Roberts R24 mistake - UK Vintage Radio Repair and Restoration Discussion Forum

Colinaps · 18th May 2020, 10:51 pm

The other day, I just swapped the PP9 tabs for a PP3 connector to get my slightly moribund R24 going with a set of AA cells. Not a special radio but adequate for chasing interference...

On opening it up, a little neuron clicked into place: 20-odd years ago, the set had been relegated to the back of a cupboard because it drained a PP9 in a couple of days. Turns out the set was drawing about 4mA from the battery when switched off.

There's an idiot diode which also prevents the battery from charging when the mains is connected. However, there's nothing to stop the battery from draining through the 2k2 R33.

Nothing that can't be fixed with another diode!

Cheers,

Colin.

Herald1360 · 19th May 2020, 10:29 am

Wouldn't it take about a month, though? A new PP9 is about 4000 mAH.

Looks like they might have used a PSU designed for plug-in applications without considering the implications.

ms660 · 19th May 2020, 11:40 am

http://www.valve-radio.co.uk/literat...ervice-manual/

Last page.

Lawrence.

Cobaltblue · 19th May 2020, 11:48 am

I see that was signed by Geoffrey Dixon-Nuttall.

Unfortunately now passed, an outstanding BVWS member and genuinely nice person.

He did some outstanding articles in early Bulletins including one on Cossor which I still refer to today.

Cheers

Mike T

19th May 2020, 2:43 pm

That is a big OOPS, I get my designs "sanity checked" by someone else trying to explain them to me. Sometimes it is an eye opener for both of us!

18th May 2020, 10:51 pm	#1
Colinaps Pentode Join Date: Jul 2009 Location: Roxburghshire, UK. Posts: 196	Roberts R24 mistake The other day, I just swapped the PP9 tabs for a PP3 connector to get my slightly moribund R24 going with a set of AA cells. Not a special radio but adequate for chasing interference... On opening it up, a little neuron clicked into place: 20-odd years ago, the set had been relegated to the back of a cupboard because it drained a PP9 in a couple of days. Turns out the set was drawing about 4mA from the battery when switched off. There's an idiot diode which also prevents the battery from charging when the mains is connected. However, there's nothing to stop the battery from draining through the 2k2 R33. Nothing that can't be fixed with another diode! Cheers, Colin. Attached Thumbnails

19th May 2020, 10:29 am	#2
Herald1360 Dekatron Join Date: Feb 2007 Location: Leominster, Herefordshire, UK. Posts: 16,536	Re: Roberts R24 mistake Wouldn't it take about a month, though? A new PP9 is about 4000 mAH. Looks like they might have used a PSU designed for plug-in applications without considering the implications. __________________ ....__________ ....\|____\|\|__\|__\_____ .=.\| _---\__\|__\|_---_\|. .........O..Chris....O

19th May 2020, 11:40 am	#3
ms660 Dekatron Join Date: Apr 2011 Location: Cornwall, UK. Posts: 13,454	Re: Roberts R24 mistake http://www.valve-radio.co.uk/literat...ervice-manual/ Last page. Lawrence.

19th May 2020, 11:48 am	#4
Cobaltblue Moderator Join Date: Dec 2010 Location: Exeter, Devon and Poole, Dorset UK. Posts: 6,875	Re: Roberts R24 mistake I see that was signed by Geoffrey Dixon-Nuttall. Unfortunately now passed, an outstanding BVWS member and genuinely nice person. He did some outstanding articles in early Bulletins including one on Cossor which I still refer to today. Cheers Mike T __________________ Invisible airwaves crackle with life or at least they used to Mike T BVWS member. www.cossor.co.uk

19th May 2020, 2:43 pm	#5
Guest Guest Posts: n/a	Re: Roberts R24 mistake That is a big OOPS, I get my designs "sanity checked" by someone else trying to explain them to me. Sometimes it is an eye opener for both of us!