N8YX
03-30-2013, 08:45 AM
Had a Tek 7603 go funky on me a couple weeks ago. For those unfamiliar with the series, they had an on-screen character generator option which annunciates range and mode selections for the numerous plugins which work with the instrument.
Except these characters - along with the horizontal trace itself - caught a case of the jitters on powerup. The instrument was working fine previously.
Playing swaptronics with a good display generator board showed the problem was still there. Off to check the power supply voltages. All looked good except for the -15V line; it was showing -12.7V.
Hmmmm.
Scoping things out (with a working scope) showed a nice half sine wave on the -15V rail. Identifying the bad filter capacitor was easy. Getting the friggin' PSU out of the scope then getting the friggin' cap out of the PSU itself was another matter entirely.
Once a replacement was fitted and the PSU assembled, scope fixed. This is the third time (on two instruments) that capacitors have played a role in their malfunctioning. 'crk's scope issues seem to revolve around bad tantalums as well.
Food for thought for those of us with "vintage" test gear.
Except these characters - along with the horizontal trace itself - caught a case of the jitters on powerup. The instrument was working fine previously.
Playing swaptronics with a good display generator board showed the problem was still there. Off to check the power supply voltages. All looked good except for the -15V line; it was showing -12.7V.
Hmmmm.
Scoping things out (with a working scope) showed a nice half sine wave on the -15V rail. Identifying the bad filter capacitor was easy. Getting the friggin' PSU out of the scope then getting the friggin' cap out of the PSU itself was another matter entirely.
Once a replacement was fitted and the PSU assembled, scope fixed. This is the third time (on two instruments) that capacitors have played a role in their malfunctioning. 'crk's scope issues seem to revolve around bad tantalums as well.
Food for thought for those of us with "vintage" test gear.