Search the Community
Showing results for tags 'bias'.
Found 2 results
My previous power amp I always just got it biased by the people who sold me the tubes and have to admit to have never adjusted them myself afterwards being scared to touch it while it was running. My new power amp came with instructions for biasing the valves and a tool to do it with. I checked the bias shortly after installing it and everything was nigh on perfect. After reading a reviewer say he checks tubes at 0, 100 and 200 hours, I then checked it again after 200 hours clocked up on the tube counter and most had drifted down slightly (.5-1mV) and I adjusted it. That's certainly not enough for a noticeable sonic difference and while I've read lots about how often the bias should (or should not be checked), I'd like to hear from others with tube amps regarding how often they check their biases.
Hello there, first of all sorry for my english. I heve sign in to this forum seeking help. 3 months ago my Sansui AU-888 right chanel has burned...most of transistors went down. I menaged to replace components with equals or similar replacements, still i stoped on bias mesurment/adjusting mA and mV. I hoped member "skippy124" with his large experiance could help me...sending instructions where to plug in multi-meter to mesure mA, i poses shematic but "plug + to 2 and - to B1" is just black magic for me. Things i have done so far: Inserted right quick acting fuses Replaced burned 1Kom resistor (same for left channel to keep them "same", as new resistors have +/-5% and old one have +/-10% tolerance) Changed all caps to Phanasonic for Audio, nichicon fine gold/fine grade, mkt, Elna for Audio, same capacity exept for main filter caps, few are bipolars as schematics sugest etc. Changed VR regulation pot's to new ones (i heared old's are preety bad) Switched voltage selector from 220 to 230 (right value in my "country", i know voltage varies +/-10% but i wanted to be on the safe side) As all right chanel transistors burned and infamous "flying sourcers" ware present i decided to change them all: 2SC281 -> 2N3904 ....(in service manual there is 2SC984 but mine had 2SC281) SC1111 -> C1402 2SC680 -> 2SC5171 2SA566 -> 2SA1930 CDC 8002 -> 2SC5171 CDC 9002 -> 2SA1930 Are transistors right choices? in the future, what to insert in place of XA-495G ? transistors whare choosen from bunch to mach hFe, are mounted on silicon thermopads and most with handcrafted "radiators" ("to be on the safe side") now i need specific photos and instructions other than from unclear (for me) manual where to plug multimeter to set proper mA (is it in place of pulled out fuse? F003/F004) mV mesurment is clear. also is "minimal counterclockwise" = "turn to the right as far as possible" ? If no one help me i will be forced to give this amp to some spec...problem is i spend most of my money reserves already =( Link to two photos, shematics, datasheet of transistors and service manual: http://www.mediafire...iokncl6stku6cou Regards and thanks in advance.