March 13, 20197 yr 19 minutes ago, mwl168 said: Happy to organize a GB if there is enough interest. Please raise your hands and state quantity desired here if interested. I guess you already had me in mind, right? Edited March 13, 20197 yr by jose
March 13, 20197 yr The main board does not need to be assembled but the regulator modules do (2 per power supply). On 3/12/2019 at 8:07 AM, JoaMat said: It looks like the LT1021 is abandoned by most supplier. Mouser is out of stock but claims that it’s on order. There is another 10 volt reference LT1236-10 that I think should be a good alternative. I’ve tested it in LTspice model by Kerry (jump here for reference and more info) and it seems to do the same as LT1021-10 but with 0.2 mA lower current with same current set resistor. Someone has to verify LT1236 works. I guess Kerry needs a couple of LTxxxx in above PSU. For the Power supply modules, using the LT1236 should reduce the heat on the CCS pad feeding the reference by about 5 deg C. I haven't tested this yet, but it seems like a good substitute and possibly preferable. PS - Just thinking out loud, the LT1021-7 might be the best option here. Edited March 13, 20197 yr by Kerry
March 13, 20197 yr Interested depending on cost Edit: If there will be runs for GRHV and GRLV as well then I am definitely in for a set. Edited March 14, 20197 yr by Scgorg Clarification
March 13, 20197 yr 3 hours ago, JoaMat said: Two sets, please. Thanks for doing this Michael. Yes. Thank you Michael!
March 14, 20197 yr We'll also need to do the GRLV boards as well. So to get this up and running is 2x GRHV78xxx, 1x GRLV78xx (mini or micro), 1x GRLV79xx (mini or micro) + the main board.
March 14, 20197 yr There are three wire jumpers on each boards. Two for big tubes filament so two good wires between the tubes. Then there is a small jumper along one side of OP27 (see silk screen component side (which one now that is…)), easy to forget - I use a piece of a wire from power resistor. It connects -15V to the balance opamp.
March 14, 20197 yr Author I started a thread dedicated to the group buy of Kerry's PS boards and JoaMat's mini T2 boards. Let's move all GB related discussions to the new thread. Thanks! Edited March 18, 20197 yr by mwl168
March 18, 20197 yr Now when there are nice tapping tools out there I think I try mount sands direct on heat sink. I've done this today. I cut of 20 mm of the board where the bracket should be so now it’s 80 mm x 160 mm. The layout was not meant for this so there is a need for a couple of extra jumper wires. Most things are doable. Here is my tapping tool with rather long shaft M3 tap.
March 23, 20197 yr To the right is a just finished mini T2. Transistors mounted direct onto heat sinks. Inner width is 159 mm (6.26 in). Most of the components are moved from my first amplifier with in kitchen made boards, including the small LEDs and diodes. Heat sinks, all connectors (STAX, Neutrik, Amphenol) are from one of my full size DIY T2 (RIP – I’ll build a new one with all original parts) This is my third mini T2. The building process has been straight forward. The only thing is that left channels of all the three amplifiers have a bloody annoying hum during the first minutes after start up. I’ve no idea what causes it. Edited March 23, 20197 yr by JoaMat
March 23, 20197 yr Author 1 hour ago, JoaMat said: The only thing is that left channels of all the three amplifiers have a bloody annoying hum during the first minutes after start up. I’ve no idea what causes it. Nicely done JoaMat! Taking a blind shot in the dark, if the hum only occurs in one channel and goes away after a few minutes, could it be 9ne of the tubes?
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