Interesting! Are you interested in the dead one from my sdl for autopsy?
If anyone needs a good KLIMA for a 450SE/SEL, I have one for sale, or i'd trade for a SDL KLIMA relay.
Loren At 05:18 PM 8/2/2006, you wrote:
FYI general list information on Alex's dead Klima. I expect that a resoldering job may cure it. The condition of the pins was good, not particularly corroded. I then opened it up. It is built on a single-sided PCB with two relays, two National Semiconductor 4-bit COP processors (COP411L-MNG/N & COP425LN), an LM2903 dual comparitor (date codes on the IC's from 84-86), four signal transistors, eleven diodes, and one power transistor. Plus the usual crop of passive components, notably five aluminum electrolytic capacitors. The two relays looked good, but the soldering on the back of one of them was fried. The board is even blackened at one pin, but the cooked pin doesn't have a trace going anywhere else, what's up with that? Fried drippy solder is in several other places, most of which aren't high power at all. Did this stuff migrate from the hot spot(s)? Did a non-solderer attack the board? Regardless, it appears that this thing might possibly be brought back to life by a good resoldering, there's plenty of solder joints that appear crystallized. If, of course, either masked-ROM COP is dead it's all over, but the rest of the components look to be generic. A fried relay contact might also be difficult to deal with, the relays are smallish and would be hard to substitute. Of note is that one relay is DPST (NC), and both contacts are wired in parallel. It's fine. The other is DPDT, both NO contacts in parallel, but with one NC contact missing, and the burned spot is the lone NC contact, yet there's no trace from it to anywhere. If both NC contacts were there and in parallel would this unit have failed? By spreading the current across two relay contacts the heat is spread out, and the intertie copper also serves as a heat sink. The pristine surfaces of the relay contacts indicate that they weren't overloaded per se, but that the poor heat dissipation ruined the contact soldering. But what heat could there be on a lone pin that doesn't go anywhere? I pulled the (identical) Klima from our SDL, and its solder looks a whole lot better, though I notice a bit of 'coldness' starting on some of the relay pins. The fried relay pin indeed doesn't appear to go anywhere, so how did it get fried? The _only_ sign of heat is at that one non-connected pin. It's a mystery. Perhaps I should try to repair it, I've got a car that it'll fit perfectly in for testing. ... Alex did try resoldering, and claims no skill at all. OK, weird blobs explained. Denies burning the spot in the board. So that's a mystery. I'll try repairing this one and swapping it into the SDL. If it works, I'll add this to my service list. New Klimas are >$100, so it ought to be cost-effective. (And will help prolong the supply of NOS spares.) -- Jim _______________________________________ http://www.okiebenz.com For new parts see official list sponsor: http://www.buymbparts.com/ For used parts email [EMAIL PROTECTED] To Unsubscribe or change delivery options go to: http://okiebenz.com/mailman/listinfo/mercedes_okiebenz.com
Loren Faeth
