64 Thunderbird 390 Posted January 6, 2005 Share Posted January 6, 2005 ---------------- On 1/6/2005 12:56:09 PM yaffstone wrote: The tube filaments are tungsten with thorium added to lower work function. The work function is the amount of energy you have to empart to an electron to convince it to leave its atomic orbital and become part of the current flow of the circuit. If the surface of the filament gets poluted or if the filament gets too hot, the throium can be blocked or blown off respectively. Heating the filament hotter causes imbeded throium to travel to the surface where it can act as a lower energy emitter again, replacing that which was there first. Impurities could also be boiled off, condensing on the cooler glass. This is the physical chemist's explanation for why over heating within reason can revive a tube. ---------------- Very good explaination, and very true! -Ryan Quote Link to comment Share on other sites More sharing options...
mike stehr Posted January 6, 2005 Share Posted January 6, 2005 It's kind of similiar to a old trick to revive CRT's Quote Link to comment Share on other sites More sharing options...
Marvel Posted January 6, 2005 Share Posted January 6, 2005 Craig, Pretty easy to bypass the tone control on this little guy. Two leads come off the input selector switch, into the PECs and tone pots, two wires to the volume pot. No stray wires heading off anywhere else. Be great if I had a schematic, but I don't. I've looked for months and no one has one for this model (KN928). I know the PECs are just caps and resistors, but without the schematic I can't replace them with newer parts. Sorry to hijack the thread. Marvel Quote Link to comment Share on other sites More sharing options...
coolrecords Posted January 6, 2005 Share Posted January 6, 2005 In instrument amplification which typically has an inverse relationship between age and quality... Tube rectification is sometimes sought for the voltage sage that can act as compression - This will happen in amps that are not up to the transients, under built, etc.... sometimes a "tighter", "cleaner" (subjective) sound is sought - thus one may find amps such from Mesa Boogie that can be switched between tube and SS rectification. What may be desirable in creating some types of music may not necessarily be the best choice in REcreating music. A well designed and built rectification system may not sound different to many ears as there should always be constant, and adequate power (not just voltage). Things get more subjective when discussion of "non-optimal" (subjective) design comes up. And before swapping from tube to SS ALWAYS go through any vintage amp and check components particularly the electrolytic caps - You can bring down a good amp/tranny by just swapping. The time the tubes take to get up to power vs. instantaneous voltage/current can mean the difference between function and junk - saw a sales demo of a "plug-in" replacement for a rectifying tube in a bass amp once - quite amusing... Quote Link to comment Share on other sites More sharing options...
garymd Posted January 6, 2005 Share Posted January 6, 2005 So Fini - Has your question been answered? Seems pretty logical to me. Quote Link to comment Share on other sites More sharing options...
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