Rectifier symbols. - UK Vintage Radio Repair and Restoration Discussion Forum

Geoff 555 · 7th Aug 2009, 1:13 pm

Hello I have just obtained a B & O Jet 507. radio. It has a selenium rectifier, I think, it's a S35DB according to the diagram stuck to the bottom of the cabinet. The diagram shows 4 diodes in line all pointing the same direction with a connection to either end and a centre connection and it looks like a voltage doubling circuit. Now the query is that the (all) diode is shown as an arrow with a line at the end in the usual fashion, sorry it's the only way I can explain it, but the arrow is only shown above the centre line, so half an arrow. Does any one recognise my carp description and is there anything special about it.
Thanks every one.
Cheers.
Geoff.
Cant find it listed any where.

Skywave · 7th Aug 2009, 2:33 pm

If I understand your description correctly, the diode symbol is shown as a conventional diode but with the lower half of the triangle missing, but with the vertical line (= cathode) complete.
I have seen this symbol on many an occasion - usually in vintage radio books, signifying a 'crystal rectifier diode'. My understanding is that it is an alternative symbol for a generic 'diode' - as such, same as the 'full symbol'. This alternative symbol seems to have fallen out of favour these days.

HTH.

Al. / Skywave.

geofy · 7th Aug 2009, 3:08 pm

I am not entirely sure but the diode symbol could be that for a metal rectifier. I don't think it is a voltage doubler, unless it has associated capacitors, the centre tap could be for another voltage supply line. Silicon rectifiers with suitable dropper resistors could be fitted instead.

G

Aerodyne · 7th Aug 2009, 3:25 pm

As I understand it, the 'half-triangle' diode symbol usually referred to a metal oxide rectifier in a power supply - but there is considerable variation on the representative symbols used. For example, some crystal diodes are shown (in vintage data) as a full triangle but with the triangle filled solid black. The metal rectifier was often shown as a half-triangle in PWs of the late 40s-early 50s. You pays your money and takes your choice, I guess.
-Tony

Sideband · 7th Aug 2009, 5:21 pm

Some companies also adopted the American style of symbols (like electrolytic capacitors where the negative plate is shown curved). Most of these early symbols have now 'standardised' into what we know as the present style but some variants still appear from time-to-time.

A picture of the symbol would help us more.

Rich.

anthonys radios · 7th Aug 2009, 5:59 pm

Can you give a description of the rectifier,+ colour,
+ encapsulation material etc.
How many connections does it have.
So far as symbols go, the arrow, whether in full, or as a half arrow, represents conventional current flow, (positive to negative) ie the broad line is the cathode, the triangle is the anode.
Need to know many connections it has to give you an idea as to how it is wired.

Geoff 555 · 7th Aug 2009, 8:42 pm

Ah thank you muchly it is as I suspected. The rectifier is grey with round fins about 11/4" dia. 12 fins. a connection either end and 1 in the middle. A -05 mf capacitor is wired across the outside connections. It is marked 220V @ 125mA.
I don't know how to upload a drawing or sketch. Sorry.
Thank you and cheers.
Geoff.

anthonys radios · 7th Aug 2009, 9:20 pm

Sounds like a selenium since it has 12cooling fins and is for 220v 125 mA it will not be a copper oxide).

I think since it has only 3 connections, the centre one is most likely to be DC out and the
two end ones are AC input, as it has only 3 tags, it sounds like a fullwave (2 diodes) HT rectifier with a common cathode in the centre.
Dont forget if you measure its resistance it will be higher even in a working rectifier than for example a silicon diode would measure.
There is usually a pungent pong (bad eggs) (hydrogen sulphide when Selenium rectifiers fail, is it smelly ? and often there are black/burn mark visable on the fins.
But note some older Selenium rectifiers used the fins for cooling only, whilst for later ones the fins were actually the rectifier diodes themselves.

mooseb9a · 7th Aug 2009, 10:13 pm

I believe it means that the rectifier is only a half wave one.

anthonys radios · 8th Aug 2009, 8:32 am

Quote:

Originally Posted by mooseb9a

I believe it means that the rectifier is only a half wave one.

You may be right of course, but it does have 3 connections rather than only the necessary 2 for a half wave rectifier.
My reasoning, from the information so far available, and subject to modification in the light of new data, is that a full wave rectifier (2x halfwave) would require 3 connections if it has a common cathode.
The plot thickens !

Can we know the voltage rating of the capacitor across the outer connections please

Geoff 555 · 8th Aug 2009, 9:54 am

Hi after trying to get a photo of the diagram I think I have succeeded, originally it was 27 Meg !
I am going to put it up and hope that it is readable.
Cheers.Geoff.

Geoff 555 · 8th Aug 2009, 10:01 am

OK capacitor is a 0-05mf. 600V DC working. Marked with a plus and minus. Curiously there are 2 rated at 2KV and 0.5 and 1.0 mf.??
Thank you.
Geoff.

jimmc101 · 8th Aug 2009, 10:16 am

I believe it was reasonably common to have a centre tap i.e. ( A AK K ) or ( - ~ + ) if you prefer
This made the device more versatile while adding little to the cost. e.g

Use as voltage doubler on 110v supply.

Use two identical devices to form a bridge rectifier.

Jim

jimmc101 · 8th Aug 2009, 10:21 am

I've just looked at the circuit again, I'm afraid it's not very clear but doesn't the top of the three plug? options (bottom right) have the extra capacitor to form a voltage doubler?
Is this the 110v setting?

Jim

anthonys radios · 8th Aug 2009, 11:10 am

The circuit will help the understanding greatly,

but is it possible to post a better copy, I for one, would not like to stick my neck out without this, as too many will knock it off !

Herald1360 · 8th Aug 2009, 12:17 pm

Not sure whether discussion of how the circuit works is on topic (which is "Rectifier symbols"), but agree that clearer copy (perhaps of just PSU section) would help.

That said, without any idea of what links are in the octal plug (voltage selector?) which presumably plugs into the socket shown, the function is a bit obscure. Voltage doubler on 117V as suggested, or maybe the heaters are being fed half wave rectified dc as a means to reduce the dissipation in the dropper resistor chain?

Geoff 555 · 8th Aug 2009, 1:57 pm

Hello thanks all. It does seem to be going off topic a bit, at the risk of being chopped.Mods would it be useful to start a new thread? I will try and get a better resolution of the diagram, it seems that every time I exceed the limits for sending pictures. When I have sorted that then I will be back. Mean while -------- yes there is a plug in unit with pins at both ends, plugged in one way it's 110V and plugged in the other it's 220V. AC/DC set will get some pictures of that up as well.
Ta.
Geoff.

7th Aug 2009, 1:13 pm	#1
Geoff 555 Heptode Join Date: Jan 2008 Location: Bristol, UK. Posts: 981	Rectifier symbols. Hello I have just obtained a B & O Jet 507. radio. It has a selenium rectifier, I think, it's a S35DB according to the diagram stuck to the bottom of the cabinet. The diagram shows 4 diodes in line all pointing the same direction with a connection to either end and a centre connection and it looks like a voltage doubling circuit. Now the query is that the (all) diode is shown as an arrow with a line at the end in the usual fashion, sorry it's the only way I can explain it, but the arrow is only shown above the centre line, so half an arrow. Does any one recognise my carp description and is there anything special about it. Thanks every one. Cheers. Geoff. Cant find it listed any where.

7th Aug 2009, 2:33 pm	#2
Skywave Rest in Peace Join Date: Jun 2006 Location: Chard, South Somerset, UK. Posts: 7,457	Re: Rectifier symbols. If I understand your description correctly, the diode symbol is shown as a conventional diode but with the lower half of the triangle missing, but with the vertical line (= cathode) complete. I have seen this symbol on many an occasion - usually in vintage radio books, signifying a 'crystal rectifier diode'. My understanding is that it is an alternative symbol for a generic 'diode' - as such, same as the 'full symbol'. This alternative symbol seems to have fallen out of favour these days. HTH. Al. / Skywave.

7th Aug 2009, 3:08 pm	#3
geofy Retired Dormant Member Join Date: Jun 2006 Posts: 1,798	Re: Rectifier symbols. I am not entirely sure but the diode symbol could be that for a metal rectifier. I don't think it is a voltage doubler, unless it has associated capacitors, the centre tap could be for another voltage supply line. Silicon rectifiers with suitable dropper resistors could be fitted instead. G

7th Aug 2009, 3:25 pm	#4
Aerodyne Octode Join Date: Jun 2004 Location: Hampton Vale, Peterborough, UK. Posts: 1,698	Re: Rectifier symbols. As I understand it, the 'half-triangle' diode symbol usually referred to a metal oxide rectifier in a power supply - but there is considerable variation on the representative symbols used. For example, some crystal diodes are shown (in vintage data) as a full triangle but with the triangle filled solid black. The metal rectifier was often shown as a half-triangle in PWs of the late 40s-early 50s. You pays your money and takes your choice, I guess. -Tony

7th Aug 2009, 5:21 pm	#5
Sideband Dekatron Join Date: Oct 2003 Location: Croydon, Surrey, UK. Posts: 7,587	Re: Rectifier symbols. Some companies also adopted the American style of symbols (like electrolytic capacitors where the negative plate is shown curved). Most of these early symbols have now 'standardised' into what we know as the present style but some variants still appear from time-to-time. A picture of the symbol would help us more. Rich. __________________ There are lots of brilliant keyboard players and then there is Rick Wakeman.....

7th Aug 2009, 5:59 pm	#6
anthonys radios Retired Dormant Member Join Date: Jul 2009 Location: Buckinghamshire, UK. Posts: 186	Re: Rectifier symbols. Can you give a description of the rectifier,+ colour, + encapsulation material etc. How many connections does it have. So far as symbols go, the arrow, whether in full, or as a half arrow, represents conventional current flow, (positive to negative) ie the broad line is the cathode, the triangle is the anode. Need to know many connections it has to give you an idea as to how it is wired.

7th Aug 2009, 8:42 pm	#7
Geoff 555 Heptode Join Date: Jan 2008 Location: Bristol, UK. Posts: 981	Re: Rectifier symbols. Ah thank you muchly it is as I suspected. The rectifier is grey with round fins about 11/4" dia. 12 fins. a connection either end and 1 in the middle. A -05 mf capacitor is wired across the outside connections. It is marked 220V @ 125mA. I don't know how to upload a drawing or sketch. Sorry. Thank you and cheers. Geoff.

7th Aug 2009, 9:20 pm	#8
anthonys radios Retired Dormant Member Join Date: Jul 2009 Location: Buckinghamshire, UK. Posts: 186	Re: Rectifier symbols. Sounds like a selenium since it has 12cooling fins and is for 220v 125 mA it will not be a copper oxide). I think since it has only 3 connections, the centre one is most likely to be DC out and the two end ones are AC input, as it has only 3 tags, it sounds like a fullwave (2 diodes) HT rectifier with a common cathode in the centre. Dont forget if you measure its resistance it will be higher even in a working rectifier than for example a silicon diode would measure. There is usually a pungent pong (bad eggs) (hydrogen sulphide when Selenium rectifiers fail, is it smelly ? and often there are black/burn mark visable on the fins. But note some older Selenium rectifiers used the fins for cooling only, whilst for later ones the fins were actually the rectifier diodes themselves.

7th Aug 2009, 10:13 pm	#9
mooseb9a Retired Dormant Member Join Date: Oct 2008 Location: Badsey, Evesham, Worcestershire, UK. Posts: 12	Re: Rectifier symbols. I believe it means that the rectifier is only a half wave one.

8th Aug 2009, 9:54 am	#11
Geoff 555 Heptode Join Date: Jan 2008 Location: Bristol, UK. Posts: 981	Re: Rectifier symbols. Hi after trying to get a photo of the diagram I think I have succeeded, originally it was 27 Meg ! I am going to put it up and hope that it is readable. Cheers.Geoff. Attached Thumbnails

8th Aug 2009, 10:01 am	#12
Geoff 555 Heptode Join Date: Jan 2008 Location: Bristol, UK. Posts: 981	Re: Rectifier symbols. OK capacitor is a 0-05mf. 600V DC working. Marked with a plus and minus. Curiously there are 2 rated at 2KV and 0.5 and 1.0 mf.?? Thank you. Geoff.

8th Aug 2009, 10:16 am	#13
jimmc101 Heptode Join Date: Mar 2009 Location: Portsmouth, Hampshire, UK. Posts: 674	Re: Rectifier symbols. I believe it was reasonably common to have a centre tap i.e. ( A AK K ) or ( - ~ + ) if you prefer This made the device more versatile while adding little to the cost. e.g Use as voltage doubler on 110v supply. Use two identical devices to form a bridge rectifier. Jim

8th Aug 2009, 10:21 am	#14
jimmc101 Heptode Join Date: Mar 2009 Location: Portsmouth, Hampshire, UK. Posts: 674	Re: Rectifier symbols. I've just looked at the circuit again, I'm afraid it's not very clear but doesn't the top of the three plug? options (bottom right) have the extra capacitor to form a voltage doubler? Is this the 110v setting? Jim

8th Aug 2009, 11:10 am	#15
anthonys radios Retired Dormant Member Join Date: Jul 2009 Location: Buckinghamshire, UK. Posts: 186	Re: Rectifier symbols. The circuit will help the understanding greatly, but is it possible to post a better copy, I for one, would not like to stick my neck out without this, as too many will knock it off !

8th Aug 2009, 12:17 pm	#16
Herald1360 Dekatron Join Date: Feb 2007 Location: Leominster, Herefordshire, UK. Posts: 16,536	Re: Rectifier symbols. Not sure whether discussion of how the circuit works is on topic (which is "Rectifier symbols"), but agree that clearer copy (perhaps of just PSU section) would help. That said, without any idea of what links are in the octal plug (voltage selector?) which presumably plugs into the socket shown, the function is a bit obscure. Voltage doubler on 117V as suggested, or maybe the heaters are being fed half wave rectified dc as a means to reduce the dissipation in the dropper resistor chain?

8th Aug 2009, 1:57 pm	#17
Geoff 555 Heptode Join Date: Jan 2008 Location: Bristol, UK. Posts: 981	Re: Rectifier symbols. Hello thanks all. It does seem to be going off topic a bit, at the risk of being chopped.Mods would it be useful to start a new thread? I will try and get a better resolution of the diagram, it seems that every time I exceed the limits for sending pictures. When I have sorted that then I will be back. Mean while -------- yes there is a plug in unit with pins at both ends, plugged in one way it's 110V and plugged in the other it's 220V. AC/DC set will get some pictures of that up as well. Ta. Geoff.