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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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#1
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tek 465b scope problem
Hi,
I'm relatively new to electronics... I've got a tek 465b that has been working fine for about 8 months. The other day without any sort of warning the crt failed to come on when I started it. It still triggers, but I see nothing even when I press the beam find button. I also happen to have another 465b from a sour ebay transaction which has no horiz scan. Is it beyond the capability of someone like myself to swap the crt following some careful instructions? I know there are high voltages involved. Is it worth it to have a professional do this or should I just forget about the old scope and consider buying something new? I'm starting to realize that ebay may not be the best place for scopes... Any opinions? Thanks, aaron |
#3
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tek 465b scope problem
In article ,
says... It's probably not a bad CRT but an electronic problem like the HV power supply.. Do you have the service manual? I think I've seen it on eBay for about ten bucks. There is a pretty detailed troubleshooting flowchart for "no visible display". -- Jay Levitt | Wellesley, MA | Hi! Faster: jay at jay dot eff-em | Where are we going? http://www.jay.fm | Why am I in this handbasket? |
#4
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tek 465b scope problem
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#5
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tek 465b scope problem
Hi:
Sorry to hear of your scope trouble ... 1. I got burned 2 for 2 on Ebay scopes 2. I have a Tek 465B and the service manual (I fixed them for a used scope dealer a few years ago). I will gladly assist you (walk you through the major tests, or compare readings from my scope, etc,. No, the CRT is very simple to swap. If you are close to PA/OH I also repair scopes, etc., for a very reasonable fee. RJ |
#6
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tek 465b scope problem
Jim Yanik wrote in message
Did you hear the hiss/crackle of the HV charging the CRT? If not,the HV may have failed. Yes. I also managed to find the manual and am running through the troubleshooting flowchart now. When I flip it around to slide the cover off I hear a nice 'jingle jingle.' I'm sure that is not good. Thanks, aaron |
#7
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tek 465b scope problem
Thanks for the responses!
Here is some more info after doing some tests. All the low-voltages check out (I don't have a hv meter.) When I disconnect the power jumper to the vertical output amp the trace shows with horizontal scan. This rules out a faulty crt. Since I have an identical board I swapped it out with the other and the same thing happens. Furthermore, I discovered that when the top connector to the vertical deflection plates is disconnected the trace also shows. This connector is sitting at +54 while the other is at +16 which seesm to be in violation, but again this happens on both boards. The delay line into the board is at +225mv and -204mv. Thanks, aaron |
#8
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tek 465b scope problem
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#9
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tek 465b scope problem
"Aaron Kentucky" wrote in message Yes. I also managed to find the manual and am running through the troubleshooting flowchart now. When I flip it around to slide the cover off I hear a nice 'jingle jingle.' I'm sure that is not good. Thanks, aaron Yuck, a jingle-jingle often means that a little bit of glass has broken off one of the internal CRT supports. Those glass support rods are under a bit of strain, and it doesnt take much to crack a piece off of them. I've seen this happen a time or two. What happens then is if you tilt the scope the bits of glass eventually put a hole or dent in this fragile little metal screen that acts like a magnifying lens-- then the scope trace goes all fireworksy and the CRT is useless. Really, really cool to play with, better than a lava lamp, but mostly useless as a scope. |
#10
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tek 465b scope problem
(TekMan) wrote in
m: (Aaron Kentucky) wrote in message . com... Thanks for the responses! Here is some more info after doing some tests. All the low-voltages check out (I don't have a hv meter.) When I disconnect the power jumper to the vertical output amp the trace shows with horizontal scan. This rules out a faulty crt. no, it doesn't rule out a defective CRT: It'S still possible you have a problem with the vert. plates because of the "jingle" you mentioned. May be something internal is broken. Just a "could be" , no "must". If he has a H sweep roughly centered in the graticule,then the CRT is probably good.Munge up the deflection plates,and he would not have a on- screen trace,and there'd be glass fragments stuck to the phosphor causing bright or dark spots.If the mesh lens gets distorted,then you can get all sorts of squiggly traces. Since I have an identical board I swapped it out with the other and the same thing happens. Furthermore, I discovered that when the top connector to the vertical deflection plates is disconnected the trace also shows. This connector is sitting at +54 while the other is at +16 which seesm to be in violation, but again this happens on both boards. The delay line into the board is at +225mv and -204mv. Thanks, aaron Looks like you have a problem in the preamp section and or interconection. He could short the delay line pins on the preamp PCB,and if the trace centers,then it's the preamp,if not,the vert output amp.He could short the CRT vertical pins and see if the trace centers,if so,the CRT is OK,and bad V-output amp.That IC may be hard to find. -- Jim Yanik jyanik-at-kua.net |
#11
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tek 465b scope problem
I don't know if anyone is interested or not but i figure this will
still be good for the archives if someone else has the problem in the future. It turned out to be the vertical output amp after all. I tried swapping them again and this time it worked perfectly! I must have made a mistake the first time. Anyway, thank you all who responded to help me out as I'm extremely happy that I got this thing going again (and got use out of the broken 465b that was collecting dust!!) On top of all that I learned a great deal about the workings of my scope. Thanks! aaron |
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