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The ultimate DIY? A Stax SRM-T2!


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2 hours ago, Rinat said:

These ones for example: 

https://www.mouser.com/datasheet/2/308/1/MBT6429DW1T1_D-2315127.pdf

https://www.onsemi.com/pdf/datasheet/bc846bdw1t1-d.pdf

https://www.analog.com/media/en/technical-documentation/data-sheets/MAT01.pdf

https://toshiba.semicon-storage.com/info/docget.jsp?did=19156&prodName=HN1C03FU

https://www.digikey.com/en/products/detail/linear-integrated-systems-inc/IT120-PDIP-8L/13688035

https://fscdn.rohm.com/en/products/databook/datasheet/discrete/transistor/bipolar/emx26.pdf

 

I would try the first one or MAT01AH if I were sure that I don't need > 80v of Vce at the battery ( 

And I am not sure that we really need here low output capacitance. If no then there are another nice options. 

But I don't think that using separate single transistors is a good idea for current mirror due to temperature drift. I prefer one crystal or at least one package. 

Have you seen this, BCV61? To be used as current mirror. You get a hundred pieces for 22 USD, less than one 2SC3381.

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36 minutes ago, JoaMat said:

Have you seen this, BCV61? To be used as current mirror. You get a hundred pieces for 22 USD, less than one 2SC3381.

No, thanks for the option!

But MBT6429DW1T1G is cheaper (It is in stock at arrow.com), has lower capacitance, higher hfe at 50nA (it is a current in the active battery), similar noise. 

BCV61 has matched halves. I will think, thanks.  

So - do you agree that the high breakdown voltage is not required here ? 

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  • 2 weeks later...
On 6/21/2021 at 3:43 PM, starcat said:

Yeah, they take a long time but are fun to make 🙂 I just completed the umbilical for the BHSE I am building (with original HeadAmp boards) and it took long as well despite using an AMP connector with crimp type pins. To be honest, I liked that connector much more than the Amphenol we use for the T2. It is like cutting wires, crimp pins on both sides and insert into the connector housing and voila. The pins are automatically isolated within the connector housing as well, so no fiddling with shrink tubing or soldering into the connector and the pins are available for different AWG sizes as well. A very nice system. 

Craig, do you have any part number for that special glass fiber insulation and how long are your umbilicals? I am planning for 90cm, 3ft. 

IMG_1506.jpeg

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Hi starcat. What are P/N of the connectors and housings and pins you are using?

I'm tempted to try these. As far as my quick search revealed, pins and wire entry seals don't come in bundle and are sold separately, aren't they?

My concerns is that CPC series seems to be rated for 250VDC/VAC only, and that there is no space between the thread and the gasket, which means that the gasket itself will be outside the panel/case. Any considerations?

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2 hours ago, Helium said:

Hi starcat. What are P/N of the connectors and housings and pins you are using?

I'm tempted to try these. As far as my quick search revealed, pins and wire entry seals don't come in bundle and are sold separately, aren't they?

My concerns is that CPC series seems to be rated for 250VDC/VAC only, and that there is no space between the thread and the gasket, which means that the gasket itself will be outside the panel/case. Any considerations?

I use these for psu to amp connectors and sockets.

https://www.ebay.co.uk/itm/254196620095?hash=item3b2f4c9b3f:g:-KwAAOSw4fpcr1Kr

https://www.ebay.co.uk/itm/264278975567?hash=item3d8841244f:g:4nkAAOSwr-Vcr1Ii

I use flexible copper stranded silicon wire rated at 1000V and put about 3cm of heatshrink over the solder joints. I test with an insulation tester they there is no breakdown between adjacent pins at 2500V. There is breakdown at 5000V but that's close to 10 times more voltage difference than the wire will actually carry in practice. I try to not have two wires with vastly differing voltages adjacent to each other and I carry ac voltages e.g. tube heaters on a separate cable to dc voltages. where possible I also avoid using adjacent pints and try to leave a circle of unused pins around a pin carrying high voltage.

Edited by jamesmking
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Wow Soviet) A good old wine)

Correct me if I'm wrong, but like AMP series, thread all the way down to gasket (rarely beautifully looking) implies that the gasket is left outside the panel. I usually like to put connector inside the case (this is low voltage Neutrik Speakon, but same idea).

 

qwer.jpg

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19 hours ago, Helium said:

Hi starcat. What are P/N of the connectors and housings and pins you are using?

I'm tempted to try these. As far as my quick search revealed, pins and wire entry seals don't come in bundle and are sold separately, aren't they?

My concerns is that CPC series seems to be rated for 250VDC/VAC only, and that there is no space between the thread and the gasket, which means that the gasket itself will be outside the panel/case. Any considerations?

I used 3 different connectors, different for AC and DC. Something like this:

https://www.aliexpress.com/item/4000011885330.html?spm=a2g0s.9042311.0.0.27424c4dG8z02S

https://www.aliexpress.com/item/32814240840.html?spm=a2g0s.9042311.0.0.27424c4dG8z02S

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I’ve tested two dozen 2SA1486 randomly out of my small supply with same meter as you. I get roughly hFE at 60 - 70 and VBE at 0.60 - 0.65V. If possible, test breakdown voltage. Some of us use transistor tester DY294 for that purpose.

Your measurements diverts to much for my taste… even compared to datasheet...

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A couple of years ago I bought some 2SA1486s from Taobao, the Chinese equivalent of eBay, for about 40 cents a piece. They all check out fine on my Tek 577 curve tracer. I got the green ones with formed leads, likely leftovers from some factories' custom orders. The same picture shows up on Aliexpress. Possibly from the same source.

The same seller sold me some 2SA1968s for a bit more money. They checked fine too but looked like rescued from dumpsters.

There are many sellers selling fakes, but if you know the right package, the right font, and can tell a grounded and then remarked top surface, with a little luck you can still have genuine parts for less.

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10 hours ago, audiostar said:

He has has been known for selling fakes. Try to return those. 

I have got lots of fakes from little diode.... they are scum. I reported them to ebay telling ebay that the fakes could result in fire or electric shock ebay did absolutely NOTHING.  I reported them to paypal... they did NOTHING.

nikkoelec on ebay also sells fakes... took 3 months to get a refund.

I even explained to the sellers how I determined they are fake. they showed zero interest in checking their stock... and continued to sell the same fake parts... I even purchased the same part from them over multiple months to prove they where continuing to sell known fake parts even after my returns...  no one cares. one day someone is going to get hurt. its disgusting.

 

 

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I agree with both of those. I *have* had good components from both, but also fakes. The worst was my original T2 build, when I bought 2SC3675's from Nikko (it was called Dalbani back then). They were fake, with low breakdown voltage. There were sparks when I turned the T2 on the first time. Major collateral damage - it killed all the lateral FETs too and a bunch of other stuff.

So in particular avoid those suppliers.

I bought fake MT200 package power transistors from an eBay seller (neither of the above). I fortunately tested them on a curve tracer before using them. Low breakdown voltage (150V instead of 250V) and heavy beta modulation. Cracked one open and found a tiny piece of silicon in there 10% the area of a genuine part. Reported it to eBay - absolutely no action. As far as I know he is still selling them.

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1 hour ago, judo said:

I did not follow the thread so maybe not appropriate I have seen 2sa1486s at bdent in stock now. Not cheap. About Dalbani I have some 2sa1968s from them definitely no fake but I bought these ten years ago about.

They have 25 pcs in stock, while the original scheme requires 26 pcs ) 

Personally, I would suggest to use 2sa1413-z if one wants to strictly follow the original scheme: it is the same transistor in TO-252 case (bdent says that it is D-PAK, but they have sent to me TO-252 version, which is even better for me). 

https://www.renesas.com/us/en/document/dst/2sa1413-z-data-sheet?language=ja

But I think that STN9360 is even better option than 1486/1413....

Edited by Rinat
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6 hours ago, Rinat said:

They have 25 pcs in stock, while the original scheme requires 26 pcs ) 

Personally, I would suggest to use 2sa1413-z if one wants to strictly follow the original scheme: it is the same transistor in TO-252 case (bdent says that it is D-PAK, but they have sent to me TO-252 version, which is even better for me). 

https://www.renesas.com/us/en/document/dst/2sa1413-z-data-sheet?language=ja

But I think that STN9360 is even better option than 1486/1413....

TO-252 = D-PAK

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