Tektronix 2445a screen problem

[casteliano]

I recently bought this scope as not working a sure enough the screen was blank on power up, however after adjusting grid bias a bright dot and very small text? could be seen. Everything elese appears to be working correctly. Any help would be appreciated. 

[singapol]

Welcome,
                 2445A may need capacitor replacement but note there are some surfacemount electrolytic caps,
see link below.

http://bradthx.blogspot.sg/2014/01/tektronix-2445b-capacitor-replacement.html

May be do a scope self test by reading user manual and finally if need repair ..the service manual.

Troublshooting oscilloscope:
www.sphere.bc.ca/test/tek-parts/troubleshooting-scopes.pdf


2445A user manual:
http://www-3.unipv.it/lde/strumentazione_strum_banco/oscilloscopio.pdf

2445A service manual : 85Mb file:330pg.
http://elektrotanya.com/tektronix_2445a_2455a_sm.pdf/download.html

[Skimask]

Do a search for the 2445 (2465, 2445a, 2445b, 2465a, 2465b, and so on), specifically look at U800 and the cooling fan.  Fan goes out, U800 overheats, only half the screen works.  There's procedures out there for figuring out if U800 is bad.  Not a difficult replacement by any stretch.  Harder to find the IC.  Mine cost somewhere around $150 if I remember right.  I also junked the stock fan and replaced it with a suitable sized squirrel cage fan in almost the same mounting holes pulling off the +15v rail.  In addition, just to make sure U800 wouldn't overheat and fry again, I grab a couple of old 40mm PC cooling fans and a cheap 12v wall wart and velcro'd the whole works to the side of the case kinda pushing air in the general direction of U800.

[casteliano]

Thanks! After replacing caps in the power supply the scope works great! Another great score from ebay.