Is there a way to test in circuit if a chip is broken or not using a multimer or some_other_instrument_lot_cheaper_than_osciloscope? Measuring temperature of chip while it has been working for a while should be indicative, but how?
It depends on the chip. If it's a digital IC (e.g., logic gate), a simple and inexpensive logic probe can tell u what u need to know. If, however, it's a complex circuit -- such as a video processor -- you often need to look at the waveforms. You can certainly test for proper voltages on the pins, but that doesn't always tell u what u need to know. Sometimes ya gotta pay to play.
Some chips run surprisingly hot, so unless it gets hot enough to split the casing there's no guarantee this indicates a fault.
All the test gear in the world won't tell you if a chip is faulty if you don't know what its supposed to do - and none of us do either because you didn't tell us!
OK, I understand. its a broken computer, Amiga 1200, it displays for a second blue screen (which means one of custom chips is broken) and then black screen with faint parallel stripes.
The faint stripes could indicate HF ripple from the PSU, maybe crashing one of the chips. In this case overheating capacitors in the PSU might be a better clue!
In the past when servicing PC monitors, I have used my sense of touch to test for overheating electrolytics but BEWARE! the can of the capacitors is not isolated and so the mains reservoir cap on the primary side will have a large voltage on it! So make sure you can distinguish between primary & secondary parts of the PSU before poking your fingers in!!!
In any event while inspecting/testing live equipment correct safety practice is absolutely vital - wear rubber soled shoes, make sure you're not touching anything earthed (chair next to a radiator?!!!) and keep one hand in your pocket so if you do touch a live part - you don't give it a path to earth via your chest!
Some engineers deal with this type of PSU by simply replacing all the electrolytics and making sure all the new replacements are good quality 105 DEG-C types to ensure future reliability. IIRC - the Amiga PSU has a small
1uF 50V electrolytic that dries up and causes the PSU to radiate RF noise!thanks for the reply, but its not PSU for sure. I've used ordinary PC AT power supply that is tested and works with other Amigas. one nice day I'll buy osciloscope and one nice year learn to use it :)
thanks for the reply, but its not PSU for sure. I've used ordinary PC AT power supply that is tested and works with other Amigas. one nice day I'll buy osciloscope and one nice year learn to use it properly :)
Amigas have very common faults. I'd give it a try to search Google for a A1200 fault database. Also the guys on
Adrian
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