jwzhan Posted July 13, 2012 Report Posted July 13, 2012 Does anyone know if Lil Knight were active last week? I was buying a set of KGSSHV boards and the communication was great. My payment went through on July 5th, and I have not heard back from Tran since that. I know that Tran is no scammer whatsoever and I have no problem waiting, but It's quite frustrating to be left in the dark.
Victor Chew Posted July 13, 2012 Report Posted July 13, 2012 I wounld not worry about it. He can go quite for a while sometimes and then he comes back with replies. I think he has school exams too.
eggil Posted July 13, 2012 Report Posted July 13, 2012 Lil Knight is a gentleman. I dealt with him quite bit when I helped him distribute boards in the US. Give him some time.
kevin gilmore Posted July 13, 2012 Author Report Posted July 13, 2012 now i need to stock .01uf 1kv wimas cheap ceramic discs. Not wimas.
jwzhan Posted July 13, 2012 Report Posted July 13, 2012 Tran just PMed me. The boards are on their way. I guess I should train myself to be more patient.
vvs_75 Posted July 13, 2012 Report Posted July 13, 2012 correct, and you will need 2 of them and they have to be 1kv rated reed relays. Anything else sparks pretty nasty. Any chance you could suggest one? Thank you.
kevin gilmore Posted July 13, 2012 Author Report Posted July 13, 2012 something like this http://www.mouser.com/ProductDetail/MEDER-electronic/SIL12-1A72-71D/?qs=6LkQJpCWFTifeu4Ctb4tFgDRzs7G8uTK would work on a 12 volt power supply line with a delay.
luvdunhill Posted July 14, 2012 Report Posted July 14, 2012 Stax uses reed relays? I'm surprised. I certainly would not attempt this.
kevin gilmore Posted July 14, 2012 Author Report Posted July 14, 2012 stax definitely did not use reed relays. since i don't have one open at the moment i can't pick the exact part they used. But they also used lower voltages too, so if you were to use the stax relay at 450 vac, it might not behave so nice. I use those sealed reed relays at work up to and including about 15kv. (well different models, but the same thing) switching AC and switching DC. work great.
spritzer Posted July 14, 2012 Report Posted July 14, 2012 The Stax amps use just a standard relay but the AC voltages are far lower. I'll check out the part number when I do final checks on this SRM-007tII I have here.
johnwmclean Posted August 20, 2012 Report Posted August 20, 2012 I’m going to do some experimenting with the bias current. My 400mm 3U Modushop heatsinks are running cold with the A1968’s . I assume the only change out is the 1.2k resistors for the current source? I don’t want to go too nuts, just enough for some get some heat happening. How to do I go about working this out?
TMoney Posted August 20, 2012 Report Posted August 20, 2012 Please do report your results, John. I'll be very interested in seeing if how high you can crank her and if you can hear a difference.
johnwmclean Posted August 20, 2012 Report Posted August 20, 2012 Please do report your results, John. I'll be very interested in seeing if how high you can crank her and if you can hear a difference. I shall, I don’t want to push her sky high, just enough to justify these big sinks. I’m going to do some experimenting with the bias current. My 400mm 3U Modushop heatsinks are running cold with the A1968’s . I assume the only change out is the 1.2k resistors for the current source? I don’t want to go too nuts, just enough for some get some heat happening. How to do I go about working this out? Well for starters I’m not using 1.2k resistors, I’m using 500R for the A1968 current source, I really should pay attention. In regards to increasing current I assume the 500R’s are to be replaced? Just after a little knowledge on how to derive mA values.
kevin gilmore Posted August 20, 2012 Author Report Posted August 20, 2012 Its the output stage current you want to bump up. You can bump up the 3rd stage a bit, but no reason to go crazy on that one.
spritzer Posted August 20, 2012 Report Posted August 20, 2012 To change the current in the fourth stage you have to increase the voltage reference, i.e. the led.
kevin gilmore Posted August 20, 2012 Author Report Posted August 20, 2012 or decrease the emitter resistors.
johnwmclean Posted August 22, 2012 Report Posted August 22, 2012 Thanks Kevin and Birgir, I really appreciate your help with this. I've been digging around here and in the Headwize forums. I can't find a formula for the final output in the fourth stage. If a 2.1V LED yields ~ 4 x 5.5ma for 20 watts. How do I for example equate a 3.8V LED? I just don't want to crap shoot this... John
kevin gilmore Posted August 22, 2012 Author Report Posted August 22, 2012 2.1v - vbe junction (.7) /180 ohms == 7ma. But the led's actually are more like 1.7 volts due to the drive current. So its about 5.5ma. You can change to a higher voltage led, but the red led's thermally match the output transistors. So you want to cut the 180 ohm resistors to something like 150 or 120 ohms.
johnwmclean Posted August 23, 2012 Report Posted August 23, 2012 (edited) Thats absolutely solid. Invaluable info, thanks Kevin. Edited August 23, 2012 by johnwmclean
wink Posted August 23, 2012 Report Posted August 23, 2012 (edited) So, 150 Ohms should give 6.60mA, and, 120 Ohms should give 8.25mA. Hopefully. 100 Ohms = 6.9mA 82 Ohms = 12.07mA 68 Ohms = 14.56mA 56 Ohms = 17.68mA 47 Ohms = 21.06mA Edited August 23, 2012 by wink
TMoney Posted August 23, 2012 Report Posted August 23, 2012 IIRC the BH and BHSE run at about 18mA. I've got the same sinks and I wonder if we'll be able to approach (or pass) that.
justin Posted August 23, 2012 Report Posted August 23, 2012 temperature rise for a 12" length is about 25C for 20W
justin Posted August 23, 2012 Report Posted August 23, 2012 if anyone is looking for 2SA1968 transistors, these visually appear to be authentic parts at a good price: http://www.ebay.com/itm/5pcs-2SA1968LS-Original-New-Sanyo-PNP-Dynamic-Focus-Transistors-A1968LS-/110935720719?pt=LH_DefaultDomain_0&hash=item19d448c30f#ht_3700wt_1398
eggil Posted August 23, 2012 Report Posted August 23, 2012 I have never bought from ebay for fear of counterfeits. I am tempted though....
livewire Posted August 23, 2012 Report Posted August 23, 2012 (edited) Do a search in the T2 thread for "Dalbani". Buyer beware! If they honor their 14 day return policy, one could dust off the trusty transistor tester and check for Vbr. VCEO should test at 900V minimum if they are the real deal. If not, return them FAST! Edited August 23, 2012 by livewire
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