KV27TS27. Refuses to quit, but now it has gone through another CRT and SBX1437. I do not want to put the fourth CRT into a set this old. Damn thing won't quit though.
After some capping and soldering, what might be the life of this chassis ? Without the load of the CRT, might be awhile huh ? OK, my intent is to turn a working TV chassis into a sophisticated diagnostic tool.
Understand what you have in a regular TV chassis, Houtput collector drive can be capacitively coupled to almost any HOT or HVOT circuit, thing is it must be regulatable by a control.
Modifications for HDTV might include sending the fly less B+, just build a regulator. Might want a higher frequency but we'll burn that bridge when we cross it. I am sure without geometry concerns or anything else we can probably tackle it.
In a regular TV chassis we have waveform generators for most functions of a similar (NTSC) set. We can replace the yoke drive, the sound carrier, sandcastrle is almost standardized for NTSC now too. With the old style video outputs we can replace cathode drive to the CRT(s).
Nothing says you can't hook a Sony chassis up to a completely different yoke and tube. Something that requires little if any dynamic geometry correction by the chassis. With the input synched to the output, you can now test any signal path. You can inject HF drive to flybacks (LOPTs), yokes, all of it. Test them at actual working voltage,,,,,,,, and dare I say it,,,,,,,,, beyond. Accelerate troubleshooting of troublesome intermittents. got a HV arc, crank it up, what arcs first has arced it's last. Think I'm kidding ?
Why not ?
To be able to apply high voltage to those things that deal with high voltage should be a very useful diagnostic tool. Even more valuable might be an old Zenith 25GC45 chassis, the ones that would run the Hout into a shorted tripler until the circuit breaker tripped ?
Now something like that could also supply about 6 Kv AC, which could be rectified and used to test focus circuits etc. It might also be better if there is a really catastrophic short in the HV to hit it with 5 or
6Kv at first. If the problem isa obvious then, you have saved not only the cost of another Hout transistor, but also the time to procure and replace it.Even on the Sony chasis, I could drive the flyback with like 4 2SC5150s and use an active crowbar "Zener" type circuit for voltage protection. Of course I would get rid of the Sony SMPS immediately. I might let it run the signal section though, I don't have all year. I want knobs connected to potentiometers to control the current limit and the voltage. I can design said circuit. It is not that difficult at all.
We would literally have all kinds of pulses etc. to choose from, and demodulation, although it may be less useful, have it and not need it then. Byproduct.
Now you can really test a CRT, see the condition of the screen. Know for sure if the yoke is good, and find those pesky intemittent arcs.
I know many techs have analysers and all that, but this is something that will probably get discarded. I can apply the vertical waveform to the yoke, leaving the original yoke in the circuit and simply not connect the feedback.
If I hook up speakers I can detect a sound carrier on NTSC.
It also has a remote detector which could be connected somehow to give a visual indication. You DO remember getting pay channels on cable by resistoring the H pulse to the IF circuit I hope. Those in the know know you need to slow the time constant of the IF AGC as well.
Anyway, I mean as a service tool. I think it would be great.
Whaddya think ?
JURB