Woodstock troubleshooting Message #5 Posted by Randy on 29 Oct 2011, 9:08 a.m., in response to message #1 by aj04062
Assuming the power supply is okay, remove the rom (1818-0154) and the ram (different numbers, depends on version). Power it up. If you get a 0.00 display, the ACT is okay, basic math should work. If not, check for oscillations at the tank circuit, pins 13/14. If it is dead there, the ACT is dead. If it good, have a look at the display driver components. Not very likely they are at fault but it happens, especially with the 27.
If the ACT is okay, re-install the rom and check transcendental functions. Add the ram and check program storage.
While the ACT is a common failure, so is the rom in the 25. With ram or rom blown, it usually kills the clock and makes it look like a bad ACT.
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