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Old 8th August 2012, 07:42 AM   #281
neychi is offline neychi  Croatia
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David, these look like genuine Toshiba
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Old 8th August 2012, 01:27 PM   #282
spurlte is offline spurlte  United States
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Default Transistors

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David, these look like genuine Toshiba
Thank you. I took off the 2SA968 last night and glad I did-one of them was a good one with a hFE reading of 317 while the other 3 gave readings 163, 175 and 183. I suspect and from my readings about counterfeit transsitors, that the lower hFEs are counterfeits. I went ahead and ordered the substitutes, 2SA1011/2SC2344, a few days ago. I just hope they are legit. Kaplaars, I tried to get your guy to send me an invoice for original replacements, no reply from him. What was really discerning about the 2SA I took off my boards, is that one of the 2sa was from a different batch (Y 050 with a K on top), the one that has a hFE reading of 183, and of the three others (9F1E with a T on top), one stood out with a reading of hFE 317; an outlier from the others who has readings 163 and 175. I did attempt to make a batch reading before soldering, but with only DMM hFE testing; maybe not a good way to get match transistors?
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Old 8th August 2012, 02:07 PM   #283
neychi is offline neychi  Croatia
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David, 2sa968/2sc2238 have a hFE between 70 and 240 what depend of the fact are they O (70-140) or Y (120-240) range. So hFE 317 is definitively out of the hFE range.
Don't mix, for example, 2sa1011 and 2sc2238 or 2sa968 and 2sc2344. Use only Sanyo's or Toshiba's.

Here is the picture of the genuine Sanyo's so you can compare with those that you will get.
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File Type: jpg 2SA1011-800x600.jpg (60.4 KB, 325 views)
File Type: jpg 2SC2344-800x600.jpg (60.0 KB, 171 views)
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Old 8th August 2012, 02:43 PM   #284
spurlte is offline spurlte  United States
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Default 2sa968/2sc2238

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Originally Posted by neychi View Post
David, 2sa968/2sc2238 have a hFE between 70 and 240 what depend of the fact are they O (70-140) or Y (120-240) range. So hFE 317 is definitively out of the hFE range.
Don't mix, for example, 2sa1011 and 2sc2238 or 2sa968 and 2sc2344. Use only Sanyo's or Toshiba's.

Here is the picture of the genuine Sanyo's so you can compare with those that you will get.
I did not get my Sanyo's yet. I really want to go with Sanyo's since it seems that would make sense to install transistors that will be available in the future (or in the Present for that matter), But I would also, just for experiment and record, try good pair of Toshiba's. Can you tell me what possible cause for the hFE 317 difference. Since I didn't get this prior to soldering, could it have been cause by to high soldering temperature? Now I am worried about these transistors. Earlier we talked about members who dropped out because of the high cost of this and other projects and this project's cost is very high, I am upset that there could be bad sellers/transistors out there who/that could sabotage the expense/projects. Right now, I ordered smoothers, transfos and transistors to build a high voltage power supply from, a project from the book, 'High-Power Audio Amplifier Construction Manual' by G. Randy Slone. I attached an image of the schematic. Kaplaars, what do you think?
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Old 8th August 2012, 03:17 PM   #285
Rewind is offline Rewind  Sweden
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Thanks Nico !

But if there is interest we can assist other prospective buyers and possibly get a better price?

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I would be in on a group buy of heatsinks. Good suggestion.
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Old 8th August 2012, 03:59 PM   #286
neychi is offline neychi  Croatia
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I did not get my Sanyo's yet. I really want to go with Sanyo's since it seems that would make sense to install transistors that will be available in the future (or in the Present for that matter), But I would also, just for experiment and record, try good pair of Toshiba's. Can you tell me what possible cause for the hFE 317 difference. Since I didn't get this prior to soldering, could it have been cause by to high soldering temperature? Now I am worried about these transistors. Earlier we talked about members who dropped out because of the high cost of this and other projects and this project's cost is very high, I am upset that there could be bad sellers/transistors out there who/that could sabotage the expense/projects. Right now, I ordered smoothers, transfos and transistors to build a high voltage power supply from, a project from the book, 'High-Power Audio Amplifier Construction Manual' by G. Randy Slone. I attached an image of the schematic. Kaplaars, what do you think?
David, this transistor, simply, is not genuine. Most likely not even 2sa968, but some generic type.
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Old 8th August 2012, 05:01 PM   #287
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Default Bench PSU

I forgot to mention that the limiting supply output are for non-continuous use as the author warns that the series pass transistors will dissipate considerable heat if the current-limiting (1.5A) values are exceeded, so they should be adequately heatsinked. This Bench Power Supply was intended to be plugged into a variac so that the dual-output voltage levels are infinitely adjustable by the variac to the voltage of whatever transfo/secondaries setup you use. I plan on using a ~62V/8A transformer.
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Old 8th August 2012, 05:05 PM   #288
spurlte is offline spurlte  United States
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Default 2SA968

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Originally Posted by neychi View Post
David, this transistor, simply, is not genuine. Most likely not even 2sa968, but some generic type.
Yes, sorry to beat a dead horse. Thanks. David
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Old 8th August 2012, 06:55 PM   #289
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Originally Posted by spurlte View Post
I forgot to mention that the limiting supply......
Hi Spurtle,

Randy had some very nice ideas and the test supply including a variac is one of them.

Keep in mind Randy did not intend this supply to be used for testing a 100 watt class A amp.

Unless you reduce the KSA100 bias to a few hundred mA just for testing purposes and once working increase the current, this power supply is a waste of money unless it is essentially for future projects.

A final comment though, there may not be much need for future projects since the KSA100 in not easily beaten.
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Last edited by Nico Ras; 8th August 2012 at 06:58 PM.
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Old 8th August 2012, 07:32 PM   #290
spurlte is offline spurlte  United States
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Default Bench Power Supply

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Originally Posted by Nico Ras View Post
Hi Spurtle,

Randy had some very nice ideas and the test supply including a variac is one of them.

Keep in mind Randy did not intend this supply to be used for testing a 100 watt class A amp.

Unless you reduce the KSA100 bias to a few hundred mA just for testing purposes and once working increase the current, this power supply is a waste of money unless it is essentially for future projects.

A final comment though, there may not be much need for future projects since the KSA100 in not easily beaten.
Now, this is what I like to hear, "....KSA100 not easily beaten!
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