Made in Oldhill, Staffordrshire (now Black Country) between 1959 and 1969. What initially drew me to this purchase was that it had been made fairly local to where I live, and it's quirky looking outer design, looking like it came from the 1930's and built in a time when the transistor was taking over from the old school valves. Good news is they are back in vogue again now. The guy I brought it from has a light fitting workshop in Kings Norton and he had found the amp when picking up some old lighting from an old Rehearsal Studio above a retail shop that was closing after 100 years in Digbeth, Birmingham.
Firstly take some photos of the inside. This help when wires fall off during cleaning process. Strip down and vacuum out the 50 years of dust collected, polish metalwork and clean valves, taking care not to remove the numbers. While cleaning some makes of valves print the year of manufacture in small print as a code number, as do electrolytic capacitors, all helps in aging unit or parts fitted later. Check on-line for circuit diagram, if one can't be found find a similar one or reverse engineer the diagram yourself, This is what I had to do.
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| The two doggy 0.1uF's fed back to Cathode and Anode of driver valve 12AU7 (ECC82) |
Taking on the faults that time brings on
I switched the unit on and stood well back, lol A quite common fault is the 0.1uF (600v) across the on/off switch going short, this will creature a big flash and blow the mains fuse in the plug. They were fitted to suppress sparks created by the on/off switch sending out radio interference. In this case all that happened was a slight hum in the speaker and the amp worked. Sadly though after a short while the humming got louder and one of the two EL34's output valves started to glow orange. I quickly reversed them over (taking care not to burn my fingers) and the other EL34 glowed in the the same valve base, telling me that the fault was in the circuit and not the valve. When anodes glow bright like this it will ruin the valve in a short time and even sometimes melt the glass housing in the valve.
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| Doggy TCC capacitor and replacement to it's right (one 16 uF inside can was still good) |
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| The amp was found above Gregory Pank Ironmongers that was closing down after 100 years in Digbeth High St. |
Finishing touches
The cabinet was very badly scratched and having seen another restored amp on line (Guy wanted £788 - now reduced) I copied his idea of painting the grill red and the back black, sort off gives it new life, the scratches on the front were 'wire wooled' and touched-up with a silver felt tip pen. The mains plug and cable is quite strange, I think it would have had a few types of cables depending on whether you used a battery or a ht vibrator unit, anyway I cleaned the cable and plug, tippexed the writing back on the plug.
Now she's working lovely again albeit only as a mono amp, it will make a lovely guitar and singer stage mixer for a small venue or home practice.
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| 9 valves in total, 5 x pre-amps left, EL34's and EZ81's mains rectifiers on right (4 pin socket on right has smoothers fitted in this achieve photo, mine didn't) |
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| Inside after clean-up & polish |
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| eBay photo before purchase |
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| The main troublemakers, Hunts 0.1 uF were leaky |
Hifi Ltd was created in 1950 by Ted Hunt and Vera Smith at High Street, Lye, the next year they moved to Derry Street, Brierley Hill, while the business expanded. In the mid-60s, they moved to a purpose-built premises at Station Road, Old Hill - which will be the period this amplifier dates from. They employed 40-50, and made valve amps, intercoms and fan heaters.
Some more Jr. info here: https://www.vintage-radio.net/forum/showthread.php?p=598273
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