Valved rectification - UK Vintage Radio Repair and Restoration Discussion Forum

toshiba tony · 8th Mar 2021, 10:40 am

When was the PY82 replaced with the solid state rectifier? I can remember a number of sets that used a valve for rectification, the furthest I can go back as being an early set that used solid state was the Bush 125. I'm sure some sets used two in parallel, and was the PY82 an unreliable valve, something at the back of my mind tells me it was, and did anyone replace the valve with a BR100. It's all so long ago, I'm just curious, ta anyone.

Craig Sawyers · 8th Mar 2021, 10:54 am

Calling Synchrodyne - the forum history man....

ms660 · 8th Mar 2021, 11:07 am

When we used to replace the valve rectifier with a silicon one we connected a coil of wire between the limiter resistor and the rectifier.

Lawrence.

Heatercathodeshort · 8th Mar 2021, 12:41 pm

The PY82 was a very reliable rectifier. A single valve was employed with early simple receivers but a pair in later models such as the 17TG series Philips. It was a much better rectifier compared with the early octal based PY32s later replaced by the PY33 with all unreliability problems cleaned up.

I think it must have been around 1961 that manufacturers went over to the first BY100s. The Regentone Ten 17 [60/61] series was I believe the first to employ the STC diode [FST1/4?] requiring two in series to cope with the voltage and supply demand. It's interesting to note that very occasionally one diode developed a S/C. I came across a number of these chassis where one diode had been shorted out and the chassis continued to work happily with just one in circuit! They were secured to a tag board with screws on the right chassis member. I think they were worried about possible heat damage from a soldering iron. They were very good receivers. I used to use the BY100 widely to replace the old RM4 and similar metal stinky rectifiers but preferred to retain valve rectifiers. John.

ms660 · 8th Mar 2021, 7:44 pm

Anyone remember the "Radiospares" silicon rectifiers that came in a transparent Yellowish tube with a Red cap? I remember them in the stores where I worked circa 1965/66.

Lawrence.

Wellington · 8th Mar 2021, 7:53 pm

Quote:

Originally Posted by ms660

When we used to replace the valve rectifier with a silicon one we connected a coil of wire between the limiter resistor and the rectifier.

I saw that you mentioned this over on the Ekco U122 thread as well, Lawrence. My curiosity is piqued - why would you add a coil of wire here?

gallowfields · 8th Mar 2021, 8:45 pm

remember replacing the metal rectifiers in the pam 600 series with a kit when the by100 first appeared it included tag strip , surge limiter think it was 25ohm w/w and 4inch length of wire to go between the surge limiter and by100 .this would be 1962 when i first started as an apprentice.

ms660 · 8th Mar 2021, 9:41 pm

Quote:

Originally Posted by Wellington

Quote:

Originally Posted by ms660

When we used to replace the valve rectifier with a silicon one we connected a coil of wire between the limiter resistor and the rectifier.

I saw that you mentioned this over on the Ekco U122 thread as well, Lawrence. My curiosity is piqued - why would you add a coil of wire here?

To cut down heat transfer to the diode from the limiter resistor.

Lawrence.

Heatercathodeshort · 8th Mar 2021, 10:50 pm

Hello Lawrence. I think they may have been RS REC53A. Silicon rectifiers were treated with almost mystical care when they first came out and the original Mullard ones were quite expensive [35/- £1-75] and packed singularly.
Pictures of a few that were stuffed into plastic boxes. Top are a couple of later BY100s. I seem to remember the early ones had a threaded cathode as well as a lead out wire. Presumably this was for an intended heat sink that was never needed as they ran cold.

Next are a couple of STC FST1/4 together with a similar couple.
The long example is another early one an OY241. very reliable but I don't know who made it.
Nasty mini version used in later Thorn chassis in HT and heater dropper positions. They used to go S/C. Just a size reduction too far me thinks.
Two styles of the BY127.
They were an service guys dream but you had to check the H.T. and adjust the surge limiter if it was too high. failing that the LOPT would probably go pop a couple of weeks later. Happy days! John.

Chris55000 · 8th Mar 2021, 10:51 pm

Hi!

Silicon Rectifiers date from earlier sets than the Regentone 10–17 or the TV125, there were Ultra sets from 1959 or thereabouts that still used the distinctive E.M.I./H.M.V./Marconi style of circuit–diagrams, that used two Lucas XU604 silicon rectifiers in series.

If I'm not mistaken, the P.T.V. "Olympic" design from 1960 also specified 2 x XU604 as well!

Chris Williams

Heatercathodeshort · 9th Mar 2021, 10:41 am

Pics added! J.

ms660 · 9th Mar 2021, 10:57 am

Quote:

Originally Posted by Heatercathodeshort

I think they may have been RS REC53A.

I remember the Radiospares REC53A's, it probably was them, used to keep them in those cardboard draw storage units with the brass plated ring handles on them.

Lawrence.

Heatercathodeshort · 9th Mar 2021, 11:29 am

The Ultra you mention Chris must be the 100C/1980C and 1984C. These true Ultra convertible models were last manufactured just before the acquisition by Thorn. They were manufactured around 1961/2. The previous models, the 1780 series employed a flat contact cooled style.

Thorn hated old style metal rectifiers using valve rectifiers almost exclusively, the PY32/33 in all their models until the introduction of the silicon diode in the 700 series, and then only the MK2 convertible version. The HMV 1922 MK2 employs the same chassis.

8th Mar 2021, 10:40 am	#1
toshiba tony Heptode Join Date: May 2006 Location: Accrington, Lancashire, UK. Posts: 978	Valved rectification When was the PY82 replaced with the solid state rectifier? I can remember a number of sets that used a valve for rectification, the furthest I can go back as being an early set that used solid state was the Bush 125. I'm sure some sets used two in parallel, and was the PY82 an unreliable valve, something at the back of my mind tells me it was, and did anyone replace the valve with a BR100. It's all so long ago, I'm just curious, ta anyone.

8th Mar 2021, 10:54 am	#2
Craig Sawyers Dekatron Join Date: Nov 2010 Location: Oxford, UK. Posts: 4,991	Re: Valved rectification Calling Synchrodyne - the forum history man....

8th Mar 2021, 11:07 am	#3
ms660 Dekatron Join Date: Apr 2011 Location: Cornwall, UK. Posts: 13,454	Re: Valved rectification When we used to replace the valve rectifier with a silicon one we connected a coil of wire between the limiter resistor and the rectifier. Lawrence.

8th Mar 2021, 12:41 pm	#4
Heatercathodeshort Dekatron Join Date: Jun 2005 Location: Warnham, West Sussex. 10 miles south of DORKING. Posts: 9,147	Re: Valved rectification The PY82 was a very reliable rectifier. A single valve was employed with early simple receivers but a pair in later models such as the 17TG series Philips. It was a much better rectifier compared with the early octal based PY32s later replaced by the PY33 with all unreliability problems cleaned up. I think it must have been around 1961 that manufacturers went over to the first BY100s. The Regentone Ten 17 [60/61] series was I believe the first to employ the STC diode [FST1/4?] requiring two in series to cope with the voltage and supply demand. It's interesting to note that very occasionally one diode developed a S/C. I came across a number of these chassis where one diode had been shorted out and the chassis continued to work happily with just one in circuit! They were secured to a tag board with screws on the right chassis member. I think they were worried about possible heat damage from a soldering iron. They were very good receivers. I used to use the BY100 widely to replace the old RM4 and similar metal stinky rectifiers but preferred to retain valve rectifiers. John.

8th Mar 2021, 7:44 pm	#5
ms660 Dekatron Join Date: Apr 2011 Location: Cornwall, UK. Posts: 13,454	Re: Valved rectification Anyone remember the "Radiospares" silicon rectifiers that came in a transparent Yellowish tube with a Red cap? I remember them in the stores where I worked circa 1965/66. Lawrence.

8th Mar 2021, 8:45 pm	#7
gallowfields Hexode Join Date: Feb 2018 Location: Durham, County Durham, UK. Posts: 325	Re: Valved rectification remember replacing the metal rectifiers in the pam 600 series with a kit when the by100 first appeared it included tag strip , surge limiter think it was 25ohm w/w and 4inch length of wire to go between the surge limiter and by100 .this would be 1962 when i first started as an apprentice.

8th Mar 2021, 10:50 pm	#9
Heatercathodeshort Dekatron Join Date: Jun 2005 Location: Warnham, West Sussex. 10 miles south of DORKING. Posts: 9,147	Re: Valved rectification Hello Lawrence. I think they may have been RS REC53A. Silicon rectifiers were treated with almost mystical care when they first came out and the original Mullard ones were quite expensive [35/- £1-75] and packed singularly. Pictures of a few that were stuffed into plastic boxes. Top are a couple of later BY100s. I seem to remember the early ones had a threaded cathode as well as a lead out wire. Presumably this was for an intended heat sink that was never needed as they ran cold. Next are a couple of STC FST1/4 together with a similar couple. The long example is another early one an OY241. very reliable but I don't know who made it. Nasty mini version used in later Thorn chassis in HT and heater dropper positions. They used to go S/C. Just a size reduction too far me thinks. Two styles of the BY127. They were an service guys dream but you had to check the H.T. and adjust the surge limiter if it was too high. failing that the LOPT would probably go pop a couple of weeks later. Happy days! John.

8th Mar 2021, 10:51 pm	#10
Chris55000 Nonode Join Date: Aug 2007 Location: Walsall Wood, Aldridge, Walsall, UK. Posts: 2,873	Re: Valved rectification Hi! Silicon Rectifiers date from earlier sets than the Regentone 10–17 or the TV125, there were Ultra sets from 1959 or thereabouts that still used the distinctive E.M.I./H.M.V./Marconi style of circuit–diagrams, that used two Lucas XU604 silicon rectifiers in series. If I'm not mistaken, the P.T.V. "Olympic" design from 1960 also specified 2 x XU604 as well! Chris Williams __________________ It's an enigma, that's what it is! This thing's not fixed because it doesn't want to be fixed!

9th Mar 2021, 10:41 am	#11
Heatercathodeshort Dekatron Join Date: Jun 2005 Location: Warnham, West Sussex. 10 miles south of DORKING. Posts: 9,147	Re: Valved rectification Pics added! J. Attached Thumbnails

9th Mar 2021, 11:29 am	#13
Heatercathodeshort Dekatron Join Date: Jun 2005 Location: Warnham, West Sussex. 10 miles south of DORKING. Posts: 9,147	Re: Valved rectification The Ultra you mention Chris must be the 100C/1980C and 1984C. These true Ultra convertible models were last manufactured just before the acquisition by Thorn. They were manufactured around 1961/2. The previous models, the 1780 series employed a flat contact cooled style. Thorn hated old style metal rectifiers using valve rectifiers almost exclusively, the PY32/33 in all their models until the introduction of the silicon diode in the 700 series, and then only the MK2 convertible version. The HMV 1922 MK2 employs the same chassis.