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Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets.

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Old 22nd Feb 2020, 11:53 pm   #1
Phil G4SPZ
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Default Dodgy? AD28 batteries

This thread https://www.vintage-radio.net/forum/...d.php?t=157218 from last year highlighted the fact that AD28 (3R25) 4.5 volt batteries seemed to have disappeared from the market, with most suppliers listing them stating "out of stock".

Quite coincidentally, I switched on my Ultra Transistor 101 this evening and was rewarded by a typical "flat battery" sound. Annoyingly, I didn't keep a note of when or from whom these batteries were bought, but I guess it must have been 3-4 years ago. The radio gets little use, apart from an occasional switch-on to test it. It could be three months since I last tried it.

Anyway, a quick check showed that one of the AD28s was still full of life, but the other was virtually dead flat. A look inside the duff battery revealed that two of the three F cells were heavily corroded. The third, oddly, looked and tested fine. Luckily, the corrosion had been contained within the plastic sleeving surrounding each cell, and no damage was caused to the cardboard case of the battery.

I re-stuffed the AD28 with three cells scavenged from a Duracell PJ-996 style lantern battery. I fully expected this to contain four F-cells, but was surprised to find four D-cells of rather unusual design. These didn't have solder tags, but a hot 90 watt iron made short work of soldering direct to the cases. Despite the 2018 date on them, they test perfect, so in they went, and the Ultra is sounding fine once more.

Moral - if you have an AD28 battery, look after it as you'll probably need to re-stuff the case sooner or later.

Phil
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Old 23rd Feb 2020, 12:44 am   #2
Julesomega
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Default Re: Dodgy? AD28 batteries

Quote:
Originally Posted by Phil G4SPZ View Post
Moral - if you have an AD28 battery, look after it as you'll probably need to re-stuff the case sooner or later.
..or a bicycle lamp
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