The difficulty with fixing electronics is that the majority gadgets are simply black bins — actually. Tear it down, look inside, nevertheless it often doesn’t matter — all you see are black epoxy blobs, taunting you with the truth that a number of of them are useless with no exterior indication of the wrongdoer.
Typically, although, you get fortunate, as [FeedbackLoop] did with this Rigol spectrum analyzer repair. The instrument powered up and form of labored, however the noise ground was unacceptably excessive. Even earlier than opening it up, there was clearly an issue; usually, spectrum analyzers shouldn’t rattle. Upon teardown, it was clear that somebody had been inside earlier than and obtained reassembly fallacious, with a free fastener and a few clearly shorted parts to indicate for it. However whereas the scorched stays of parts made an excellent place to begin analysis, it doesn’t imply the repair was going to be straightforward.
Determining the values of the nuked parts required somewhat detective work. The blast zone appeared to as soon as maintain a few resistors, a capacitor, a set of PIN diodes, and a few tiny inductors. Additionally close by have been a pair of chips, sadly with the markings lasered off. With some on-line snooping and somewhat little bit of widespread sense, [FeedbackLoop] was capable of give you believable values for many of those — even the chips, which turned out to be HMC221 RF switches.
Cleansing up the board was a little bit of a chore — the shorted parts left fairly a crater within the board, which was stuffed with CA glue, and a bunch of lacking pads. This referred to as for some SMD soldering heroics, which sadly didn’t repair the noise drawback. Changing the 2 RF switches and the PIN diodes appeared to repair the issue, albeit at the price of some loss. Typically, ok is nice sufficient.
This isn’t the primary time [FeedbackLoop] has gotten fortunate with alternative take a look at tools in want of repairs — this reminiscence module transplant on a scopemeter involves thoughts.