Sometimes the tools required to keep these vintage machines running are as old and as finicky as the patients. For example I have an old EPROM burner which if not powered and charged in a while goes into a sulk and needs to be coaxed back into life with some repetitive jabbing of the reset button.
Vintage Computer Club - Restoration and Maintenance
Below is a list of some of the essential items in my toolkit arsenal:
Good quality soldering station.(Not one of those pencils you buy for about £15) this has serious temperature control and also a hot air SMD re-work gun too. If you're serious about doing any soldering work you will cause less damage than if you use underpowered equipment.
Multimeter.Again quality is better, a continuity and diode check are essential, then voltage both AC and DC, if you're going to work on power supplies then make sure the voltage range on AC goes well beyond 250V, I normally look for 500V and also that DC is comparable too. A lot of power supplies regulate mains direct which will give exposed voltages of over 300V DC!
If you're not used to working with electronics and electrics then its probably best left to someone who is qualified. Luckily I used to repair these things when they were new and know what I'm doing (well almost).