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Re: been there before(twice)

Tea,

Here is what you do, take a wire cutter and clip the leads of the old single cap off. Remove cap and put in trash. Trust me it now thinks it is a resistor due to old age! Take new poly cap and run leads through board and attach to connecting pin by wraping and solder. Move on to next cap and continue. The original design does not use bypass caps, do not screw up the sound by hearsay engineering. Trust Sydney Corderman on the engineering side, his designs tend to have high resale.
The power supply caps are FP twist lock type and see my previous post for sources. Remove the old ones paying attention how everthing is connected and install the new ones the same way. If you wire them wrong they may explode on turn on so make sure of your work and/or wear safety glasses!
If you replace all of the caps your noise will decrease along with the distortion and the amp will play loud and clear.
Yes, the original transformers could have a concave shape to the sides. This is the original shape on some of the ones I have seen. The transformer can be dented as the can is only aluminum so it is somewhat soft. The way to tell if the transformer is good is to replace the defective power supply caps and measure the voltages. If the voltages are correct the tranny is fine.
You need a voltmeter and a schematic to start this process. Remove all of the tubes and turn the amp on. Remove bottom cover and ground your voltmeter to the chassis. Measure the voltages on the pins one tube at a time starting with the output tubes. Be carefull as you will be dealing with hundreds of volts, 440 hopefully!The voltages may read 10% or more high as you will not have the tubes in the amp. This is OK for now as the ratios should match the schematic before you measure with the tubes installed.
Be sure to check the 220 ohm five watt sand block resistors on the output tube sockets WITH THE AMP OFF. If any of them read open or low this means a tube has arched over. Replace the 220 ohm sand blocks with 5 WATT ONLY. These are the fuses that protect the output transformer from tube failier. Higher wattage resistors will take out an output trans if a tube fails.

Ron-C


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  • Re: been there before(twice) - Ron-C 07/15/0218:56:51 07/15/02 (2)


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