Hello, I am repairing a Technics Se-A3 amp and while testing the 2sc2224 and 2sa964A transistors I realize that the hfe are lower than the minimum 180 announced on certain sites. So I wonder if these transistors are starting to be damaged or not. I'm testing them with the dca75pro, I can't really find the technical sheet, it doesn't seem to be available on the internet. I attach a photo with the measurements taken at 5ma. Sincerely
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Service manual states the necessary hfe groups.
If complementary match npn and pnp.
As well match left and right.
If complementary match npn and pnp.
As well match left and right.
Does anyone know at what current hFE is supposed to be measured? It is difficult to find anything but rather useless shortform data about these transistors.
Sorry for the translation my phone does it automatically. I mentioned that the datasheet on the websites of these transistors indicated an hfe of 180 minimum which does not correspond at all to what I measured. I just wonder if they haven't degraded over time or is it an error on the websites because the real datasheet can't be found anywhere, I looked on alltransistors etc but nothing. I just found on the Nikko alpha manual service which also mentions having an hfe of 180 minimum at 1ma I will provide you with the diagram and screenshot. I hope the translation is good and that you understand, I wouldn't want to replace them for nothing but I don't want to take the risk of restarting it with degraded transistors.
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The saturation voltage of these transistors is rather high. Did you measure at a collector-emitter voltage of about 10 V?
You quite consistently measure somewhat lower hFEs than the specified 160 to 200 at 1 mA, 10 V. Some difference in the measuring conditions might explain that. 160 to 200 is an unusually tight specification, by the way.
I also found 180 minimum at some sites, but that is inconsistent with the 160 to 200 in the table. It was 180 under unspecified conditions, though.
You quite consistently measure somewhat lower hFEs than the specified 160 to 200 at 1 mA, 10 V. Some difference in the measuring conditions might explain that. 160 to 200 is an unusually tight specification, by the way.
I also found 180 minimum at some sites, but that is inconsistent with the 160 to 200 in the table. It was 180 under unspecified conditions, though.
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I measured with the dca 75 pro, normally I have never had a problem with this device on low power transistors, the values are often quite good compared to the datasheet. Yes I often measure the hfe because I have already had breakdowns where I noticed that the transistors were OK but that the hfe were very low or almost zero, but I really have a doubt and I would not want to replace them for nothing because they are impossible to find. There are a few which measure quite low 92 and 102. I have 2sa1306 and 2sc3298 which I thought of putting instead but This would really be a last resort.
Apparently a DCA 75 pro can even be used as a curve tracer, so presumably it can measure at 10 V. Did you measure at 10 V, 1 mA?
Yes I often use it as a curve tracer. I did it for the 2 transistors which measure the lowest and the result and almost the same on the other hand I don't know if it's at 1ma for me it does it at 5ma. On the document that I shared on the Nikko alpha 6 where there is the information of these transistors and they mention a rank Q or P on these transistors mine are Q, nowhere else have I found that there 'had a classification on these transistors just a min hfe of 180. When I measured the 2sa1306 and 2sc3298 I found it in the same parameters as the datasheet.
These are the transistors which were already on the amplifier one channel was hs. I started a total restoration and when measuring these I noticed that the hfe were not the same as indicated on the internet, but I cannot find any real datasheet except in the alpha 6 documentation as I I attached it. Sincerely
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The Technics se-a3 maintenance manual does not indicate at all the hfe necessary for these transistors, the documentation on the internet is almost non-existent. I searched for the real datasheet for several days without success. The transistors already come from this amp and they are nowhere to be found.
Good morning, Yes I had seen it but as I said there is no datasheet on the 2sc2224 and 2sa964A so we have no idea what these ranks correspond to or what hfe value. Apart from some vague information on the internet which talks about minimum hfe of 180. I will have the datasheet it would be simpler.
hFE does not normally degrade or change over time and the fact you have all these multiple transistors that seem to disagree with some data sheet value tells me there is not an issue here. The hFE will be the same now as the day they were made.
If the manual states so much ranks, it doesn't matter. You measured hFE, so pick some with the closest values. And as Mooly wrote, there's no issue in using yours.
Well I hope that will work out, I hesitate to replace them with 2sa1306 and 2sc3298. I have already had transistors in amplifiers break down with a hfe which was bad but this was really visible because it was really low or even close to zero. I don't have any extra transistors because it all comes from the amp, so either I have to put them all back in or I replace them with those mentioned above. I am still surprised by the big gap between them, there will inevitably be a channel with those lower down. This is the first time I have come across this case and as no datasheet is available apart from the Nikko document alpha which indicates an hfe of 180 minimum for ranks P and Q is still strange. Thank you anyway for answering me
Yes it indicates that many ranks but in the Nikko alpha doc it indicates that for ranks P and Q the minimum value and 180 is still weird... Mine are rank Q, in short it's the first time I'm faced with this yet I've repaired quite a few amps and I've also built a lot of them but I always have doubts. And as mentioned to Molly I have already seen transistors in failed amps with a very low or almost zero hfe, I had missed the failure just by measuring the transistors without checking the hfe. That's why I'm careful about it now.