Cait’s Vintage Radio Conversion – Part 1 – The Concept

A Vintage Radio conversion for Cait’s birthday. Gail bought the case, I am buying the conversion bits and doing the labour.

The radio puchased was a PYE R31 Caprice valve radio, in turquoise. Looks like it’s hand-painted but quite nice and should fit-in with Caits cottage look.


A bit History….

Known as ‘Caprice’, the Pye Model R31 is a 5-valve AM/FM receiver in a Bakelite case that operates on AC/DC 200-250V, with MW/LW & VHF wavebands. The Caprice was made probably late 50’s to early 60’s.  A ‘1476’ Trader Publishing Co Ltd Service Sheet dated 1960 references differences between this version and earlier versions, thus giving an approx. date of manufacture.




The new amplifier – with Bluetooth…

I had previously bought a cheap all-singing, all-dancing Bluetooth Amplifier of Banggood (Mono Digital Amplifier Board 220V Car Bluetooth HiFi Bass AMP) for a sum of £8.28. This amp has 240v mains input (via a fig-8 connector), USB, SD card I/P, Aux I/P, DC 12-24V I/P, volume/treble/bass controls and small I.R. remote control. The stated impedance is 4Ω.


The Spec from Banggood…


Play MP3 music from TF card, U disk, bluetooth.
Remote control: Full function, with number key it can directly control.
Self-equipped with switch.
Fit for all vehicle.


Voltage: 220 V
D type amplifier
Output power: 30W
Maximum power: 50W
Impedance: 4(Ω)
Loudspeaker unit: 133(mm)
Sensitivity: 200 hv
Frequency response range: 20-20000

Package includes:

1 x Car bluetooth amplifier
1 x Remote control
1 x Power line
2 x Connecting line

The amp did not come with any docs and there is nothing available on the web, although the amp comes in a few flavours – Stereo, Woofer O/P, mine is the ‘Mono’ version.  Although it was stated to be Mono, it has two O/P’s on the rear panel. After testing for stereo, woofeer etc, it is indeed a Mono amp, but with two mono O/P’s. The problem is that the O/P’s MAY be parelled-up causing any connected speaker Impedance to be halved if two speakers are connected. If using two speakers, it may be better to use 2 x 8Ω giving 4Ω if they are parralled, else the 8Ω Impedance on each channel would be less of a load on the amplifier/s. Testing with the DMM tells me they are in parallel!

I did find a Youtube video on the BASS/(woofer) version where the author did a good tear-down showing the pcb’s etc. He did state that there was no real isolation gap between the Live AC and transform DC voltage parts, something that is a bit worrying in the event of a fault. It could though be powered from 12-24V DC, albeit the On/Off switch will then not work as in my own strip-down I did measure 240V across the ‘open’ switch.

I wil include pcb images of the Amp taking from my mobile in the next post.