View Single Post
Old 8th Jan 2016, 12:11 am   #23
FERNSEH
Dekatron
 
FERNSEH's Avatar
 
Join Date: Mar 2005
Location: Gateshead, Tyne and Wear, UK.
Posts: 7,019
Default Re: PYE TT1 - First Transistor Portable UK TV

Hi John,
The Ferguson 743T is the rarest of the early UK made all transistor TV sets. Information for the set can be found in the 1961/62 Radio and Television servicing book. Pages 325 to 331. The 743T seems to be a considerably more developed set compared with the Pye. The latter is somewhat crude in it's construction. The Ferguson has five stages of vision IF amplification using five AF114 transistors. The Pye uses the earlier OC171 in the four stage vision IF amplifier.

More progress with the Pye. The no sound fault was traced to one of the output transistors gone base to emitter short. The original push-pull output stage employed OC72 transistors, these must have failed a long time ago and were replaced with two AC128s. It was one of those AC128s which had failed.
Work is going well with this set. The sound stages are working and so are the vision circuits up to the base of the video output transistor.
The video amplifier does not work because the -60volt supply from the line output stage is absent.
Interesting to note that in the Ferguson and Pye the CRT is grid modulated, supplied with a positive going video waveform.
The reason for this is because the sync separator transistor is a pnp type.
The transistor conducts only on the negative going sync pulse tips.
In normal valve practise the valve conducts on the positive going sync.

The next stage of the restoration is line output stage. The 2G221 is unobtainable but there is a limited number AU101/3 transistors available from on-line traders.

DFWB.
FERNSEH is offline