Go Back   Home > Forums > Design & Build > Equipment & Tools

Equipment & Tools From test equipment to hand tools

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 8th October 2010, 07:07 AM   #1
diyAudio Member
 
Join Date: Oct 2009
Default Tektronix 468 horizontal problem in storage mode

Hi there!
Im having some trouble with my Tektronix 468 and I would be very gratefull if you could give me some advice.

In real mode it works perfectly (even the uncal knob and light), but in storage mode it goes crazy.
Here are the symptoms in storage mode:

-The time/div is not correct (it is about 20 times what it should be, so the signal looks 20 times wider)
-The wave displayed is distorted (square wave looks like a rounded trapezoid)
-The display jumps sideways a bit.
-The uncal lamp, when on, is very dark
-The uncal knob when turned on does nothing
-There is a vertical line at the end of the beam with 2 dots on the edges (see pic)

On both input channels the results are the same, and the vertical circuits and trigger circuits are both working fine, so I guess it is something on the top board, the storage part?
Do you have any idea of what this could be?

Pictures taken:

Click the image to open in full size.
Click the image to open in full size.
Click the image to open in full size.
Click the image to open in full size.
  Reply With Quote
Old 18th October 2010, 02:15 PM   #2
macboy is offline macboy  Canada
diyAudio Member
 
Join Date: Oct 2003
Location: Ottawa, Canada
If you don't already have them, you can download the service manuals from
Welcome to EBAMAN
(free, but need to register)
  Reply With Quote
Old 18th October 2010, 11:59 PM   #3
diyAudio Member
 
indianajo's Avatar
 
Join Date: Jan 2010
Location: Jeffersonville, Indiana USA
Default aging 468

Bought a Tek 468 25 years ago at work - thank you Generous Elec. Yours has to be nearly as old and expensive electrolytic capacitors last - - - 20 years. My favorite rant, you should stop thinking, look at the part list, and buy one of everything electrolytic. Discharge caps with resistor , measure below 25 VDC before touching - lethal voltages in there. Change two caps at a time and then test, since you might mess up or the new ones might be unsuitable in some way. If doesn't work as least as well as before the latest caps went in- back up with the old ones and think a bit about the circuit.
If you want it to stay fixed, use caps that are rated 2000 hours or more by the manufacturer. Newark.com or farnell.co.uk have the hours shown in their selector tables for caps. Don't buy sale caps, they are going out of date already.
Left that job 15 years ago, now making do with a 20 MHz B&K non- memory scope. Oh, well, back to reality as the song goes.
__________________
Dynakit ST70, ST120, PAS2,Hammond H182(2 ea),H112,A100,10-82TC,Peavey CS800S,1.3K, SP2-XT's, T-300 HF Proj's, Steinway console, Herald RA88a mixer, Wurlitzer 4500, 4300

Last edited by indianajo; 19th October 2010 at 12:25 AM.
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Itu-r 468 gbmaizol Class D 0 16th August 2010 06:33 AM
PCX1250 2ohm mode Problem ctg353535 Car Audio 1 15th April 2007 02:26 AM
Tektronix 2235 problem Dhul Parts 8 15th January 2007 12:28 AM
Using a spdt switch to select between triode mode and pentode mode on a guitar amp. G Tubes / Valves 19 15th March 2006 09:15 AM
Calculating watt requirements for multi-mode/tri-mode operation? Datoyminaytah Solid State 1 14th August 2004 07:43 AM


New To Site? Need Help?

All times are GMT. The time now is 11:05 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2