Hi All,

Anyone know if authentic 2SC730 markings stand up to isopropyl alchohol? I have a few of these that look identical to the "61C" transistors from Mixin's thread ("2SC730 Transistor questions" from April 2021) but I put some isopropyl on a cotton swab to them and was able to get the markings to start rubbing off. I know with some chips that's a sure sign of a fake, but I don't know with these transistors.

Anyone know if original 730 markings are susceptible to isopropyl, or did I get a well constructed fake?

Thanks!

You can usually tell just by looking at them, the genuine ones should have long gold legs and gold where they go in to the metal part around them at the bottom of the transistor.

...Have you got a photo?

I had a photo I tried to attach, however the board won't let me for some reason. I tried both adding it here as an attachment (drag and drop and the attach button) as well as hyperlinking to an image file. Neither worked. I posted a message about it in Site News, Suggestions, and Feedback section.

What I can tell you is that they look EXACTLY like the 61C transistors in the thread I mentioned. Same font/logo placement/positioning, can colour, gold leads 20mm long (spec sheet says min 19mm) isolated from case, gold bottom, same shine to the can as in that photo. I'm reasonably sure they're not fakes but one of the tests that is sometimes used on chips and TO220 packaged transistors is to swab the writing with alcohol because its not supposed to come off. I thought I'd try that test on these- probably shouldn't have because it confused me further.

I guess the only way to know for sure is to put them in a circuit, but I have some personal stuff going on that will prevent me from doing that for a bit.

I have one burnt and 2 used original
I will try with alcohol and report back with pictures .can you post the circuit of the amplifier they are used in.i think ft 150mhz and 1.5 watt as I remember for Mitsubishi.

Thanks radium!

The circuit is the rev fm transmitter. Experimentation purposes.

fourier not forgetting you , but far a bit from things ...

radium98 wrote: ↑Sat Sep 03, 2022 8:03 pm fourier not forgetting you , but far a bit from things ...

No worries. Im starting to get swamped on this side as well. September is going to be a hell month for me.

Sorry for delay again , sadly i lost one , i get the pictures with a digital magnifier. oneis scratshed , barely appear the markinfg but also old removed from something japenese .the other still have the original marking , legs are gold but the collector is at the case , and not like the c1947 wich the emitter in original is isolated also .I get one of the 47 with little marking barely visible , wich get hot and nothing at output .

Why are you trying to use 1970's transistors anyway? Try something newer like the Mitsubishi RD01MUS2 which will give over a Watt at 7.2V supply for just 12mW input power! You can get them from Enigma for <£2. I've used them since they came out.

My latest exciter uses just a DGFET for the Colpitts oscillator (at ½f), then another two FETs for the doubler and the buffer to drive the RD01 to 1.2 Watts - just right for a Motorola MRF101 or MRF300. The exciter uses four cheap CMOS ICs and a dual op-amp for the PLL (and the second half of the op-amp provides a mod buffer). The crystal is a 4 MHz temperature-compensated "oscillator in a can", and everything (apart from the inductors) is done in surface-mount.

Frequency selection is done by solder blobs between tracks (which prevents the average numpty "builder" changing the frequency of a stolen rig). The boards now arrive from India with the components already loaded, and they just have to have their frequency set, and be installed into their little tinplate box. The first production run was 400 pieces, and we were pleasantly surprised by just how cheap the boards were to get manufactured. Their spectral purity is really good for such a simple circuit, and with eight coil changes, they can be made to work on most of Band 1 (or the Japanese FM band).