up.
John

[SurreyNick]

Thanks John. I won't discard until tested
Nick

[Herald1360]

For a 120V HT battery, the easiest solution is 13 PP3s. They can be clipped together using their own connectors except for the actual +/- outputs at either end. Another possibility is this:

https://www.vintage-radio.net/forum/...ad.php?t=66030

though you wouldn't need the multiple tappings which makes it slightly less of a chore to build and you would "only" need 80 AA cells. Maplin do 100 for fifteen quid at the moment.

Have fun!

[Phil G4SPZ]

I am restoring a pre-war McMichael portable which needs 108 volts at 10mA (a dozen Pound Shop PP3s work fine) plus 2 volts at around 200mA for the filaments. The small Cyclon 5Ah cell works very well in this role and is easy to recharge from a 12 volt supply via a series resistor of adequate wattage.

[SurreyNick]

Thanks Chris and thanks Phil.
Thirteen PP3s and a Cyclon 5Ah cell it will be
Regards
Nick

[kestrelmusic]

If the valves have failed you will have no problem finding replacements - they go on Ebay for pocket money prices.

[SurreyNick]

Thanks. I shall be sure to source them there.
Nick

[Chindit]

These Mazda 2 volt filament types perform very well provided no one has over-driven the filaments in the past. You should get good performance even with just 90 volts HT, provided the TP25 frequency changer is a good one. They were favorites of the War Department (simply because the then new 1.5volt all glass miniature valves were not available in the UK until after the war) and many similar Mazda types were used in WW2 manpack transmitter/ receivers such as the Wireless Set 18, 22, 38, 46 and 68. With the exception of the WS22 these sets were driven by 150 volt HT batteries with a 3 volt LT section - the filaments being fed via dropping resistors.
Hope you get it going soon! Colin.

the filaments being fed via dropping resistors.

One per valve so if one goes O/C the rest don't get an increase in voltage.

[SurreyNick]

Interesting and informative. Thanks guys
Nick

[Chindit]

I restored a similar Murphy B53 4 valve battery receiver; the HT battery was a Ever Ready type Portable 56 of 136.5 volts. I made a replica of this and filled it with around 90 AA cells held in nine holders holding 10 batteries each. Not as expensive as you might think as I can get 100 duracells on the net for £25 and with a current draw of 10mA they would last for years with occasional use.
The LT was provided by a 8Ah cyclon cell which I got from Farnells; these work well especially with a good charger. I used a German brand that automatically configures itself to the cell(s) attached, providing 24, 12, 6, 4 and 2 volts as necessary.
I have never used battery eliminators; if I wanted to connect a set to the mains, I'd just buy a mains operated set. 10 cheap PP3s and a cyclon will do fine and, as mentioned, clipping them together to form a string using their own connectors is the way to go. Once you've done this bind them up with tape to hold them securely together. I've tried putting batteries side by side and making up dedicated re-useable leads, but sooner or later the connectors on these loose their spring and you get annoying intermittent crackles. Colin.

[Chindit]

Originally Posted by merlinmaxwell

One per valve so if one goes O/C the rest don't get an increase in voltage.

Yes that's right. They were arranged to drop the 3 volts to around 2.2 or 2.3 volts in the Wireless Set 46 - the idea being that a bit of over running could be tolerated initially as the LT would soon drop to around the 2 volt mark anyway. On MCW receive the LT consumption was 850Ma - rather a lot for a dry battery to provide!

[G6Tanuki]

Same approach was used in the 18-set, which also used Mazda 2-volt valves (VP23=ARP12) and a 3V LT battery. Indeed, if you look at the design of the ATP4 transmitting-pentode it used, I'm 99% sure that valve is actually a 1930s Quiescent-push-pull audio double-pentode with both halves strapped internally and a top-cap fitted.

[Phil G4SPZ]

Originally Posted by Chindit

I can get 100 duracells on the net for £25... Colin.

Keep an eye on Maplins, too. Every so often they have a half-price sale, when their boxes of 100 alkaline AA cells go for just £14.99.

[Herald1360]

Originally Posted by Herald1360

Maplin do 100 for fifteen quid at the moment.

http://www.maplin.co.uk/p/maplin-ext...100-pack-n43cy

for reference......

The reference to holders could be met by these:

http://www.maplin.co.uk/p/10-aa-battery-box-rk45y

which would be a whole lot less of a chore than soldering 80 odd cells in series......

Halfords also do a good deal on packs of AA cells, and do PP9's too FYI. See https://www.vintage-radio.net/forum/...ad.php?t=66030