1967 Philco 23" color horiz problem

[Chad Hauris]

I got a Philco 23" set from the Helping Hands thrift store today. They wanted $20! for it but I said $5-10 is what I usually pay so they sold it for $5. There was no cheater cord and it was missing the damper and 6AQ5 tubes.

The first problem was that the power switch was bad, no power on testing. I bypassed the switch and was able to get the power on.

The problem I am having is some kind of overload on the HO tube. The normal screen voltage on the 6KD6 is 145 volts according to schematic.

With the plate and cathode of the 6KD6 connected I get only 59 volts on the screen. I tried supplying the screen with an external power supply and had to shut it off as the current draw at the screen was more than 150 ma.

The grid voltage is -40 volts.

With the plate disconnected but cathode still connected the screen voltage is also 59 volts.

The voltage at the screen pin with the 6KD6 out of the socket is 265 volts.

Whats weird is that the overload seems to be occuring even when the plate is not connected. Also I get weak sound with the plate disconnected and no sound with it connected.

I also tried a new 6KD6 but same results. All the voltages in the B+ power supply look normal.

[Don Lindsly]

1. Remove the damper tube and apply power. See if there is any high voltage AC arc at he 6KD6 or 3AT2 plate caps.
2. Remove power and the 3AT2 high voltage rectifier. Reapply power and check for plate arc.
3. Test or replace 6KD6.
4. Apply power. Let TV run for about 10 minutes. Remove power and feel flyback windings close to the ferrite core for excess heat.
5. If flyback is running cool, bypass electrolytic caps to check for open.

Let us know what you find.

Don

[smoker76]

Great find!
I like the Grand Marquis also.

[vintagecollect]

Flyback may be shorted out, I could see wax at bottom of coil disk where it oozed out. A good capacitor checker will apply voltage to caps and a power rating, showing any caps that are borderline or WORSE. Broader problems almost suggest power supply related issues. Fly may still work, check condition with flyback tester and ohmeter.

[Carmine]

Chad,

Want me to look for a Grandmaquis tailight in my junkyard travels? Looks like somebody poked your eye out. I had one just like that....so did Timothy McVeigh

[Chad Hauris]

I get a reading of about 98 volts through the flyback when disconnecting the plate cap from the 6KD6 and connecting the meter to the plate cap lead...usually I get the full B+ voltage here so there may be a flyback problem. I disconnected the plate cap from the HV rectfier tube with no change. I'll try laying the neon lamp against the HV lead to see if HV AC is being developed but I don't think any is.

Here's the strange thing...when an external power supply is connected to the 6KD6 screen (orginal connection broken) and the voltage is set to 145 volts, and the set is off, there is no current draw from the external supply. Then when the set is plugged in (with the 6KD6 plate cap disconnected) the screen current begins to increase as the tube warms up and keeps going past 150 ma. Normal screen current draw is only 20 ma.
If the cathode lead is disconnected from the 6KD6, the screen current draw is then zero.

It is like there is something going on in the screen to cathode or screen to grid circuit that is causing an overload as the tube warms up. This is not related to the flyback because it occurs when the plate lead is disconnected from the 6KD6. Thanks for your suggestions, I will look at it a little some more tonight.

Carmine, the original tail light probably got broken by vandals at the car lot where I bought the Grand Marquis. It just has a small hole in it but they would not allow a repair to pass a state inspection, the inspector said it needed a new intact taillight. If you ever come across one though let me know. Most junkyards seem to have sent this age car to the car crusher already so they seem very rare.

[Don Lindsly]

Chad:

I would expect excessive screen current with the plate disconnected. The screen is acting as the plate and the only place to sink the massive amount of electrons pouring from the cathode.

I would not expect any screen current from any source with the set off or with an open cathode circuit. Prognosis - normal.

The tests outlined above will narrow down the flyback condition quickly. Removing the damper tube tests the boost to B+ caps.

Have you tested or replaced the 6KD6?

Don

[Chad Hauris]

Don I will try your tests and report. Was working on a radio tonight and didn't get to the Philco. The 6KD6 tested good and I subbed in a new one with same results. Also, with the 6KD6 plate connected the screen current appears excessive too.

[Chad Hauris]

I was able to test the TV some more at lunch time today.

1. Removed damper...no indication of HV at horiz output plate or HV rect.
2. Tested damper, tests good, reinstalled. still no HV.
3. Left set on for 10 min., flyback is cold.

There is continuity through the flyback as I do read some DC voltage (98 volts) at the horiz output plate lead when disconnected. This should be the full b+though (265 v.)
All of the voltages at the filter choke and capacitors are good. Tuning eye lights good and tuner/IF section is working.
Seems like there may be a problem in the power supply to the damper plate? Will check voltage there.
Strange thing is this set had no damper tube when I got it! maybe the previous owners knew of some problem in that circuit??

It had a ton of repairs done...new CRT, new power transformer, new circuit breaker, new diodes, new tubes.

[Don Lindsly]

Chad:

The chassis looks clean. I agree that there is a B+ power delivery problem to the horizontal circuit. There are not many parts between the filtered B+ and damper plate.

If nothing is smoking or running hot, measure damper plate and cathode voltages.

Check for an open electrolytic and/or open chokes in damper circuit. Look for a snipped wire or component as well.

Do you have a chassis number?

Thanks,

Don