AM503 with replaced capacitors
The single most valuable instrument in my possession is Tektronix current measurement system, which consists of AM503 probe amplifier with accompanying A6302 AC/DC probe. While probe itself doesn’t need much attention besides occasional wiping the dirt off the jaws, the amplifier recently became quite noisy in several attenuator positions so I decided to give it a good spring cleaning.
I adopted the procedure described on a web site dedicated to restoring Tektronix oscilloscopes; the guy was talking about fixing fuzzy trace by cleaning input attenuator contacts of Tek475. I am unable to find this site anymore; if anyone knows the link, please let me know so I can give him proper credit.
The places in need of cleaning are attenuator contacts and range resistors R206, R208, R212, R214, as well as terminating resistors R204 and R216. For cleaning I use Deoxit from Caig Laboratories and a piece of clean printer paper. A match or a toothpick could be helpful in tight places; don’t use anything metal though; you don’t want to scratch your old Tektronix gold.