ha escrito:

b wrote:
ha escrito:
b wrote:

Hello,

Hope this reaches older TV techs from Uk or Europe ;-)

Set in question: ITT model 1922u, with 20 axu chassis.

Am trying to restore this early transistorised colour, ultrasonic
remote set. Estimated vintage 1976 or thereabouts.
At present there is no sound or raster, no tube filaments lit. Just an
audible whine when set powered up.

HOT is ok, 300v at the mains rectifier OK, 26v line Ok. I suspect I
need to replace the LOPTX, but have no reference number to go by. If
anyone still has a schematic for this beast and could scan in the
relevant section, or just look up the transformer ref. for me, I'd be
grateful .

By whine do you mean horizontal frequency whine? Doesnt fit with no
filaments. 'HOT ok' is a bit vague too... with more info maybe the many
of us without schematics could help too.

thanks for the reply.
a few pics:

http://img164.imageshack.us/img164/3364/itt1yf9.jpg

http://img164.imageshack.us/img164/1254/itt2nm0.jpg

http://img144.imageshack.us/img144/2376/ittchasmi5.jpg

Right, more recent than the sets I had in mind. Probably not a dropper
psu. Once you get it going the ultrasonic remotes, at least of the
another brand sets I played with, work much better than the later IR
ones.


By HOT ok, I meant there is no short on the horizontal output
transistor which i measured out of circuit. The whine is a faint line
whistle. There is no EHT being produced. Typical LOPTX failure symptoms
in these early sets?

What V / waveform have you found on the supply to the horiz outputs,
and what output from the trs to the transformer? Also does it have
separate tripler or one built in to the loptf? What ac v is on the tube
filament pins? I wonder if the horizontal section is running at well
reduced output for some reason, dont know though.

Least your lucky its not one of those horrid sets where the horiz
section and main psu are heavily interdependant, and the psu wont start
without passing stuff all round the set.


NT

Hi,
This set has a tripler separate from the LOPTX, I will take some better
pictures of the board this evening . Also, the PS is switch mode - no
beefy transformers.I haven't got a scope (yet!) so can't check the
waveform for the horizontal. I will have another go at it later on,
and check the voltages you mentioned though.

At present my money is still on the LOPTX due to the lack of EHT and
heater , which i think may be derived from one of its turns, plus the
familiar quiet whine - maybe open winding?

thanks again for your contribution,
Ben.