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Closed - Megatron and GRHV PCB GB

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Got my boards today. Thank You! I have posted pics before but here are some more of my build. I noticed these boards have a 12 V for the filaments. The old board did not have it.  

12v filament version posted pretty sure the original was done the way it was to accomodate the 6dj8 tubes for those that wanted to do that edit: the filaments of the output tubes are tied to

All international-destined packages have been sent too. I'll PM each with the postage. Happy building!

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11 hours ago, gepardcv said:

Are you thinking a two-box build? The GRHV will need external heatsinks for the 10M90S and the SiC MOSFET parts, which complicates a single-chassis layout, given the size of the Megatron board, or calls for a huge box.

Yes, I am planning for a two-box build for the Megatron for the reasons you stated.

it would need to be a huge chassis for a single-box Megatron with the large amp board, power supply and all the transformers. Unlike the HV Carbon, BH and Grounded Grid, I expect the GRHV will run much hotter for the Megatron with all the tubes it needs to power. So yes, external heatsink for the GRHV for sure.

I have most of the layout done in my mental execution:D But I have one snag I have not figured out - how to get the AC main supply to the two filament transformers for the CCS tubes that need to be mounted in the amp chassis.

I love to hear people's ideas. 

Edited by mwl168
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Maybe a separate umbilical for the AC lines? Annoying to build, yes, but should help keep the EM noise away from everything else.

I'm seriously thinking about joining this GB, if only to have the boards for the future. Which GRHV version do you plan to run? I suggest the split ones for layout flexibility, but could be convinced otherwise.

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Either the split or dual GRHV boards is fine with me. But best to have one version made instead of two - the number of boards effects the cost greatly as is the case always. 

If people can respond with their interest here we can start to shape the plan. 

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Looks like most of the interest is in the split version of GRHV. 

If those interested can respond with your desired quantity I can get a quote from PCBnet.

No restriction on number of Megatron amp boards and GRHV boards - any combination is fine. 

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I got quotes back for the GRHV split boards and we have a decision to make.

For 2mm thickness and 3oz copper GRHV split boards, with the current number of boards people have shown interest for,  it will be about $57 USD per set (one positive and one negative PCB) from PCBnet. If we go with SeeedStudio, it's about $30 USD per set.

The amp board (2mm and 4oz copper) from PCBnet will be about $36 per set (two channels on one board). We can save about $10 per board going with Seeed but Seeed only have 3oz option for copper weight.

The numbers above include my estimated shipping cost from the fab house to me. You'll need to add shipping from me to you for the total cost.

I suggest we stay with PCBnet for the amp board.

For the GRHV, which option do you all prefer?  

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12 hours ago, Whitigir said:

The more copper the better :) I vote 4oz

I did not get quote for 4oz copper option for the GRHV split boards from PCBnet. Obviously it will be more than $57 per set.

3oz copper really should be plenty for the PS boards IMO. The reason I suggested 4oz copper for the amp boards is because of those traces for the EL34 filament supply. 

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I plan to close this GB by end of day Sunday, May 7 and hopefully collect payment and get the boards ordered the following week. 

Here is what we have so far:

                  AMP board         GRHV split

Jose                 2                         2

PICaudio          2                         3

Whitigir             1                         1

gwrskien           1                         1

Looser101        2                         2

gepardcv          1                         1

mypasswordis   0                         2 Neg.

chiguy               1                         1 


Please let me know if corrections.

Also, we'll take a democratic approach toward the decision of whether to go with PCBnet or Seeed for the GRHV boards. One vote per set. Majority wins :) 


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