Tektronix 2215 60 MHz oscilloscope repair

Tektronix 2215 - 60 MHz oscilloscope repair

Tektronix 2215 - 60 MHz oscilloscope repair

Tektronix 2215

60 MHz oscilloscope

With inputs grounded
both channels displayed a small
amount of ripple.

The lower trace is from a signal
around 46 KHz.
The diagnosis is switching power
supply ripple.

Partial schematic Diagram

I used the scope to look at its own
power supplies.

Excessive ripple was found
on the -8.6 volt power supply

Capacitor C976 (red circle)
was found to have excessive ESR

C976

There are several 840 uF 12 volt capacitors
in the various power supplies.
all are either Sangamo or Mallory.

Capacitor (C976) value as measured is well
above stated value of 840 uF,

All of the 840 uF capacitors measured well beyond
printed value. 1100 - 1300 uF.
Regardless of brand name.
A second capacitor checker confirmed the values.

ESR meassured at 1.9 ohms.

Normal ESR for a 12 volt capacitor around 840 uF is .1 ohms.

ESR is nearly 20 times normal value.

Replacing C976 restored scope to normal.