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Kerry Design mini GRHV\GRLV and JoaMat mini T2 Group Buy


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I am moving Kerry's mini GRHV\GRLV GB discussion to its dedicated thread here. I also included JoaMat's mini T2 here to see if we have enough interest for a GB.

The table will be updated periodically as more people participate. Apologize if I missed someone or something - just let me know so I can correct the data.

I put down one set for those that have not decided on the number of sets they want. 

The plan is to have assembled GRHVxxx boards, rest of boards will be PCB only.

See discussions on the PS in this thread. mini T2 build discussion in this thread.


Construction notes:

  • R3 and R2 determine the regulated voltage for GRLV. The formula is Vout = (R2 + R3)/R3 * Vref. Vref is the reference voltage of U4 (LT1021).
  • R7, R8, R9, R10 determine the regulated voltage for GRHV. The formula is Vout = ((R8 +R9 + R10)/R7 + 1) * Vref.  Vref is the reference voltage of IC1 (LT1021). You want to keep R8, R9 R10 values close so they have even voltage drop across each of them.  
  • On the PSU Main board, R22 (100K) and C17 (470uf) set up the delay time for HV. The 100k/470uf combination provides a roughly 45 seconds delay. Increase R22 or C17 to increase the delay time. C17 needs to be rated 5VDC or higher.


Board dimensions:

mini T2: 160mm x 100mm 

GRHVxxx: 41mm x 31mm

GR78xx/GR79xx: 30mm x 20mm

Main board (PSU): 140mm x 90mm


See BOM for boards at the bottom.


Blank in the GRHVxxx-bare column indicates that the participant has not responded on this thread to indicate the preference for bare or partially-assembled boards and is deemed to opt for partially-assembled board by default as previously communicated.   





GR78xx - V2 .xlsx

GRHVBase-BOM - V2 production.xlsx


Edited by mwl168
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Micheal, can you add me/skooby to the PCB list:

4 x grhv, 4 x grlv78**, 4 x grlv79**, 2 x psu main board, 2 x t2 mini

T2 mini board is married right, not separated (one board for both left/right chn)?  Thanks for doing this, Micheal!  Thank you to Kerry and Joachim for sharing the designs!

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22 hours ago, Whitigir said:

Please count me in, GRHV 6x, GRLV 78- 2X and 79 -2X...uhm what is this mainboard ?

You can find the information in this thread. 

The main board has the rectifiers, filtering caps and timed delay circuit for the HV among other things.

Edited by mwl168
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