My Tektronix 465 - Page 1
Forum section: electronics / repair

author: SympaTek
author_rank: Newbie
timestamp: March 24, 2018, 06:01:35 pm
content: Hello,I have a Tektronix 465 oscilloscope, it does not work anymore. It no longer displays any signal, nothing on the screen. I checked the reference voltages and they are all good. The fuse is good. I would like to know if there are recurring causes to this problem. If anyone has ever encountered this problem or are familiar with these oscilloscope.Thank you for your help.

author: anachrocomputer
author_rank: Regular Contributor
timestamp: March 24, 2018, 09:35:25 pm
content: When the scope is on, does the CRT heater light up?

author: tggzzz
author_rank: Super Contributor
timestamp: March 24, 2018, 09:42:49 pm
content: There are many possibilities.Follow the faultfinding guide in the manual; that should help you isolate what is working - and isn't.

author: PaulAm
author_rank: Frequent Contributor
timestamp: March 25, 2018, 12:52:11 am
content: Did you check the LV supplies for ripple? A very common fault is the filter caps dry out or the bridge rectifiers go bad which causes all kind of weird symptoms.If you have a decent HV probe, check the HV (if you do not have a decent HV probe, do NOT check it directly).Those would be my quick checks, but otherwise follow tggzzz's advice; you need to find out what isn't working so you can concentrate on that area and you should approach that in a systematic manner.

author: rhb
author_rank: Super Contributor
timestamp: March 25, 2018, 04:23:16 pm
content: With the system under power and the covers on, whack both hands against opposite sides of the unit and watch for a flicker on the CRT.Then take the covers off. Get a 12-14" length of wooden broomhandle or similar. Whack the corners of the frame while again watching for signs of life. Make sure you just hit the frame. And stay away from the HV section until you've read the manual. If you're not familiar with working around HV read up on it before starting. Finding someone dead tends to ruin everyone's day.I learned this from a retired Tek field service tech when I took my 465 to him for advice. I did the actual repairs myself, but I wanted expert diagnosis before I started. The instrument sort of worked when I took it to him. His diagnosis was bad connections.Old gear like the 465 will have numerous issues with cracked solder joints and corroded connectors. My 465 is socketed transistors through out. So you have to wiggle all the transistors in their sockets to scrape off the oxidation.Once you have checked the PS, check the calibrator output. If it works you've got a convenient signal source for checking the vertical section. Then start checking the input attenuators and the sweep generators. Proceed from there. Do NOT spray tuner cleaner on the attenuator switches. Very bad for the capacitors. Mentioned in the manual. Close switch contacts on a piece of bond paper and pull it out to clean the contacts.

author: Chris56000
author_rank: Frequent Contributor
timestamp: March 25, 2018, 08:51:19 pm
content: Hi!I would be very, vary careful about whacking old CRT–based Tek and Hewlett–Packard instruments with the palms of your hands, etc., as the internal structures of the CRTs weren't always as robustly made as they needed to be, and it's easy to cause irreparable damage to the deflection–plate structures that would show up as a distorted trace that cannot be straightened of centred correctly!Begin with the fault–finding flowchart in the manual, concentrating on the +55V and +110V supplies first, as all the remaining supplies are referenced from the +55V!Next, once you've got the +55V and +110V H.T. lines o.k., check the lower–voltage supplies for the intermediate and earlier stages, then look to see if the CRT heaters are alight – these are lit up from a highly insulated separate winding of the EHT transformer!Only once you've checked the +55V, +110V and lower–voltage lines and and confirmed ALL are present and correct do you need to worry about the CRT supplies!(We can advise on these later)Chris WilliamsPS!If you've not got an original paper manual and have to rely on PDF copies, have a good look through your PDF to make sure you have all the schematic sheets and layouts, there are too many doing the rounds with parts of the Vertical/Trigger or the Horizontal Amplifier diagram sections missing – please let us know if your manual isn't complete!

author: rhb
author_rank: Super Contributor
timestamp: March 26, 2018, 12:31:14 am
content: Quote from: Chris56000 on March 25, 2018, 08:51:19 pmAny CRT that would be damaged by what I watched the Tek service man do is already toast. The impact is about on a par with dropping one end of the scope a couple of inches onto a desk. My 465 looks as if it spent a lot of time in the back of a seismic processing truck. It's pretty battered. So long as it only contacts the frame, you can't possibly hurt the CRT with a piece of broom handle. The hand clap is just that, a hand clap. The Tek repairman had a very well used piece of 2x2. I suggested the broom handle as a way of limiting the impact without being physically present to demonstrate.A blow to the case and frame of any scope sufficient to damage the CRT would irreparable harm to the case. The CRTs would not survive shipment from the factory if they were as fragile as you are suggesting. There might have been some very high end laboratory scopes which were as fragile as you suggest, but the 465 was the work horse of the field service techs. I'm sure a lot of 465s standing on the back bumpers got knocked over. At the first major oil company I worked for there were three standing on the floor next to the where we submitted punch cards unless they were out on a call. I never saw one get knocked over, but I'm sure they did.

author: bd139
author_rank: Super Contributor
timestamp: March 26, 2018, 08:54:02 am
content: Check the fuse on the main board first. This is the main HT sudden failure outcome on these I have found so it's worth checking first. There's a capacitor which at this age and type seems to go short which causes it to blow. This one:If that fuse is popped, check the big blue tantalum capacitor at the bottom left side of the board under the shield with a DMM in ohms. If it's reading low ohms snip it out, then replace with a 100uF 25/35v electrolytic cap and see if it works. This is the one:Don't go whacking it with a broom handle. That's a silly idea.If it still doesn't work, hit the manual as tggzzz says. It's pretty good.

author: Gyro
author_rank: Super Contributor
timestamp: March 26, 2018, 12:31:07 pm
content: Quote from: rhb on March 26, 2018, 12:31:14 amI remember receiving a Tek scope, a T912, that had been used in a mobile application (clamping frame on the bottom). After much debugging of a brightness problem, I spotted that the grid contact weld had failed. There's nothing more frustrating than seeing a tiny gap of a fraction of a mm that's totally out of reach in a vacuum!

author: bd139
author_rank: Super Contributor
timestamp: March 26, 2018, 12:36:10 pm
content: I would be so pissed if I saw that on a tube. Have been lucky so far.

author: tggzzz
author_rank: Super Contributor
timestamp: March 26, 2018, 01:00:35 pm
content: Quote from: Gyro on March 26, 2018, 12:31:07 pmYes, I know the feeling, and there was only one thing to do - and it definitely illustrates TEA. Seehttps://entertaininghacks.wordpress.com/2016/03/09/rescuing-a-broken-tektronix-465-crt/

author: bd139
author_rank: Super Contributor
timestamp: March 26, 2018, 01:16:22 pm
content: I've seen that before. Had no idea it was your web siteNice ornament out of it at least!

author: Gyro
author_rank: Super Contributor
timestamp: March 26, 2018, 01:36:53 pm
content: Nice idea (I have X-Ray tubes on the mantelpiece!). The T912 is an analogue storage tube too, so flood guns.

author: bd139
author_rank: Super Contributor
timestamp: March 26, 2018, 01:46:49 pm
content: Oh very nice, especially with the lightingBeats lego, two coffee cups and colouring pens which is my current mantle piece

author: Gyro
author_rank: Super Contributor
timestamp: March 26, 2018, 02:55:21 pm
content: Haha, thanks. That's real filament lighting too, none of your tacky LED nonsense.They're plain tungsten filaments, well under-run.Sorry for the tread diversion.

author: oventech
author_rank: Contributor
timestamp: March 27, 2018, 01:14:10 am
content: Found the Tek Wiki site on the 465. Good for manuals,http://w140.com/tekwiki/wiki/465Saw some others, will put them up. have a 475 to work on.