Hi, I just inherited a Crate BS-160 bass/keyboard amp. It does not power up, so I looked inside. It has one fuse and it was blown. It's 250V 5A. I replaced it and it blew again instantly. I did notice the amp says to use normal blow fuses and I ended up replacing it with a rapid blow type. Could this make any difference? Any idea where I should start?
Thanks :)
QuoteAny idea where I should start?
Current limiting (e.g. light bulb series in mains line). Does the amp draw too much current, IOW, has the amp short circuited?
I don't know. How can I test it for this?
Normal, rapid, same thing... as opposed to slow blow or timed fuse.
You have power transistors inside on a heat sink. You need to check them to see if any are shorted. I'd wager my lunch money they are.
I looked them over and don't see anything that looks shorted. How can I test if one of them is shorted?
Well, they won't LOOK any different. One gets out an ohm meter, and measures between terminals of a transistor, looking for low resistance where it doesn;t belong.
Ahh Haa, I'll check that out as soon as I get home from work.
I checked them all (4) and all read about the same. No drastic differences in resistance.
Well what was that same reading, and from which terminals to which? AFter all four burned out light bulbs all will read the same too. I am looking for collector to emitter shorts mainly.
Might as well check the main rectifier diodes as well.
*Each* transistor or , in this case, presumably mosfet, can have 6 resistance measurementes possible: C-E , C-B, B-E plus the same with the multimeter pins inverted. The same with the functionally equivalente MosFet pins. Besides, we should know the transistor codes to know what to expect. A couple close-up pictures showing them clearly would help a lot (both component-side and solder-side). Thanks.