Electronics > Beginners
Took the Plunge - GoldStar OS-7020 Oscilloscope
Brumby:
--- Quote from: olafwagner on January 21, 2020, 03:17:55 am ---.... is this a DC voltage (service manual doesn't say)
--- End quote ---
You can safely assume any voltages specified in circuit diagrams will be DC - unless they are very clearly annotated otherwise. Power supply voltages tend to be the safest bet as being DC.
james_s:
If it gives you a range of -1,995v to -1,805v and you're seeing only -1,650V that's way low, I'm not sure offhand why it's low but that definitely isn't right.
olafwagner:
I removed Q621 from the board and popped it into my component tester, and it recognized it as being a BJT-NPN transistor (see attached).
Unfortunately I don't know what the hFE, Ube and Ic values mean, but considering the tester recognized this as a NPN transistor, does it still mean that Q621 is bad?
I googled for a data sheet, and found one for a Hitachi 2SC1907, and also attached some of the electrical characteristics below (unfortunately I don't know what to look into)
james_s:
Those characteristics are useful if you are designing something around a transistor or trying to find a suitable sub but that isn't important right now. You are correct in assuming that if the tester accurately identifies it as an NPN transistor it is almost certainly just fine. 99% of the time a fault will clearly manifest itself as a short or open between two or more pins.
AVGresponding:
Agreed, normally the failure mode is a fairly clear open or short.
Does seem strange that the blanking signal ends there though...
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