Mystery Transistor - is Dr. Sherlock Holmes out there?

[gjohnson]

Dr. Holmes - I have a puzzle I cannot solve. I recently aquired a number of transistors from an associate whose only accompanying information is the markings on the case itself. All the information I have is as follows:<p>-TO-3 case type
-Motorola insignia
-markings: (3 lines)
50221700
MEX
8631<p>The best minds in England have searched (ok, I tried Google and Motorola's website) and were unable to come up with any information on this device. I have no idea how old the unit is, and therefore it is possible that I have a discontinued item.<p>Does anyone out there know about this transistor?

[haklesup]

Other than knowing it was packaged in Mexico on the 31st week of 1986 by motorola the part number is not one of their standard lines. It may be a house number and you would need to go to the equipment manufacturer to cross it with their schematic (good luck). I checked several databooks and could not find a similar part code, almost all Moto products have some letters in them.<p>Any chance it is not a Motorola logo? What kind of circuit is it used in?<p>Given the package you can make a reasonable guess that it is a bipolar transistor but it is not a 100% guarantee. A few measurements with a multimeter can confirm this guess and maybe determine if it is NPN or PNP.<p>You could characterize it with a curve tracer to find out most of the critical DC parameters (Vceo, Vbeo, Icsat, Beta etc.) but the AC performance would be somewhat of a mystery. These would be good in a DC or large signal circuit but may not work well at high frequency.<p>Unless you have a whole bunch of these or an application you want to use them for you may ultimately find it to be more cost efficient to buy new known parts than to fool around with unknown devices of unknown reliability.<p>[ May 18, 2004: Message edited by: haklesup ]</p>

[dyarker]

If that really is a Motorola logo, there is a possibility they made it for there own equipment. As in police car radios, base stations, repeaters, aircraft radios, etc. This is a very old memory fragment; but I seem to remember Motorola used long part numbers starting with 20x----- in their government/industrial equipment.<p>It could be for a radio's power supply, a PA/sireen amp, or VHF output transistor. Maybe you can find the person that repairs police/fire/highway dept or civil aviation radios in your area.<p>Using "in-house" part numbers and letting only authorized repair centers have schematics made the competion work harder.

[ljbeng]

Sherlock Holmes was not a Doctor. His companion was Dr. Watson so maybe that was your confusion. I hope this helps.

[gjohnson]

My apologies - Thanks for the correction, ljbeng. Now if only it was that easy to clear up the confusion! <p>The logo is a circle with what appears to be two curvy upside-down 'V's... it's exactly the same as the logo on Motorola's website, so I have to assume it's a Motorola part. I was only planning on using these parts if I could obtain accurate datasheets, but it appears that's not going to be easy, if indeed its possible at all. <p>I understand they're transistors, but I can't remember if they're PNP or NPN. If anything, I was going to use them in an Audio amplifier, but I"d like good clear sound and I think I should stick with parts of known performance characteristics as suggested by haklesup. <p>Thanks for checking up on this for me - if you ever come across anything about it please let me know!

[Timothy Rasch]

If you can measure the transistor to determine if npn or pnp ,darlingtons have a internal diode across the collector to emitter in reverse to the type IE pnp ,npn. Npn: diode cathode at collector;pnp iode anode at collector.Hope this helps. Also if a curve tracer is available darlingtons have a lot of gain like 3000.Most output regular transistors have low gains like 30 or 50. It might be like a NtE218 which replaces 50221400-01. Good luck!!! Tim Rasch [email protected]

[Timothy Rasch]

Ignore the green smiling face icon someone put in place of d for diode . Someone edited my original typing for some reason. Tim Rasch [email protected]

[haklesup]

Most high power audio amps schematics I have seen (any worth building that is) are based on FETs anyway. The BJT transistors you have would be better placed in a linear power supply or something similarly DC.<p>Timothy, that happens to me sometimes. It's the punctuation A colon followed by a "D" will give you that smiley :p <p>Only you can edit or delete your posts<p>[ May 24, 2004: Message edited by: haklesup ]</p>

[Edd]

Weelll…Glenn Johnson…EEiT…(itrr)…if those units were in quantity, and the presenter
did not seem to consider them to be high dollar items. Two very popular Rota Mola numbers of high volume manufacture come to mind in that ’86 period of time and prior. Great use of one of them was made in audio power amplifiers and linear power supplies. That device was the 2N3055 NPN sil power transistor.
The other thing was tons of computer monitors and TV’s back at that time using a TO-3 encased Hoz output xstr. Quite a surplus of these flooded the market on the introduction of the newer plastic housed counterpart replacement units.
The Hoz output TO-3 type would be readily identifiable by its inherently higher C-E PIV rating , typically 1500v or possibly down to 900v if used in a smaller kine B&W mon/TV. Also, easy to test for, there possibly might be the incorporation of an internal damping diode across C-E…as mentioned by Tim.
In the end you just might to take a sample of them and hop over to O’Connell and have Ken or Mike roll out the Tek 575/6 and sample at least 5 current stair steps on your units for an averaging and then drop in a 3055 for reference comparison.
Back in those times I have seen upwards of 12 of the 3055’s used in the output stages of AF power amps. (Other higher alpha/power/CBEo transistors being available nowadays) However, their price is definitively right for an initial expanding of your learning curve with them..<p>ADDENDA: Another mechanical variance that might be quite useful for ID also was the fact that the 3055's tended to use a flanged press in top hat that was steel. The latter mentioned HOT units utilized a stamped aluminiyumyum top with a moderate doming to the top. Placing one in each hand, one can readily discern the extra heft of the 3055 unit. <p>73's de Edd
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<p>[ May 26, 2004: Message edited by: Edd Whatley ]</p>