Flickering oscilloscope image Tek 454 - Page 1
Forum section: electronics / repair

author: Ferroto
author_rank: Frequent Contributor
timestamp: July 07, 2017, 01:27:40 am
content: I have recently acquired a Tektronix 454 off ebay and I'm having an issue with the trace flickering even if the intensity is turned up to full the flicker is noticeable and if the intensity is about half way the trace can completely disappear and come back. This seems to get worse as the unit warms up. I don't think this is an issue with triggering as the flickering happens even when I turn the tim/div down to 1sec/div the signal will flicker as the trace is going across the screen. There's also an issue with x,y mode where the trace will gradually climb the y axis to the point where the position knob cannot get it back.

author: alm
author_rank: Super Contributor
timestamp: July 07, 2017, 01:48:51 am
content: I would start with measuring the power rails (including the ripple). Pretty sure there are instructions for this in the service manual. Sounds like it might be a dried up electrolytic. Stay away from the high voltage parts unless you have the proper equipment and experience.

author: GreyWoolfe
author_rank: Unknown
timestamp: July 07, 2017, 01:57:28 am
content: I have you beat on download at 65.8 Mbps but you have me beat on upload, only 6.04 Mbps. However, my internet service only costs me $12 USD a month-----after deducting what my company pays me to use my service to do my job.Not bragging or anything

author: welpester
author_rank: Contributor
timestamp: July 07, 2017, 01:34:34 pm
content: PING 16 msDOWNLOAD 194.13 MbpsUPLOAD 19.26 Mbps-welpester

author: lukier
author_rank: Unknown
timestamp: July 07, 2017, 01:54:36 pm
content: What's so special about 38M/24M? I mean nowadays in many places you can get 100M download or even 1G for not that much money.And then one should have 10G ethernet card (that's what I guess limits my speeds at work):

author: Cyberdragon
author_rank: Super Contributor
timestamp: July 08, 2017, 08:59:47 pm
content: PEOPLE, this is a discussion about an oscilloscope, not his forum tag!Might be a loose connection/bad solder joint in the HV circuit. Could also be a bad cap. The deflection issue seems like an intermittant short somewhere (another cap?) since the deflection plates should be floating with no input in XY mode.

author: Armadillo
author_rank: Super Contributor
timestamp: July 08, 2017, 09:17:47 pm
content: Quote from: Ferroto on July 07, 2017, 01:27:40 amTry cleaning those switches and knobs selection contacts with deoxit or contact cleaner.

author: Ferroto
author_rank: Frequent Contributor
timestamp: July 09, 2017, 02:33:35 am
content: I checked the low voltage regulator board and all the voltage lines were dead on except for the +12v line needed a minor tweak. I also replaced two wax capacitors on the z-axis amplifier board (.22 and .1 uF) and checked all the test points as per the service manual.The only thing I haven't checked is the -1960 volt HV test point because I don't have a HV probe Icurrently got one orderedbut it could take a month to get here.In the mean time I'll check for more wax capacitors and pick up some contact cleaner.