Hi,

the first anode (EHT) of my old 475 scope is arcing, either under the cap or to chassis. How do I get to it? (yes I have already got the outer casing off) Is it already a boat anchor?
Allan

On 7/4/2013 2:03 AM, Allan Mac wrote:

Hi,

the first anode (EHT) of my old 475 scope is arcing, either under the cap or to chassis. How do I get to it? (yes I have already got the outer casing off) Is it already a boat anchor?
Allan

is the display shrunk?
One failure mode is that the HV bleeder resistor goes open.
High voltage goes up.
Display shrinks depending on intensity level.

Allan Mac wrote:

Hi,

the first anode (EHT) of my old 475 scope is arcing, either under the cap or to chassis. How do I get to it? (yes I have already got the outer casing off) Is it already a boat anchor?
Allan


Over 1000 members in this group to ask:

http://tech.groups.yahoo.com/group/TekScopes/

A lot of former Tek employees, knowledge & spare parts info.


You can download the manual he
http://w140.com/tekwiki/wiki/475

On Thursday, 4 July 2013 13:41:51 UTC+1, Michael Terrell wrote:
Allan Mac wrote:



Hi,



the first anode (EHT) of my old 475 scope is arcing, either under the cap or to chassis. How do I get to it? (yes I have already got the outer casing off) Is it already a boat anchor?

Allan





Over 1000 members in this group to ask:



http://tech.groups.yahoo.com/group/TekScopes/



A lot of former Tek employees, knowledge & spare parts info.





You can download the manual he

http://w140.com/tekwiki/wiki/475

Thanks for that. Been smelling ozone for a while, now nasty fizz from 1st anode area but can't see anything due to protective can. Don't want to leave it on long enough to look for display, was working ok. Have manual, no help.

Cheers Allan

"Allan Mac" wrote in message
...

Hi,

the first anode (EHT) of my old 475 scope is arcing, either under the cap
or to chassis. How do I get to it? (yes I have already got the outer
casing off) Is it already a boat anchor?
Allan

Grab a copy of the service manual (google) and read up on removing the CRT.
There is no removable HV PDA cap. The HV lead is soldered to an electrode
and potted in RTV. The 475 is a very fine 200 MHz scope and worth saving.

tm

"Allan Mac"


the first anode (EHT) of my old 475 scope is arcing,
either under the cap or to chassis. How do I get to it?
(yes I have already got the outer casing off) Is it
already a boat anchor?


** When ( not if ) you fix it, treat yourself to one of these:

http://www.dutchtronix.com/ScopeClockH3-1-Enhanced.htm

Amaze your geek friends for only US$30 or so.

https://www.sparkfun.com/products/9306


..... Phil

"** When ( not if ) you fix it, treat yourself to one of these:

http://www.dutchtronix.com/ScopeClockH3-1-Enhanced.htm
"

I don't see a Z axis output on that. What does it do, just greatly exceed the writing speed of the scope ?

On Sat, 6 Jul 2013 19:19:05 -0700 (PDT), wrote:

"** When ( not if ) you fix it, treat yourself to one of these:

http://www.dutchtronix.com/ScopeClockH3-1-Enhanced.htm

I don't see a Z axis output on that. What does it do, just greatly exceed the writing speed of the scope ?

If you look at the schematic at:
http://www.sparkfun.com/datasheets/Widgets/o-clock-v12.pdf
you'll find JP2, which has ZLINE and ZINV pins.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

On Thursday, 4 July 2013 10:03:16 UTC+1, Allan Mac wrote:
Hi,



the first anode (EHT) of my old 475 scope is arcing, either under the cap or to chassis. How do I get to it? (yes I have already got the outer casing off) Is it already a boat anchor?

Allan

Finally got around to tackling this. Found old RTV hard and conductive at anode connection. Removed, cleaned and replaced. Good fix. Many thanks for help.

Allan

Well since nobody else has the decency, thanx for letting us know. Alot of people get stuff fixed only to reemerge a year later with another problem.

wrote:

Well since nobody else has the decency, thanx for letting us know. A lot of people get stuff fixed only to reemerge a year later with another problem.


What do you expect from a 40 year old scope? My 475 manual is
copyright 1973. Like all electronics: caps fail, plastics disintegrate
and components age. I currently have a Tektronix 324, a 453A, two 2465
and a 2465A that need routine maintenance. I had to spend almost $100
for the six missing knobs & three broken shaft extenders for the three
265 series scopes.

I have a 7603 sitting in my truck that I bought to convert into a
test bed for repair plug-ins. It came with a 7D01 logic analyzer plug-in
and the DF1 Display Formatter. I have to make room on the bench before
I can even get it into the shop.

I also have a pile of 1720, 1730 and 1730D TV scopes that need work.
I need to get busy before none of them work.


I've never owned a used scope that didn't need some work. My first
was given to me with a shorted power transformer. The next had open
resistors in the intensity & focus chain.

--
Anyone wanting to run for any political office in the US should have to
have a DD214, and a honorable discharge.

Well I haven't had much luck with them lately. When my 7603 was running there were scads of them on eBay and everywhere for less than a hundred bucks, notny more.

Anyway, I dunno about requiring a DD214 to hold political office, but I do tnink they should have had at least one honest job in their life. Youknow what I mena by honest job right ? Well they don't.

wrote:

Well I haven't had much luck with them lately. When my 7603 was running there were scads of them on eBay and everywhere for less than a hundred bucks, not any more.


There have been at least three for $25 since this post that didn't
get any bids. I bought a 7603 With 7A18, 7A26 &7B70 plug ins for $25
during that time.

--
Anyone wanting to run for any political office in the US should have to
have a DD214, and a honorable discharge.