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Crate BT-100 Bass Amp Blowing Fuses

Matthew 677

Nov 11, 2016
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Got this Crate BT-100 bass amp, the other day, real cheap, and took out amp, thought it was bridge rectifier, no, so unhooked the power amp, and held, until i plugged it back in. I'm thinking it is the mosfets, can they short out and, blow the fuse?
Here is the schematic, tried to upload, but said to large.


file:///C:/Users/SONY/Downloads/crate_bt100_sch_and_parts.pdf

http://elektrotanya.com/crate_bt100_sch_and_parts.pdf/download.html only 2 downloads a day.
 

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davenn

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Sep 5, 2009
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file:///C:/Users/SONY/Downloads/crate_bt100_sch_and_parts.pdf

I think you erred .....that's a location on some one's computer probably yours... not a www address

no one can access that
 
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duke37

Jan 9, 2011
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Run the amp with a series bulb (say 100W) to stop the fuses blowing. Does the light glow?
Disconnect C20 and C21. Are the tops flat or domed? Does the light glow? Note that these are shown as 0.1, this will be 0.1F i.e. 100,000μF.
 

73's de Edd

Aug 21, 2015
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Sir Matthew667 . . . . .

Considering that you do have a 100 watt incandescent lamp connected in place of F1 and it does light up brightly.
Consider that indicative of this linear supply STILL trying to function, but just being power starved by that lamp.
Try taking dc meter measurements at the + 40 and - 40 outputs from the FWB . Power up for a short time to be able to make those measurements, which would be at a highly reduced value.
Use the same procedure to test across D to S of the Q17 and Q16.
This should give you some idea as if the whole FWB is blown or just a portion.
Also confirm if only one or both of the power FET's have been blown.
There might also be ancillary damage to the Q 18 and Q15 drivers or the Q19 bias divider.

73's de Edd
 
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