[Test-Equipment] Tektronix 323 'scope

[Bill Abate]

Picked up a 323 scope last month and finally got around to checking it 
out.  If you have not seen one its a cute little field scope that has 
internal NICAD batteries.  Only goes to 4 MHZ but good enough for those 
places you can't drag a 100  MHZ monster.  I thought it was only good 
for parts but to my surprise it does work partially.  The CRT is fine 
and works except for horizontal display.  Traced the problem (at least 
one of them) to the sweep generator.  They used a proprietary tunnel 
diode, Q305, in the circuit.  I have a square wave on one side of a 
differentiating capacitor but nothing on the other side where the diode 
is.  I eliminated other surrounding components as the cause but the 
diode seems OK, resistance wise. 

Goggle tells me that the tunnel diode was a STD930.  Anybody know of a 
source or a substitute?  Anyone have a parts donor they want to part 
with or want to buy mine? :)

Bill, K3PGB