Transistor with 8720 on it.

[daves66nova]

I need 2 transistors, like this, Transistor the number on top is 2N5884, under that it says MEX then under that 8720. Does the 8720 matter? I dont know anything really about electronics, so I dont know exactly what I need, I'm just going by the part no. It also has the Motorola symbol above everything.

 

[Jim_Truett]

2N5884 is what is important. The 8720 is most likely the 20th week of 1987 for manufacture date. Buy from a reputable house like Mouser or Digikey . A picture of the original would help just to be sure of the case type, but it looks like T03. Also, what is the circuit? Do they need to be a matched pair?

 

[daves66nova]

Ok. That T0-3 is also important?

 

[Jim_Truett]

Originally Posted By: daves66nova
Ok. That T0-3 is also important?


Certainly, if it mounts to a heatsink. Fortunately it seems to be available in only T0-3 and T0-204 which are similar.

 

[daves66nova]

The circuit board is detached from where it goes onto.I burned a few resistors as shown on top left. If these trans. were bad, then it would allow the resistors to burn?

 

[mk378]

If you buy a 2N5884 it will be the same shape. The package is part of the 2N number specification.

Transistors usually fail shorted and this is prone to damage other parts.

What does the board do? And yes it was made in 1987, 30 years ago.

 

[Lubener]

Originally Posted By: daves66nova
Ok. That T0-3 is also important?

TO3 refers to the case style.Mounting is important if it is going on a heatsink. Out of circuit, you can easily check for shorts between base, emitter and collector(case)with an ohm meter. Those almost always short and very rarely open between junctions.

 

[46Harry]

If you can't find a 2N5884, the NTE cross reference is either an NTE #30 or NTE #180 for audio use.

 

[Jim_Truett]

Originally Posted By: daves66nova
[img:gal:37685aa892ea495d9]
If these trans. were bad, then it would allow the resistors to burn?


It is definitely possible that if the transistor failed shorted, it would cause the supporting resistors to fail. Do you have access to a multimeter with a diode check function?

 

[Virtus_Probi]

If possible, it would be good to get ON Semi versions of these transistors as that is a lineal descendant of the old Motorola Components group.
I had a friend who worked in procurement of obsolete components for a military supplier and he told me that many parts were sold under the same number as "functionally equivalent", but they would find that one would have an ft of, say, 4MHz while an "equivalent" would be maybe 40MHz and cause the old circuit design to oscillate like crazy.
It's certainly not a given, but it's possible that ON Semi parts would have been made in the same fab as your old parts, or at least in one with a very similar process flow.

Impossible to say for sure if those resistor got burned due to the failure of those PNPs, but I'd guess that it's quite likely. Far more common for xtors to fail than resistors, active components are generally more liable to damage to passives (maybe excepting inductors and transformers).

 

[Johnny2Bad]

Just be sure to buy from a known good supplier with traceable procurement paperwork. As someone pointed out Digikey or Mouser (USA), Farnell (UK), etc.

DO NOT buy from eBay, counterfeiting of semiconductors is unfortunately part of our modern life and I strongly suggest you don't buy from other online vendors even if they are based domestically, unless you know exactly what you are doing. Sad but true.

 

[daves66nova]

Ok, just ordered some from digikey