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Discussion in 'Amateur Radio Modifications' started by Crambone, Jul 28, 2019.
how can a pill be tested without removing from circuit?
Use it try it out on a watt meetAr see if it puts out the right wattage the only way to knoW ! OUTHER THAN TAKING IT OUT TO TEST IT!
You can always tear the cover off and look
de-solder base and collector , resistive test .
wash rinse repeat.
This is a typical input circuit to a pair of transistors.
Note the 10 ohm resistors , base to ground.
If those resistors are zorched it's a good possibility gawd killed a kitten.
Checking a component "in-circuit" only works when the circuit it's connected in has a fairly high resistance.
Just one problem. All the resistances in a power amplifier are low.
Prevents any kind of test, when the circuit is draining all the test current away from your tester.
The most-common kind of failure is for the circuit between the base (input) and emitter (ground) of the transistor to become an open circuit.
Lifting the base terminal loose from the circuit allows you to test that terminal alone. It should check the same as a silicon diode, as if the diode's cathode side is connected to ground.
This won't identify every kind of transistor breakdown, only the most-common kind.
But it's a lot less trouble than removing the whole part to test.
KOPCICLE has it right. For a true test Lift the BASE and COLLECTOR . If you have access to a transistor tester or a component tracer. Check my albums for images of component tracings.
Sheesh. Just look at the die quality differential between the fake and the real dealeo.
Toshiba is extremely advanced in their manufacturing of Solid State devices. I have no idea how long DEI has been around. Maybe they should talk to Toshiba and get a license to manufacture them and share their processes.
Does anyone use dei anymore? I keep hearing that everyone uses the HG brand now. 5 to 10 years ago the guys that tried the HG transistors were lucky if they ever worked. I guess they've made improvements.
I still have a small stash of origonal 2879 transistors in storage.
The others use MRF 454 or 1446 transistors and I have a set of each.
Everything else is running modern Toob's now.
I seriously doubt anyone will ever build a clone of the Toshiba that will match the original ones.
Build quality is a statistical thing.
The more widgets you make the better you get at it.
The more of a widget you make, the lower the percentage of duds.
Toshiba made the 2290 and 2879 for decades. Got to be REALLY good at it. Took them a while. The 2SC2879 wasn't nearly as reliable in 1980 as it was in 2005.
Just how long it would take another outfit to reach that level of reliability?
Maybe better to ask how many zillions they have to make before they're as good.
Actually there is nothing "fake" pictured, those are genuine 2sc2879 finals. The DEI is just a cheaper inferior final compared to the Toshiba.
Yea kinda sad, the DEI finals are gone now as well so all there is are the HG finals. Last time I checked rfparts.com the NOS Toshiba finals were very expensive.
That is just ridiculous. You can’t justify that, purchasing or selling, just <insert expletives> ridiculous.
RF Parts has been in the game for decades.
They started stashing Motorola and Mitsubishi transistors a very long time ago, and the Toshiba's as well.
Seen the writing on the wall.
Southern California has a long history that involves RF Amps and Radios of many brands and kinds.......
But if you are the only game in town and you got all the cards, you can set your own price.
Kind of like Sweep tubes we used to buy at Thrifty Drug store for 8 bucks that now cost 60+ dollars each.