Hoffman 600 scare

[frenchy]

I was redoing the cable and digital tuner hookups to my old '50 Hoffman 600 b/w tv yesterday, and while I had it on and working fine, all of a sudden the screen went dead. By the time I spun it around to look thru the back, I was smelling the scary stench of burning plastic. Then even scarier I saw orange flickering shining thru the HV cage onto the inside of the cabinet! Boy that really spooked me thinking about the whole set flaming up and me trying to lug it out of the house before it burned it down. But when I turned it off fortunately the apparent flame went out quickly.

So I thought well well, my first fried flyback. Luckily it turned out to be something simpler - one of the wires that led to one of the tube's cap connections (the HV rectifier tube I think) had cracked, and it was arcing against the HV cage where the wire was touching it. Wrapped up the insulation break (and most of that wire just in case) with plenty of layers of electrical tape and all is well again. : )

[Sam Cogley]

I think I'd replace any questionable wire in there!

[frenchy]

I wrapped the entire wire up like a mummy with insulated tape, especially where the arc broke thru against the cage. At least I'm pretty sure it was the HV rectifier tube, it was the one with a plastic cap, the other capped tube in the cage had an exposed cap clip, the HO tube I think. What would the voltage normally be on the cap and cap wire of the 1B3 tube? If it is anywhere near or equal to the actual HV for the pic tube, maybe I should completely replace the wire... Otherwise the wire looks to be in solid shape, it just punched thru right at the exact contact point with the cage, perhaps from the cage finally melting thru it after 60 years.

[old_coot88]

Originally Posted by frenchy

... What would the voltage normally be on the cap and cap wire of the 1B3 tube? If it is anywhere near or equal to the actual HV for the pic tube, maybe I should completely replace the wire.

Uh, the actual peak voltage on the 1B3 "cap" is substantially higher than the smoothed-out DC high voltage on the pic tube anode.

That little arc-over was an object lesson on why one should never, ever, ever leave any vintage TV running unattended.
oc(Bill)

[old_tv_nut]

Best bet is to replace with Teflon wire. The existing wire is probably carbonized to some extent now, and just looking for a surface leakage path to start arcing again.

[kvflyer]

I might add that replacement of the wire would be a good preventative measure.

[miniman82]

This is exactly why the first job I always do to a set is replace all the HV wiring with newer stuff from another set, it prevents these things. It can be tricky on some sets though, like the 1X2 equipped sets that always seem to be in impossible to disassemble metal sockets. On the Philco I used to have, I was even able to salvage a nice silicone anode connector from a console.

[leadlike]

I had a similar scare with an RCA 21". The vertical collapsed, so I turned down the brightness and began to pull the back off when I could see flames through the vent holes, and thick choking smoke pouring out of the back! Boy, did the house stink after that one! It turns out all of the drama was caused by a bad ground trace, which burned up a dinky 1/4 watt resistor! WAF was extremely low that week, until the stink cleared out....

[frenchy]

I had already been smart enough to never leave one of my old sets unattended, reading about old stories about flybacks melting and burning down houses, but yeah this first-hand experience learns ya REAL good! Didn't know about wires becoming carbonized, I'll replace the wire before I use the set full time again.