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Rob KI6USW · #21 04-16-2009, 10:21 PM

I ordered 6/2SC1969's and 6/2SC2314's for $13 online on eBay. They are manufactured by Fairchild, so I am not too sure of the quality. Especially considering the price. But I will give them a shot.

What I cannot understand about this mod as published, is how can a single 1969 transistor put out 50 watts? It is only rated for 25 watts - so how does that work? Is the 2314 acting more as a final than a driver - and thereby paralelling the output for the added power? Like I said, I'm a newbie to this - so don't be too harsh with the criticism!

If people are getting 50 watts from this mod. so be it. When I get the parts, I will put them in and give a report here. The eBay source may play out and be a good, inexpensive source for the hard-to-get 1969's. I'll be using a Dosy meter for the numbers I publish, so keep that in mind...

moleculo · #22 04-16-2009, 10:44 PM

I ordered a bunch of 1969's and 2314's off ebay from a supplier in Hong Kong. The first combination of transistors I tried was bad. I hope you don't have the same problem.

Here's why you can get that much power out of a 1969 on an AM radio. This was posted by NomadRadio a while back. He is one good tech...I hope he comes back one day:

Quote:

an AM-only radio uses a voltage step-up transformer to modulate the final and driver. This roughly doubles the peak voltage FED INTO the final and driver. If you fed steady direct current into this radio's power stages, 28 Volts DC would get you a 45 to 50-Watt carrier. But not for long. A steady carrier that large would be very brief. Since every (28-Volt) voice peak is followed by a (zero-Volts) voice VALLEY, the stress on the final is averaged out, and it will deliver 40-plus peak Watts. Since this remains only 10 to 12 Watts AVERAGE power, the final will take it just fine. Modern SSB radios do NOT contain that step-up transformer, and will only give you about half as much PEP per transistor.

Rob KI6USW · #23 04-16-2009, 11:40 PM

Were ALL of the Hong Kong transistors bad - or just a few? If I can expect a few bad ones, and the rest are good - that is still a good deal. Right?

The one thing you can do with a bipolar transistor that you can't with a MOSFET - is test them with an ohm meter. The MOSFET's need a minimum voltage before they turn on, so it takes a bit more effort to test them. I had a bad experience buying ERF2030's and IRF520N's on ebay - all were bad...

moleculo · #24 04-17-2009, 12:39 AM

I have too many of them to test all at once.

I have a multimeter with a diode tester that you can use to do a basic trasnsitor test. Both transistors that I had tested good on that, but apparently had no gain. That tells me that these transistor may really be good, but may be something else that they just silk-screened the part number on

I won't be able to tell until I have a reason to try a few more.

OBJ1946 · #25 04-21-2009, 02:07 PM

Hi Guys, The Mitsubishi 2SC1969 RF Output Transistor is on sale at.. http://www.premiere-electronics.net/store/parts.shtml at $5-95, this is a genuine Mitsubishi part, a lot of copys don't work at all or don't produce the correct power output....BEWARE OF FAKES...Made in China i'm told.

purenrg · #26 04-24-2009, 08:57 AM

Quote:

Originally Posted by OBJ1946

Hi Guys, The Mitsubishi 2SC1969 RF Output Transistor is on sale at.. CB Radio Parts | Repair & Upgrade at $5-95, this is a genuine Mitsubishi part, a lot of copys don't work at all or don't produce the correct power output....BEWARE OF FAKES...Made in China i'm told.

Just wondering has anyone ordered these from Premiere, and are they any good ?

Rob KI6USW · #27 04-24-2009, 11:58 AM

Quote:

Originally Posted by purenrg

Just wondering has anyone ordered these from Premiere, and are they any good ?

Yes I tried, and they were 'Out of Stock'.
Bummer...

However, I has a friend show me this site has EVERYTHING in stock...but at a premium price:
RF Parts Company™ Amateur Radio Catalog

dudmuck · #28 04-24-2009, 07:53 PM

I was looking for alternatives in bipolar transistors in the TO-220 package.
The most important specification is the "gain bandwidth product", and must be far above 27MHz to be useful. The others are the power dissipation rating and max. collector current.

One item that comes up is the On-semi MJF44H11. Its worth looking at because its gain-bandwith-product is at 50MHz, and is an 80v part with 10A current rating, 36 watts.

Similarly from fairchild, there is the KSE44H. 50MHz for unity gain, 50 watt @ 25C, 10 amps.

I'm sure theres more, just takes time to look for them.

OBJ1946 · #29 04-30-2009, 01:52 PM

Me again- go to Grandata Online -they have 14 available as of 30/04/2009 20:40 GMT...At the fantastic price of £1.60...which I think is around $2.30 ? + post & packing....does'nt mention posting to the states...if you have any trouble getting these RF Output transistors either over there or here in the UK let me know and I could send for them here and post them on to you Guys over there in the good old US of A...Noooo problem, just give me a nod...Dave ( Near Manchester,England)

coyjohn · #30 07-02-2009, 08:55 PM

Can i get more power if i switch 2sc1969 with 2sc2312? 2sc2312 have Pmax 25w. Also the Pin is 1.5 watt. 2sc1969 have the Pin 1watt. Will be enaugh to use 2sc2314(1.8watt) as a driver for 2sc2312?

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Cobra 29 High Power mod with 2sc1969 transistor