When I saw the title of this post, I was interested, and then went to check my small stash of 2SC1583's. Sure enough, two of them had the 52G date code, but in this case they are actually dual NPN, common emitter. Are they real? I don't think so, the vintage 2SC1583's I have lying about measure around 620 on Hfe, but the ones with the 52G date code only measure around 350 or so.
They came from a x0x kit that was being sold on eBay over the summer. One of my former students had bought it, and sought my help in building the kit. It's a good thing he's intelligent, and a fast learner, as it only took me 10 minutes to teach him how to solder correctly! So, he wound up doing most of the grunt work. He was a bit annoyed at first that I insisted on putting every chip, and all the C1583's and the C2291 in sockets. Turned out later he was very glad I did. When we first started testing his x0x after assembly, with all the parts that originally came in the kit installed (except the tantalum caps, I substituted from my stash of electrolytics) it played just fine. However, with my background (besides teaching music) being in high-end audio repair and mods, and more recently vintage analog synth repair, I was no stranger to the counterfeit part issue (You want spectacular? Watch a $2,000 power amp go up in smoke because the new output transistors were fake). After playing with it awhile, I plugged some of my vintage C1583's and a vintage C2291 in, and the difference in the sound was amazing, as in MUCH better. It seems that the C2291 in the kit was real at least, as swapping just that transistor out with the vintage one seemed to make no difference at all. Yes, we swapped it back and forth a couple times.
I guess I have too much of a soft spot, because his x0x has two of my C1583's in, both in the filter, as it seemed to make no real difference in the VCO, and I have two of his C1583's in my parts bag. I knew they sounded different, but I didn't think of measuring Hfe until I saw this post. I guess I can use the two 'fakes' as expo converters, or the bottom of a Moog filter, since the lower Hfe will actually not be too far off the Hfe of a 2N3904.
As an aside, the most commonly faked transistors are Motorola/On semiconductor power transistors in the TO-3 package, MJ15003 and MJ15004, and MJ15024 and MJ15025. Odd thing is, they are not rare, and still in production, but they are not banned. If I remember correctly, even Mouser had a batch (BIG batch) of fakes shipped to them, and did not discover the problem until a few complaints came rolling in.
Don Taylor, a.k.a. Brassteacher
"Jack of all trades, master of none, proficient at even fewer..."