Oh so close, but now what (new problem)

[TinCanAlley]

Originally Posted by zeno

Just to clarify the bulb does 2 things
1) limit the current to HOT to protect it. If something
is drawing to much the bulb drops the voltage to the HOT.
If you do it with a shorted HOT or damper the bulb will have
all the 125 V across it & it lights normal but fuses wont blow.
2) trouble shooting aid. Some sets like GE used one of the
white caps instead of five. If it opened the HOT will blow in
milliseconds. Other things also could. you usually WILL NOT
find the bad cap with simple test equipt. The bulb trick allows
you to "unload" one thing from the FBT at a time till you
get a dim bulb with some HV.

73 Zeno

So the four replacement HOTs are safe. No need to sacrifice any of them. I'm still am glad I bought 4 of them. At $3 each and $4 shipping, it's well worth having some spares.

[TinCanAlley]

Originally Posted by zeno

Just to clarify the bulb does 2 things
1) limit the current to HOT to protect it. If something
is drawing to much the bulb drops the voltage to the HOT.
If you do it with a shorted HOT or damper the bulb will have
all the 125 V across it & it lights normal but fuses wont blow.
2) trouble shooting aid. Some sets like GE used one of the
white caps instead of five. If it opened the HOT will blow in
milliseconds. Other things also could. you usually WILL NOT
find the bad cap with simple test equipt. The bulb trick allows
you to "unload" one thing from the FBT at a time till you
get a dim bulb with some HV.

73 Zeno

Okay, why did I think the wire would actually be in a socket with a male/female connection. So now this leads me to ask for assistance so I make sure I get it right.

I'm looking for the power feeding the collector of the HOT, right? If so, it's not in a socket. It's actually up on the HV area soldered with a couple of safety caps. I've attached a pic.

So if I have this correct, I need to unsolder one of the blue wires and put the bulb in between it. One of the wires is coming off of the transformer and supplying 125V, and after passing through two safety caps, it goes to another wire directly to the collector of the HOT.

[zeno]

OK the raw 125 VDC goes through interlocks on the
modules then to the FBT pin 4. You want to brake it
there. it is USUALLY a red or orange wire on a Zenith.
The pin you show looks like pin 9. Check the terminal guide
in the Sams.

73 Zeno

[TinCanAlley]

Originally Posted by zeno

OK the raw 125 VDC goes through interlocks on the
modules then to the FBT pin 4. You want to brake it
there. it is USUALLY a red or orange wire on a Zenith.
The pin you show looks like pin 9. Check the terminal guide
in the Sams.

73 Zeno

Are you talking about a lead on the underside? The leads on the FB are inaccessible and go through hole to the underside. Their colors are yellow, green, purple and white w/red stripe. Those go under the chassis and are soldered to different points.

[TinCanAlley]

Originally Posted by zeno

OK the raw 125 VDC goes through interlocks on the
modules then to the FBT pin 4. You want to brake it
there. it is USUALLY a red or orange wire on a Zenith.
The pin you show looks like pin 9. Check the terminal guide
in the Sams.

73 Zeno

Okay, here's what I got. The FBT (T207) is fed via wires from the bottom. From there the wires coming out of it are bare. They connect to points on a white board I'm assuming to be the "terminal" board. I am attaching pics of the board, the terminal guide and the layout of the FB from the SM. I'm hoping from this we can identify exactly which wires need to have the bulb between them. I can see that the focus lead is tied to point 11 of the guide. And it looks like 9 goes back and feeds the collector of the HOT.

[TinCanAlley]

Well the new HOT is installed. I kind of like the ease of the NTE Thermo Pads. They replace both the mica and thermal compound. I also used them for the reinstallation of the LV transistor. I tested for insulation from chassis and found them completely isolated. Don't foresee any issues using these, but time will tell.

Since I can't figure out exactly where to put the bulb for testing, I'm going to sacrifice one of the 4 HOTs I purchased. If there isn't and existing condition, it should survive. If there is, I'll go the other route of limiting current, etc.

[TinCanAlley]

Okay, new HOT is in and working. It's been up and running for about 15 minutes and the HOT is running at about 81 degrees. So far, so good.

I'll give it a few hours running. If it doesn't die in that time I'm pretty sure the dead HOT was my shorting of the collector of the wave shaper to the capacitor lead on the horizontal board.

So if all goes well, I'll be back to scoping the jail bars tomorrow.

[Electronic M]

Congratulations! Glad You didn't smoke any silicon.

[TinCanAlley]

Originally Posted by Electronic M

Congratulations! Glad You didn't smoke any silicon.

Been running about 2 hours now. All is well!

[zeno]

Originally Posted by TinCanAlley

Been running about 2 hours now. All is well!

If its running that cool you are OK 99%. Now put alligator clips on your
bulb tester, easy to use that way.
Next fun thing to build is a "killer cord". Take any AC cord & put
alligator clips on the end. Very useful tool, you can even toss it in the
bath tube of someone you want to be rid of.

73 Zeno

[marty59]

"Killer Cord" aka a "Suicide Cord" but oh so very handy in experienced hands!

[zeno]

Originally Posted by marty59

"Killer Cord" aka a "Suicide Cord" but oh so very handy in experienced hands!

Yes its a must have but one does have to treat it with respect.
Dont leave home without it.

73 Zeno

[Reece]

Suicide cord just a tad safer if the alligator clips have full hoods that extend over all the metal. Some larger shrink tube (unshrunk over the 'gator jaws but shrunk onto the wire) can be pressed into service.

[Electronic M]

Originally Posted by marty59

"Killer Cord" aka a "Suicide Cord" but oh so very handy in experienced hands!

Especially for 'disposing' of old electrolytic capacitors..