Rectifier replacement - UK Vintage Radio Repair and Restoration Discussion Forum

Ken Taylor · 27th Jun 2022, 1:30 pm

The rectifier in the Bush PB51 I am working on (still) has o/c heater. The valve is a U14, but the original spec was a DW4/350.

I doubt there are many spares at reasonable cost in the wild by now so I am considering going down the silicon route (too much of this set was missing to attempt originality).

The service sheet suggests a HT voltage of 337 on the anodes so the two-root-two formula gives 953v PIV which is very close to the top end of a 1n4007. Can anyone suggest a better diode?

Ken

turretslug · 27th Jun 2022, 1:48 pm

The BY133?

Ken Taylor · 27th Jun 2022, 2:08 pm

That looks like a possibility. Thanks.

cathoderay57 · 27th Jun 2022, 2:22 pm

Hi Ken, I can provide you with a used DW4/350 that tests anode 1: 42% / anode 2: 37%. Well used but should work OK. I have found that directly heated rectifiers including AZ31 always seem to read low on the VCM163 for some reason, but work OK in the vast majority of cases. In the PB51 it won't be working particularly hard. You have a PM. Jerry

Ken Taylor · 27th Jun 2022, 6:29 pm

Thanks Jerry, I've replied to your PM.

Ken

paulsherwin · 27th Jun 2022, 7:00 pm

Two 1N4007s in series should be OK.

JonSnell · 27th Jun 2022, 7:32 pm

DGP15-E3/54
1500v PIV at 1.5A
RS part number 812-2026
would be my choice.

Cruisin Marine · 27th Jun 2022, 8:33 pm

Stick two or three 4007's in series, they are small enough and cheap enough too.

Ken Taylor · 28th Jun 2022, 8:43 pm

If you put 1N4007's in series, do you need parallel resistors?

Ken

Ken Taylor · 28th Jun 2022, 8:57 pm

Quote:

Originally Posted by JonSnell

DGP15-E3/54
1500v PIV at 1.5A
RS part number 812-2026
would be my choice.

Discontinued apparently.

Cruisin Marine · 28th Jun 2022, 9:23 pm

If you put 1N4007's in series, do you need parallel resistors?
I do, normally anything from 470K to 1 Meg suffice as voltage equalising/sharing resistors.
I have seen as low as 100K before.

Herald1360 · 28th Jun 2022, 9:41 pm

Use UF4007s for less slow recovery turn off spike induced RF noise.

Costs about the same as a 1N4007 plus 10nF snubber!

yestertech · 29th Jun 2022, 1:21 pm

Ken, if you're still looking for one of these, I have 3 listed ( without their specs just 'OK' ) and I also have a NOS U14 which is listed as an equivalent

Andy

Ken Taylor · 1st Jul 2022, 5:17 pm

Thanks Andy, but I am OK now thanks to cathodray57. Also thanks to all the others who contributed information on semiconductor diodes, which may well be useful for the next one!

Ken

27th Jun 2022, 1:30 pm	#1
Ken Taylor Pentode Join Date: Dec 2015 Location: Abingdon on Thames, Oxon, UK. Posts: 116	Rectifier replacement The rectifier in the Bush PB51 I am working on (still) has o/c heater. The valve is a U14, but the original spec was a DW4/350. I doubt there are many spares at reasonable cost in the wild by now so I am considering going down the silicon route (too much of this set was missing to attempt originality). The service sheet suggests a HT voltage of 337 on the anodes so the two-root-two formula gives 953v PIV which is very close to the top end of a 1n4007. Can anyone suggest a better diode? Ken

27th Jun 2022, 1:48 pm	#2
turretslug Dekatron Join Date: Nov 2011 Location: Surrey, UK. Posts: 4,398	Re: Rectifier replacement The BY133?

27th Jun 2022, 2:08 pm	#3
Ken Taylor Pentode Join Date: Dec 2015 Location: Abingdon on Thames, Oxon, UK. Posts: 116	Re: Rectifier replacement That looks like a possibility. Thanks.

27th Jun 2022, 2:22 pm	#4
cathoderay57 Nonode Join Date: Oct 2017 Location: Bristol, UK. Posts: 2,386	Re: Rectifier replacement Hi Ken, I can provide you with a used DW4/350 that tests anode 1: 42% / anode 2: 37%. Well used but should work OK. I have found that directly heated rectifiers including AZ31 always seem to read low on the VCM163 for some reason, but work OK in the vast majority of cases. In the PB51 it won't be working particularly hard. You have a PM. Jerry

27th Jun 2022, 6:29 pm	#5
Ken Taylor Pentode Join Date: Dec 2015 Location: Abingdon on Thames, Oxon, UK. Posts: 116	Re: Rectifier replacement Thanks Jerry, I've replied to your PM. Ken

27th Jun 2022, 7:00 pm	#6
paulsherwin Moderator Join Date: Jun 2003 Location: Oxford, UK Posts: 27,966	Re: Rectifier replacement Two 1N4007s in series should be OK.

27th Jun 2022, 7:32 pm	#7
JonSnell Hexode Join Date: Oct 2019 Location: Weymouth, Dorset, UK. Posts: 476	Re: Rectifier replacement DGP15-E3/54 1500v PIV at 1.5A RS part number 812-2026 would be my choice. __________________ Valve equipment repairs since 1968 https://jonsnell.co.uk

27th Jun 2022, 8:33 pm	#8
Cruisin Marine Octode Join Date: Jul 2018 Location: Worthing, West Sussex, UK. Posts: 1,002	Re: Rectifier replacement Stick two or three 4007's in series, they are small enough and cheap enough too.

28th Jun 2022, 8:43 pm	#9
Ken Taylor Pentode Join Date: Dec 2015 Location: Abingdon on Thames, Oxon, UK. Posts: 116	Re: Rectifier replacement If you put 1N4007's in series, do you need parallel resistors? Ken

28th Jun 2022, 9:23 pm	#11
Cruisin Marine Octode Join Date: Jul 2018 Location: Worthing, West Sussex, UK. Posts: 1,002	Re: Rectifier replacement If you put 1N4007's in series, do you need parallel resistors? I do, normally anything from 470K to 1 Meg suffice as voltage equalising/sharing resistors. I have seen as low as 100K before.

28th Jun 2022, 9:41 pm	#12
Herald1360 Dekatron Join Date: Feb 2007 Location: Leominster, Herefordshire, UK. Posts: 16,536	Re: Rectifier replacement Use UF4007s for less slow recovery turn off spike induced RF noise. Costs about the same as a 1N4007 plus 10nF snubber! __________________ ....__________ ....\|____\|\|__\|__\_____ .=.\| _---\__\|__\|_---_\|. .........O..Chris....O

29th Jun 2022, 1:21 pm	#13
yestertech Nonode Join Date: Dec 2002 Location: Coulsdon, Surrey, UK. Posts: 2,135	Re: Rectifier replacement Ken, if you're still looking for one of these, I have 3 listed ( without their specs just 'OK' ) and I also have a NOS U14 which is listed as an equivalent Andy

1st Jul 2022, 5:17 pm	#14
Ken Taylor Pentode Join Date: Dec 2015 Location: Abingdon on Thames, Oxon, UK. Posts: 116	Re: Rectifier replacement Thanks Andy, but I am OK now thanks to cathodray57. Also thanks to all the others who contributed information on semiconductor diodes, which may well be useful for the next one! Ken