Posted: February 18, 2013 in Test Equipment

martinjonestechnology

Over on the Vintage Radio Forum, someone asked recently about the Henelec PA25 power amplifier module. The PA25 was produced by Henry’s Radio of London in around 1970. Since I have a pair of them, including the associated MU442 power unit, I’ve documented them here.

Here are a couple of general views. The MU442 has sockets for mains in, signal input (3-pin DIN) and speaker outputs (DIN again). There are also a pair of power supply fuses. Connections to the PA25 modules are via wiring harnesses with edge connectors.

Img_3997

IMG_3999

 

Here’s what one of the modules looks like. It’s a sandwich of a PCB and heatsink.

 

IMG_4000

 

This is what’s on the PCB…

 

IMG_4003

…and on the heatsink…

IMG_4004

 

…and the back of the PCB.

IMG_4001

 

The heatsink has a pretty label on it:

Img_4005

 

This is the MU442.

Img_4006

 

Inside, there’s a mains transformer with 2x 22VAC…

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