Eddystone External S-meter 669 circuit - UK Vintage Radio Repair and Restoration Discussion Forum

Pamphonica · 23rd Jul 2015, 6:10 pm

I recently bought an Eddystone 669 external S-meter. It has an original, working meter and is pre-wired to an octal plug, correctly wired for an Eddystone s-meter socket.

I tried it on my newly-acquired 888A but the meter pinged backwards and stayed there.

I looked up the circuit (article here) and noted the component values.

So I checked the components and found that the 300R is actually 56K, the 600R pot is 500K and the 47K resistor is 62K. No wonder the poor meter was reverse biased!

Now here's the weird bit. All those components look original, as the res are dog-bone parts, and the soldering looks un-mangled and old.

So, before I replace them with the correct parts, is there any reason this S-meter should have these values?

regards

Jeremy

HamishBoxer · 23rd Jul 2015, 6:32 pm

Mine has a 330 Ohm and a 56K or reads that (it is just black with an orange spot) .Not able to check the pot.

bc312 · 23rd Jul 2015, 6:46 pm

There was an item on this S-Meter in the Eddystone Lighthouse magazine, issue 95 pages 10-11. Available to download from the Eddystone User Group website. http://eddystoneusergroup.org.uk/
Regards
Mike

Pamphonica · 23rd Jul 2015, 8:57 pm

Hi both,
HamishBoxer, thanks for the confirmation. It sounds like the correct configuration per the article.

Mike, I think the article you refer to is the same one, but through another link.

I wonder if this was a "special" for a different receiver (but still an Eddystone).
Anyway, I connot see any point in keeping it non-functional so it will be carefully and sympathetically modified back to the "original" configuration.

If anyone else has any insights please do post them here.

regards
Jeremy

ms660 · 23rd Jul 2015, 9:22 pm

According to the 888a schematic the HT feed for the meter is taken from the screen grid of the IF amp valve, in some earlier models it's taken from the main HT line, I'm not sure if that will effect things.

Lawrence.

Pamphonica · 23rd Jul 2015, 9:29 pm

Hi Lawrence, yes, I had spotted that. I feel that the "zero set" pot should be working at the very bottom few volts of the voltage range. Mine was able to set the zero point on one side of the meter at anything from 15 to 150 volts! Strange
Jeremy

23rd Jul 2015, 6:10 pm	#1
Pamphonica Nonode Join Date: Mar 2008 Location: Virginia Water, Surrey, UK. Posts: 2,879	Eddystone External S-meter 669 circuit I recently bought an Eddystone 669 external S-meter. It has an original, working meter and is pre-wired to an octal plug, correctly wired for an Eddystone s-meter socket. I tried it on my newly-acquired 888A but the meter pinged backwards and stayed there. I looked up the circuit (article here) and noted the component values. So I checked the components and found that the 300R is actually 56K, the 600R pot is 500K and the 47K resistor is 62K. No wonder the poor meter was reverse biased! Now here's the weird bit. All those components look original, as the res are dog-bone parts, and the soldering looks un-mangled and old. So, before I replace them with the correct parts, is there any reason this S-meter should have these values? regards Jeremy __________________ Jeremy, G8MLK, BVWTVM Friend, VMARS, BVWS Secretary. www.pamphonic.co.uk www.bttt.org.uk

23rd Jul 2015, 6:32 pm	#2
HamishBoxer Dekatron Join Date: Aug 2007 Location: W.Butterwick, near Doncaster UK. Posts: 8,935	Re: Eddystone External S-meter 669 circuit Mine has a 330 Ohm and a 56K or reads that (it is just black with an orange spot) .Not able to check the pot. __________________ G8JET BVWS Archivist and Member V.M.A.R.S

23rd Jul 2015, 6:46 pm	#3
bc312 Pentode Join Date: Feb 2005 Location: Longfield, Kent, UK. Posts: 240	Re: Eddystone External S-meter 669 circuit There was an item on this S-Meter in the Eddystone Lighthouse magazine, issue 95 pages 10-11. Available to download from the Eddystone User Group website. http://eddystoneusergroup.org.uk/ Regards Mike __________________ Leave me alone - I know what I'm doing. BVWS member, EUG, G-QRP Radio Bygones/Radiophile

23rd Jul 2015, 8:57 pm	#4
Pamphonica Nonode Join Date: Mar 2008 Location: Virginia Water, Surrey, UK. Posts: 2,879	Re: Eddystone External S-meter 669 circuit Hi both, HamishBoxer, thanks for the confirmation. It sounds like the correct configuration per the article. Mike, I think the article you refer to is the same one, but through another link. I wonder if this was a "special" for a different receiver (but still an Eddystone). Anyway, I connot see any point in keeping it non-functional so it will be carefully and sympathetically modified back to the "original" configuration. If anyone else has any insights please do post them here. regards Jeremy __________________ Jeremy, G8MLK, BVWTVM Friend, VMARS, BVWS Secretary. www.pamphonic.co.uk www.bttt.org.uk

23rd Jul 2015, 9:22 pm	#5
ms660 Dekatron Join Date: Apr 2011 Location: Cornwall, UK. Posts: 13,454	Re: Eddystone External S-meter 669 circuit According to the 888a schematic the HT feed for the meter is taken from the screen grid of the IF amp valve, in some earlier models it's taken from the main HT line, I'm not sure if that will effect things. Lawrence.

23rd Jul 2015, 9:29 pm	#6
Pamphonica Nonode Join Date: Mar 2008 Location: Virginia Water, Surrey, UK. Posts: 2,879	Re: Eddystone External S-meter 669 circuit Hi Lawrence, yes, I had spotted that. I feel that the "zero set" pot should be working at the very bottom few volts of the voltage range. Mine was able to set the zero point on one side of the meter at anything from 15 to 150 volts! Strange Jeremy __________________ Jeremy, G8MLK, BVWTVM Friend, VMARS, BVWS Secretary. www.pamphonic.co.uk www.bttt.org.uk