tektronics 2225 repair attempt (no trace nor beam finder) - Page 1
Forum section: electronics / repair

author: v0ltair3
author_rank: Contributor
timestamp: August 23, 2018, 11:59:48 pm
content: Hi Everyone,I've opened my old tek to replace the vertical adjustment pots after purchasing spare ones from ebay. Now the problem is that after reassembly everything I don't have any trace on the screen. When I've turned it on the first time I had the beam finder for one time only and then no single line trace.When I push the beam finder I can only see a bright glare... on the repair attempt I've removed and reassembly the front board and reassemble everything back again, but clearly I've made some mistake or the scope just got faulty.here's how is right now.https://photos.google.com/share/AF1QipNUlAY8iBQhxMzaC7WR_5lYeOGzbfnmQYqEwLOgGKk7tZCM2oTCqkCTjDuBE83aZg?key=ZnpZVmZ2VmZBUUJrcTFlT083SFBISFNTRUxldldnI'm looking for some support from the community as I am just a noob apprentice on electronics, I'm more of a software guy...

author: lordvader88
author_rank: Frequent Contributor
timestamp: August 24, 2018, 12:24:45 am
content: No idea but maybe something came loose ? Hopefully it's not like some crack in some PCB trace if u took the PCB out.I have a Tek 2215, I'm looking forward to taking it apart, I had it apart once to improv/fix the power switch, but didn't have the time to even look around.

author: v0ltair3
author_rank: Contributor
timestamp: August 24, 2018, 08:33:26 am
content: PS: I've check the PSU output and all voltates match...

author: v0ltair3
author_rank: Contributor
timestamp: August 25, 2018, 09:56:33 pm
content: Ok, so I've spent some time trying to understand where the problem might be (on top of my very limited knowledge) and here what I find.When I start the scope, for a fraction of a second I see a trace (more frequent if I have the beam finder pushed). Does this mean the CRT is still working ?Once the scope is working, if I push the beam finder I see nothing.I was then trying to see if there where some signal in the defl plates and I found that I do have on both horizontal and vertical.I see also that on the ASTIG I do have some signal as well, but still no single sign of trace... to be honest, I do have much knowledge to understand if even I'm going in the right direction.. should I be seeing anything ? or this can simply mean the problem is someplace else ?PS: according to the service manual, the horizontal signal should be between +25v and +63v from the wave forms but I no longer have an oscilloscope to test it ... if so, getting 7.3v only on point 9 means something is wrong already ??Thank in advance for the inputs.

author: particleman
author_rank: Regular Contributor
timestamp: August 25, 2018, 11:21:47 pm
content: Anyone troubleshooting an oscilloscope that does not have this manual is starting off at a severe disadvantage.http://www.sphere.bc.ca/test/tek-parts/troubleshooting-scopes.pdf

author: v0ltair3
author_rank: Contributor
timestamp: August 31, 2018, 11:08:49 am
content: Quote from: particleman on August 25, 2018, 11:21:47 pmThank you particleman, I've read it and is indeed extremely useful...I've read the generic part till the troubleshooting fluxogram (page 20), start -> no display -> beam finder -> no display -> inject -10v -> no display - check power supplyHere I've check the service manual of the scope and I saw that all power distribution links and they are all working fine:now, according to the manual, I'm left with the CRT / Z-Axis but here the manual doesn't provide much information... I'm afraid I could have a broken CRT, but I am not sure how to test it... is there any quick way to be sure the CRT is fine ?Thank you

author: particleman
author_rank: Regular Contributor
timestamp: August 31, 2018, 07:14:57 pm
content: I would say if you get a trace even occasionally then your CRT is fine. I think you are seeing the CRT become bright when pressing the beam find is because the trace is off the screen. If it was working before disassembly and not working after I would check everything thing I did when doing my repair. 9 times out of 10 your new issue will be related to the work you just did.

author: v0ltair3
author_rank: Contributor
timestamp: September 01, 2018, 01:05:10 am
content: Quote from: particleman on August 31, 2018, 07:14:57 pmIt was indeed... one of the flat cables had a broken wire, its working now perfectly with the brand new positioning pots.thank you for the support!