June 15, 201115 yr Author Woot!!! Mine just needs to have the heaters hooked up plus sort the earth but I sadly have no time to spend on it...
June 15, 201115 yr Great work Kerry! Spritzer, if I was that close to finishing, I think I'd just pull an all nighter if necessary. I can't wait to hear what both you guys think of the amp.
June 19, 201115 yr birgir's unit up and running. Evidently he has a noisy pot in one of the batteries, same as the problem andy had. Must be a large batch of bad trimpots.
June 19, 201115 yr Which pot? Is it perhaps the one that is (nearly) directly over one of the LED legs and a resistor?
June 20, 201115 yr I'm wondering if it's related to the hissing issue that Inu found (and fixed). Seems like some extreme oscillation, that's cured once the amp gets a little more to a stable operating point. Then, once the pot is replaced, the other pot in that battery is already at a more sane location and the issue goes away. This would sorta make sense, given the fix that Inu performed (see link I posted a while back).
June 26, 201115 yr I've got two questions for the group: 1 - Does anyone have the part number for the coupler that goes from the Alps RK50 to the extension rod? 2 - The Neutrik connectors seem to push in a bit when you press the release tab. There is an unthreaded hole on the bottom of the neutrik connector where it mounts to the board. Has anyone tapped this and screwed it in? Is this recommended? Thanks. Also, I thought I would throw these pictures up...
June 26, 201115 yr The Alps shaft is about 8mm and the extension shaft is .25". I can look at McMaster, but wanted to see what other people did first.
June 26, 201115 yr Author I just enlarged the hole with a 8mm drill. I'll have to redo them since I can only get 6mm shafts here and it just makes a lot more sense to use a 8mm shaft. Speaking of my amp, I got new pots but the right channel is still fubar. Anybody whose dealt with loktal tubes knows this sound so the tube sockets are at the top of my suspect list.
June 27, 201114 yr Hi All Just wanted to share my (slow!) progress: PS Amp Seems i keep find small new components, i forgot to order ... peter
June 29, 201114 yr Assembling the mosfets 2sk216 and 2sj79 now is there any way to match them? (since there are a lot of parameters etc., and I dont know the operating mode/conditions). I allready did the simple test: http://www.4qdtec.com/mostest.html all K216 turned out fine. But got trouble with J79: I have 5 (1 extra - but from a different production batch. The 4 reads "6 G5" and 1 "0 J15 5yx"). Now one of the 4 cant be turned permanently on by the diode-tester (or my finger). the internal diode reads about 450 when off. Which suggests "some issue" with the internal capacitance. But i have no clue wether this is relevant. The extra from another batch works, but reads 425 when off. Which one to discard? Or better: what other test to perform? peter
July 5, 201114 yr Assembling the mosfets 2sk216 and 2sj79 now is there any way to match them? (since there are a lot of parameters etc., and I dont know the operating mode/conditions). I allready did the simple test: http://www.4qdtec.com/mostest.html all K216 turned out fine. But got trouble with J79: I have 5 (1 extra - but from a different production batch. The 4 reads "6 G5" and 1 "0 J15 5yx"). Now one of the 4 cant be turned permanently on by the diode-tester (or my finger). the internal diode reads about 450 when off. Which suggests "some issue" with the internal capacitance. But i have no clue wether this is relevant. The extra from another batch works, but reads 425 when off. Which one to discard? Or better: what other test to perform? peter Build myself a rough curvetracer, for testing/matching and the K216 seemed rather similar. And alle the J79 was ok - but the one from the different batch was quite different. However just as i finished, i somehow burned one of the good quad - and the dealer doesnt have any more from that batch So i need buy 2 new "low gain" types, to put in one of the channels peter Edited July 5, 201114 yr by pedefede
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