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Old 19th Jul 2021, 11:57 am   #1
G8vsjDave
Tetrode
 
Join Date: Jul 2010
Location: Nottingham, Nottinghamshire, UK.
Posts: 98
Default Ferranti TC1004. Baptism of fire.

I have a small collection of sixties transistor radios which have been repaired and cleaned and are displayed round the house and Iíve been looking out for a 50ís or early 60ís television to complete my small collection. I doubt if my wife would let me have much more. I recently found a Ferranti TC1004 not far from me and at a price that I thought was acceptable. This is intended to be a long term project for the winter months with some minor cabinet repairs, but I wanted to see what the electronics was like. A visual inspection showed no sign of previous repairs. All the fuses were intact and looked original and both dropper resistors were fine. Initial cleaning was limited to a soft brush and the vacuum cleaner on blow out on the patio.
Once the chassis was out and on the bench I decided to check out the big smoothing capacitors (C115 andC116)
The reforming operation suggested one half of the smoother (C115 200uf) is leaky. Iím feeding mains via my variac, a diode and an 8.2k resistor. The leakage current is steady at 6mA but with only about 160 volts across the capacitor. The other half of the smoother (C116 100uf) charges to 230v with no detectable leakage. I guess ultimately, this a re-stuff job, but at this stage in the project, itíll be tack-on .
I snipped out the mains filter capacitor and replaced the boost capacitor then decided on a test. I reset the mains selection options so I could have full heater current but limited the HT to 160 volts (because of C115,) controlled by the variac. Powered up, the speaker clicked on channel change, and I could hear what I thought was a 50 Hz buzz, so Iím guessing the frame TB is doing something. The Line stage however was dead apart from a blue glow in the O/P valve. I havenít yet changed C105, (I believe it falls into the category of ĎThat Capacitorí). The test was limited to just a few minutes and after, I noticed the smoothing capacitor had a slight liquid leak Iíve ordered two electrolytes to replace the smoothing block and some capacitors to replace the wax capacitors. The biggest problem that I know about is that I have a duff tube (see wanted section). The very long term aim is to have some fifties television material on a hard drive feeding a standards converter . For now, I am using a processor based 405 line pattern generator and a VERY crude modulator. I have a digital multimeter, avo8 and a scope and although I have zero experience with valve equipment, I have worked with transistor televisions and repairing professional TV colour monitors.
ANY advice or suggestion is welcome.
Dave
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