Philco 48-2810 - Page 4 - UK Vintage Radio Repair and Restoration Discussion Forum

usradcoll1 · 7th Mar 2018, 6:48 pm

Quote:

Originally Posted by ms660

Yes, S100 is the on/off switch, it says so on the schematic snippet.

If the pilot lamp is short circuit there will be a direct connection between pins 2 and 4 and part of the rectifiers heater won't function.

It's really not half of the 35Y4's heater, It's tapped around a 6 volt section of the heater. If the pilot light is open and left that way, it'll shorten the life of the 35Y4 or the 35Z5 rectifier valve. If that part of the heater is open, I just jumper that part, until I finish restoring the set. It only makes a 6 volt difference in the heater chain. The 35Z4 doesn't use a pilot tap.

ms660 · 7th Mar 2018, 6:55 pm

I know it's not half the heater, I never implied that it was, data here:

https://frank.pocnet.net/sheets/127/3/35Y4.pdf

Lawrence.

Station X · 7th Mar 2018, 7:01 pm

Quote:

Originally Posted by ms660

I know it's not half the heater, I never implied that it was,

Lawrence.

It was me who implied that in post #60. I had wrongly assumed that the heater was centre tapped.

Boater Sam · 8th Mar 2018, 2:41 am

That's cleared that point then.

Put a 6.3V 0.15mA bulb in and you should be back to the original idea. 35Y4 is a very unusual valve it seems.

If this set works when you connect to 115V then my idea of using a light bulb as ballast will work too.
I remember many USA sets that had the lamp fitted on top in a battern lampholder with a shade on. It was a standard way of replacing line cords when they failed as they were hard to find in the correct current range later. I have a set with a barreter, works the same way.

usradcoll1 · 8th Mar 2018, 5:26 pm

The 35Y4 rectifier valve was very popular in the post-war US sets. Almost all the manufacturers used the Loctal range of valves except RCA. There was still the cold-war going between Philco and RCA.

The Loctal valve was developed by Philco engineering and Sylvania Electric.

Dick Glennon · 21st Mar 2018, 7:21 pm

Hello again, Good news on the Philcoradio ,I have it working on 120 volts. I must now try to get it working on mains voltage. What strength (watts) resistors could I use. Thanks again everyone. Dick

Boater Sam · 22nd Mar 2018, 12:55 am

They are going to be big ! And get very hot.
Measure the current it draws on 120V, do Ohm's law for value, then volts dropped X current gives watts + 20% at least.
Suggestion, capacitor dropper, runs cold, simpler.
Or my original idea, a light bulb.

Dick Glennon · 22nd Mar 2018, 10:02 am

Hi.

Could someone post a circuit of a capacitor dropper that would suit with values shown.

Thanks, Dick.

ms660 · 22nd Mar 2018, 10:26 am

Quote:

Originally Posted by Boater Sam

Suggestion, capacitor dropper, runs cold, simpler.
Or my original idea, a light bulb.

How do you work out the value of the capacitor if it has to supply for heaters and HT and reservoir charge current?

What would the resistance of a cold light bulb be?

Lawrence.

ms660 · 22nd Mar 2018, 11:56 am

Quote:

Originally Posted by Dick Glennon

Hello again, Good news on the Philcoradio ,I have it working on 120 volts. I must now try to get it working on mains voltage. What strength (watts) resistors could I use. Thanks again everyone. Dick

Power dissipated = Isquared*R.

For R100B it's straight forward, the heater current squared multiplied by the resistance of the resistor, to two decimal places that's 6.52 watts power dissipation.

For R100A it's not so straight forward because the current flowing through it consists of the heater current and the rectifier current, the rectifier current is complex to work out as it consists of the HT load current and the ripple current but as an estimate I would say approx 11 watts power dissipation.

Based on that I would go for 10 watt rating for R100B and 20 watt rating for R100A.

Lawrence.

Herald1360 · 22nd Mar 2018, 12:52 pm

I'd stay with 120V. A suitable inline autotransformer with a US outlet socket matched to a US plug on the set would be fine. If you want a possibly useful piece of test gear as well, make the transformer an isolating type which could make working on similar sets in future a bit easier/safer.

usradcoll1 · 22nd Mar 2018, 4:39 pm

For now, try to locate a travel adaptor set. The one I have has the adaptors for European and BS 1363 receptacles. It comes with a combination diode dropper and autotransformer. The transformer is rated for 50 watts. There's a switch that selects either mode.
These items came from charity shops.

Herald1360 · 22nd Mar 2018, 7:13 pm

I'm intrigued as to what's in on of those adaptors. An iron cored autotransformer will likely cope OK with the mixed ac/dc load the set presents as long as it's conservatively rated but I'm not so sure about some of the leerier SMPSU type adaptors that are on the market.

Where do diodes come into it?

TonyDuell · 22nd Mar 2018, 7:41 pm

Be warned that a number of those 'travel adapters' are triac-based circuits, effectively the same as a fixed lamp dimmer. They are fine for heating applianced, but not for anything electronic (I had the job of sorting out an SMPSU that had been plugged into one, it was a right mess...)

A true autotransformer will be fine for the radio, of course.

Dick Glennon · 22nd Mar 2018, 7:58 pm

I have a radio somewhere that has a transformer with a120 volt tapping on it. It may be no good. If not what amps would be suitable for the auto transformer. Dick.

MotorBikeLes · 22nd Mar 2018, 9:20 pm

I have never had a "line cord" or equivalent radio, but somewhere I either heard, or just thought maybe, that a 110v incandescent lamp wired permanently in series would do the job safely. If I interpret above calcs, a 30W 110v bulb would do. Obtainable from continental Europe or the US of A.
Les.

turretslug · 22nd Mar 2018, 9:40 pm

Wouldn't a 110V bulb take a bit of an excessive initial hit whilst the radio heaters were warming up? An appropriate 230V bulb would start quite bright, then settle to a gentle glow, it could even be made into a "period ambience" feature- and last a whole lot longer than a 110V bulb hit with a repeated initial overload!

Boater Sam · 23rd Mar 2018, 1:48 am

Use a 240v bulb, 40w should do, maybe 60w. It glows up while the heaters warm up, then settles to a steady glow.
It doesn't over run, the heaters warm up, but there is no HT draw till then so it balances out. A barretter was only an iron filament in hydrogen, a clever light bulb, and they worked fine. You may even still find one for sale.

usradcoll1 · 23rd Mar 2018, 2:27 am

Quote:

Originally Posted by TonyDuell

Be warned that a number of those 'travel adapters' are triac-based circuits, effectively the same as a fixed lamp dimmer. They are fine for heating applianced, but not for anything electronic (I had the job of sorting out an SMPSU that had been plugged into one, it was a right mess...)

A true autotransformer will be fine for the radio, of course.

The setup I referred to is evidently a combination diode type dropper and a small auto-transformer. It's rated 50 watts in the transformer mode and 1500 watts or so in the heating appliance mode.
I'm probably going to see if I can reverse engineer the unit.
IIRC, the instructions state to use the 50 watt mode for radios, tape recorders etc. These items were designed before the switch-mode universal power supplies of today.

usradcoll1 · 24th Mar 2018, 4:17 pm

I just looked over this unit again! There definitely is a transformer in there. You can see the laminations and winding through the vent slots. The thing is all glued together so I can't disassemble it without destroying it.
I was wondering how the high current heating appliance mode worked.
If it just had a diode half-cycle circuit, all the appliances used with it would be over-voltage. 240 X .707 = 169.68 volts, too high.

7th Mar 2018, 6:55 pm	#62
ms660 Dekatron Join Date: Apr 2011 Location: Cornwall, UK. Posts: 13,454	Re: Philco 48-2810 I know it's not half the heater, I never implied that it was, data here: https://frank.pocnet.net/sheets/127/3/35Y4.pdf Lawrence.

8th Mar 2018, 2:41 am	#64
Boater Sam Banned Join Date: Dec 2013 Location: Middlewich, Cheshire, UK. & Winter in the Philippines. Posts: 3,897	Re: Philco 48-2810 That's cleared that point then. Put a 6.3V 0.15mA bulb in and you should be back to the original idea. 35Y4 is a very unusual valve it seems. If this set works when you connect to 115V then my idea of using a light bulb as ballast will work too. I remember many USA sets that had the lamp fitted on top in a battern lampholder with a shade on. It was a standard way of replacing line cords when they failed as they were hard to find in the correct current range later. I have a set with a barreter, works the same way.

8th Mar 2018, 5:26 pm	#65
usradcoll1 Heptode Join Date: Mar 2017 Location: Cedar Grove, Wisconsin, USA. Posts: 823	Re: Philco 48-2810 The 35Y4 rectifier valve was very popular in the post-war US sets. Almost all the manufacturers used the Loctal range of valves except RCA. There was still the cold-war going between Philco and RCA. The Loctal valve was developed by Philco engineering and Sylvania Electric.

21st Mar 2018, 7:21 pm	#66
Dick Glennon Hexode Join Date: Oct 2006 Location: Edenderry, Republic of Ireland. Posts: 428	Re: Philco 48-2810 Hello again, Good news on the Philcoradio ,I have it working on 120 volts. I must now try to get it working on mains voltage. What strength (watts) resistors could I use. Thanks again everyone. Dick

22nd Mar 2018, 12:55 am	#67
Boater Sam Banned Join Date: Dec 2013 Location: Middlewich, Cheshire, UK. & Winter in the Philippines. Posts: 3,897	Re: Philco 48-2810 They are going to be big ! And get very hot. Measure the current it draws on 120V, do Ohm's law for value, then volts dropped X current gives watts + 20% at least. Suggestion, capacitor dropper, runs cold, simpler. Or my original idea, a light bulb.

22nd Mar 2018, 10:02 am	#68
Dick Glennon Hexode Join Date: Oct 2006 Location: Edenderry, Republic of Ireland. Posts: 428	Re: Philco 48-2810 Hi. Could someone post a circuit of a capacitor dropper that would suit with values shown. Thanks, Dick.

22nd Mar 2018, 12:52 pm	#71
Herald1360 Dekatron Join Date: Feb 2007 Location: Leominster, Herefordshire, UK. Posts: 16,536	Re: Philco 48-2810 I'd stay with 120V. A suitable inline autotransformer with a US outlet socket matched to a US plug on the set would be fine. If you want a possibly useful piece of test gear as well, make the transformer an isolating type which could make working on similar sets in future a bit easier/safer. __________________ ....__________ ....\|____\|\|__\|__\_____ .=.\| _---\__\|__\|_---_\|. .........O..Chris....O

22nd Mar 2018, 4:39 pm	#72
usradcoll1 Heptode Join Date: Mar 2017 Location: Cedar Grove, Wisconsin, USA. Posts: 823	Re: Philco 48-2810 For now, try to locate a travel adaptor set. The one I have has the adaptors for European and BS 1363 receptacles. It comes with a combination diode dropper and autotransformer. The transformer is rated for 50 watts. There's a switch that selects either mode. These items came from charity shops.

22nd Mar 2018, 7:13 pm	#73
Herald1360 Dekatron Join Date: Feb 2007 Location: Leominster, Herefordshire, UK. Posts: 16,536	Re: Philco 48-2810 I'm intrigued as to what's in on of those adaptors. An iron cored autotransformer will likely cope OK with the mixed ac/dc load the set presents as long as it's conservatively rated but I'm not so sure about some of the leerier SMPSU type adaptors that are on the market. Where do diodes come into it? __________________ ....__________ ....\|____\|\|__\|__\_____ .=.\| _---\__\|__\|_---_\|. .........O..Chris....O

22nd Mar 2018, 7:41 pm	#74
TonyDuell Dekatron Join Date: Jun 2015 Location: Biggin Hill, London, UK. Posts: 5,213	Re: Philco 48-2810 Be warned that a number of those 'travel adapters' are triac-based circuits, effectively the same as a fixed lamp dimmer. They are fine for heating applianced, but not for anything electronic (I had the job of sorting out an SMPSU that had been plugged into one, it was a right mess...) A true autotransformer will be fine for the radio, of course.

22nd Mar 2018, 7:58 pm	#75
Dick Glennon Hexode Join Date: Oct 2006 Location: Edenderry, Republic of Ireland. Posts: 428	Re: Philco 48-2810 I have a radio somewhere that has a transformer with a120 volt tapping on it. It may be no good. If not what amps would be suitable for the auto transformer. Dick.

22nd Mar 2018, 9:20 pm	#76
MotorBikeLes Nonode Join Date: Dec 2012 Location: Kirk Michael, Isle of Man Posts: 2,350	Re: Philco 48-2810 I have never had a "line cord" or equivalent radio, but somewhere I either heard, or just thought maybe, that a 110v incandescent lamp wired permanently in series would do the job safely. If I interpret above calcs, a 30W 110v bulb would do. Obtainable from continental Europe or the US of A. Les.

22nd Mar 2018, 9:40 pm	#77
turretslug Dekatron Join Date: Nov 2011 Location: Surrey, UK. Posts: 4,398	Re: Philco 48-2810 Wouldn't a 110V bulb take a bit of an excessive initial hit whilst the radio heaters were warming up? An appropriate 230V bulb would start quite bright, then settle to a gentle glow, it could even be made into a "period ambience" feature- and last a whole lot longer than a 110V bulb hit with a repeated initial overload!

23rd Mar 2018, 1:48 am	#78
Boater Sam Banned Join Date: Dec 2013 Location: Middlewich, Cheshire, UK. & Winter in the Philippines. Posts: 3,897	Re: Philco 48-2810 Use a 240v bulb, 40w should do, maybe 60w. It glows up while the heaters warm up, then settles to a steady glow. It doesn't over run, the heaters warm up, but there is no HT draw till then so it balances out. A barretter was only an iron filament in hydrogen, a clever light bulb, and they worked fine. You may even still find one for sale.

24th Mar 2018, 4:17 pm	#80
usradcoll1 Heptode Join Date: Mar 2017 Location: Cedar Grove, Wisconsin, USA. Posts: 823	Re: Philco 48-2810 I just looked over this unit again! There definitely is a transformer in there. You can see the laminations and winding through the vent slots. The thing is all glued together so I can't disassemble it without destroying it. I was wondering how the high current heating appliance mode worked. If it just had a diode half-cycle circuit, all the appliances used with it would be over-voltage. 240 X .707 = 169.68 volts, too high.