Rectifier questions - UK Vintage Radio Repair and Restoration Discussion Forum

phildil · 4th Oct 2020, 8:24 pm

Hello all

I'm working on this PSU card (see photo) which has two separate circuits. I'm wondering about the markings on the Siemens grey rectifier visible at the top of the card. How does one read these values?

B 13 10
B 60 C 2000/1400

Also, according to the cct diagram, when supplied with 24v AC the rectifier is supposed to output 28v DC but when I set up a test it is actually outputting 32v. Should this be considered within tolerance? The companion rectifier below is much closer to spec.

thanks
Phil

high_vacuum_house · 4th Oct 2020, 8:51 pm

Good evening,
That 32V output instead of 24V output is quite normal if the power supply is off load. I expect with a suitably rated load the output will fall back down to 24V DC

Christopher Capener

Electronpusher0 · 4th Oct 2020, 8:52 pm

24V times 1.414 = 34V approx. Less 2 diode drops for the bridge = 32.5.
Allowing for the ripple on the cap 32V is as expected.
Check the reservoir capacitor on the companion rectifier, it could be that it is low value and has excess ripple giving the lower value.

The 28V specified is probably the on load voltage.

Peter

Post crossed with Chistopher

phildil · 4th Oct 2020, 9:31 pm

Thanks you have confirmed my suspicions: I was thinking along the same lines re off load testing.

How about the markings - how to decode those?

Phil

Cobaltblue · 4th Oct 2020, 9:42 pm

I have come across various Siemens rectifiers and they seem to follow this pattern
B for Bridge? Voltage C Current in mA

so this would mean a Bridge rectifier 60V 2A rectifier.

I suspect that the /1400 is to do with running at a higher temperature ( derating)

Cheers

Mike T

Radio Wrangler · 4th Oct 2020, 11:57 pm

A great many Siemens parts, pot cores, bobbins clips that I've used over the years have Siemens stock/part numbers beginning with B.

I'm not sure we can read anything into it.

David

ms660 · 5th Oct 2020, 12:47 pm

For the old Siemens contact cooled ones B and E was for the max AC input voltage, B indicating a bridge and E indicating a half wave, C was for the maximum load current in mA's.

Lawrence.

paulsherwin · 5th Oct 2020, 2:24 pm

You don't really need to worry about this. Silicon rectifiers are all the same apart from the voltage and current ratings (that's a simplification, but it's accurate enough for the case in hand). If you ever need to replace the Siemens part, 4 4A 100V diodes or better will be fine and cost pennies. These parts rarely need replacement though.

4th Oct 2020, 8:24 pm	#1
phildil Pentode Join Date: Sep 2014 Location: London, UK. Posts: 115	Rectifier questions Hello all I'm working on this PSU card (see photo) which has two separate circuits. I'm wondering about the markings on the Siemens grey rectifier visible at the top of the card. How does one read these values? B 13 10 B 60 C 2000/1400 Also, according to the cct diagram, when supplied with 24v AC the rectifier is supposed to output 28v DC but when I set up a test it is actually outputting 32v. Should this be considered within tolerance? The companion rectifier below is much closer to spec. thanks Phil Attached Thumbnails

4th Oct 2020, 8:51 pm	#2
high_vacuum_house Octode Join Date: May 2003 Location: Belper Derbyshire Posts: 1,936	Re: Rectifier questions Good evening, That 32V output instead of 24V output is quite normal if the power supply is off load. I expect with a suitably rated load the output will fall back down to 24V DC Christopher Capener __________________ Interests in the collection and restoration of Tefifon players and 405 line television

4th Oct 2020, 8:52 pm	#3
Electronpusher0 Nonode Join Date: Jun 2016 Location: Bognor Regis, West Sussex, UK. Posts: 2,302	Re: Rectifier questions 24V times 1.414 = 34V approx. Less 2 diode drops for the bridge = 32.5. Allowing for the ripple on the cap 32V is as expected. Check the reservoir capacitor on the companion rectifier, it could be that it is low value and has excess ripple giving the lower value. The 28V specified is probably the on load voltage. Peter Post crossed with Chistopher

4th Oct 2020, 9:31 pm	#4
phildil Pentode Join Date: Sep 2014 Location: London, UK. Posts: 115	Re: Rectifier questions Thanks you have confirmed my suspicions: I was thinking along the same lines re off load testing. How about the markings - how to decode those? Phil

4th Oct 2020, 9:42 pm	#5
Cobaltblue Moderator Join Date: Dec 2010 Location: Exeter, Devon and Poole, Dorset UK. Posts: 6,880	Re: Rectifier questions I have come across various Siemens rectifiers and they seem to follow this pattern B for Bridge? Voltage C Current in mA so this would mean a Bridge rectifier 60V 2A rectifier. I suspect that the /1400 is to do with running at a higher temperature ( derating) Cheers Mike T __________________ Invisible airwaves crackle with life or at least they used to Mike T BVWS member. www.cossor.co.uk

4th Oct 2020, 11:57 pm	#6
Radio Wrangler Moderator Join Date: Mar 2012 Location: Fife, Scotland, UK. Posts: 22,905	Re: Rectifier questions A great many Siemens parts, pot cores, bobbins clips that I've used over the years have Siemens stock/part numbers beginning with B. I'm not sure we can read anything into it. David __________________ Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done

5th Oct 2020, 12:47 pm	#7
ms660 Dekatron Join Date: Apr 2011 Location: Cornwall, UK. Posts: 13,454	Re: Rectifier questions For the old Siemens contact cooled ones B and E was for the max AC input voltage, B indicating a bridge and E indicating a half wave, C was for the maximum load current in mA's. Lawrence.

5th Oct 2020, 2:24 pm	#8
paulsherwin Moderator Join Date: Jun 2003 Location: Oxford, UK Posts: 27,975	Re: Rectifier questions You don't really need to worry about this. Silicon rectifiers are all the same apart from the voltage and current ratings (that's a simplification, but it's accurate enough for the case in hand). If you ever need to replace the Siemens part, 4 4A 100V diodes or better will be fine and cost pennies. These parts rarely need replacement though.