465b manual oscilloscope service tektronix

It's easy to damage the main board pulling out caps or bridges, so have the proper equipment and exercise care. The caps have 3 ground pins and one center pin. Quote from: PaulAm on January 30, , am. NZ Siglent Distributor. Often one can work around it and for other than a complete disassemble there is little need to disconnect it. IF you do, an earthed screwdriver to chassis can be carefully slipped under the grommet where it connects to the CRT to discharge it. Quote from: tjg79 on January 30, , am.

Quote from: tautech on January 30, , am. Quote from: NilByMouth on January 30, , am. If you run the scope in a darkened room with the cabinet off, you might be able to see the filament glow on the crt. If you have to check it, you need to pull the socket off the tube and check the pins. No glow doesn't mean the crt is bad, the HV supply which also provides the heater supply might be dead.

CRTs do go bad, but a bad transistor in the HV supply is more likely. Before doing a wholesale rework, I'd get it at least partially working first, then do things in stages.

Much easier to catch a mistake that way. If you do need measurements from a type CRT tube, I happen to have one that I know is good sitting on a shelf. The IPA is a universal cleaner for these scopes and the brushes will help you get into hard to reach places. IPA soaked printer paper is still the preferred method for cleaning gold finger contacts, but you will need to disassemble the scope almost entirely to get to them all. I like to put a tiny amount of deoxit gold on the contacts to ensure good conduction in the future, but plenty of people choose not to do so.

As for stuck x10 switch or any like it, shoot some deoxit d5, IPA, or contact cleaner into the switch and operate it multiple times. I've also had pots stick before, but not on any scopes - mostly the older AB style ones on square wave gens and similar. I just turned them shaft up, put a few drops of deoxit on the shaft and let it soak in, then operated it a bunch until it loosened. Turn the holdoff pot all the way CCW and leave it for now, you don't need it.

Also, don't bother with cosmetic replacements like plastic knobs until you get the circuitry figured out and working. As for tantalum caps..

I bought quite a pile of them and usually just replace them regardless. There's one guy that started a repair a bit ago and chose to replace all the radial tantalums with Nichicon PW series. With that setup, higher uF caps such as PSU caps will be hard to distinguish as being bad until you get them out of circuit and test them at higher voltages, but it's a great method for testing the tantalums and other small caps above 1uf and below uf or so. Quote from: Addicted2AnalogTek on January 31, , am.

Quote from: tjg79 on January 31, , pm. The two pins that connect to the rear-most part of the CRT internals are the two directly below the index pin, and it measures 12 ohms across them. Before you get too far into things, it would help immensely for you to read the "Theory of Operation" section of the manual and reference the schematics in the process.

Take your time doing so This is the advice I was given and didn't follow which would have saved me a lot of time and trouble.

Hi The filament can fail in two ways. One is to go open circuit. Notify me of new comments via email. I have read and agree to the terms and conditions. By submitting a comment, you are declaring that you agree with these rules: Although the administrator will attempt to moderate comments, it is impossible for every comment to have been moderated at any given time.

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These terms and conditions are subject to change at any time and without notice. You can see some Hz ripple on it at some trace speeds so I suspect caps are shot.

Not too bad yet however so will leisurely replace them. How do I check for double peaking. Quote from: bd on October 24, , am. Thanks for the explanation. I assume the best configuration to test this should be X-Y mode, dot at center with astigmatism, focus and "working brightness" set for best shape?

Quote from: bd on October 24, , pm. Quote from: David Hess on October 24, , pm. Further to the post by David Hess about double peaks, reading through the manual for my HP scope I came across the following extract "Common CRT problems consists of open filaments, grid-cathode shorts uncontrollable beam , and "hollow cathodes", sometimes referred to as "doublepeaking".

Hollow cathodes can be detected by increasing intensity. As the intensity knob is rotated clockwise, the beam will get brighter, up to a point; beyond this point it will decrease in brilliance and may defocus. Quote from: Specmaster on October 24, , pm.

However they both defocus. You can control that with the focus control. I think all CRO's will defocus if you turn the intensity up to high, besides who would want to it adds to the screen burn. You need to at very high sweep speeds and that's it. Quote from: bd on October 25, , am. The following users thanked this post: JoeO.

Thanks for the tip - will look at that. I suspect there are a few problems with the B like this that need resolving. I'm going for an all out tantalum capacitor replacement first as there are several issue so far across two scopes which were solely down to the things. Ok tants done. Trace very sharp now. Also fixed the channel selector switches which are perfect after some contact cleaner has been applied. It seems odd to me that the solid tantalum capacitors would fail in a way that yielded high noise do to poor decoupling without shorting.

Changing them without evidence of failure would not have been my first suggestion. Usually all that is required for the big pushbutton switches Tektronix used is contact cleaner and lubrication. They are a wiping type of switch so be sure to lubricate them as well or the switch contacts will destroy themselves.

The green ones seem to crack slightly I found and go open or intermittent as well. If you wiggle them all a little bit, if the trace changes, so you just replace those ones. I've never bothered with lubrication myself. I have had Philips switches, which are the same type, live for a decade or more after just cleaning. In fact I sold the thing in and it's still going strong apparently PM Anyway it's done now and is fully working.

Vertical and horizontal cal and compensation is pretty much spot on so don't need to do anything there. All inputs, outputs, switches and functions are working too. Final outcome picture trace is pin sharp - just looks crap because of the phone camera. Lucky for me that nomad86 had the exact same problem and posted about it.

I'm wondering how much of a pain it is to replace all the tantalums in these things. But I did notice a lack of razor sharpness after getting it up. Mine doesn't seem to have any double peaks and has a constantly increasing brightness, so I guess the crt isn't weak. That is good stuff to know.