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Old 16th Feb 2018, 5:18 am   #21
Boater Sam
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Default Re: AD35/B126 Batteries

I work mine down to 1.36 v happily. The long term recommendation is 1.45 v absolute max for good life.
Quiet or completely dead? If the latter, is the oscillator stopping? If so, the 1st valve may be soft/low.
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Old 16th Feb 2018, 5:58 am   #22
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Default Re: AD35/B126 Batteries

I love these valve battery portables too. Most of mine are Vidor, but I have a few Every Ready, one of the Marconiphone pocket sets, etc too. In fact I got another Vidor yesterday, CN441 ('96 series valves on a PCB).

One thing I have learnt, alas, is that the previous owner often tries any batteries they can find and burns out the filaments.

I must get round to making up some batteries for mine. Most use the B126 for HT and AD35 or AD4 for LT. But at least one uses the B114, and I have some battery/mains sets (including one with a mains transformer and valve rectifier, an EZ40 I think) that use a 7.5V LT battery (all 5 sections of the 'D' series filaments in series).
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Old 16th Feb 2018, 9:25 am   #23
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Default Re: AD35/B126 Batteries

Quote:
Originally Posted by TonyDuell View Post
I have some battery/mains sets ... that use a 7.5V LT battery (all 5 sections of the 'D' series filaments in series).
I have a Murphy BU183 that has this arrangement - using an AD38 for the 7V supply (in my case a replica containing five "AA" cells.
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Old 16th Feb 2018, 10:40 am   #24
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Default Re: AD35/B126 Batteries

Regarding LT voltage, the DK96 frequency changer will start to drop out and stop oscillating at progressively higher Lt voltages as it ages. A good one should still function down to around 1.1 volts, but a tired one may well stop functioning when the LT drops to 1.3 volts or so.
Again, be very careful to avoid over volt-ing these battery valves - A pair of new alkaline C or D-cells will put out close to 1.6 volts, even on load, when first installed in a set. Consequently, I've taken to incorporating a 1.2 ohm resistor in the LT+ feed from battery to socket in all my battery portables.
The main problem I've found with the LT circuits on these sets is poor contacts within the McMurdo B7G valve holders leading to seriously reduced voltage across pins 1 and 7 of the valve itself. A clean up of the lid-operated LT switch (where fitted) and individual valve pins along with changing any broken contact elements in the valve holders will help.
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Old 16th Feb 2018, 10:52 am   #25
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Default Re: AD35/B126 Batteries

I have put a silicon diode in series with my D cell, and 3 in series (reverse) across the battery when working on these.
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Old 16th Feb 2018, 12:38 pm   #26
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Default Re: AD35/B126 Batteries

Quote:
Originally Posted by Dave Moll View Post
I have a Murphy BU183 that has this arrangement - using an AD38 for the 7V supply (in my case a replica containing five "AA" cells.
The normal reason for that was that, of course, these little directly-heated valves need a DC filament supply. In battery/mains sets this was often obtained by a dropping resistor from the HT+ (90V or so) line in mains mode. Having the filaments in series reduced both the voltage dropped across the resistor and the current through it, thus saving power, and more importantly heat production.

When making replicas, what do people do about (a) the casing (folded cardboard, or something stronger) and (b) the socket? I am assuming I don't have an old battery to re-stuff.
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Old 16th Feb 2018, 12:57 pm   #27
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Default Re: AD35/B126 Batteries

In my case I used the services of forum member batterymaker1, whose constructions were sturdy and of excellent quality. As he has not accessed the forum since last August, it looks like he may no longer be an active member of the forum.
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Old 16th Feb 2018, 1:00 pm   #28
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Default Re: AD35/B126 Batteries

I print the cover on paper, glue it onto good card, board really, with pva.
Cut out, crease and fold.
Stiffen by putting a sleeve of card inside, load batteries and pack out with expanded polystyrene cut to fit.
Sockets I make with old B4,5,7,9 valve sockets cut up and plastic sheet, with valve pins and plastic sheet again, potted in epoxy.
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Old 16th Feb 2018, 1:23 pm   #29
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Default Re: AD35/B126 Batteries

Battery Maker also has an excellent You Tube channel

Here is an example of his excellent work

https://www.youtube.com/watch?v=s7t9kZsLtMw

Cheers

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Old 16th Feb 2018, 3:22 pm   #30
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Default Re: AD35/B126 Batteries

Sounds good Sam! So far, I've never used the interweb downloads for making battery graphics - just photocopied my own cases from my battery carton library. I generally re-use existing sockets from old B126, AD35, B136 or B141 batteries although I did come across some brand new B114 style sockets at a sale years ago.
I did make an Ever Ready Portable 56 HT battery from scratch for use in a 2 volt valve battery Ecko that I had years ago. This had a QP25 push-pull output stage that delivered about a watt! Shame I sold it really. I've also made combined HT/LT/GB 162/3 volt batteries for use in Wireless Sets 18 and 46, again from first principles. I did the graphics on the PC and printed them out on brown cardboard taken from filing cabinet suspension files. I then folded the box and lined it with thin aluminium sheet glued in place. Like you, I used dismantled B4 valve holders to make up the rather unusual 5-pin sockets that these batteries use.
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Old 16th Feb 2018, 3:59 pm   #31
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Default Re: AD35/B126 Batteries

Quote:
Originally Posted by TonyDuell View Post
One thing I have learnt, alas, is that the previous owner often tries any batteries they can find and burns out the filaments.
Too true: I once walked in to a second-hand shop whose proprietor was in the act of trying every possible way to get a response from an Invicta valve portable using only a six volt lantern battery. If only it had been a model with series filaments...

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Old 16th Feb 2018, 4:41 pm   #32
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Default Re: AD35/B126 Batteries

This is an original B141 and the Ever Ready 'Sky Casket' that it was fitted in. I pulled it complete with battery, off the tip years ago.

Batteries were expensive and didn't last very long. John.
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Old 16th Feb 2018, 7:30 pm   #33
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Default Re: AD35/B126 Batteries

In an Ever Ready model 'T' that I was working on recently, and seen in the thread linked to here:-
https://www.vintage-radio.net/forum/...d.php?t=143283
I was using up some old alkaline AA cells that had gone down to around 1.4 volts for the LT supply to run the set after it had been put back together. I found that the oscillator stopped dead when the AA cell had reached about 1.0 volt. I taped together a block of seven 12 volt lead acid 'gel' batteries for the HT, seeing as I already had a few ex-equipment ones that I'd been given several years ago. This gives me a theoretical voltage of 84 volts, however, due to the fact that some of them had been left in the shed and not kept properly charged, three of them seem to have the odd dead cell, so the actual voltage seems to settle out at around 74 volts. I've got several more that are ok, so I may yet replace the three not so good ones. I would probably have gone for using eight batteries giving me an initial voltage of 96 volts, but eight won't fit in a line between the chassis and the side of the cabinet. I probably ought to fit an inline fuse in the HT line just in case anything goes wrong with the switch gear or other circuitry when the set is not in use, as there's a bit of current available from those gel batteries to do some damage - or worse!

In the picture below you can see the 'lash-up' with the seven gel batteries and you can just see the single AA cell. Somehow I don't think that lot will fit in a replica case of the correct B103 battery, although I've not taken measurements and tried yet.
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Last edited by Techman; 16th Feb 2018 at 7:58 pm.
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