| Need help with Commander power section [message #19113] |
Tue, 13 August 2013 13:03  |
Ted M
Messages: 5
Registered: August 2013
Location: RI
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Junior Member |
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I have a Kustom commander that I would like to get going.
It has blown output transistors, a blown rectifier, and a blown fuse.
While looking over the schematic posted here https://docs.google.com/a/olenik.com/file/d/0B1FxxpOmGO8vWVY 4bVplTTVVZ3M/preview?pli=1&rm=demo
I noticed some dependencies between the schematic and parts layout.
Are R22 and R24 mixed up with R23 and R21 in the layout drawing?
That would seem to be the case when comparing my amp to the drawing. Has any one else noticed this, or was my amp assembled incorrectly? These are the big cement resistors next to the drivers. Mine are labeled .51 10% 5 watt. When I measure them in circuit, I'm getting 1.4 ohms. Ad these to the list?
I'm sure I'll have other questions as I make a list of parts needed.
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| Re: Need help with Commander power section [message #19115 is a reply to message #19113] |
Tue, 13 August 2013 13:35  |
chicagobill
Messages: 2006
Registered: April 2003
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Senior Member |
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I never really noticed that before, but you're right the part numbers are wrong/mixed. I don't really look at the layout drawings that often though.
When you touch the two meter leads together what reading do you get? The resistors may be off value, but meter lead resistance is probably a big part of that.
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| Re: Need help with Commander power section [message #19119 is a reply to message #19113] |
Tue, 13 August 2013 15:00 |
chicagobill
Messages: 2006
Registered: April 2003
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Senior Member |
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Yes, it would seem that the emitter resistors are okay. Test every transistor on the board and every diode as well.
Watch out for the diode that mounts to the heatsink, the leads can be very brittle and will break off right at the case if you are not careful or lucky for that matter.
The only part that I would have a problem with is the rectifier bridge, 25 amps is way high, but okay, the 50 volts is a little too close for me. I'd rather see a 100 volt part there, but the 50 will work. Are you sure the original one is dead? I really don't see them go bad that often.
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| Re: Need help with Commander power section [message #19124 is a reply to message #19113] |
Tue, 13 August 2013 16:12 |
chicagobill
Messages: 2006
Registered: April 2003
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Senior Member |
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Which red and green wires did you remove from the caps, the ones to the circuit or the ones to the choke?
If the rectifier, choke and filter caps were hooked up and the fuse did not blow, then the power supply would seem to be okay.
You can run the power amp without the outputs, but don't connect the speaker or you may damage the drivers.
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| Re: Need help with Commander power section [message #19126 is a reply to message #19124] |
Tue, 13 August 2013 16:20 |
Ted M
Messages: 5
Registered: August 2013
Location: RI
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Junior Member |
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I removed both sides (the dual wire and single wire) from both red and green.
Should I do this test again with the transformer to caps connected but the PS board disconnected?
Ok I did the test with the choke connected to the filter caps, and the power board disconnected, .5 amp fuse held.
From testing in circuit, think maybe just one of the outputs is blown. If I power it up with the 3055's unplugged, the caps connected to the power board and the fuse doesn't blow, can I assume the rest of the board is ok?
[Updated on: Tue, 13 August 2013 16:30] Report message to a moderator |
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| Re: Need help with Commander power section [message #19127 is a reply to message #19113] |
Tue, 13 August 2013 16:27 |
chicagobill
Messages: 2006
Registered: April 2003
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Senior Member |
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That would be the next test to see that the filter caps are okay and that you getting the normal + & -40 vdc from the power supply. You can also test the ac voltage on each of the filter caps to see how much ripple there is.
A 1/2 amp fuse may or may not hold with this test, as the caps may initially draw a pretty good surge.
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| Re: Need help with Commander power section [message #19130 is a reply to message #19129] |
Tue, 13 August 2013 17:05 |
chicagobill
Messages: 2006
Registered: April 2003
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Senior Member |
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I personally never assume that there is no other problem when an output shorts, because maybe 60-80% of the time there are other things damaged on the board, typically the drivers.
Why not test the rest of the transistors on the board?
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