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Re: kustom k100-1??! fuse specifications... [message #9299 is a reply to message #9293] |
Sat, 08 March 2008 18:49 |
drbambam
Messages: 12 Registered: March 2008 Location: portland, or
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Junior Member |
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my double clicking's a bit much!!!... sorry for the repeats alot of FUD's error messages showed up & i didn't get the cancel until i retried about 3-4Xs,... i'm better now... ...
reggaeallonebassforfundancemusicpoetryonelove!!!
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Re: kustom k100-1??! fuse specifications... [message #9305 is a reply to message #9302] |
Wed, 12 March 2008 16:22 |
drbambam
Messages: 12 Registered: March 2008 Location: portland, or
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Junior Member |
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a bit back ~2007's messages on this subject said that a slo-blo might be a possibility?!?... well, i've lost 2 3A fast-blo fuses so far... so now i'll just trouble shoot the components to see what's the cause??!... the 2 power capacitors both showed 40 volts before discharging, so they seem to meet the specs brought up on this site... i'll check on some of the other suggested problems: the rectifier, power transistors,... this being a serial #53000's K100-1, i notice a thermistor and also a small transistor-like component heatsinked between the 2 power transistors(all in the same heatsink w/ the thermistor)... the thermistor's hooked up to the 117VAC line(hot side)& transformer... could that be a problem in the fuse blowing??!, by the way, i do have access to an occilloscope for troubleshooting, will do if necessary...
reggaeallonebassforfundancemusicpoetryonelove!!!
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Re: kustom k100-1??! fuse specifications... [message #9307 is a reply to message #9306] |
Wed, 12 March 2008 18:06 |
chicagobill
Messages: 2005 Registered: April 2003
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Senior Member |
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drb:
Now you know why the fuse was missing in the first place!
You should be able to turn on the amp with no speaker load without any problems.
As the fuse blows on power up, with no load, I would suggest checking the filter caps for either a short or low ESR.
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Re: kustom k100-1??! fuse specifications... [message #9308 is a reply to message #9292] |
Thu, 13 March 2008 06:22 |
stevem
Messages: 4745 Registered: June 2004 Location: NY
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Senior Member |
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I would start by trouble shooting it like this.
First disconnect the red and green wires that come off the 2500 mfd filter caps and go to the driver board, replace the fuse, turn the amp on, and if the fuse holds then the rectifier bridge is ok.
Next reconnect the two wires to the filters and slde off the connectors from each output transistor making note of what color wire was facing the rear of the amp. with this done repower the amp and if the fuse holds, then one or both of the output transistors is shot.
If the fuse still blows then one or both of the driver transistors in the square heat sinked case( if they are original) is bad, and so is one or both of the output transistors.
Most times when a output transistor goes, it takes the 5 watt emitter resistor next to each driver with it, so it will read open.
The Item you wondered about in the clip in between the two output transistors is a thermal diode that keeps check on the bias of the output transistors in realtion to heat.
These rarly go bad, but they should be held tight in their clip, and their should be some thermal compound grease on it for good heat conductivity.
I find it helps and saves time in a troubled amp like this to clip in a circuit breaker untill I get the shorting problem resolved.
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Re: kustom k100-1??! fuse specifications... [message #9311 is a reply to message #9308] |
Thu, 13 March 2008 18:30 |
drbambam
Messages: 12 Registered: March 2008 Location: portland, or
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Junior Member |
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it shows the rectifier to be the culprit as of now,... now to see ??? the hell was meant by 25W to 35W radioshack bridge rectifier replacements,... rectifiers're only rated by voltage & amperage, ouch!!!... so i'm assuming(hoping not to make a fool of myself)that what was meant was: 25A to 35A bridge rectifiers(again assuming the voltage to be ~50V to 100V!!!), this voltage from the 40 to 43 Vdc charge of the filter power caps!!!... so the radio shack here in no po, or only has 1A to 25A, 200V to 50V range bridge rectifiers... the 100V to 200V are all between 1A to 6A, whereas the 50V is 25A... so am i right about the 50V, 25A bridge for a replacement??!
reggaeallonebassforfundancemusicpoetryonelove!!!
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Re: kustom k100-1??! fuse specifications... [message #9316 is a reply to message #9314] |
Fri, 14 March 2008 12:39 |
chicagobill
Messages: 2005 Registered: April 2003
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Senior Member |
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Steve: The 1N4007 diodes do not have enough current capacity for this application. They're fine for a tube amp, but not for the Kustoms.
I've used 200 volt/25 amp bridges as a generic replacement for all Kustom amps, other than Frankenstein heads. The only real problem is that the push-on terminals that are on the wiring harness will not fit the new rectifiers and must be removed or replaced.
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Re: kustom k100-1??! fuse specifications... [message #9342 is a reply to message #9325] |
Fri, 21 March 2008 12:02 |
C4ster
Messages: 686 Registered: June 2001 Location: Mukwonago, WI (Milwaukee...
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Senior Member |
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One other thing about the bridge rectifier. The caps hold at 40. Because of the bridge arrangement, the total reverse voltage is across 2 diodes in series, so a 50 volt bridge is more than sufficient to withstand the voltage in a Kustom. The current supplied to the output transistors is in excess of 5 amps at 100 watts into 4 ohms. A K100 would be 2.7 amps into 8 ohms.
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