Regentone A353/2

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Regentone A353/2, last updated 2018-11-13

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When doing odd jobs in the workshop, I like to listen to Arrow Rock Radio, a Dutch station on 675kHz that plays mainly late 60's through to 70's rock music with some more modern stuff thrown in.

This kind of material sounds best on a valve radio, so I was delighted when this non-working example came up on eBay for a fiver. The model is the Regentone 353/2 and the cabinet is in good condition for a radio that is from around the 1949-1950 era. Everything looks original.

	24-Apr-2005: Here it is after being picked up from the South Coast. There's no back panel, there's no radio stations, and the tuning cord is missing. It covers LW/MW/SW (6-18MHz) and has a gramaphone pickup input socket. Finally - the voltage selector is set to 200V to give it a little more 'oomph'.
	The radio is dead and tweaking the tuning capacitor by hand doesn't give any results either. Plugging a signal into the gramaphone input works OK. As the valves all look original and are 55 years old, I'm testing them before taking the soldering iron to the receiver.

Results of valve tests:

Valve	Sect	Function	Ia	Result	mA/V	Result	Notes
6C9	Triode	Oscillator	5.0	4.7	3.0	0.6	Replace
6C9	Hexode	Mixer	8.0	3.7	2.5	1.3	Replace
6F15	Pentode	IF Amplifier	7.0	3.2	2.3	1.0	Replace
6LD20	Triode	Audio amplifier	5.0	0.7	2.3	0.1	Replace
	Diode 1	Detector	-	Fail	-	-
	Diode 2	AGC	-	Fail	-	-
6P25	Beam tetrode	AF output	40	33	8.8	7.5	Serviceable
UU9	Rectifier 1	Rectifier	-	85%	-	-	Recommend replacement
UU9	Rectifier 2	Rectifier	-	75%	-	-	Recommend replacement

Given the readings above, I'll be replacing all but the 6P25. Most of the Mazda valves have Philips equivalents or near equivalents (6C9~=ECH41, 6F15=EF41, 6LD20=EBC41, UU9=EZ40).

	06-May-2005: Four of the valves have been replaced and I can now get a 'tune' out of it. It does seem somewhat deaf, so the chassis has been removed to carry out some troubleshooting. It doesn't look like anything has been touched for 50 years.
	The electrolytic can is bulging (not a good sign), and the wax capacitor next to it has started disintegrating (an easy replacement job). A couple of resistors had gone high in value and these have also been replaced. The alignment of the IF was way off although tweaking it up caused the set to oscillate at 465kHz.
	This radio has no RF decoupling near the valves instead relying on the main electrolytic capacitor (which is well screwed) to do all the work. To get by I've temporarily clipped a 0.1uF across the HT line and all the squegging has stopped. Radio stations are now roaring out of the speaker at high volume. To do: 1. Replace the electrolytic can, or wire new ones across, 2. Put 0.1uF permanently across the HT line near the mixer and IF bottles, 3. Replace all the TCC wax capacitors with new caps, 4. Replace the missing drive cord and do the final lineup on the RF side.
	07-May-2005: Nearly there - I thought I had some drive cord, but it's lacing cord. Not an ideal substitute (neither is the makeshift 'spring') but it will do until I can order up some springs and a reel of proper nylon cord.