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Post by Mr Whippy on Nov 6, 2016 16:19:52 GMT
Anyone know what can be used as an alternative? Recently got a Yamaha P2100 power amp with a shorted output on one channel. It's been repaired once and left when blown again. Two "fusistors" had been replaced first time with standard ones. These are showing signs of distress and another "fusistor" has failed. The values are 22R/150mA and 330R/55mA.   |
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Post by pre65 on Nov 6, 2016 16:23:28 GMT
Have you traced the fault that is causing the problem ?
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Post by Deleted on Nov 6, 2016 16:40:13 GMT
An old fashioned component for a late 70's amp!
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Post by MartinT on Nov 6, 2016 21:17:18 GMT
You could wire a standard resistor and miniature fuse in series to accomplish the same protection.
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Post by Mr Whippy on Nov 6, 2016 22:13:47 GMT
Have you traced the fault that is causing the problem ? Err...No. I have got the front panel nice and shiny, though. I can say (without fear of contraception) that previously the output had encountered a catastrophic short resulting in a driver transistor, two fusistors, all four output devices and six of the seven power resistors needing replacements. Oh yes... Can't help thinking the protection elements were just a tad, just a tad on the slow side. The only original power resistor.   Must admit the previous fixer didn't skimp with the thermal compound. It's everywhere. |
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Post by Mr Whippy on Nov 6, 2016 22:49:12 GMT
You could wire a standard resistor and miniature fuse in series to accomplish the same protection. That's an idea. |
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Post by pre65 on Nov 6, 2016 22:52:24 GMT
Have you traced the fault that is causing the problem ? Err...No. I have got the front panel nice and shiny, though. Must admit the previous fixer didn't skimp with the thermal compound. It's everywhere. |
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Post by Mr Whippy on Nov 6, 2016 23:11:06 GMT
Well at least one pair of output devices are, as they say, shagged.
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Post by kettlechips on Nov 7, 2016 10:06:09 GMT
I've repaired similar amps in the past where a previous owner had replaced transistors, and had used an excess of thermal compound. Unfortunately he had not rectified the short between the transistor and the heat sink, so it kept blowing fuses!! Simple fix once I'd identified where the short was. I suggest that's where you should start the investigation. There should be an insulating layer between the transistors and the heatsinks, not just thermal compound. Test for continuity with a multimeter as a first step.
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Post by Deleted on Nov 7, 2016 15:32:41 GMT
You only need to use a spot of Thermal Paste. Messy stuff anyway. I use Thermal transistor insulator pads.
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