Hi all....I tried to search but to no avail so I'm asking if you guys can tell me if I should or should not use it.
Well, I have 4 x antique Motorola 2n3055. hfe tested fine on all of them and they are all having very close gain. At first, I wanted to use them on my JLH build. But during testing with an analog AVO meter, I found one of them has a slight leak when in reverse between B-E and C-E, in the order of 5-10 Mega ohms. I went ahead and bought some cheap Toshiba 3055 from the *bay and finished the project. To my surprise the amp sounds great with the Toshibas.
I know many of you will recommend forget it and put MJ15003 (which I have just received from ON-semi and will use them to replace the fake Toshiba 2n3055) in the amp, but I want to build another JLH amp using original Motorola 2n3055. I remember reading somewhere from the internet that the Motorola 2n3055 sounds good compare to the ST brand 3055.
Definitely I want to use all of them in the same amp. But is that leak significant ?
Thanks.
-AC
Well, I have 4 x antique Motorola 2n3055. hfe tested fine on all of them and they are all having very close gain. At first, I wanted to use them on my JLH build. But during testing with an analog AVO meter, I found one of them has a slight leak when in reverse between B-E and C-E, in the order of 5-10 Mega ohms. I went ahead and bought some cheap Toshiba 3055 from the *bay and finished the project. To my surprise the amp sounds great with the Toshibas.
I know many of you will recommend forget it and put MJ15003 (which I have just received from ON-semi and will use them to replace the fake Toshiba 2n3055) in the amp, but I want to build another JLH amp using original Motorola 2n3055. I remember reading somewhere from the internet that the Motorola 2n3055 sounds good compare to the ST brand 3055.
Definitely I want to use all of them in the same amp. But is that leak significant ?
Thanks.
-AC
Both Toshiba and National (Japan) made genuine spec. cloned 2N3055s for specific markets. There are images here of other TO3 power transistors cloned by Toshiba.
If those transistors hold up to DC collector currents of 4 amps or so at 12V (on a heatsink), they may not be fakes at all. See a datasheet SOA diagram. Fakes are usually small, cheap chips that are excellent on Hfe and Vceo but current capacity, which is harder to measure, is more telling.
If those transistors hold up to DC collector currents of 4 amps or so at 12V (on a heatsink), they may not be fakes at all. See a datasheet SOA diagram. Fakes are usually small, cheap chips that are excellent on Hfe and Vceo but current capacity, which is harder to measure, is more telling.
The Toshiba I've got has less then half the hfe of the Motorola 2n3055. I also believe the beta droop is large because as I raised the Iq to above 1A, the sonic of the amp deteriorated obviously. I've to settle the Iq at around 1A.
But my original question is the small leak in one of the Motorola transistors. Is it still good to use ?? I remember in the old days when we used germanium transistors, the reverse leak was expected but not so for silicon devices.
But my original question is the small leak in one of the Motorola transistors. Is it still good to use ?? I remember in the old days when we used germanium transistors, the reverse leak was expected but not so for silicon devices.
Yes, way to go. I don't know your method, but Hfe measurement at anything less than half an amp is a waste of time. Measurements of unmatched genuine Motorolas I bought as old stock many years ago gave me a huge range from 30-150 beta on a simple meter.
The real values were much tighter at typically 20- 35 with 4 amps which is within spec.
Electronic circuit, componnent data, lesson and etc….: 2N3055 Power Transistor
This source puts leakage current at 0.7mA but doesn't refer that to a specific source and there are dozens of manufacturers from nearly 50 years ago and changes from homotaxial to epitaxial and case insulation, attachment and heat spreader types, price and spec. drops etc. It's not so simple. My Motorolas were in aluminium cases IIRC.
It's too late to say "why buy something cheap for a small saving?" but I guess you knew that since the last time we all got ripped off on Ebay for silicon. There are very good Chinese traders out there, as long as they know and care that their sources are good. We can't know that.
The real values were much tighter at typically 20- 35 with 4 amps which is within spec.
Electronic circuit, componnent data, lesson and etc….: 2N3055 Power Transistor
This source puts leakage current at 0.7mA but doesn't refer that to a specific source and there are dozens of manufacturers from nearly 50 years ago and changes from homotaxial to epitaxial and case insulation, attachment and heat spreader types, price and spec. drops etc. It's not so simple. My Motorolas were in aluminium cases IIRC.
It's too late to say "why buy something cheap for a small saving?" but I guess you knew that since the last time we all got ripped off on Ebay for silicon. There are very good Chinese traders out there, as long as they know and care that their sources are good. We can't know that.
Well, then you need at least to mount them on a good heat sink and measure after a precise repetitive time, or at a precise case temperature. The WILL heat up VERY fast at 4 A and hfe WILL change a lot. I have problems to reliably match the hfe of my 15003/4 TO3s at 1 A without heat sink.
Yes, it was not in my home, for sure. Actual voltage was not much, so the big slab sink I used (like a huge industrial heatsink extrusion) ~ 500x250x 80mm was fine. You can measure within seconds, no problem. When you have ~ 200 semis to measure, you get quick and consistent. (I was a laboratory tester at the time). Of course, you record local sink temp. as you proceed. and sometimes retest to reduce errors.
Here, you don't need so much care, just a single proof test.
- Status
- Not open for further replies.