RGD 700 Radiogram - UK Vintage Radio Repair and Restoration Discussion Forum

newlite4 · 15th Apr 2021, 2:44 pm

I had the call on Monday from an antique dealer who had bought an RGD700 for £25 from a junk shop in Bristol. He had removed the PP3 output valve to sell on and was scrapping the case and asked me if I wanted any of the remains. Reluctantly I agreed recognising the sacrilegious aspect of this type of behaviour as something that we all pour scorn upon, however it is what it is, that is a sign of the times. Anyway, on a brighter note, I plan to get the radio chassis going again as it is very well made and is an early model dating from 1934.
I understand that the direct equivalent of a PP3 is the PX4. I have a stock of PX4s, and assume that they are a direct drop-in replacement for the PP3, is this correct, are there any necessary biasing alterations? Also, the mid-high speaker has an O/C field winding, can I just bridge its respective field supply sockets with a 1Kohm resistor? There are separate sockets for the woofer field supply. I have taken the precaution to fit a piece of steel angle to the rear to protect the incoming PX4 and the equally vulnerable rectifier. Ultimately I plan to build a basic case just for the radio chassis, the Garrard AC1 turntable will probably be moved on as it is a very heavy and cumbersome unit.
Neil

15th Apr 2021, 2:44 pm	#1
newlite4 Octode Join Date: Nov 2003 Location: Bath, Somerset, UK. Posts: 1,805	RGD 700 Radiogram I had the call on Monday from an antique dealer who had bought an RGD700 for £25 from a junk shop in Bristol. He had removed the PP3 output valve to sell on and was scrapping the case and asked me if I wanted any of the remains. Reluctantly I agreed recognising the sacrilegious aspect of this type of behaviour as something that we all pour scorn upon, however it is what it is, that is a sign of the times. Anyway, on a brighter note, I plan to get the radio chassis going again as it is very well made and is an early model dating from 1934. I understand that the direct equivalent of a PP3 is the PX4. I have a stock of PX4s, and assume that they are a direct drop-in replacement for the PP3, is this correct, are there any necessary biasing alterations? Also, the mid-high speaker has an O/C field winding, can I just bridge its respective field supply sockets with a 1Kohm resistor? There are separate sockets for the woofer field supply. I have taken the precaution to fit a piece of steel angle to the rear to protect the incoming PX4 and the equally vulnerable rectifier. Ultimately I plan to build a basic case just for the radio chassis, the Garrard AC1 turntable will probably be moved on as it is a very heavy and cumbersome unit. Neil Attached Thumbnails __________________ preserving the recent past, for the distant future.