joemagiera
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- Joined
- Mar 22, 2003
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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.
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.

