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I'm trying to fix a newer acoustic B200 that was blowing fuses. He says that something happened with the power at their practice space. I plugged it up to a current limiter with a new fuse. The bulb burns bright. I disconnected everything from the poweramp board except for the transformer secondary. Same thing. I unplug the secondary, no light. The voltages seem to be ok coming out of the transformer. The filter caps seem to be charging up properly. I am not sure how to check the rectifiers while they are in circuit. Is it safe to assume it is the output amp IC? I actually have the right one, but don't want to change it for no reason.
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- disconnect the rectifiers from the filter caps, power cycle the amp; does the bulb light up hard? If yes, the rectifiers are toast. If this is difficult because they're all soldered into the same PCB, remove the caps and the rectifiers and test them outside the PCB.Originally posted by antieatingactivist View Post
- if no, reconnect the first filter caps to the rectifiers but disconnect them from the rest of the circuit, so DC goes into the caps but not out. Now does the bulb light hard? If yes, bum caps.
- if no, something in the circuit is eating current; see below. And while you're at it, make sure the caps hold the correct voltage, and don't get hot when left at voltage for a few minutes. Then be careful bleeding them down when you turn power off.
No.Is it safe to assume it is the output amp IC?
Only after you check the stuff before here would you even look at the output amp IC.
Continuing from above, if the rectifiers and caps were OK, remove the power amp IC so as to disconnect it from eating power; this does not make it a suspect, just removes it as a load. Power cycle. Bulb light hard? If yes, something OTHER than the power IC was a problem. If no,
- OK, now you can suspect the power IC.
Debugging shorts is a game of finding where the current is going by disconnecting things that could be eating it.Amazing!! Who would ever have guessed that someone who villified the evil rich people would begin happily accepting their millions in speaking fees!
Oh, wait! That sounds familiar, somehow. -
Thanks for the info. I just wanted to make sure there wasn't an easy way to diagnose without desoldering components. I will try this tomorrow and let you know what I find.Comment
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It was the amplifier IC. I swapped it and the amp is working fine. Thank you for the help.Comment
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I have one on the bench now, blown STK303-140S. I'm seeing alot of posts online with this issue. Gonna fix it and see if it comes back, then I'll look into adding more protection, like a thermal switch on the heatsink to remove the speaker per JM Fahey's suggestion on this thead. http://forum.ampage.org/forum.php?cmd=vt&tid=37510
Any suggestions on where to purchase the obsolete STK404-140S? Mouser has this newer version? http://www.mouser.com/ProductDetail/...uKynUesQ%3d%3d But I think that's the whole board assembly.Last edited by lowell; 01-09-2017, 06:28 PM.Comment
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Saw that but theyre out of stockComment
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pacificsemi has them but they have $50 minimum. If you are already dealing with them or need a bunch of stuff...Originally posted by Enzo
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I see "0" quantity there. Can u send a link? Thanks!Comment
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Sorry, my mistake. They are out of stock.
I had dealt with their 'retail-no minimum' affiliate Intek before, but they seem to have disappeared.Originally posted by Enzo
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Dang. Ok thanks for the help!Comment
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