loewe-opta: 3940; Lissy

Can somebody please tell me the maker and type number of the original HT battery? None of the standard UK batteries appear to be correct - the closest is Ever Ready B131 but the terminal spacing is too small and the battery too tall!

I think maybe this was a German battery and not standard?

Regards,

Colin Boggis

UK

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Hello.

The 90 Volt Battery is from BAUMGARTEN  Germany Type: EMC 650

regards,   Knoll

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Thank you for your help Hans.

I wanted to make a copy of this battery using 10 modern PP3  batteries in series, but having found the dimensions elsewhere on Radiomuseum, I realise the case is not big enough! 

From a picture of the EMCE 650 I have made up my own graphic of the opened out case, from which I will make a dummy battery. I might fit an inverter inside it to create the 90 volts from 3 or 6 volts from "AA" cells. I'll post some pictures later once I've finished experimenting.

I've replaced the DEAC cell with a LM317T regulator inside a box suitably labelled to simulate the original DEAC. This required a minor change to the LT wiring on the switch bank, just one link to cut. Again, I'll publish the circuit later.

Regards,

Colin

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Hello Colin.

Thats fine. I am happy for you.

hans  

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A DEAC acts as a parallel shunt regulator. A normally wired LM317 etc will not be correct. I use a 3500mAH NiMH cell soldered into a replica case.

Smaller 45, 67 and 90V  HT packs can be made from 3V Lithium Coin cells. Only use about 21 to 26 coins as the old 90V packs had "endpoint" of 56V approx. The end point of the Lithium coins is about 2.75V and peak fresh is about 3.2V. You need to parallel stacks of the coins using 1N4148 diodes as one stack isn't low enough source resistance. I use 2, 3 or 4 sets of 21 coins depending on pack. You need a small value fuse for safety on each stack. A very fine piece of wire may be sufficient.

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Thanks for your information Michael.

I'll look at the lithium battery approach, seems a good solution although I imagine that there might be a good contact issue between cells with the passing of time?

I appreciate that the original DEAC was a shunt regulator (a "Super zener" as some call it) and I did initially use a NimH cell in a custom container but found that the filament voltage was rather low for good performance and that it very quickly "killed" a 1.5 volt D cell when on battery. So I opted for a series regulator using LM317T. Breaking the link between the two sets of switch contacts (b2,3 & c2,3 on the circuit diagram) and feeding the input from b2 with output to c3 was a simple modification.

I take it that when you say it's not right, you mean from an originality point of view as technically it's a reliable solution and the filament voltage is very stable. Of course I had to add some large electrolytics to emulate the DEAC capacitance, but the result is fine.

Regards,

Colin

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Low?

The Filament voltage is 1.1 to 1.4. a voltage of 1.3V is ideal. The 1.5V dry cell is only for emergency top-up of a DEAC if you are away from mains. It shouldn't be left in. The original DEAC (actually a NiCd is about 0.05V lower or more than a modern NiMH. A modern NiMH is practically perfect for all D*91, D*92 D*94 and D*96 valves.

I make "spring flaps" out of cut up coffee can (using sissors). See batteries via my Collection page. look for blaukatz dot com too.

The Zinc Carbon are more than 1.6V fresh dropping to 0.9V exhausted. The end point for dry Battery valves though is just under 1.1V. Combo packs used sizes of cells assuming 0.9V on the HT at perhaps 9mA (100V fresh down to 54V) and  1.6V down to 1.1V for the LT at about 128mA down to 110mA (a four valve AM DK96, DF96 DAF96 DL96 set).  Alkaline D cells are of couse slightly better than the old Zinc Carbon F cells with flatter discharge.

If the Local Oscillator AM or VHF fails before 1.1V then the valve (tube) is low emission, worn. Or a bad socket. HT is much less critical.

At low current the PP3 layer cells are better value than Alkaline PP3 and can "chain together" more easily. Often the Alkaline don't as they are slightly bigger than orginal PP3 as they are 6 cells similar to AAAA. Hence the Alkaline PP3 are only about 50% better than PP3 layer cell, but Alkaline D cell at 300mA is perhaps x3 better than Zinc Carbon or Zinc Chloride for filaments.

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Actually I have set the filaments at 1.3 volts and HT is around 85 volts and the radio performs very well on VHF, but I do have an issue on MW & LW. Sometimes works and other times it doesn't but as there is some background noise I'm fairly sure the oscillator stops although it always runs Ok on SW. I'll get the ,scope out and sort it in due course.

I'm not sure why my use of the NiMH wasn't successful - I will try the approach again.

Thanks for all the advice and help - much appreciated.

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