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Part Sourcing Assistance/Advice Thread


n_maher
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3 hours ago, johnwmclean said:

It’s really dried up out there, I’ve looked everywhere for KSC5026M for a HV supply, if any one has stock kicking around I need 4 pcs?

Happy to trade on something you may need, have quite a few bits and pieces.

You got PM.

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  • 5 weeks later...

Hi all! 

I've just bought via a friend in Tokyo a few transistors in a strange japanese shop (it has not it's own site). I want to test them and if they are genuine, then I will buy more. 

But how should I test them ? I've measured a breakdown voltage: 

230-240 volts for 2sk216/2sj79s from Japan

228-233 volts for 2sk214s from bdent.com 

Is it ok for genuine parts ?

Is it ok that 2sk214 and 2sk216 have almost the same breakdown voltage ? 

I am measuring with DY294 and etracer (tube curve tracer). 

I am going to trace full curves for 2sk216/2sk246gr via etracer at this thursday.

Do good curves mean that transistors are genuine ? If no, then what should I measure ? 

 

Thanks for help! 

Ps: example of breakdown measurement for 2sk214:

2sk214-breakdown-example.JPG

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If you test parts into hard avalanche breakdown at large numbers of mA, you can permanently change their characteristics. Generally if you want to check if the breakdown voltage corresponds to datasheet values you need to limit breakdown current to the tens of microamps region.

For example check the static characteristics in the original Toshiba datasheet of the 2SK246, where the breakdown voltage at each characteristic curve is limited to about 100uA.

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2 minutes ago, Craig Sawyers said:

If you test parts into hard avalanche breakdown at large numbers of mA, you can permanently change their characteristics. Generally if you want to check if the breakdown voltage corresponds to datasheet values you need to limit breakdown current to the tens of microamps region.

For example check the static characteristics in the original Toshiba datasheet of the 2SK246, where the breakdown voltage at each characteristic curve is limited to about 100uA.

I can't find what current measures DY294 in the breakdown test ( 

In the datasheet for 2SK246 Vgds is 50V and in my measurements I have 69-73 Volts. Maybe DY294 just can't detect 0.1 mA ( 

Unfortunately I can't limit current to 100uA in my etracer, but I will think what can I do. 

I hope the measurements will not damage the FET, because it measures using pulses with duration up to 5-10 ms. But I know it is still not safe. Thanks.  

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58 minutes ago, Rinat said:

I can't find what current measures DY294 in the breakdown test ( 

In the datasheet for 2SK246 Vgds is 50V and in my measurements I have 69-73 Volts. Maybe DY294 just can't detect 0.1 mA ( 

Unfortunately I can't limit current to 100uA in my etracer, but I will think what can I do. 

I hope the measurements will not damage the FET, because it measures using pulses with duration up to 5-10 ms. But I know it is still not safe. Thanks.  

on the 200V breakdown setting my dy294 initially puts out a maximum of 712uA (tested on a brymen bm869s) and about 530uA on the 1000V setting. This is with the dy294 powered at 6Vdc from a bench power supply.

if you reduce the input voltage to the dy294 to about 3VDC from the usual 6V, the 200V breakdown outputs about 180V at 375uA and the 1000V range gives about 570V at 270uA. 

about the lowest you can go is 2VDc input before the microprocessor crashes or the breakdown readings on the display get radically incorrect. At 2VDC input the 200V settings gives about 105V at 225uA and on the 1000V setting 365V at 171uA

Edited by jamesmking
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^^^ Not sure exactly what you're asking, many of us have used switches like what you're describing but not knowing what or how you're proposing to use one it's impossible to answer your questions.  Most uses that I'm aware of have been to trigger relays (power on/off, source selector) in which case it sees very little voltage or current and is serving its intended function.  If you're thinking about some other application, it'll require careful consideration.

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44 minutes ago, penmarker said:

Thank you, that made perfect sense. This switch is rated for 220V and I was planning to use it as the power switch. A trigger for a relay sounds a lot more safe it seems.

Well, go with the switch rating then, relative to your intended usage. What exactly does the data sheet say, and what are you planning to install the switch in?

I use a locking anti-vandal switch rated for 250V @ 3A for mains power switching duties in a couple of pieces of gear. They are running on 120V, draw about 0.25A steady-state, and are behind 1A fuses. Rating exceeds operating conditions, part is good to use.

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I use illuminated latching anti-vandal switches on all my gear. The interesting thing is that although the LED connections have a + and a - moulded in, the LED is bidirectional, and illuminates equally whichever way it is connected. At least with the ones I use.

Blue LED of course.

I also set the current on all front panel LEDs to be very low, so they don't intrude when listening in the dark.

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5 hours ago, Craig Sawyers said:

The interesting thing is that although the LED connections have a + and a - moulded in, the LED is bidirectional, and illuminates equally whichever way it is connected. At least with the ones I use. 

The polarity is usually there for the dual color LEDs. I bet the single LED and dual LED units are identical to streamline manufacturing and save costs, except the 'single' units have two LEDs of the same color.

7 hours ago, penmarker said:

These came from china so there are no datasheets. I was planning to put these in a new Dynahi but I've decided to get the momentary counterpart to trigger a relay instead.

Maybe I'm overly cautious, but I wouldn't use a part if I didn't have a spec sheet.

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43 minutes ago, Craig Sawyers said:

Yep, looks about right. I bet they use the same casing across all the styles, and just use two of the same LED for the single color version, meaning polarity doesn't matter. And for the 19+ mm sizing, contacts rated at 250V 3A just like the eSwitch I've used recently.

To @penmarker, again, maybe I'm overly cuatious, but I think you are much better served using a quality switch of known providence.

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  • 2 months later...

I don't Kerry, but I used to buy directly from Linear Technology. Now that they have been bought by ADI, I don't see how to do that on their website. I couldn't check to see if they even have availability.

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So I'm curious what the current SOTA is with respect to non-potentiometer volume control for a balanced DIY amp.

Context: I'm working through an repair/refine/replace blitz of all my DIY gear. My Exstata - which if you can believe it is still kicking after 10+ years - has one of the dual PGA2320 volume controls that Marc developed way back then. It works great, and was incredible $$$ value, but it seems ripe picking for a small update project.

I see the TPA Joshua Tree is still kicking, still dead easy to implement, still has limitations of variable input impedance and always-on relays. AMB's δ1 uses latching relays and has constant impedance, but having to do a full Arduino control board build seems a but nutty for just an attenuator. And Kevin was busy a few years back with something that seemed technically excellent, but getting PCB's and programming done is probably way beyond my skillset and the time I am willing to invest.

Thoughts or suggestions? Thanks! :)

 

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The Gerbers for Kevin's attenuator board are still available. I believe Kerry had worked up a controller board with rotary attenuator for that as well, including the software?

One control that looks good and has good reviews is the Muses72320. I'm currently (very slowly) building a UGS Muse preamp based on the Pass UGS and using the NJR MUSES72320V-TE2-ND IC. There is a project on diyaudio using these chips and apparently can handle up to an 8 channel control. https://www.diyaudio.com/forums/swap-meet/322983-muses-volume.html. The chips seem to be in short supply right now (both Digikey and Mouser carry them, both out of stock).

 

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3 hours ago, Pars said:

The Gerbers for Kevin's attenuator board are still available. I believe Kerry had worked up a controller board with rotary attenuator for that as well, including the software?

One control that looks good and has good reviews is the Muses72320. I'm currently (very slowly) building a UGS Muse preamp based on the Pass UGS and using the NJR MUSES72320V-TE2-ND IC. There is a project on diyaudio using these chips and apparently can handle up to an 8 channel control. https://www.diyaudio.com/forums/swap-meet/322983-muses-volume.html. The chips seem to be in short supply right now (both Digikey and Mouser carry them, both out of stock).

 

That Muses project looks really neat. But yeah, availability of the chips is quite bad, and it will almost certainly preclude it as a pre-Xmas project. Will definitely keep an eye on it for new builds though, so thanks!

I'm sure the Kevin/Kerry option is probably the best, but making my own boards is the difference between a weekend soldering/wiring project, and learning an entire new skill. Unfortunately, I think my brain is full.

Edited by Beefy
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