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Okay, for reference, these are the voltages on one of my MTX machines:- All are respect to 0V (I use the modulator case). 11.28V @ FS1 (R62 left leg, Q4 emitter) 10.6V @ R62 right leg (Q4 base and input to 7805) 4.8V @ 7805 output (Q4 collector) If you subtract 10.6V from 11.28V you get 0.68V which ...

Those resistance readings look okay.

Thinking.....

Will add to this...

Mark

It is possible, but unlikely that the transformer has gone. Much more likely is a fault in the control and feedback system. I will be able to suggest more once I have looked in detail at the pictures and compared the circuitry/wiring to the example circuit in the second of the data sheets that I lin...

See edited post above.

Hi. Before replace the tip2955 i got around 7v between the legs at r62. After replace, i get the same, so its another problem. I get around 20v in at 7812, and 12v out, so it seems to be right. I get only 6v in at 7805 by the way, and only 3v out, could it be a faulty 7805? So are you getting about...

:arrow: Do you mean R60, a 1k ohm normal 1/4W resistor that feeds the -5V line (check this supply voltage), or R62, a 10 ohm (normally coloured green) larger power resistor that feeds the 7805 voltage regulator? :?: See picture:- R60 and R62 resistors.JPG R60, the 1k ohm resistor, is only likely to ...

And if there are "spare" key caps available, I'm after one of the reset key caps (either side of the space bar).

Mark

is the switch sat next to a cut-out in a case you are thinking about? Yep, the cut-out was made for the switch :mrgreen: And why the "coils" in the LED and resistor leads? - Just to get a grip of for testing, or do they serve a purpose? Makes the connection more robust and easier to solde...

Hi all :-) Here are some preview pictures of the development and construction of a replacement mains PSU for MTX computers :D New MTX PSU Sneakpic01.JPG New MTX PSU Sneakpic02.JPG New MTX PSU Sneakpic03.JPG Edited to add: The schematic is here A UK parts list (BOM) is here A USA parts list (BOM) is ...

Should have posted this earlier :oops: Since writing about using Andy Key's memory board, I have received a REMEMOrizer from him (thanks again Andy). After studying the documentation on his site, I realised that I could just remove the memory board and fit the REMEMOrizer. Powered up and found it wo...