SyncroGuide tannin my hide!
 

I have a Admiral 20X1 chassis I recaped and was working fine. The picture later went out. Flyback and yoke resistance is good and no smoke. The horizontal drive seems to be way high. Right now the Output tube is pulled while I am testing. The drive seems to be too high in frequency. Incomming sync is good but there are extra pulses beween the sync (PIN 1 6SN7 oOsc Control) even with the tube HO tube removed. With the HOT installed all I get is a lone vertical line up the CRT. There is Horiz drive but I suspect it is too high for the deflection to deal with but good enough for some HV. QUESTION: Will the H osc run close to normal without the output stage? Is feed back from the output needed to oscilate or just to keep locked?
This is driving me nuts. Someone told me the output transformer could be bad But it's not open, resistance is very close , and I suspect a shorted turn of even 1 turn would kill it big time. This is the RCA type syncro-guide the used in the late 40's into the mid 50's. HEEEEEELP.

In every case I have seen there wont be enough voltage to heat the hv rectifier filament long before you loose deflection. (no hv) I would look at the yoke area.
The osc should run close to the right frequency without the feedback. If the fly had shorted turns I dont think you would get any hv.

One other thing that comes to mine is those domino style capacitors. I have seen so many of those fail a week or two after getting an old set working.

Can you post a schematic of the area?

I was just looking at an article in a 50s tv repair mag talking about this deflection. I will try and find it.

If the stabilisation coil is misadjusted, the horizontal oscillator may double trigger. This makes it appear it is running at a higher frequency.

The simplest check is simply to short out the stabilising coil which a jumper. If the oscillator then runs normally, then the problem is with the adjustment or the 0.01ufd tuning capaitor across it.

Have you tested this?

Terry

On the correct path. First, disable the AFC (synch) and jumper the stabilizing coil. If you can adjust the horiz for a correct picture (remember, no sync, so it will "float") then the osc is OK. re-enable the synch, and if it goes off freq, that is where to start looking.

Tried all the above. I too would think that if there were enough HOTrans current to light the rect fillament to get any HV there would be some sweep. Very curious. I have checked the winding resistance and the yoke also. I even disconected the horiz winding and applied a function generator to it and got some defelection so I will assume the yoke is OK for now. Schematic file to big to post. I'm going to try another 6SN7 in the morning (tried one before). This has me really stumped! The pf dominos have been replaced as suggested to no avail. Still trying, still need help.

Try posting some photos and the schematic diagram so we can have a better look.

Don't overlook electrolytic caps. Bridge them with a good one to check, the Sangamo brand first.

Remove the damper and see if any picture recovers. It will be distorted. Check for B+ on (removed) damper cathode. There should be none.

electrolytics have been bridged, cathode volts go away when pulled. I can tease more than a half inch arc off the HV rect plate with an insulated driver. Still a vertical line up the screen and yes the yoke is properly level and the vertical hold moves bumps up or down the line. Cathode curent is very low at the HO tube and hdrive is over 50v PP. Freq still seems high. 6SN7 subd, All parts replaced in h osc ckt, trimmer caps have some effect but no where near enough. I even lifted the doorknob cap to verify it wasn't breaking down under voltage. I am suspecting an unortodox failure in the HO transformer due to the fact I have enough drive to light the rectifier but not result in any sweep. Resistance measurments seem very close but we all know how that goes. I subed the yoke on the bench but the H drive remained the same on the scope. I suspect that the HO trans is somehow significant to the H osc freq via feedback somehow. I still need the expertise thats out there I don't know how to post the schematic for the 20Y1 Admiral.

Try this: Disconnect 1 lead from the horizontal section of the yoke. Now, measure the resistance from that lead, to the point it was hooked up to. You should read a low resistance. (thru the yoke and part of the HOT winding) I suspect you will find an open.

There is .47 cap in series with the yoke. the resistance at yoke is about 15 ohms and the resistance of the trans is about 11 ohms seems good to me. If i jump the cap, the line moves to the left a bit so I believe the yoke is good at present. The cap provides DC isolation for centering purposes. I still suspect the transformer; but is is so strange to be able to provide enough fillament and voltage (albeit low) to the HV rect to give a light on the screen. Lifted the width coil to check the readings while I was at it.

no horizontal sweep
 

If you have a VTVM I would check across the wires going to the horizontal section of the yoke where they attach under the chassis. I would be hesitant to use a digital meter as they can be damaged too easily by the RF. There should be some AC (high frequency) across the wires. It sounds like an open in the yoke circuit to me. That set will give high voltage with the horizontal yoke circuit open, just not alot. The yoke is actually across pins 4 and 5 of the flyback with the yoke coupling in series with pin 5. Also, with the yoke disconnected and the coupling cap jumpered, do you get a fairly low resistance across the wires going to the flyback. Sorry if I may have repeated ideas but just thinking out loud.

So, to be perfectly clear, with everything hooked up, (and the set off) you measure 26 Ohms across the .47? (right at the .47)

23.8 ohms

Did a ring test on the output transformer. Seems good to me. This was with the wires disconected to the rest of the ckt but connecting them didn't make much difference.

http://i375.photobucket.com/albums/o...s/DSCF0159.jpg

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