Philco 19" Briefcase Chassis 11J27 Question

[Chris K]

Hi guys...the signal diode on the sweep board is something I'd like to replace. Any suggestions regarding type? Paid $50 for this TV and it's got a very strong 19ABP4 with excellent cutoff. I should probably sell it as a Predicta replacement!

[zeno]

Must be the hoz AFC diodes. If so there will be 3 legs & come in
3 flavors.Sometimes 2 separate diodes are used.
1) series
2) common anode
3) common cathode.
A common fault so change it if you can get at it. These sets are not for the
faint of heart so take it slow ! I started in 1970 & we avoided them
like the plague along with GE's. We would only "make them just work again".
But sometimes you would get a real good runner.

73 Zeno

[Chris K]

Originally Posted by zeno

Must be the hoz AFC diodes. If so there will be 3 legs & come in
3 flavors.Sometimes 2 separate diodes are used.
1) series
2) common anode
3) common cathode.
A common fault so change it if you can get at it. These sets are not for the
faint of heart so take it slow ! I started in 1970 & we avoided them
like the plague along with GE's. We would only "make them just work again".
But sometimes you would get a real good runner.

73 Zeno

It’s a 2 diode, 3 pin setup with the cathodes from each diode going to the center pin. One of the anodes goes to ground and the other anode to the K3 couplate with 1.8v on it.

[zeno]

When they go generally the H Hold gets rubbery or the pix "rolls"
side to side. If OK I wouldnt do major surgery, it can be tough to
get at things & has risks. Thats one reason Philcos were not loved.
Had they made them physically serviceable we wouldnt have minded
them...

good luck
Zeno

[Chris K]

So you’re suggesting I just keep the diode as is and don’t mess with creating a substitute?

[zeno]

I would change it if you can get to it easily. Someone will pipe in
with sub info. IIRC almost anything will work. OEM was
germanium IIRC.

[Chris K]

Interesting…parts list says selenium dual cathode. I’ve already pulled the sweep board out of the chassis and it’s a plug in type…3 pins that plug into a receptacle on the circuit board

[bandersen]

Originally Posted by Chris K

... it's got a very strong 19ABP4 with excellent cutoff. I should probably sell it as a Predicta replacement!

Sell the 19ABP4? It's not the right size. Predictas are 17" or 21".

[bandersen]

Originally Posted by Chris K

Interesting…parts list says selenium dual cathode. I’ve already pulled the sweep board out of the chassis and it’s a plug in type…3 pins that plug into a receptacle on the circuit board

Sure that's the horizontal AFC dual diode. I replace them with modern dual cathode schottky diodes.

[Chris K]

Originally Posted by bandersen

Sure that's the horizontal AFC dual diode. I replace them with modern dual cathode schottky diodes.

So the 3 pin dual cathode schottky diodes I see sold on Mouser for around $3.50 is what I’d get? Remember Bob…still a learning novice here!! Can I adjust the leads and just drop it into the socket on the board?

[bandersen]

More like $0.72. Yes, you can bend the leads and insert in socket.
https://www.mouser.com/ProductDetail...rs/WNS20S100CQ

Or solder together a couple small signal diode cathodes and stick in the socket. 1N914 or 1N4148 if you have them.

[Chris K]

Hmmmmm. Link is dead

[bandersen]

https://mou.sr/3Q27AuC

[Chris K]

TV is completely restored. The diode works great Bob. Terrific sharp picture. Hope I don't jinx it but I've had a great run of about 5 sets bought untested that have like new CRTs. I probably just royally screwed my CRT Karma!