[Heathkit] HELP! SB-104

[Ronald KA4INM Youvan]

> I have a dear old friend who is having a problem with his SB-104. He can't  
> afford to replace it and I'm trying to help him out. The third digit from the  
> left does not light up. Example:
> 14.X50.2  Other than this, the rig works perfectly. The two top  segments on 
> the X light for about five seconds and then go out. None of the  others light 
> at all. I'm a fair technician, but have no experience with these  type of 
> indicators. He can't find his manual so I'm stuck. I checked each of the  pins for 
> voltage on the rear of the light and compared the readings to the   others. 
> They seem to be OK, but without the manual I'm kind of stuck. Has anyone  had 
> this same problem?

   I don't know the rig, but: Did you mover the display devices around?
Are the IC's socketed, so you can move the display drivers around?
   Nixie tubes have a common anode and 11 (or more) cathodes, the anode
commonly has a large value (47 k Ohms or greater) in series that can
change value (up or dn), measure the voltage on the anode directly,
compare the bad with the others.
   LED's sometimes have a resistor (sometimes in the driver IC) for
every cathode and possibly a similar common resistor, more often to
a "strobe" line from logic that lights one display device at a time,
the output for this device may be pa-poot or a bad connection to
any of the above.
-- 
        73 (= Best Regards) de: Ron ka4inm at tampabay.rr.com
     100% LINUX, since July, 1997   SENT Time and Date are UTC
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