My BAD deal find/pick up (Defender)

joemagiera

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People post about their good deals and finds all the time. But none of us post about our bad deals. I'm not proud of this, but in fairness, I'm posting this bad deal and how I made it horrible.

Picked up a non-working $50 Defender. Sounds good so far, but read on...

PCB has lots of battery acid damage. The original power supply, after putting in replacement fuses, was putting out acceptable voltages. I put in a known good CPU. The TI SN7404N @ 5B immediately starts flaming like a small flare. The power supply middle light goes out and fuse at F3 is blown.

I swap the entire boardset, including the power supply board, with a known good set (i.e., a second CPU). The power supply is putting out good voltages. I plug it in and again, immediately the same chip starts flaming. I pull the plug. At least this time I didn't blow the F3 fuse because I got it quicker.

So now I've got two fried Defender CPUs (and who knows what else got fried). Why oh why didn't I learn the first time?

It appears that it's pins 3 and/or 4 on the 7404 that are flaming. It isn't the power supply or the boardset, so it's got to be something faulty in the wiring.

This Defender isn't going to be so cheap after all. Sometimes you win and find a good deal, sometimes you don't. This one is a wolf in sheep's clothing and got me big time this time.
 
Well, on the bright side you got an entire cabinet and monitor for $50. And believe me, I've been in the same spot - frying something twice because you didn't "think of everything." Sometimes you have to troubleshoot and part of the process is seeing if the same behavior happens again after you have changed something. In your case, the problem has the awful side effect of toasting the board. Very frustrating indeed.
 
I feel your pain, Joe. I'm still grappling with my *great deal* Defender that I got around Xmas.

Long story short, I now have to send my boards to another KLOVer to take a look at them for me. They were working when I got the game. :(
 
Yipe! I would've tested the SHIT out of that power supply using dummy loads after the first board. I learned this lesson the hard way with my own computer -- my stalwart Athlon rig (that would. not. die!) finally got killed at the hands of a seemingly good power supply that instead cooked things.
 
I agree, either way you got a cabinet and monitor for $50. You win some and you lose some. But I say you are still up...not down yet! Make sure you take breaks when working on this arcade, I had a few moments myself and if you search KLOV for broken defender threads, you'll realize your far from alone :)

Well, on the bright side you got an entire cabinet and monitor for $50. And believe me, I've been in the same spot - frying something twice because you didn't "think of everything." Sometimes you have to troubleshoot and part of the process is seeing if the same behavior happens again after you have changed something. In your case, the problem has the awful side effect of toasting the board. Very frustrating indeed.
 
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