Author Topic: Tektronix 2424L Oscilloscope Repair  (Read 503 times)

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Online Tomorokoshi

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Tektronix 2424L Oscilloscope Repair
« on: April 26, 2019, 02:36:47 am »
I got a Tek 2424L that had been in service for many years somewhere in an industrial building. It is loaded with an accumulation of dust mixed with oil.

It was relegated to the scrap metal bin because it stopped working. Upon retrieval, the first noticeable symptom was chirping of the power supply. A search for a 2424L manual was not successful. In fact, most anything about it was not forthcoming. Therefore I tried to use the Tek 2430A service manual. The more I got into it, the more it seems the 2424L is a down sampled version of a 2430A. The A16 power board appears to be identical.

Various measurements and sequential disconnection of various boards narrowed it down to the A16 power supply once everything else was disconnected. This included unstable DC outputs. When powering up, it would chirp 3 or 4 times before finally running the fan, if it made it at all.

I made a list and measured all the electrolytic capacitors in circuit for capacitance and dissipation. As it happens the problem was in the first capacitors I measured. A16C305 was 326 pF at D = 0.2, while the identical A16105 was 673 uF at D = 0.16. Out of circuit was similar. These are specified as 680 uF at 200 V.

After a cursory reassembly I was able to get almost full functionality. Cleaning, replacing RIFA capacitors, etc. will happen later.

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