I need to ID what this part is?

[Ric Harris]

The MPC70 21N6 & 21N4 are transistors? I have queried those numbers and haven't found anything. These have just 2 contacts wire rather three.
Transistors and Semi Conductors must have values like caps but I just don't know what I'm see here.
It's for a Rotel receiver that is basically toast as most of the caps are leaking but I figure if I am going to learn how to fix this stuff this ones as good as any. Can't make it deader.

 

[audiodummy]

The white "MPC70" brick looks like just a regular 0.22 ohm power resistor, not a semiconductor... Is there a zigzag diagram underneath of it indicating a resistor?

Possibly a emitter current sense resistor....

 

[elnaldo]

+1, emitter resistors, 0.22 ohm

 

[Ric Harris]

Awesome.

 

[Ric Harris]

+1, emitter resistors, 0.22 ohm

I saw the .22 ohm but it didn't dawn on me that they were a type of resistor.

 

[Ric Harris]

Well the closest thing I found on Ebay was a MPC 71 .22 ohm 5W
Is the wattage important or not a big deal.

 

[Ric Harris]

3W min.

3 watt min? So 5 watt is okay?

 

[I LIKE MUSIC]

It is not a bad idea to become familiar with the basic symbols. You can see the symbol for a resistor below the part in question.

Below is a very basic example.




The picture below shows the lead markings for a transistor (the transistor on the left) and what looks to be (picture is not real clear) the lead makings and the symbol for transistor for the transistor at the top to the picture. This may also show the symbol for a transistor, again the picture is not real clear.



There is a wealth of information on the net regarding what various devices look like and their symbols.

Transistors and Semi Conductors must have values like caps

In general, transistors, diodes, capacitors, resistors and inductors do not have similar values (units of measure).

if I am going to learn how to fix this stuff

If you are going to work on gear, it is not a bad idea to spend some time to become familiar with this so that you can accurately identify parts. And in basic terms what each part does and how it does it as you make progress, this will make it easier to use your DMM to test parts and understand the results. It will make the job easier, more enjoyable and increase you chances of success.

 

[audiodummy]

Beware each time you bump up power, the physical size of the resistors and possibly wire lead diameter goes up.

According to the datasheet stoN_Cold found, the MPC70 is a 2W unit. The MPC71 is a 5W unit that's 1cm taller, but fortunately the lead spacing is similar (1mm wider), 1mm thicker, and on the bright side, the wire thickness is the same. It looks like you have space, however.

Then again, is there any reason why they need to be replaced? Usually resistors don't go bad unless they go up in flames (or is a flame proof/fusable unit that's been overloaded.) Do they actually measure bad?

 

[gadget73]

Are these actually bad? They rarely fail unless the output transistors bit the dust.

 

[Lavane]

Did you, replace the output transistor? The mounting screw look like its unscrewed some.

 

[Ric Harris]

Are these actually bad? They rarely fail unless the output transistors bit the dust.

I plugged it in with the top off and 2 of them started to smoke. Then I saw all the leaking caps. I got replacement resistors and still need to order caps for it. This might be a waste of money but I need to work on my soldering skills before I recap something that is of a bit more importance to me. Even though the guinea pig is a Rotel, if I screw up I got the rig for basically nothing.

 

[Ric Harris]

Beware each time you bump up power, the physical size of the resistors and possibly wire lead diameter goes up.

According to the datasheet stoN_Cold found, the MPC70 is a 2W unit. The MPC71 is a 5W unit that's 1cm taller, but fortunately the lead spacing is similar (1mm wider), 1mm thicker, and on the bright side, the wire thickness is the same. It looks like you have space, however.

Then again, is there any reason why they need to be replaced? Usually resistors don't go bad unless they go up in flames (or is a flame proof/fusable unit that's been overloaded.) Do they actually measure bad?

That is what 2 of them did they started smoking and I cut the power. I noticed soon after a whole bunch of leaking caps.

 

[petehall347]

output transistors on the heat sink are toast if fitted without insulators .
or the bias circuit is foobar . this needs a close looking at .