help with TV relic: ITT model 1922u, 20 axu chassis

cant help with a cct diag, and dont recognise the model, but those machines are some of the easier ones to fix with no schematic, because you've typically got a simple dropper supply and little or no fire protection circuitry. IOW the psu takes no notice of what the horizontal section or anything else does, so you've got no interaction complications.

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.

NT

snipped-for-privacy@care2.com ha escrito:

thanks for the reply. a few pics:

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?

regards,

-B

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.

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

snipped-for-privacy@care2.com ha escrito:

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.

thats good news

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

snipped-for-privacy@care2.com ha escrito:

an

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:

-B.

Just an

you found out its faulty? If it is thats bad news, terminal I'd say. Unless you have another similar set and time on your hands.

NT