DIYbanter - View Single Post - help with TV relic: ITT model 1922u, 20 axu chassis

b

ha escrito:

b wrote:
ha escrito:
b wrote:
ha escrito:
b wrote:

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 .

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.

This set has a tripler separate from the LOPTX, I will take some better

thats good news

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?

heater voltage should tell us quite a lot. I dont see how this could be
caused by an open winding, but who knows. With the loptf usually
producing various supply lines theres no knowing what it may be failing
to power up. And of course one may boost a supply line as well... messy
things.

NT

have traced the board and in this set the LOPTX provides heater, rgb
stage and various other low voltages. I removed it and after clearing
away the dust and crud, under an outer plastic laminate layer the
reference TFAT 1109/201.57 was visible (EQUIVALENT hr 1127). so will
look into it.

pics:
http://img171.imageshack.us/img171/8...triplerjy1.jpg
http://img97.imageshack.us/img97/765/loptxlw9.jpg

-B.