Oh so close, but now what (new problem)

[DaveWM]

that is a common bulb limiter by a lot of folks for checking major shorts in a set, but I think zeno was looking more for shorts of the HOtransistor

quoting here

After replacing since you prob dont have a variac you should use
a "rubber fuse" to protect it. You have many of them, a 75W
lamp. Remove the wire from pin 4 of the FBT. Hang in the lamp in
one end to pin 4 & the other end to the wire. If it lights dim
& you get a small dim pix things are OK for now. If it glows
bright you have problems.........

stop quote.

the prob with just using a dim bulb as you have it (at the primary of the power trans) is if there is a prob in the circuit around the HOT it may still blow even with the dim bulb. I could be wrong though, as I thought these chassis have loosely coupled power trans that should limit the current to some degree. Zeno needs to chime in to clear up.

[TinCanAlley]

Originally Posted by DaveWM

that is a common bulb limiter by a lot of folks for checking major shorts in a set, but I think zeno was looking more for shorts of the HOtransistor

quoting here

After replacing since you prob dont have a variac you should use
a "rubber fuse" to protect it. You have many of them, a 75W
lamp. Remove the wire from pin 4 of the FBT. Hang in the lamp in
one end to pin 4 & the other end to the wire. If it lights dim
& you get a small dim pix things are OK for now. If it glows
bright you have problems.........

stop quote.

the prob with just using a dim bulb as you have it (at the primary of the power trans) is if there is a prob in the circuit around the HOT it may still blow even with the dim bulb. I could be wrong though, as I thought these chassis have loosely coupled power trans that should limit the current to some degree. Zeno needs to chime in to clear up.

Well I can jumper the hot and neutral of the outlet and put the hot and neutral of the plug end in-line with pin 4 of T207. That way don't have to undo all whole DBT and rewire it.

[DaveWM]

Originally Posted by TinCanAlley

Well I can jumper the hot and neutral of the outlet and put the hot and neutral of the plug end in-line with pin 4 of T207. That way don't have to undo all whole DBT and rewire it.

there you go, and you still have the dim bulb tester for other stuff.

[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

[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.