I got a Compaq Portable III for very cheap -- mainly because it was considered dead. Disassembling, cleaning and reassembling it somehow took it back to life, with the exception of the CMOS battery and the floppy drive.
I'd usually not mention the CMOS battery, because it is obvious those old batteries can only be exhausted, if they didn't leak. But in some Compaq computers, the issue is worse because there is no BIOS user interface built-in; you have to run a MS-DOS setup program. When CMOS battery is clear, the computers assumes there is no hard disk, and that the floppy drive is a 360 KB one. It's one rare case where I purchased another battery to avoid the hurdle.
The floppy drive had another issue. The spinning speed would be very random, making it impossible to read a single disk. I had the issue on my IBM P70 and remembered bad caps were the likely cause. However, when opening the floppy drive I thought I could only access the capacitors by disassembling the counterweight disk. It proved to be a bad idea, both because it was not necessary to really access the circuit board and because I broke a screw in the process. It was a left handed screw and it was completely stuck, and I've not been patient enough.
In the end, I had to purchase another floppy drive. This one is working fine, except it sees all disks as being write protected. Another fix needed soon...
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