Need help to repair two phase 400 amps

[LarryD]

Good afternoon Lee, How's it going? Here is the pic with the probe.

 

[laatsch55]

That emitter resistor shows 1600 ohms?

 

[LarryD]

Lee, I have to go back out and work in the garage. Here are some numbers from the small black D shaped transistors on the board.

RED C / BLACK B
1 O
2 O
3 O
4 O
5 O
6 O
7 029
8 029
RED C /BLACK E
1 O
2 O
3 O
4 O
5 O
6 O
7 034
8 028
RED E / BLACK B
1 O
2 O
3 O
4 O
5 O
6 O
7 O
8 O
BLACK C / RED B
1 029
2 O
3 025
4 O
5 038
6 O32
7 O
8 O
BLACK C / RED E
1 O
2 O
3 O
4 O
5 049
6 097
7 O
8 O
BLACK E / RED B
1 O
2 O
3 O TRIES TO CLOSE BUT THEN STAYS OPEN
4 O
5 O
6 O
7 O
8 O
-------------

　
　
　
　
　
　
　
　
　
　
　
　
　
　
　
　
　
　
　
　
　
　
　
　
　
　
　

 

[laatsch55]

We still haven't checked all the stuff on the backwall. Please answer my last post...

 

[LarryD]

That emitter resistor shows 1600 ohms?/QUOTE]

Lee, I do not know where the hell that number came from. I want you to look at my meter in diode mode and tell me if it is correct.

 

[LarryD]

I just checked them and they are closed !

 

[LarryD]

Sorry Lee, I can't tell you what happened there. Going back to work. I will check back soon. Oh And I was at a loss as what to continue to check so I just went for the transistors. Hope it was ok.

 

[laatsch55]

Resitors are checked in ohms only...the red-red-silver-silver are the emitter resistors. They are .22 ohm. You are showing .4 ohm, which is probably as closer as that meter will get. The .4 figure is ok. You also need to check the brown-green-brown on the bottom row....

 

[LarryD]

Lee it should have been 16.57. I missed the decimal. It was on the very small resistors where the wires from the board enter! Seems like I am constantly F#@#king up! I thought you would be happy that I continued on to check things. If that was a no no , then I'm sorry. I couldn't sleep and thought I was helping. Damn!

 

[laatsch55]

I guess you better point that one out too.....

 

[LarryD]

I really do not trust the meter. I am going to ask to borrow my friends fluke. It is possible to see a transistor closed on one pass and the open on the next check? I swear I was being meticulous while checking and a couple changed. I checked eight times because of it. That's why I asked you to look at the meter. Does it look correct at idle? Ok leave me instructions and I will follow them to the best of my ability Lee. And sorry for the screw ups.

 

[LarryD]

I guess you better point that one out too.....

I don't understand ?

 

[laatsch55]

Take and post a pic of the resistor that is showing 16.57 ohms....

 

[NavLinear]

Here's a link to a good AK thread on testing transistors. FYI - The type of transistors you're testing are Bipolar Junction Transistor (BJT). The output transistors for a semi complementary system are all NPN BJTs.

http://www.audiokarma.org/forums/index.php?threads/bipolar-junction-transistor-testing-basics.43186/

There's a lot of information available on the web that can help. Understanding semiconductors you should begin with diodes as they are a stepping stone before transistors.

 

[laatsch55]

Larry, I don't want you to worry about the driver board..I want you to do what I ask so we can figure out if there are any problems with the back wall or power supply. I will then send you a complete set of outputs and an assembled White Oak Rev A driver board. You will then follow very explicit step by step instructions to desolder the old board and install the new board. The board is one of 4 boards that were built and sent to me as a gift from Dr. Lucitt when he thinned his herd. They did not cost me anything nor will it cost you anything. I have some band new MJ 21194's which are perfect for the 400. I don't use those in 700's so you can have them too. But to do this you must listen to me and do only what I suggest and when I suggest it. I Don't Believe At your present skill level you can troubleshoot the board and repair it. I do believe you can change one out with help.
These boards are also complete with the Phoenix connectors so no soldering is needed to install them, and a wiring mistake can be spotted abd changed without desoldering and resoldering....

 

[Northwinds]

A thread like this is exactly why I don't mess with electronics

<iframe width="560" height="315" src="https://www.youtube.com/embed/_VrFV5r8cs0" frameborder="0" allowfullscreen></iframe>

 

[LarryD]

Larry, I don't want you to worry about the driver board..I want you to do what I ask so we can figure out if there are any problems with the back wall or power supply. I will then send you a complete set of outputs and an assembled White Oak Rev A driver board. You will then follow very explicit step by step instructions to desolder the old board and install the new board. The board is one of 4 boards that were built and sent to me as a gift from Dr. Lucitt when he thinned his herd. They did not cost me anything nor will it cost you anything. I have some band new MJ 21194's which are perfect for the 400. I don't use those in 700's so you can have them too. But to do this you must listen to me and do only what I suggest and when I suggest it. I Don't Believe At your present skill level you can troubleshoot the board and repair it. I do believe you can change one out with help.
These boards are also complete with the Phoenix connectors so no soldering is needed to install them, and a wiring mistake can be spotted abd changed without desoldering and resoldering....

Ok Lee, Understood! You are right, I need to learn to walk before I can run. And the 16.57 came from the four green brown and silver striped resistors. Here is the pic. And I would like to say thank you very much for the gift, that is simply awesome! but mostly for putting up with me. And I noticed that the power supply was very loose on it's mount. I snugged it up with equal torque but did not over
tighten.

 

[LarryD]

A thread like this is exactly why I don't mess with electronics

<iframe width="560" height="315" src="https://www.youtube.com/embed/_VrFV5r8cs0" frameBorder="0" allowfullscreen=""></iframe>

Northwinds, I can relate to that! But I am hanging in until Lee gets tired of me and gives me the boot and sends me packing! And I really hope that does not happen!

 

[laatsch55]

Ok Lee, Understood! You are right, I need to learn to walk before I can run. And the 16.57 came from the four green brown and silver striped resistors. Here is the pic. And I would like to say thank you very much for the gift, that is simply awesome! but mostly for putting up with me. And I noticed that the power supply was very loose on it's mount. I snugged it up with equal torque but did not over
tighten.

View attachment 23526

Those are 150 ohm resistors, were you on the 200 ohm scale?

 

[LarryD]

Here's a link to a good AK thread on testing transistors. FYI - The type of transistors you're testing are Bipolar Junction Transistor (BJT). The output transistors for a semi complementary system are all NPN BJTs.

http://www.audiokarma.org/forums/index.php?threads/bipolar-junction-transistor-testing-basics.43186/

There's a lot of information available on the web that can help. Understanding semiconductors you should begin with diodes as they are a stepping stone before transistors.

Thanks Nav, As you can see I can use all the help I can get! But what you can't see is my red in the face every time I screw up. Oh and I am going to pm you. I have something for you to see . And I want your opinion.!