Tektronix 465 Repair (Horz sweep Issues)

First off let me say THANK YOU to all that have joined the lab and helped us get there we are today. Content is based of viewer questions and comments. And will continue to be. In this case this upgrade is so we can do some testing as requested by viewers specifically on 10Mhz references. So as always more is on the way.
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In this video we take a look at another 465 that hit the lab for repair. This one has stopped sweeping as we will see what we can do about it and get this one up and running again for the user.
** Repair exposes the Tech to mains electric and should only be done by trained personnel. Errors can be fatal. **

[@davesdigitaldomain]

would love to see some more calibration videos especially on the 400 series Tektronix scopes. Really enjoy your videos keep them coming.

[@ZenwizardStudios]

I will see what we can make happen!

[@Cristi4n_Ariel]

You know, I don't even own an analog oscilloscope. Today, I just received my new digital oscilloscope (used, from eBay), and I thoroughly enjoyed your video. I might consider getting an analog scope in the future once I have more space in my lab. I'd love to own a piece of history. Thanks for sharing!

[@SirMo]

I have an old Tek 465B in storage I've been wanting to restore for awhile. This was helpful to get me in the mood to tackle this repair. Thanks!

[@jeffreyyoung4104]

Excellent! I love the Tektronix scopes! I would recommend replacing ALL of the electrolytic caps along with the tantalum caps, otherwise you will end up replacing them after other components get damaged! I have many pieces of test equipment, and I have replaced all of the electrolytic, and tantalum caps in a preventative maintenance procedure in all of them. After 36 years in avionics, and seeing the damage the caps do just from leaking the electrolyte on to the PC boards, and having the tracks corrode to the point of needing to be replaced with wires due to the damage caused, it isn't worth ignoring them!

[@nikig0]

Great video and great timing! I am trying to fix my own 465 which seems to have a problem in the horizontal amp. I isolated the problem on this board and I am getting around ~100V on the collector side of Q1282 and Q1286, and ~15V on the collectors on Q1262 and Q1266. According to the schematics it should be 50.2V. I pulled out the transistors and they test fine. I can not locate anything strange visually. Can you drop a hint on what I shoud try? The other voltages seem within specs.

[@goodowl1]

Would you like to calibrate a previously calibrated KS 15750 L-1 Western Electric Tube Tester? Please advise.

[@LutzSchafer]

Thanks for the video. Could you please post a link for the STL for the feet? I would also be interested in front panel knobs on 3d printing.

[@ZenwizardStudios]

Here is several options for the 400 series feet. www.thingiverse.com/search?q=Tektronix+465&page=1

[@LutzSchafer]

@@ZenwizardStudios perfect, thank you so much 😀

[@FireandFrostHVAC]

Good video. I’m just wondering, you mentioned that the unit sat without power for a few days, could high voltage still be sitting in the CRT and could that back feed into any of the boards? I have an elderly Kikusui 40 MHz oscilloscope that I want to service, there’s a lot of noise on the controls so I have to clean them, and I want to check the capacitors for leakage and ESR, but I want to make sure everything is discharged before I get too far into it. Thanks!

[@ZenwizardStudios]

That is a tricky questions and very much depends on the CRT. There are 2 main types of CRT displays electrostatically deflected and magnetically deflected. In electrostatically deflected CRT’s the charge bleeds of rather quickly (Caution is still needed when any cover is removed!). However is magnetically deflected CRT’s they can hold a charge for MONTHS! I go blasted (not badly but enough to hurt) from a computer CRT that had been sitting unpowered in a basement for 3 months. The capacitor that holds the charge in this case is the entire back of the bulb of the tube. This forms an lowish value cap of a few 10’s of pF but then you apply 125Kv to it and it can bite HARD!. The glass of the bulb creates and extremely high quality dielectric that can hold a charge for quite some time. In terms of back feeding in to the circuit usually things will stop at the rectifying diodes and current cant get past them. Some of the CRT rectifying (dc recovery diodes) can have a Vf as high as 150Vdc but this is also for rectifying a 4,000 Vdc supply so some of the “normal numbers" get kind of nuts.

[@FireandFrostHVAC]

@@ZenwizardStudios thank you for the advice.

[@pa1wbu]

125 kV would be a bit over the top (...) for a computer CRT. 😋

[@jonka1]

@@pa1wbu suggest there should be a point between 2&5

[@wovada]

And I have a Russian oscilloscope S1 - 73, I also really like it. My oscilloscope has a 27 Volt battery power, like the on-board power supply on airplanes.

[@t1d100]

👍

[@NicksStuff]

I could not find a series on a full repair of a 465 (non-B). Have you done one?

[@ZenwizardStudios]

I should be some 465 content on the channel but I am not sure if I have done a full calibration and alignment video yet. I think in this new batch of equipment I got for the repair que there are some non B 465's. If i recall correctly the alignment process for the 465 and 465B are very similar.

[@NicksStuff]

@@ZenwizardStudios What about diagnostic and things to check? Like the dozen transistors you have to check first on the 475 you did

[@ZenwizardStudios]

After further investigation it seems I got that wrong on the 475 and have switched stance on that. For the transistors leave them in place until they prove themselves faulty. The reverse diode was because this was a 1.4 Ghz part. For starters on a 465 assume the attenuators will need service and cleaning. (EVERYTHING) I have put on the bench has needed cleaning due to age. Even gold plated they still oxidize and need service. Time base sections seem to be more reliable. Check the power rails for shorts. If no shorts a power up might be attempted if the condition warrants it. After power up check the power rails for correct voltage and ripple. At this point there might even be a trace on the screen sweeping. If there is check for a noisy vertical (expect to find this) try servicing the attenuators in place if possible these can be awful to dig out of the scope). Disturbing the attenuators will then require some alignment as this area is very sensitive to capacitive changes and wave shaping. But if not doing a full alignment check for proper voltage deflection and attenuator function. Check sweep timing this should be mostly working. Most of the sweep issues I have run in to were power supply issues. At this point the scope should be working 90-95% a full alignment will bring out any more related bugs and cross the finish line to 100% but this can require some exotic signals. A 465B is really just a 465 with a MUCH better amplification chain. The 465 struggled to meet its 100Mhz rated bandwidth where the 465B can hot 120 to 150 and was tuned DOWN to 100Mhz at the time of sale.

[@NicksStuff]

@@ZenwizardStudios Thank you! I thought they were built differently, the 465B using many ICs while the 465 was purely transistor-based. But maybe I remember all that wrong.

[@NicksStuff]

@@ZenwizardStudios Thanks!! I thought the B used some ICs (so easier to manufacture, harder to fix) when the normal version was transistor-only. Maybe I misremember

[@georgegardei8074]

Is this the scope I saw at the December meeting? 'vqw

[@ZenwizardStudios]

This IS the scope that was at the December meeting yes.