1947 fada tv 125

[timmy]

hi all well i powered the set up but this stuff is to early for me but ill get to the point there is no induction at the fly at all no glow of the rectifier tube. tubes all new and there is voltages at the fly and the ho tube has a blue glow so i guess its putting out. any ideas from anyone that knows these old sets?

[ctc17]

I'm amazed I understand this.

You changed all the paper caps and domino style caps in the horizontal circuit?

[DavGoodlin]

You're speaking my language too Timmy.

This brings back memories of every no-HV RCA set I ever worked on ...LOL

Keep up the good diagnostics

[timmy]

electrolytic and paper caps for now to get it up and running to see where im at.

[ctc17]

Change any of those domino style mica or paper or maper or pica whatever they are if there in the horz circuit change them.

A glowing blue tube can be normal or can indicate excessive current. Its hard to tell without measuring the cathode current.

Im not a fan of working on the old sets either. Way to many caps and so easy to get a wrong value installed.
Im much more a fan of the 60s color stuff.

Check the HOT grid voltage and make sure its negative.

[timmy]

the blue glow is in the hot but when you take the wire off the top the blue glow is gone so you may think that its oscillating in the fly but the fly is total dead . all the important caps in the horiz were the wax paper caps and they are changed, the fly looks great no wax, burn marks, its clean just no noise or output,lol,lol. i really didnt want to get into something this old but my girlfriend brought it home so its mine now to get working.

[DavGoodlin]

Wow Timmy, I never had a girlfriend that would fetch a TV for me. They used to consider my hobby AS their competition!

Do a resistance check of your windings, maybe one is not soldered to the fly terminal, etc. One can only hope

I attached the pages from my book that may help you. I will be looking for the other volumes since I have pre-52 BW sets; Emerson, Motorola, Philco and RCA. No Zeniths though
20120330111528554.pdf

[timmy]

resistance checks in circuit? i dont know what they should be the sams dont show it. i left the set on for awhile and the fly is cold.

[timmy]

took all wires off the fly and went to the sams and checked all coil connections for contiuity and it has readings on all coils. its like the circuit is not oscillating but if it were not then with standing voltage the flyback should be hot but its cold.

[Electronic M]

Run some voltage checks on the HO tube base.....If the screen is too low or the cathode is open that will kill the HV and probably leave the fly with 0 current running through it regardless of the state of the oscillator stage.

[timmy]

the hot has 99 volts neg grid and 200volts screen and i was told that the voltage should be 35v and 250-300v. not sure what it all means lol,lol.... and the odd thing is that it appears the the wire on top of the rec tube has about 300 volts on it.

[DavGoodlin]

Measuring the rec tub cap when powered on was only possible because there is no AC going thru the fly, only DC that feeds from the Damper tube (6W4?)

Try this with Power off ; What is your resistance measured from the horizontal tube cap to the HV rect tube cap? Should be about 500 ohms or what the sams lists. Its probably OK, since you got DC there.

Then this: Lift the 6CD6 hor out cathode pin 3 off ground and put an ammeter between that pin and ground. Leave it there and start trouble shooting the output and oscillator stage. If you have -99 volts, the tube is probably completely cut-off (not conducting)

My guess FWIW is that the horizontal oscillator is way off frequency. Start there. Check everything. Disconnect AFC circuit in case sync signal is causing issue.

[timmy]

the hot in this set is 6bg6 so i dont know if pin 3 is the same to use and the sams lists nothing in the way of voltages. i dont think there is an AFC like the 60s sets. there is something said about cathode currant in these old sets and i dont know where to set it. the sams dont even list what the cathode currant should be. would the pin 3 be the same for the tube i have because i dont know? from both rec cap and hot cap is around 200 ohms since this this set dont use much hv 7-9kv and the fly is small so i dont think it would be the same for bigger and newer sets.

[Electronic M]

There were TWO AFC's in 60's sets....the tuner AFC (which is what I think you mistook Davgoodlin's comments to refer to), and Horizontal oscillator AFC (that dates back to the 40's).

The horizontal AFC is meant to compare the oscillator frequency to the synch, and pull the horizontal oscillator frequency to match the synch. If the horizontal AFC circuit is bad it can pull the horizontal oscillator waaaay off normal operating frequency. The horizontal AFC circuit comprises all tubes on the schematic that are between the synch tube and horizontal oscillator tube. Pulling the tubes in the AFC will disable it and make trouble shooting oscillator issues easier.

[timmy]

well there is a horiz sync discharge tube, horiz react, and horiz osc.