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mwl168

DIY mini T2 Build Thread

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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?  ;D

Edited by jose

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At least one full set for me, and depending on cost some more.

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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 by Kerry
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Hands raised :), two full sets.

Edited by MLA

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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 by Scgorg
Clarification

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3 hours ago, JoaMat said:

Two sets, please. Thanks for doing this Michael.

Yes.  Thank you Michael!

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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.

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i'm in for; 

2x GRHV78xxx

2x GRLV78xx (mini or micro)

2x GRLV79xx (mini or micro)

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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.

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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 by mwl168

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Now when there are nice tapping tools out there I think I try mount sands direct on heat sink. I've done this today.

IMG_0267.thumb.JPG.3607637bfc702129704707a4be036cae.JPG

IMG_0266.thumb.JPG.e0e1349bac3f6607f7c01ab35419d002.JPG

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.
IMG_0268.thumb.JPG.b7492bc2f7366a57d97c37b79b921c0e.JPG

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To the right is a just finished mini T2. Transistors mounted direct onto heat sinks. Inner width is 159 mm (6.26 in).
IMG_0275.thumb.JPG.5924658f1a5706227252a28f5640b5f4.JPG

Most of the components are moved from my first amplifier with in kitchen made boards, including the small LEDs and diodes. IMG_0273.thumb.JPG.64d92b0cf0260fd3d45ee9a7addf2fc0.JPG

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 by JoaMat
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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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