Stroboconn 6T5 Tuning Unit

[nigelr2000]

I have never seen one of these before and probably won't again. It came my way from Pete the guy who does musical instruments on the repair shop.
It was made in the early sixties but the original design was alleged to be from the 1936 and is used to tune instruments.
It has 2 units, the bottom one is a frequency clock to run the motor unit and consists of an excited tuning fork tuned to exactly 55 Hz which locks the motor to this frequency and runs via precision gears several strobe discs in the upper unit. It has an oscillator section and an output stage using 4x 6V6 valves in push pull.
The upper unit contains an amplifier which instead of running a speaker runs a huge U shaped neon lamp to illuminate the strobes flashing at whatever frequency the microphone is picking up again a 6V6 in push pull is used.
It can then show the note and all harmonics as well.

It required a lot of work to bring it back to life including the main rectifier in the lower unit, 5U4G which showed it's demise with a big burn on the side of the valve and lots of mica rattling around in it. I changed all the coupling capacitors and the electrolytic's in the top unit, the lower unit had new ones fitted fairly recently. A first run of the motor showed it was making nasty noises, this was the start up cap (3.5 µF ac) cleverly hidden behind the original big can one which had been replaced with an ordinary 10µF 400V DC one which unsurprisingly had blown out leaving a mess on the bottom of the case.

After this it ran fine and the neon lit up once the amplifier warmed up. I then plugged in the lower unit and after a while the pilot neon lit meaning it was running. I threw the switch from warm up to run and the motor locked to 55Hz, success. I then hummed various nots into the microphone and was rewarded with various strobe line dependant on frequency.

Overall it was fun to do and an ingenious device using electronics and precision engineering to give a simple but precise frequency measurement.

I have a link to all the pictures and a video of it running here https://photos.app.goo.gl/vPpkbushmstg3pb96

[Andrewausfa]

Conn Strobo tuner, very nice and lovely to watch!

Out of interest and size comparison, here's my modern Peterson version, Peterson started making strobe tuners back in the late 1960s.

Andrew

[nigelr2000]

Originally Posted by Andrewausfa

Conn Strobo tuner, very nice and lovely to watch!

Out of interest and size comparison, here's my modern Peterson version, Peterson started making strobe tuners back in the late 1960s.

Andrew

At least it's a lot more portable the Conn is a real lump