Call Search
     

New to Ham Radio?
My Profile

Community
Articles
Forums
News
Reviews
Friends Remembered
Strays
Survey Question

Operating
Contesting
DX Cluster Spots
Propagation

Resources
Calendar
Classifieds
Ham Exams
Ham Links
List Archives
News Articles
Product Reviews
QSL Managers

Site Info
eHam Help (FAQ)
Support the site
The eHam Team
Advertising Info
Vision Statement
About eHam.net

   Home   Help Search  
Pages: [1]   Go Down
  Print  
Author Topic: Tektronix 466  (Read 2795 times)
AD7JL
Member

Posts: 9




Ignore
« on: July 29, 2012, 07:03:25 PM »

I have a Tek 466 oscilloscope that is in need of repair. There is no high voltage to the CRT. Looking closer I noticed that the high voltage oscillator circuit that drives the CRT was not oscillating. I was wondering if anyone has seen this problem before and might know where I should start to look. So far I have checked a lot of resistors and transistors in the circuit and they all seem good.
Logged
KE3WD
Member

Posts: 5689




Ignore
« Reply #1 on: July 30, 2012, 01:56:16 PM »

Old Teks are known for coughing out a Bad Cap...

Check every cap that has anything to do with the oscillator, starting with the oscillator's timing cap. 

Don't overlook power supply filter caps as well, AC ripple on the B+ to the oscillator can also stop the show. 


73
Logged
AC5UP
Member

Posts: 3893




Ignore
« Reply #2 on: July 30, 2012, 04:33:35 PM »

On a related note, several years ago my Tek 475 puked & died. Power switch lit up the graticule lights but no sweep, no trace, no go.

I'm still amazed that I nailed the fault with near-zero troubleshooting, but if you know your way around a Tek power supply you know how fond they are of a +150 VDC 'master' regulated voltage that serves as a reference for all other regulated voltages. In this case the +150 was around +130 and the power supply went south because of it. The filter electrolytic was a two-screw computer type and easy to pull so it came out, was checked, and my cap meter gave me exactly * zero * microfarads.

At first I thought the tester had gone toes up but it wasn't kidding... The can was wide open and with no peak charge action in the ripple filter there was no way to regulate +150 VDC from a +130 VDC source.

The next amazing part to the story is that I had a brand new exact replacement part on hand. I tend to hoard things like caps and this was pure luck. 1,000 uf at 250 VDC and skinny. Popped the new cap in the 'scope and it charged up to something like +165 VDC. All the regulated voltages came back spot on the mark and the 'scope was fixed in something like 20 minutes.
Logged

Never change a password on a Friday                
N4NYY
Member

Posts: 4799




Ignore
« Reply #3 on: July 31, 2012, 05:55:30 AM »

I have a Tek from the 1980's, and the beam focus went out and was thick as hell. I joined their Yahoo group, and they told me to replace 6 carbon comp resistors that are notorious for for failing and causing that problem. Sure enough, several of them were over 2 Mohms when they should have been like 470K.

Parts cost less than a $1. However, I needed to buy 2 different torx drivers to get access to the resistors. $20 for the 2 sets.
Logged
Pages: [1]   Go Up
  Print  
 
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.11 | SMF © 2006-2009, Simple Machines LLC Valid XHTML 1.0! Valid CSS!