Mercurial > whatever / changeset

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+++ b/content/TeK2445.rst	Thu Mar 10 22:00:19 2016 +0100
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+==================================
+ Tektronics 2445 scope PSU repair
+==================================
+
+:Author: David Douard
+:Date: 2016-03-06
+:Category: Electronics
+:Tags: Tektronics, 2445, analog scope, repair, test equipment
+
+I've recently took my good old Tek 2445 scope from the cellar
+(along with my {tag}HP8904A signal generator), and it showed signs of
+tired PSU: unstable display, noise, then the typical noise of a
+capacitor failure.
+
+Here is the beast:
+
+.. image:: {filename}images/tek2445/tek2445.jpg
+   :alt: My old Tektronics 2445 scope
+      
+And some pictures of its womb:
+
+.. image:: {filename}images/tek2445/tek2445_A1.jpg
+   :alt: The main analog board.
+	   
+.. image:: {filename}images/tek2445/tek2445_top.jpg
+   :alt: Top view of the scope.
+
+The PSU consists in two PCBs coupled with long jumpers. It's not very
+difficult to disassemble them but not that straighforard either. I've
+seen easier test equipments to take apart.
+
+Whatever, its problem was a classic failure of several X2 and Y
+capacitors on the regulator board (A2):
+
+.. image:: {filename}images/tek2445/PSU_A2.png
+   :alt: The regulator board os the PSU.
+
+.. image:: {filename}images/tek2445/board_a2.jpg
+   :alt: The regulator board os the PSU.
+	 
+.. image:: {filename}images/tek2445/board_a2_C1018.jpg
+   :alt: Dead C1018 capacitor.
+	 
+
+and the inverter board (A3), mainly C1020, C1051 and C1052:
+
+.. image:: {filename}images/tek2445/PSU_A3.png
+   :alt: The inverter board of the PSU.
+
+	 
+For now, I've replaced them with parts from old switching power
+supplies (from old Dell and IBM computers), but I'd rather replace
+them with brand new components. I also still have some small display
+instabilities, which I need to investigate a bit more. I'll probably
+replace most of the electrolytics caps on the PSU so that I won't have
+to repair again any time soon (famous last words).
+
+

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