Good News/Bad News

[veg-o-matic]

Did some work on my Sylvania last night. There's good news and bad news.

The good news is that I didn't make it any worse. The bad news is that I didn't make it much better, either!

I soldered in 4 new tube sockets, three of them on the chroma board. The fourth was on the IF board. I also found what I think was the source of the puff of smoke from last time. Chad (I think) hit it on the head--there was a trace on the bottom of the board that self-destructed. I patched that up with some self-adhesive copper tape I got at the electronics supply store.

The screen is not totally dead like it was before I replaced the sockets and fixed the trace. There's an occasional purple sort of haze over the screen, like it's trying to make a picture.

Anyone have any experience with that copper tape? I'm wondering if that's where the problem lies because none of the tubes on the chroma board light up, and that's what happened when the trace blew. Oddly, one of the tubes (the 6GU7 G-Y Amp/Horiz Blanking Amp) on the board gets hot, but I can't see anything glowing. That's the only tube on the chroma board that shows any sign of life. The others are all dark and stone cold. I'm guessing it would be better to fix that trace by soldering in a piece of wire, huh? I'll go ahead and do that, but the traces are all "painted over" with some kind of semi-sheer coating. What should I use to remove it to get to good copper?

Now about those tube sockets. When I desoldered what was left of the old ones, in addition to the 7 or 9 pin holders, each had a bigger sort of tubular "plug" in the middle that I also removed. The new sockets don't have anything like that, just a hole in the middle. Do those plugs serve a purpose? I saved 'em just in case. Do I need to put them back?

I guess it would also be a good idea to check all the solder joints on the new sockets. I have a DMM, but it doesn't have any instructions for using it to check continuity. Can you even do that with a DMM? I thought they could pretty much do everything.

Shoot. I was hoping to be able to watch TV last night!

veg, the ever-confuddled

[andy]

Copper tape is fine, but you need to still solder it at the ends. It won't make a good electrical connection otherwise. A tube that's getting hot, but not lighting is probably full of air. It may still have enough of a vauum to keep the getter silver.

[Chad Hauris]

I would recommend a wire going from a good solder joint on either side of the burned trace. This way you know you will have a solid connection. Make sure the wire is soldered to a point where a component is already soldered.

[vintagecollect]

Some Sams photofacts have a picture of PCB boards with parts as a reference!!! Double check to see if your chassis has this. Also , have you ever etched a PCB??? Ratshack still has limited supplies to do this, larger electronic suppliers would have more PCB options(such as double sided copper boards, etc). If you have experience doing this consider this an option, using Sams pictures of PCB as a template, these are actual size I believe. Maybe your best bet as I doubt anyone would have replacement in stock. A set I have shows half darkened PCB and runs great, some circuits just run hot & tubes, crisping PCBs over the years. It's a matter of time before my set will need this remedy. Junker set available????

[Chad Hauris]

I think in this case just wire across the bad part connected to good solder connections is the best. I think Veg only had one burned trace on the board... I have never had trouble repairing circuit board problems this way...trying to repair circuit boards using foil can be problematic.

Recreating that circuit board would be a near Herculean task, I don't think it is warranted here. I do remember that manufacturers would offer replacement PC boards but what a difficuilt job, removing all the components from the old board and replacing on a new one. I would only do this if the old circuit board was really crushed or cracked.

[veg-o-matic]

Did some work last night.

Checked continuity on all the new tube socket pins. Found a couple that were dodgy and fixed 'em.

Oddly, the trace that I fixed with the copper tape had good continuity. Chad, I took your advice and ran a wire from two components across the bad section anyway. Sort of like wearing a belt with suspenders

The chassis is still out of the set, as I ran out of time and want to double-check things before I go shoving it back in again.

There's another thread about an HV anode connecter in one of the forums that's making me think. Last time I put the chassis back in and snapped the HV connector back in the little hole on the tube, I noticed that the fit wasn't real tight. There was some lateral play and--I think but am not totally sure--a little up and down play as well. Should the little springy thing fit in the hole really tight?

Thanks for all the help, guys! With any luck, I'll be watching the set soon!

[old_tv_nut]

You may be able to move it, but it should be gripping the inside lip of the metal anode cup - it should be obvious that the contact is scraping on metal. And HV silicone grease under the rim of the suction cup is a good thing.