I took your link down because I am no longer selling them. Sorry. But I don't want a bunch of people emailing me about it.
FYI, my kit included over one thousand parts, all of very high quality, and three professionally-made boards. And even if I bought enough of everything for ten or twenty units at a time, the parts cost was too large a fraction of what I could sell them for. I guess I got a little carried away with the last re-design.
FYI, my kit included over one thousand parts, all of very high quality, and three professionally-made boards. And even if I bought enough of everything for ten or twenty units at a time, the parts cost was too large a fraction of what I could sell them for. I guess I got a little carried away with the last re-design.
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Ah, but don't forget that mine also needed an oscilloscope.
Price by value, not cost, and hope the two never meet!
Oh, I went ahead and expunged my ordering instructions and put the link back up.
P.S. I used to sell mine as a 12V-DC-powered unit, only. I think maybe you could sell more of them if they included the power supply and plugged into the AC Mains. After all, almost everybody has a PC. But not everybody has a spare lab power supply.
Price by value, not cost, and hope the two never meet!
Oh, I went ahead and expunged my ordering instructions and put the link back up.
P.S. I used to sell mine as a 12V-DC-powered unit, only. I think maybe you could sell more of them if they included the power supply and plugged into the AC Mains. After all, almost everybody has a PC. But not everybody has a spare lab power supply.
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That is a good investment in any case -- learning Chinese.
But honestly, if you want to measure small signal transistors, you can buy his, or many other testers on the market. If you want to match 50 power transistors at high current (say 2A), there is so much drift in the reference resistors that you cannot really rely on the measurements. Plus that the power supply transistors will get so hot !!!!!!
If you get proper low tempco hardware, dimension them liberally, put in massive heat sinks, double copper thickness PCBs, ..... the price goes up 10~20 times easy. But you have something you can rely on. The cost is not in the ICs, but in the passives, mechanicals, .... OK, the On Semi audio transistors we use for the dynamic power supply (3 of them for the 3 legs) cost quite a bit as well. So you are basically buying 3 very high quality power amps. (Can't use chip amps because they are not designed to operate at DC -- below 10Hz.)
We are basically changing the hardware for our own purpose.
If we sell a few, it's fine. If not, we aren't too bothered.
Patrick
But honestly, if you want to measure small signal transistors, you can buy his, or many other testers on the market. If you want to match 50 power transistors at high current (say 2A), there is so much drift in the reference resistors that you cannot really rely on the measurements. Plus that the power supply transistors will get so hot !!!!!!
If you get proper low tempco hardware, dimension them liberally, put in massive heat sinks, double copper thickness PCBs, ..... the price goes up 10~20 times easy. But you have something you can rely on. The cost is not in the ICs, but in the passives, mechanicals, .... OK, the On Semi audio transistors we use for the dynamic power supply (3 of them for the 3 legs) cost quite a bit as well. So you are basically buying 3 very high quality power amps. (Can't use chip amps because they are not designed to operate at DC -- below 10Hz.)
We are basically changing the hardware for our own purpose.
If we sell a few, it's fine. If not, we aren't too bothered.
Patrick
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We don't have a business for this.
Just trying to get some financial support for our DIY development.
And if you know the stories, the ones who is making real money from "cheap" Chinese goods are not he Chinese, but the importers, and in Europe the state (import tax). The Chinese goods are cheap (and often nasty) not because the Chinese do not know how to make them good, but the importers are the ones who set the price.
If you know how much some of our high end loudspeaker chasses cost to make, you will be equally amazed. The manufacturer gets way less than 10% of the price the end consumer pays.
Patrick
Just trying to get some financial support for our DIY development.
And if you know the stories, the ones who is making real money from "cheap" Chinese goods are not he Chinese, but the importers, and in Europe the state (import tax). The Chinese goods are cheap (and often nasty) not because the Chinese do not know how to make them good, but the importers are the ones who set the price.
If you know how much some of our high end loudspeaker chasses cost to make, you will be equally amazed. The manufacturer gets way less than 10% of the price the end consumer pays.
Patrick
That all sounds right! I put a lot of money (and time) into things like high-quality low-tempco, high-power current-limiting resistors, and lots of 0.1% resistors, and various temperature compensation circuits' designs, too, as well as things like the highest grades of precision voltage references, and feedback control system circuits to try to keep voltage and current amplitudes exactly where they were supposed to be, no matter what the load was trying to do to them. Then all of the sensing circuits also have to stay correct.
I did basically everything with analog circuits (except for a little binary counter and resistive D-to-A ladder to form the basic base/gate staircase waveform). I also used a lot of _very_ expensive rotary switches. And trying to make it all work at various frequencies spanning 30 Hz to 22 kHz was quite a challenge. Also, not having a computer for processing and display, it was "fun" making it be able to display any of the three device currents versus any of the three device voltages, with any displayed polarities, while still keeping everything calibrated.
I did generate the three sweep waveforms with analog circuits, too, and used an LM1875 power amplifier (with precision ALC using adaptive level detector) to drive them into the SUT, but later wondered why I didn't just simplify it and use the AC Mains voltage and current, since that could have given high voltages and currents so much more easily! I guess I liked the idea of using a "perfectly linear" sawtooth ramp sweep too much, but didn't realize that I could have probably done that almost directly from the AC mains, too, with a different scheme. I even designed an LDR-based multi-stage adaptive "tracking filter", to convert the triangle sweep into a very-low-distortion sine wave (and remember that the triangle's frequency could be anywhere from 30 Hz to 22 kHz).
I did realize that with a computer to capture the data points, the actual shape or sequencing of the "sweep" signals wouldn't even really matter, since the data points could later be sorted and displayed however you wanted! Even "random" sweep and base/gate signals would work, if you waited long enough. Much of the tempco compensation might also have been able to have been done more easily in software, on one end or the other.
So there is a lot I would probably do differently, if I had it to do over again! But, like you, I started out doing it only for my own use. And I happened to enjoy the analog design aspects of the project, more than anything else, at the time.
Oops. Sorry to have blathered-on about all of that, for so long.
No, I like to hear your experience too.
The software has a calibration facility, so 0.1% is not required. Low tempco is.
And we use whatever low tempco resistors we can get for reasonable cost.
One holy reference is a Caddock TF020, 1% but precalibrated.
Triangular wave is still essential if you want even distribution of measurement points.
People see a simple piece of kit without realising what has gone into the design.
Getting something to work is easy; to work reliably and accurately over long period of time is something else.
Patrick
The software has a calibration facility, so 0.1% is not required. Low tempco is.
And we use whatever low tempco resistors we can get for reasonable cost.
One holy reference is a Caddock TF020, 1% but precalibrated.
Triangular wave is still essential if you want even distribution of measurement points.
People see a simple piece of kit without realising what has gone into the design.
Getting something to work is easy; to work reliably and accurately over long period of time is something else.
Patrick
Contrary to our understanding, the owner of the design has apparently decided to go his own way, after receiving feedback from us on both software and hardware design.
http://www.diyaudio.com/forums/solid-state/151253-diy-curve-tracer-pc.html#post2254974
Of course he has the right to, as we only have a verbal understanding of helping him with the hardware and user interface. And we wish him well.
You can probably get the MCu board from him for very little expense.
And you should take care to change components as necessary to guarantee thermal stability.
We have different expectations, I guess, of what quality a product should process.
So it is unlikely we shall go further with this, even though we have own own version of the 2-board design almost done.
The last software version we received from him did not meet our full expectations as a product.
But as a low cost DIY project, I am sure it is still worth trying.
Sorry to have to disappoint you guys,
Patrick
http://www.diyaudio.com/forums/solid-state/151253-diy-curve-tracer-pc.html#post2254974
Of course he has the right to, as we only have a verbal understanding of helping him with the hardware and user interface. And we wish him well.
You can probably get the MCu board from him for very little expense.
And you should take care to change components as necessary to guarantee thermal stability.
We have different expectations, I guess, of what quality a product should process.
So it is unlikely we shall go further with this, even though we have own own version of the 2-board design almost done.
The last software version we received from him did not meet our full expectations as a product.
But as a low cost DIY project, I am sure it is still worth trying.
Sorry to have to disappoint you guys,
Patrick
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If Rudy out of the Fat Albert show was here he would probably say:
"Man, that is like school during the summer. No class."
Would it not be possible to write our own software?
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I was wondering (see Figure 5-- "Real Life Test Setup") whether the gate might be modulated by connecting the CCW end of the potentiometer to the stator of the drain resistor switch.
This might solve that issue:
An externally hosted image should be here but it was not working when we last tested it.
Well, here it is -- this time I used a computer fan and the devices are pressure fitted with a clothes pin -- worthy of Rube Goldberg:
An externally hosted image should be here but it was not working when we last tested it.
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