Analog Scope Traces appear for a short while and then fades out - Page 1
Forum section: electronics / beginners

author: T4P
author_rank: Super Contributor
timestamp: December 07, 2012, 03:58:52 pm
content: The traces appear once in a moonlight and when they do ... fades out slowly, what could be the problem?

author: w2aew
author_rank: Super Contributor
timestamp: December 07, 2012, 04:44:05 pm
content: We'll need a lot more information from you. What kind of scope? Model number? Did it just start doing this, or has it gotten worse over time? Is it a CRT trace fading away issue, or a triggering problem? Many more details please...

author: T4P
author_rank: Super Contributor
timestamp: December 07, 2012, 05:25:22 pm
content: Er ... It's a LEADER 8040, they are also relabelled as kenwoodsIt just started doing this today and this was the scope that was more perfectly normal and yeah, the CRT trace is fading away only to appear somewhat later after some intensity fiddling then dissapearing again like a damn cometKinda like a TV show that is so poor in reception that it appears once in a fortnight

author: w2aew
author_rank: Super Contributor
timestamp: December 07, 2012, 06:17:25 pm
content: The first place to start is checking supply voltages, particularly those that supply the Z-axis, blanking and intensity circuits. If it is also losing focus as it fades out, it might be the HV section. Be very careful poking around in there, the HV voltages can kill you. If you don't have the right equipment for this, or are unsure what is safe to touch and what is not - leave it to a professional.

author: T4P
author_rank: Super Contributor
timestamp: December 07, 2012, 06:30:45 pm
content: Damn, not gonna touch them. Not sure if i know anyone that knows their way around these scopes

author: M0BSW
author_rank: Frequent Contributor
timestamp: December 07, 2012, 06:45:11 pm
content: Quote from: w2aew on December 07, 2012, 06:17:25 pmThat would be me chicken out !!!, I remember getting a semi shock of a Capacitor on the output side of my Kenwood 820, never ventured into that section again, that bit I leave for a professional Kenwood tech friend of mine, who repairs for a living ,not happy with those large voltages, he stuck a label on the pa out screen " Paul keep out " good enough for me.

author: w2aew
author_rank: Super Contributor
timestamp: December 07, 2012, 07:24:06 pm
content: Quote from: T4P on December 07, 2012, 06:30:45 pmAny decent TV repair tech should be able to diagnose and test this (old school, as in TVs with CRTs...). I would expect that you'd be able to find a schematic online if you search...

author: Mechatrommer
author_rank: Super Contributor
timestamp: December 08, 2012, 11:15:41 am
content: Quote from: T4P on December 07, 2012, 06:30:45 pmso whats the point of this thread?

author: T4P
author_rank: Super Contributor
timestamp: December 08, 2012, 06:28:07 pm
content: Just wanna know what's wrong with my scope, if it's the HV i'm not touching it. Not that i have much experience unless i'm wearing my surgical gloves

author: M0BSW
author_rank: Frequent Contributor
timestamp: December 08, 2012, 07:07:51 pm
content: Quote from: Mechatrommer on December 08, 2012, 11:15:41 amHe wants to find how not to die, which seems a good idea to me, I wouldn't touch the HV either, I'm to young to die