kevin gilmore Posted May 14, 2017 Author Report Posted May 14, 2017 (edited) using Kerry's servo, but a resistor to make +200 by the way the alternate name of this board will be t8000DR (DR as in done right) edit: fixed font sizes Edited May 14, 2017 by kevin gilmore 10
Whitigir Posted May 14, 2017 Report Posted May 14, 2017 You are amazing, how about this in combination with Grounded Grid !
kevin gilmore Posted May 14, 2017 Author Report Posted May 14, 2017 9 minutes ago, Whitigir said: You are amazing, how about this in combination with Grounded Grid ! that's enough for today 3
Laowei Posted May 14, 2017 Report Posted May 14, 2017 One request Kevin, if this is applied to the GG circuit layout some day. If possible, would be nice if the PCB height could be kept within 130mm/5-1/8 inch max.
kevin gilmore Posted May 14, 2017 Author Report Posted May 14, 2017 looks like the best I can do is about 5.7 inches current gg board is 4.7 inches 3
Laowei Posted May 14, 2017 Report Posted May 14, 2017 58 minutes ago, kevin gilmore said: looks like the best I can do is about 5.7 inches current gg board is 4.7 inches Thanks for taking the time to look into that, Kevin. Will gladly work around the larger dimension on my end (new cases) when this new tube input GG happens. Got a gut feeling this will be a killer amp!
nopants Posted May 15, 2017 Report Posted May 15, 2017 far too many projects to keep up, but it's always so tempting once you see the artwork...i remember reading that kevin was championing the el34 ccs in the megatron, should wire that in instead so everyone gets the tube complement they want even if it's not the grounded grid output. kidding of course, even if it does sound monstrous.
kevin gilmore Posted May 15, 2017 Author Report Posted May 15, 2017 well that is one way to make a fully dc coupled megatron 1
mwl168 Posted May 15, 2017 Report Posted May 15, 2017 1 hour ago, kevin gilmore said: well that is one way to make a fully dc coupled megatron i thought Megatron is already DC coupled?
mwl168 Posted May 15, 2017 Report Posted May 15, 2017 (edited) Should have looked at the schematic before I spoke - yes, .22uf coupling capacitors between the stages. Edited May 15, 2017 by mwl168
kevin gilmore Posted May 16, 2017 Author Report Posted May 16, 2017 (edited) not to scale, carbon board is 5.45 x 4.72, tube output board is 5.6 x 5.52 newest versions of the boards Edited May 17, 2017 by kevin gilmore 9
Whitigir Posted May 16, 2017 Report Posted May 16, 2017 (edited) Woahhhhhh!!! Thanks Kevin ! I am in for a group buy of these boardS please! if my wife could fix this kinda sandwich Edited May 16, 2017 by Whitigir
Rossliew Posted May 16, 2017 Report Posted May 16, 2017 Anyone intending to build a working model soon? ?
joehpj Posted May 16, 2017 Report Posted May 16, 2017 I was thinking to build one adjustable DC supply to use some P88CC or 6N23P. Those have much more reasonable prices. Filament will sit a little bit at negative. So negative LDO is preferred?
kevin gilmore Posted May 16, 2017 Author Report Posted May 16, 2017 actually the cathode sits at +1.5 volts, very similar to T2. 1
kevin gilmore Posted May 17, 2017 Author Report Posted May 17, 2017 Kerry needs to publish the latest schematic with his servo. posted version does not have enough current to drive the opto. would still work without the servo 1
Kerry Posted May 17, 2017 Report Posted May 17, 2017 (edited) Looking good @JoaMat Here's the new schematic with the updated servo. It would be very much appreciated if some folks could check Kevin's boards against this schematic. Thanks EDIT: Updated schematic to match transistor values. Edited May 17, 2017 by Kerry 4
JoaMat Posted May 17, 2017 Report Posted May 17, 2017 Great, a new version of offset servo. I can’t remember how many versions we have seen so far, but as I remember one of the first was found in Kerry’s KGST (and Stax T2 of course). 1
mypasswordis Posted May 17, 2017 Report Posted May 17, 2017 Any chance to shave just a few more mm off the length of the tube input Carbon boards? Maybe on the left side the zener string has space to be moved and the traces adjusted a little? Then I would be able to squeeze it into this standard size ebay case, which has 300mm internal length: http://www.ebay.com/itm/122099811096 1
congo5 Posted May 17, 2017 Report Posted May 17, 2017 (edited) 10 hours ago, Kerry said: check Kevin's boards against this schematic minor differences: board looks good, don't see any problems board uses resistor + zener string instead of U10 D3 has a 350K resistor to ground connection of R15 changed and values of that and R16 adjusted Q7 Q8 Q9 Q10 are KSA1156 instead of STN9360 on schematic trimpot added to R12 for offset Q13 collector has an added 100k 2W resistor Edited May 18, 2017 by congo5 silkscreen reading error
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