*** M E M O R U M ***

So, the capacitors have now been changed and there's no difference. I decided to run a longer powered test to see if I could find and chips which were getting warmer than normal: http://www.lingula.org.uk/~steve/images/Memotech-on-test.jpg As it turns out the video chip and all the video memory chip...

Removing C57 made no difference. Oh well, the tricky C11 will be next. I'll get replacement capacitors from Maplin's at the weekend and replace them both anyway.

OK, so after replacing the power transistor and the zenor diode (which is what let out the magic smoke) I'm back to where I was. It still blows the fuse. But... with a meter where the fuse should be I'm measuring 0.86 amps and the machine is operating seemingly normally. As you can imagine, the heat...

Hi Stephen, I guess that you don't need any comments on the "wisdom" of bypassing the fuse :D The burning smell is not a good sign, the problem could be pretty much anywhere on the board. A good, easy anyway, starting point would be to remove all of the socketed chips and try that first. ...

The 7805 voltage regulator and the TIP transistor work together to regulate the voltage for the +5V line. If the fuse is blowing, too much current is flowing, which indicates that something is breaking down and drawing too much current. But first, if your multimeter has a diode test function, test ...

I recently bought an MTX512 on eBay which the vendor had previously tested but arrived in a non-working state as the internal fuse had blown. Having replaced C39 and C40 just in case I could get the machine operational by bridging the fuse, though the rectifying diodes got a bit warm. I replaced the...