eBay purchase – it listed a bit on the high side, but after a quick chat the seller revised the price down to something very reasonable, so I couldn’t pass it by.

External references: Tim Robbins blog. Radio Museum

Table of Contents

PHILIPS MODEL 976B, VALVE PA AMPLIFIER

Made in Australia in the mid to late 1950s, this compact valve PA head is rated 8 watts. Here’s a link to another more recent purchase of the same model.

I wasn’t super excited when I cracked the lid open – I think this is referred to in the USA as a ‘barn find’. Fortunately it was mostly superficial and it cleaned up OK. The transformer rust came off without much effort. The electrolytic filter caps didn’t look good at all, but they seem to be fine.

Worth noting that the output transformer can be changed to a very affordable transformer from Altronics – the M1120 model. The original is difficult to reconfigure, and to be honest, the little transformer from Altronics sounds great, and will drop pretty much straight in – just as good as a more expensive Hammond.

VALVE LINE-UP

2 x Brimar UK 12AX7 dual triodes
2 x Miniwatt 6M5 pentodes, cathode biased (EL80)
1 x Miniwatt 6V4 full wave rectifier (EZ80). 9 pin miniature type

INPUTS / OUTPUTS / CONTROLS

INPUTS: PU (phono input for crystal cartridges) & Microphone
CONTROLS: PU Volume, Mic Volume, Tone (music / speech)
OUTPUT: Speaker binding posts, fixed impedance, currently set to 1200 ohms!

TRANSFORMERS

POWER:
CZ344217
300-CT-300 for B+
6.3-CT-6.3 for heaters

OUTPUT:
OT 903
0, 300, 600, 1200 + 2 ohm FB winding

An input transformer has been wired in, which is connected to both inputs (PU and Mic in parallel) – the PU volume control has been disconnected. I doubt this is a factory mod, but who knows.

I am happy to see a lot of poly caps, as I was expecting mostly the wax paper type that always leak. These test well, happy to leave them in.

CONVERSION SCHEMATIC

I converted it to something resembling a Marshall 18watt lite – sounds great, I’m happy with the results.

The switched tone pot was converted to a power on/ off switch
Completely rebuilt the preamp and phase inverter.
Power stage left as is
Original electrolytic filter caps left in place
Reused coupling caps & pots
OT changed to a hammond, as the original was designed for a 100v line system

PHILIPS 976B SCHEMATIC & TECHNICAL MANUAL

PHILIPS: 976B Valve PA Amplifier, 8 watts