Thread: Pye CTM4.
View Single Post
Old 19th May 2018, 10:37 am   #17
FERNSEH
Dekatron
 
FERNSEH's Avatar
 
Join Date: Mar 2005
Location: Gateshead, Tyne and Wear, UK.
Posts: 6,480
Default Re: Pye CTM4.

The Pye CTM4 is connected to the main via the variac. Supply set to 200 volts because the mains dropper resistor is open circuit and is at present shorted is out.
The 250mA line output stage fuse removed for the preliminary tests.
Oscilloscope analysis reveals the line and frame oscillators are working delivering sawtooth drives at the correct frequencies to the grids of the output valves.
Sound output stage working but no activity from the tuner. The HT supply to signal stages was found to be missing, the 200ohm decoupling resistor R45 was found to be disconnected from it's anchor tag.
Now signals can be heard and after turning down the sensitivity control a video waveform is present at the video detector load resistor.
The video amplifier stage is not working so that stage will be next for testing.

Will report back my findings later today.

DFWB.
FERNSEH is offline