Tektronix 475A restoration - Page 1
Forum section: electronics / projects

author: worsthorse
author_rank: Super Contributor
timestamp: February 19, 2017, 07:40:36 pm
content: I spent yesterday morning at the Salem Hamfair. Back in the corner of the the back building, I found a Tek 475A.Dual trace 250Mhz with two clean traces and the basic functions (that I could test) working. Other than being covered with grime and needing a couple of the back feet replaced, it looked pretty good. The ham selling it said he had another one at home and needed to clean out the shack. He asked $125, about $75 less than the two 465s I saw at other tables. I didn't even bargain lest he change his mind.When I got home, I scanned the forums and found this post, about a 465 restoration...https://www.eevblog.com/forum/projects/tektronix-465-repair-and-restoration/...and I thought, boy that was a nice piece of work. and then,I can do that. Going to post before photos here then start tearing it down. I tracked down the service and calibration manuals and will take care of that after going over the internals, cleaning it up, and see whether everything works.I also picked up a "non-working" Tek CPS250 three output power supply for thirty bucks. Got home changed a couple of blown fuses and now have a much needed lab quality bench power supply. I love ham fleamarkets!

author: james_s
author_rank: Super Contributor
timestamp: February 21, 2017, 08:49:46 pm
content: Nice! I love these old Tek scopes, it's great to see people keeping them going.

author: calexanian
author_rank: Super Contributor
timestamp: February 24, 2017, 02:53:50 am
content: Still perfectly useable, especially for linear circuits.

author: xrunner
author_rank: Super Contributor
timestamp: February 24, 2017, 03:37:05 am
content: Pics!

author: tombi
author_rank: Regular Contributor
timestamp: February 24, 2017, 03:57:23 am
content: Very interested to see how it goes. I wouldn't mind tidying mine up a bit.I fixed a 475 that had quite a number of electronic issues a while back. I did try to remove the panel to do some cleaning etc but found it was really hard to remove nuts off the back of the panel etc. I also ended up damaging one of the fibre glass rods in the process of removing a knob so was shy of going further (I was able to repair it again).This project was pretty much my first foray into electronics after a very long hiatus. Lots of details, errors and stumbles documented here in case this helps (although it probably won't as yours works).http://wahz.blogspot.com.au/p/tektronix-475-restoration.htmlBest place to ask about stuff is the Tektronix yahoo group if you get stuck.Tom

author: tggzzz
author_rank: Super Contributor
timestamp: February 24, 2017, 10:14:57 am
content: Quote from: calexanian on February 24, 2017, 02:53:50 amWhich specifically includes nominally "digital" circuits such as TTL/CMOS/ECL circuits. The only true digital circuits are femtoamp and photon counting applicationsA 475 is much better than, say a DS1054Z when assuring signal integrity, simply because it has a higher bandwidth.

author: worsthorse
author_rank: Super Contributor
timestamp: February 24, 2017, 02:05:58 pm
content: i am traveling right now but will post "before" pics when i get back. i have been searching the web for tear down information... the tek scopes are mechanically complex and i am approaching the cleanup gingerly. i don't want it to end up with bent rods or stripped threads! same goes with calibrating, if it needs to be done. i will try to take photos of the tear down, too.i bought a rigol 1054Z right before i found the 475A. the rigol's advantage is size and features. the tek... bandwidth and familiarity. i will keep both handy, though the reality is i will probably use the rigol more day to day.i seem to be on a vintage equipment kick. i just picked up a working wavetek 11Mc sweep generator. Between that, the nixie tube frequency counter and the 475A, my bench is starting to look a lot like the one I had in 1980.

author: tggzzz
author_rank: Super Contributor
timestamp: February 24, 2017, 02:18:58 pm
content: Quote from: wch on February 24, 2017, 02:05:58 pmIt is axiomatic that all scopes lie, so use both of them on the same circuit. That will help you understandhowthey are lying to you and which bits of information are being "discarded"QuoteBe careful; that way lies GAS, TEA, NTSC, PETA and other problematic behaviour.FFI seehttps://www.eevblog.com/forum/chat/test-equipment-anonymous-%28tea%29-group-therapy-thread/

author: yuzuha
author_rank: Contributor
timestamp: February 25, 2017, 03:51:28 am
content: Quote from: james_s on February 21, 2017, 08:49:46 pmI'm doing my part

author: Unknown
author_rank: Unknown
timestamp: April 23, 2018, 03:48:07 pm
content: Bought a dead (and smoking) 475A for a steal.Changed a toasted tantalum and now have a working scope... Albeit in need of calibrating and a general service.One question.Is it supposed to have a blue trace? (see photo)

author: james_s
author_rank: Super Contributor
timestamp: April 23, 2018, 05:59:37 pm
content: Quote from: Gazucha on April 23, 2018, 03:48:07 pmThat was one of the optional phosphors in many of the Tek scopes, it's faster than the more common bluish green. Quite rare as far as I know, I've never actually seen one in the flesh.

author: oldway
author_rank: Super Contributor
timestamp: April 23, 2018, 06:10:06 pm
content: Blue trace is low decay phosphor...Very good for slow events but a little boring for normal use.

author: james_s
author_rank: Super Contributor
timestamp: April 23, 2018, 06:13:00 pm
content: I guess it depends on which specific blue phosphor it is, there are several. I looked it up and here's a list:http://w140.com/tekwiki/wiki/Phosphor

author: oldway
author_rank: Super Contributor
timestamp: April 23, 2018, 09:22:45 pm
content: Quote from: james_s on April 23, 2018, 06:13:00 pmYes, you are right.....I looked at the technical specifications of the 475 and optional phosphor is P11, not the long decay P7. (standart P31)

author: Unknown
author_rank: Unknown
timestamp: April 25, 2018, 10:57:02 pm
content: Ok. I see.The P11 is for photography.That might explain why there was some camera stuff in the mix with all the cables and accessories.Thank you very much.