Repairing old 1951 sentinel 424

[Patnukem]

I am repairing an old tv got all new caps put in. The audio works now but still no picture, I suspect the HV transformer is bad. The back of the picture tube still warms up and lights all the tubes glow now too. I cleaned the HV transformer off and tried again this time I noticed the wire coming of the transformer to the HV rect. was arcing back to the transformer from about a millimeter away and started to smoke from the same area. the sound then stoped working after I cleaned the HV transformer, Possibly drawing to much power for the rest of the tv to work properly. I now need to find a new HV transformer, My photofact says it is a sentinel part 22E61 or merit part HVO-6. If anyone has some Ideas, That would be great The wire finaly fell off of the HV transformer So I am sure I need a new one know. I am also new here so I am so happy to finally be a member of this forum good stuff for vintage tv/radio hobbyist. Ive included the best picture of my HV transformer I could get. the wire that is missing was from the black ring in the middle of the transformer to the board where the black marks are on the other side from the red wire to the rect.

Thank you for your time
Patrick

[Bill Cahill]

Ouch! That flyback is cooked. This flyback also has an agc winding. When hv finally totally failed, so did your agc. Ran out of that fly myself. You should be able to find one. Good luck. Bill Cahill

[Patnukem]

I think I found a NOS transformer replacement. If I keep repairing this tv the parts are all going to be new, lol. What is a ring test? on a sencore, how is the readings on it interpreted? anyway he said the wax was in good condition and such so yeah awsome I will post back after I get it and install it and retest. Thank you again for your feedback on this.

Patrick

[Randy Bassham]

Are you still looking for an HVO-6 ? I have one in the box that I was given to use in my Zenith 23H22, the Sams says it will work but it's way different from what's in the TV. A couple of weeks ago I found an HVO-11 on ebay which is an exact replacement for all Zeniths that have the flyback under the chassis. If anybody needs the HVO-6 you can have it for what I've got in it $0.00. BTW the guy on ebay has another HVO-11 if anybody needs one for a Zenith.

[Tubejunke]

Hey Patnukem, you need to check or better yet replace all of the capacitors in the High Voltage related circuits before you fry your replacement flyback.

Many transformers are bad only because some other part has caused a heavy load to be applied to it. So replacing only the most obviously ruined part will be a futile repair attempt. Take it from me!

[Tube TV]

Im with tubejunke on this , it most likely is a bad cap that cooked the HV .
did you do the HV caps ?
also check that there are no wires touching around the transformer .
best of luck .

[Patnukem]

sorry to revive this thread (3 years later) but I had this tv fixed.... for a while then it died, then it sat for several years, and now I have time and a better place to work on it at. So as I am starting to go though it, last time it was on there was no sound, this time I found the sound problem and can receive audio from a rf modulated dvd player. The HV was working, but no picture. Replaced some bad tubes cleaned the chassis well and the HV cage (I guess I should have left it alone) now with the good tubes there is no HV and no picture, tubes still light up and sound still works. I have been testing the HV by setting a CFL bulb by the flyback to see if its working but now I do not even get a faint glow. While checking other things today I noticed L23 (Horiz. Lin) coil was shorted, I repaired it and it still shorted when powered on and the coil made a few small crackle sounds then I shut it off it was then at 100ohms, I think I could see where the coil shorted on the surface, cleaning it a bit and moving the shorts away from each other made the ohms drop back to 0 when turned on the same thing, The photofacts suggest is should be at 15ohms. Thank you to anyone wanting to help me with this headache

[Patnukem]

I found a Thordarson Linearity Coil that is IND .75 - 3.9 MH 16Ω do you think this is close enough to function in my set, the factory one was 15Ω but I do not know the IND. of it, I do know there is about 556 turns and the coil is 1 3/8 inch in length the overall tube length is 2 1/2 inches and the wire size is about 27AWG I can get the diameter of the tube it was on tomorrow I forgot to write that number down for some reason, the sentinel part is 20E524.

[Patnukem]

what kind of resistors are the best for replacement in tv's? I need to order a bunch while this tv is out. the schematics do not have a voltage rating but they do have power rating most at 1/2 watt I was thinking of getting 350v or higher 1/2watt metal film resistors do these sound acceptable?

[bandersen]

That's what I generally use. Sometimes I get 1/2 watt carbon composition to preserve the original look.

[Patnukem]

thanks there are too many different kinds making my head spin a little!

[Patnukem]

since the capacitors are new I started replacing some of the resistors and checking the circuit against the schematic got most of the video ones replaced and found at least 2 faults and 1 error on the schematic

one of the Horizontal Sync Coupling Caps were replaced with a resistor

a voltage divider resistor was placed on the wrong side of the Horz. Lin. Coil.

R41 incorrectly leads to +245vdc there is no +245vdc it should be +345vdc.

also I did find a NOS miller brand coil that is a drop in replacement for the coil that was dead in mine, it should be here tomorrow then I am going to fire it up with the dim bulb tester after triple checking the circuit and hope I did not screw anything up.

[bandersen]

Good luck. I restored a 1951 Sentinel 430 recently. It's one of my favs.

[Patnukem]

I saw some pictures it is a very nice set, very similar chassis layout to mine. I wish mine would work again

The resistor I thought I found was an old ceramic cap with the old color code, this always throws me off I am glad I am double checking everything.

[bandersen]

I can't view the image you attached - bummer. If your cabinet is in rough shape, maybe the chassis would fit in this cabinet http://chicago.craigslist.org/chc/fuo/1740283831.html