Electronics > Repair

broke jumper wire?? HP 6177A. What is this failure mode?

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Gyro:
Maybe it was a 'cut on factory test' jumper and you just didn't notice the gap.

coppercone2:
nah like I said the pieces come together like two ice cream cones with elon musk characteristics. no cutting tool will do that.

i looked at cuts under a microscope for wire before with everything from cheap dykes to ultra flush cutters and wire shear, none of it looked close to this. they usually leave a 'mowhawk' type thing or just crap pushed to the side with shears. this is like weird fracture

coppercone2:
why would transistors make this reference circuit, with all new diodes and no carbon comp resistors (replaced with metal oxide) be noisy in the tens of mV range when the spec is in the 1mV or less range (100uV)? The caps are new too

I replaced everything in red.


Can the rectifier diodes be involved in the problem? I think its the transistors since they look sooty and get hot (R11, R12). Every single rail is basically noisy. I left the metal film and WW alone. The stabistor replacement is a stabistor, not a hack of many diodes. I did R28 too, I just forgot to circle it

I just wonder if maybe the transformer can be over loaded and that is creating ripple/noise (ACV measurement fail). But the DCV was all pretty close. I figure it would be really sagged if the transformer was getting beaten down

I think that maybe there is damage to the transistor that still makes it read fine on diode mode. I heard this is possible with over heated transistors.

coppercone2:
Well i randomly got two of the cheapest transistor types to replace,

 but during work I found that of course, I forgot to solder in TWO of the leads of one of the transistors I replaced in the pair where I found a broken one. All my inspection steps missed this hole, even with bright lights... this one actually read open circuit in the diode test


So its possible I fixed the problem but missed soldering in the transistor fully, and now have to replace more transistors since I cut them off.


But it still does not explain the tested but super over heated looking transistor.  ???


I assumed the powerful light would reveal all the missing solder, but it seems the transistor can is just too good at blocking light. so if you do the flashlight inspection trick, make sure you renember it wont work on some large parts. I only noticed it because I  touched it and it moved.

coppercone2:
alright the hell with this machine, I think I replaced every transistor and trouble shoot in a circle for way too many times, I got the upgraded model that is built sensibly. Even though I put alot of work to get rid of the carbon comps and stuff, I will see what parts can be transplanted and I will throw this one out  >:(

I am almost certain I measured every part and even replaced transistors that said they were good.

the B version gets  :-- :--

I think its haunted 👻👻👻 , its making my stomach hurt to think about this one anymore

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