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Tek Scope Attenuator Deep Dive
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- čas přidán 2. 09. 2021
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A many viewer requested video this is a deeper look at the attenuator section of a 465B scope. Hopefully this will demystify what goes on in the front end when turning the knobs on the front panel.
** Repair exposes the Tech to mains electric and should only be done by trained personal. Errors can be fatal. **
Hi Zen, oh this brings back memories! When I got my first 7000 series scope so many decades ago, it was one that I could afford.. it needed some help. The vertical plug in was a mess. I had to adjust trim caps to get it to have square wave on every position. I learned instantly that settings were interactive, and without a manual, it took a few evenings... That plug-in is still working, now almost 4 decades later. I later got a manual for it and followed the procedures to re-cal.. I had it mighty close the first time, more dumb luck than skill.. and I did it without an extender.. what a pain, but also, what an education.
Indeed I fell down that rabbit hole with a 485 so I know the feeling.
I just found your channel, really great content! I’m looking forward to your 485 videos. I’ll be sure to become a patreon.
Glad you found it and welcome! There is a lot more on the way.
Really interesting! Thanks for showing how the drum switches work. You might try a small amount of silicon grease on the drum detent mechanism, it should be safe for all plastics. Fluorosilicon grease is another possibility, however it is expensive.
Indeed, some came from the factory with a white grease on them. But it has LONG dried up by now. Just need to be careful not getting any on the switch contacts.
I recently got a 465B. These videos are really helpful. My channel 1 is having problems whenever the 4x attenuator is selected. I tried cleaning the pins and contacts with alcohol and q tips but it is still flaky. I may try the paper method and some D5. If I adjust the 4x around sometimes it starts working but turning the barrel causes it to be flaky again. Is something still dirty with the 4x? Is there something in the attenuator that can be adjusted? Is it possible the joints where the pins go in the board need to be resoldered? Also what are you using to clean the switches? I assume some type of spray that you can squirt inside them from a distance. Thanks.
I have the exact same issue with the 7A26 plugins I have to go back in and clean them again but this time I am going to do it my way. When Tek created the service manuals they could not have dreamed of a 75 year service life. What seems to be working so far is straight D100 red NOT in the spray can. I disassemble the attenuator and put a as small a drop as possible on the finger switch there are some very sensitive materials that these are made out of and in this case less is more. I have also needed to clean the pins and sockets for the plastic blocks. Also check the resisters they are small 1/8 watt resisters in there. I have a 7a26 where one of the range resisters is cracked in half. This has gone back in line for the to be bench to be fixed.
@@ZenwizardStudios I am going to take my DMM and measure each attenuators resistance. Then with just the 4x installed check for good continuity on the board when the 4x is selected. Have you ever had to resolder the bottom of the board where the two middle pins are seated? Can the individual attenuators be opened up and maintained? Are those two little black trimmers in them adjustable? I imagine I shouldn't touch them.
@@ZenwizardStudios I believe I know what the problem is now. I think one of the middle pin sockets on the board for the 4x is cracked. Looking at the 6 pin sockets they are little dark dots where the pin slides in. Except for one that looks like a dot with a dark line extending from the center. This might explain why it works when I adjust how it sits and then goes bad when I move the cam. I think I need to learn to live with not using the 4x (20mV, .2V and 2V) on this channel. That or replace the attenuator board. No fun. I will see how i can get by for now. I am going to focus on cleaning switches and maybe doing some adjusting. Thanks for your videos and your help.
The socket being cracked would be repairable. Those sockets are soldered in to the attenuator board so they can be removed. it could also be a bad solder joint. Soldering on the ceramic however requires care and the correct iron. Correct Iron being something with good temperature regulation and high heat capacity. The ceramic PCB will take a LOT of heat from the iron to solder but it can also be cracked with to much heat.
@@ZenwizardStudios how about a video on replacing the sockets on the attenuator board? 😀 Seems like delicate work. Worried I would destroy the whole channel.