AC/DC version of Philips 170A (1946) - UK Vintage Radio Repair and Restoration Discussion Forum

ted_ntsx · 27th Jun 2009, 2:37 pm

Does anyone know if there ever was an AC/DC version of this set?

The circuit diagram shows it as AC only with a mains transformer, but the one I have has a mains dropper. The dropper, heater wiring, etc, looks old and in keeping with the rest of the set, and does not look like an amateur modification.

If there was no AC/DC version of this set I can only assume that some service dept has done a conversion job on it a long time ago when someone wanted it to work on DC mains.

Valve line up is the same (EF39 ECH35, EM34, etc) except that the EBL31 is a CBL31 and the AZ31 is a UR1C

Was this sort of conversion common thing?

Ted.

Leon Crampin · 27th Jun 2009, 3:23 pm

I have no documentary evidence of a "170U". The give-away will be a change to the model number on the ID plate. There would need to be provision for proper isolation of all the rear sockets (A/E Gram and LS.) together with measures to prevent accidental contact with the chassis - including the grub screws securing the knobs.

Knowing the 170A well, I'd be very surprised if Philips ever did this. Their usual approach on many sets of this era was a DC/AC converter unit fixed to the inside top of the cabinet - difficult on a 170A as it's bakelite.

Your set looks like a bodge (adaptation). I've seen a push button HMV set similarly converted - a potential death trap.

Leon.

ted_ntsx · 27th Jun 2009, 8:29 pm

Further inspection does show that the Ae, Earth and other sockets have been isolated with waxy paper capacitors (all seriously leaky), but there are a number of places where it is easy to touch metalwork.

As you say, a potential death trap, so it does look like a bodge although it has been very neatly done apart from the safety aspects! The original reversible 2 pin plug (now bypassed) would have made a live chassis a 50/50 chance.

BTW, I have it running on an proper isolating transformer

Ted.

yestertech · 28th Jun 2009, 12:33 pm

I've also seen this done on a ( if I recall ) 747A - No Mains transformer and a substantial dropper resistor instead. It looked quite professionally done, but must have been a heck of a lot of work, rewiring all the heaters
I also seem to recall it had the 747A plate on the rear.
Maybe these were 'specials' done by a dedicated contractor somewhere ??

Andy

Tim · 28th Jun 2009, 9:44 pm

I have an HMV 1117 that has been converted to Universal.Also a neat job, but later repairs not so. As it now uses a CY31 and (I think) KT33 (although a PL33 works very well, with a 2.2k resistor in the screen)-total heater voltage of 67 volts at 300mA you can imagine the size of the dropper!

ted_ntsx · 30th Jun 2009, 8:37 am

That's what I first thought. The mods do look a bit too well done for an "amateur" job. Of course, by today's standards the safety aspects leave a lot to be desired (reversible 2 pin mains plug and several exposed bits of non-isolated metalwork) but safety seemed to be far less of a issue in those days...

Ted.

27th Jun 2009, 2:37 pm	#1
ted_ntsx Pentode Join Date: Jul 2008 Location: Winterton-on-sea, Great Yarmouth, Norfolk, UK. Posts: 137	AC/DC version of Philips 170A (1946) Does anyone know if there ever was an AC/DC version of this set? The circuit diagram shows it as AC only with a mains transformer, but the one I have has a mains dropper. The dropper, heater wiring, etc, looks old and in keeping with the rest of the set, and does not look like an amateur modification. If there was no AC/DC version of this set I can only assume that some service dept has done a conversion job on it a long time ago when someone wanted it to work on DC mains. Valve line up is the same (EF39 ECH35, EM34, etc) except that the EBL31 is a CBL31 and the AZ31 is a UR1C Was this sort of conversion common thing? Ted.

27th Jun 2009, 3:23 pm	#2
Leon Crampin Octode Join Date: Nov 2005 Location: Surrey, UK. Posts: 1,870	Re: AC/DC version of Philips 170A (1946) I have no documentary evidence of a "170U". The give-away will be a change to the model number on the ID plate. There would need to be provision for proper isolation of all the rear sockets (A/E Gram and LS.) together with measures to prevent accidental contact with the chassis - including the grub screws securing the knobs. Knowing the 170A well, I'd be very surprised if Philips ever did this. Their usual approach on many sets of this era was a DC/AC converter unit fixed to the inside top of the cabinet - difficult on a 170A as it's bakelite. Your set looks like a bodge (adaptation). I've seen a push button HMV set similarly converted - a potential death trap. Leon.

27th Jun 2009, 8:29 pm	#3
ted_ntsx Pentode Join Date: Jul 2008 Location: Winterton-on-sea, Great Yarmouth, Norfolk, UK. Posts: 137	Re: AC/DC version of Philips 170A (1946) Further inspection does show that the Ae, Earth and other sockets have been isolated with waxy paper capacitors (all seriously leaky), but there are a number of places where it is easy to touch metalwork. As you say, a potential death trap, so it does look like a bodge although it has been very neatly done apart from the safety aspects! The original reversible 2 pin plug (now bypassed) would have made a live chassis a 50/50 chance. BTW, I have it running on an proper isolating transformer Ted.

28th Jun 2009, 12:33 pm	#4
yestertech Nonode Join Date: Dec 2002 Location: Coulsdon, Surrey, UK. Posts: 2,130	Re: AC/DC version of Philips 170A (1946) I've also seen this done on a ( if I recall ) 747A - No Mains transformer and a substantial dropper resistor instead. It looked quite professionally done, but must have been a heck of a lot of work, rewiring all the heaters I also seem to recall it had the 747A plate on the rear. Maybe these were 'specials' done by a dedicated contractor somewhere ?? Andy

28th Jun 2009, 9:44 pm	#5
Tim Dekatron Join Date: Jan 2003 Location: Bradford on Avon, Wiltshire, UK. Posts: 3,307	Re: AC/DC version of Philips 170A (1946) I have an HMV 1117 that has been converted to Universal.Also a neat job, but later repairs not so. As it now uses a CY31 and (I think) KT33 (although a PL33 works very well, with a 2.2k resistor in the screen)-total heater voltage of 67 volts at 300mA you can imagine the size of the dropper! __________________ "Nothing is as dangerous as being too modern;one is apt to grow old fashioned quite suddenly."

30th Jun 2009, 8:37 am	#6
ted_ntsx Pentode Join Date: Jul 2008 Location: Winterton-on-sea, Great Yarmouth, Norfolk, UK. Posts: 137	Re: AC/DC version of Philips 170A (1946) That's what I first thought. The mods do look a bit too well done for an "amateur" job. Of course, by today's standards the safety aspects leave a lot to be desired (reversible 2 pin mains plug and several exposed bits of non-isolated metalwork) but safety seemed to be far less of a issue in those days... Ted.