Re: TDS744


 

There's 4 or 5 TO-39 transistors on the CRT neck board. One of them is prone to shorting and causing that problem. Later revisions had a heatsink on it to keep it cooler.

Sometimes it will be discolored from thermal stress giving it away visually.

The TDS544A schematic with the early revision color CRT driver board is on Hakan's page; it may be of some help...

There's also a capacitor that often leaks and causes the same problem. Facing the front of the board, it is located on the left side/edge somewhat towards the rear - there's three in a row, and it's the largest of the three. 100uF 50V I believe. the leakage gets so bad that it begins conducting under the cap and starts burning the PCB due to carbonizing (sp?)

Jay

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