Hah, I only discovered yesterday that my SW CP had made it to the news page !!! I already wondered what the all-of-a-sudden high rates of view on the pictures came from. Thanks Saint, I feel honoured !
OK. Let's face it, in this hobby and on this forum it's great to report about your successes. However, sometimes you f.u. in the proces. It's normal, we're only human after all (from a well-known Level 42 song
However, sometimes it's REALLY embarrassing how stupid you can be. So first I thought not to post this, but then again... what the heck:
Yesterday I found a couple of hours to work on the CP. Now, as you remember, the cab is stored in a good friend's shed so when I go there I have to bring my stuff like docs, equipment etc.
I started working on the HV-board, replacing all the suspected/defective parts. It turned out that only the 7824 was really defective and of course the 50 Ohms resistor that burnt out. However I still replaced the 7924, the 1N4001 diodes, the other resistor and all the elco's ("caps"). However, for some stupid reason I had de-soldered the resistor wire and the 1N4001 diode wire the last time I worked on it.
For those who don't know, these diodes and 50 Ohms resistors were added to the design of the HV board later, it's a factory mod. So there's no clear indication on where goes what (The diodes are on the tracks side of the PCB).
So I thought I had figured it out and remembered how things were connected.....so I soldered away. (I regretted very much not printing out the picture I took from the track-side....should have prevented this mistake)
Then it was power-up time, and of course I was checking the resistor as soon as it powered up, and I freaking almost burnt my finger, so it was again/still heating up like nuts......
So I thought something else must be making this happening, a part I hadn't replaced. (FYI I hadn't put back in the BU406D which I had removed before. This way, there is no drive to the HVT, so the HVT can't blow up the first stages of the circuit....
I looked at the schematics and decided that only a couple of transistor could cause this, but all of them checked out fine.
Then I had another look. Sadly, the 50 Ohms resistors are not represented in the schematics, so I looked at the great Amplifone FAQ doc by Michael Kelley (http://www.gamearchive.com/Video_Games/Manufacturers/Atari/monitors/amplifone/amplifone_faq_1_2.pdf
) and there it was: I had connected the resistor to the wrong pins...DUHHHH, I was directly feeding the output of the 7824 into the 50 Ohms resistor, no wonder it got hot !!!! (It should have been across pins 1 and 3 of course....!)
I'm not sure if I fried the 7824 by doing this....I had little time left. I did correct the mistake of course and now the resistor stayed cool. Then I decided to try and put in a fresh BU406D....
Fired up and, no picture.......I bet the HVT is dead, as very much expected. I ordered one, gotta wait for it to arrive...
Sorry if this all gets very technical.....bottom line is to check and check again....I'm embarrassed that this happened to me, being en electronics professional, but at least there is no permanent damage. "The force is still with me" when I throw in a coin, and I can hear the deflection sound changing during attract mode, I hope that's another indication of the game PCB's still working OK