Lisa dead !

[Gary C]

Well, almost.

The video has failed though there is a good output on the rear video port.

Exploring further there appears to be no EHT, and loop checking the LOPT, the output coil for the grids red to white is giving a good reading but from the red to the anode cap there appears to be no continuity (reading on my fluke set up to 20M ohm range.

The circuit diagram shows it as a block. I am assuming its meant to be another coil ?



Might be one for Hugo but what reading would people expect from Red to HV ?

 

[Gary C]

Now thats interesting, with the horizontal deflection coil disconnected, I get HV and vertical scan

Obviously with these in circuit its preventing horizontal getting to the flyback



Coils check out at 0.6 ohm, so looking at C26, R46 & L2.

 

[Gary C]

The drawing misses out inductor L3 !, it runs from P2-1 to P2-3 ?

Took it out and its a coil of very chunky wire with almost negligible DC resistance. Soldered it back in and the screen is working.

It is singing a bit though.

 

[Al Kossow]

L3 was removed at ref F of the board
see http://bitsavers.org/pdf/apple/lisa/hardware/Lisa_Video

 

[Gary C]

Cheers.

Not sure why its now working but it 'might' have been a bad joint.