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Title: Leader LBO-518 Scope W/ Y axis drift Post by: KA2PTE on October 19, 2021, 08:05:00 PM Someone donated this to me a while back. The voltage / div controls were noisy and
the trace drifts randomly, so I cleaned up the wafer switches today and the controls are less noisy but theres still drift on both channels. The drift seems worse when you do the mag x10 pull on the knobs, eventually the trace floats all the way off the top of the crt, usually when measuring something. If nothing is measured, and its set to gnd, theres mostly negative drift, moreso if you tufn the knob to lower div settings. I did just scrounge up the manual, any ideas on where to start looking? Title: Re: Leader LBO-518 Scope W/ Y axis drift Post by: KA2PTE on October 20, 2021, 08:34:38 PM Someone linked me to this post:
https://www.electro-tech-online.com/threads/2n30809-dual-fet.104271/?highlight=#post851692 Apparently those FET's are a common problem, then he I guess isolated an issue with a Hybrid encapsulated IC which is likely unobtanium. When the scope is on a short time, the issue is not very prevalent, but seems the longer its on the worse it is so it could be heat related. 2N3809 (Q23a/b) looks like a typo on the drawing (pg 38/39). Not sure if thats a dual FET....symbol looks wrong. Guess I will have to eyball the board and see whats there. Title: Re: Leader LBO-518 Scope W/ Y axis drift Post by: W1RKW on November 04, 2021, 07:15:37 AM Steve, AMfone - Dedicated to Amplitude Modulation on the Amateur Radio Bands
Check your private messages. Bob |