Need help to repair two phase 400 amps

[laatsch55]

No, the internal connection of the transistors. There will be no conduction of one of the 3 main conductions...

 

[laatsch55]

Post a pic of your meter...

 

[laatsch55]

Can you identify the Base, Emitter and Collector of an output transistor?

 

[LarryD]

Can you identify the Base, Emitter and Collector of an output transistor?

As much as I hate to say it no! But hold on a sec, maybe you can give me a simple crash course.

I am lookin at the transistors from the front of the amp right side I see where they connect together with a solid shinny wire. That is one pin from the transistor connect to four correct? And that solid wire is called?? And I will write this stuff down I promise.I have never even seen this transistor out. there are three pins correct what is the center pin called and the pin to the left !

 

[LarryD]

Hey Listen, All I need for now is someone to tell me how to hit the pins with the ohm meter. I feel stupid enough as it is. Can you please just tell me. I am embarrassed as hell right now!

 

[laatsch55]

That solid shiny wire is a "bus". There are only 2 pins on an output transistor of the TO-3 outline. The case is the collector. When holding a TO-3 in your hand with the pins up and short side to your left the pin closest to you is the base, the further one the emitter.

 

[laatsch55]

Hey Listen, All I need for now is someone to tell me how to hit the pins with the ohm meter. I feel stupid enough as it is. Can you please just tell me. I am embarrassed as hell right now!

If you're thin skinned, this ain't gonna go well. No need to be embarrassed......


Post a pic of the meter.....

 

[LarryD]

If you're thin skinned, this ain't gonna go well. No need to be embarrassed......


Post a pic of the meter.....

Your right I do have a bit of thin skin. I want to thank you for trying to help anyway. I going to pull out and maybe come back when I at least have the basics. Take care

 

[laatsch55]

That'll help, my main concern is that a 400 is a BITCH to learn on, but it's what you have. Are you a member of Audiokarma? They have a very good tutorial on transistor testing basics....

 

[frhodes]

It's not like making a bologna sandwich. That's why I do the dis-assembly, cleaning, painting and re-assembly
and my brother-in-law does the stuff where electrons and killer amperes and voltage occur.

The stuff my brother-in-law measures with his meters and oscilloscope I call MAGIC.

I understand that I am an emitter (at my age) much to my embarrassment and a collector is the guy
that shows up every Monday morning if I remember to put the can out.

 

[WOPL Sniffer]

Larry, as I said on the phone there are videos showing how to do this. Look online, here is a hokey vid showing the basics. Even if you have to pull every transistor out of the backplane (one at a time, which gives you a chance to clean all the old thermal paste off and put new on, or the new SILPADS), and, As I mentioned, you have a good working amp to compare reading to. Make sure the amp/amps sit for a bit so the caps bleed down or you will get bit. Start with the big output transistors (write on a piece of paper which goes where, if you take more than one out), and when you are done, there are transistors on the control board which are just shaped different but they test the same way. I have observed OPEN and SHORTED transistors on the backplane of amps so check each one. I had 50volts on one pair of speaker posts and it was an output but it may or may not be your problem. Check them ALL. Then move on to your control board. Don't stop checking at the first sign of failure, check everything. This is how you are going to learn what you are doing. That's why I had you build a DBT. It was your first shot at a mini schematic.

https://www.youtube.com/watch?v=b0jCUsenNsY

 

[LarryD]

Larry, as I said on the phone there are videos showing how to do this. Look online, here is a hokey vid showing the basics. Even if you have to pull every transistor out of the backplane (one at a time, which gives you a chance to clean all the old thermal paste off and put new on, or the new SILPADS), and, As I mentioned, you have a good working amp to compare reading to. Make sure the amp/amps sit for a bit so the caps bleed down or you will get bit. Start with the big output transistors (write on a piece of paper which goes where, if you take more than one out), and when you are done, there are transistors on the control board which are just shaped different but they test the same way. I have observed OPEN and SHORTED transistors on the backplane of amps so check each one. I had 50volts on one pair of speaker posts and it was an output but it may or may not be your problem. Check them ALL. Then move on to your control board. Don't stop checking at the first sign of failure, check everything. This is how you are going to learn what you are doing. That's why I had you build a DBT. It was your first shot at a mini schematic.

https://www.youtube.com/watch?v=b0jCUsenNsY

Well, Now that I have my head firmly pulled out of my ass, I hope that I did not loose my teachers in the process. I am going to post my findings on the transistors in detail. I want to say again that I am sorry again for my actions guys.

Here is what I have so far for the right bank using the method you provided Perry, Using a good meter!
NUMBERED TRANSISTORS AND FAULTS AS FOLLOWS
1 RED ON BASE BLACK ON COLLECTOR (OPEN
2 RED ON BASE BLACK ON EMITTER (OPEN
3 RED ON BASE BLACK ON EMITTER (OPEN
4 DRIVER DEAD ALL OPEN
5 RED ON BASE BLACK ON COLLECTOR (OPEN
6 RED ON BASE BLACK ON COLLECTOR (OPEN PLUS MORE
7 RED ON EMMITER BLACK ON BASE (READS 5.1
8 DRIVER DEAD ALL OPEN

I am going to pull from the left channel now.

 

[LarryD]

Sorry, a little revised

NUMBERED TRANSISTORS AND FAULTS AS FOLLOWS
RIGHT CHANNEL
1 RED ON BASE BLACK ON COLLECTOR (OPEN
2 RED ON BASE BLACK ON EMITTER (OPEN
3 RED ON BASE BLACK ON EMITTER (OPEN
4 DRIVER ALL OPEN
5 RED ON BASE BLACK ON COLLECTOR (OPEN
6 RED ON BASE BLACK ON COLLECTOR (OPEN/
( RED ON EMITTER BLACK ON BASE 5.5)
7 RED ON EMMITER BLACK ON BASE (READS 5.1
8 DRIVER ALL OPEN

LEFT CHANNEL
1 RED ON BASE BLACK ON COLLECTOR (OPEN
2 RED ON BASE BLACK ON COLLECTOR (OPEN
3 RED ON BASE BLACK ON COLLECTOR (OPEN
4 DRIVER ALL OPEN
5 RED ON BASE BLACK ON COLLECTOR (OPEN
6 RED ON BASE BLACK ON COLLECTOR (OPEN
7 RED ON BASE BLACK ON COLLECTOR (OPEN
8 DRIVER ALL OPEN

 

[WOPL Sniffer]

Sorry, a little revised

NUMBERED TRANSISTORS AND FAULTS AS FOLLOWS
RIGHT CHANNEL
1 RED ON BASE BLACK ON COLLECTOR (OPEN
2 RED ON BASE BLACK ON EMITTER (OPEN
3 RED ON BASE BLACK ON EMITTER (OPEN
4 DRIVER ALL OPEN
5 RED ON BASE BLACK ON COLLECTOR (OPEN
6 RED ON BASE BLACK ON COLLECTOR (OPEN/
( RED ON EMITTER BLACK ON BASE 5.5)
7 RED ON EMMITER BLACK ON BASE (READS 5.1
8 DRIVER ALL OPEN

LEFT CHANNEL
1 RED ON BASE BLACK ON COLLECTOR (OPEN
2 RED ON BASE BLACK ON COLLECTOR (OPEN
3 RED ON BASE BLACK ON COLLECTOR (OPEN
4 DRIVER ALL OPEN
5 RED ON BASE BLACK ON COLLECTOR (OPEN
6 RED ON BASE BLACK ON COLLECTOR (OPEN
7 RED ON BASE BLACK ON COLLECTOR (OPEN
8 DRIVER ALL OPEN

Now flip your leads with Black (Negative) on base red (Positive) on collector. You know that all your transistors are not bad so you should be able to see a difference if you find a bad one. Your first set you kind of jumped around (Highlighted in red). Stay consistent. Do all of them one way, then all of them the other way. Check them thouroughly... Ie...

Red collector Black base all of them
Red collector Black emitter all of them
Red to emitter black to base all of them

SWAP LEADS AND DO IT AGAIN

Black collector red to base
Black to collector red to emitter
Black to emitter red to base

That's 6 checks per transistor

You will see a pattern, you will see your failure if you are consistent and thorough. If you make yourself a drawing, you can easily keep track of reading. Don't let the drawing confuse, one lead is red (+) one is black(-) but you can see there is 6 ways to check each transistor. This transistor shows 3 pins (you can use this on your control board) but your backplane transistors have 2 pins and the case is considered a pin. The results you see in the diagram may not be your results. They are examples. They will change from an NPN to a PNP tranny

 

[laatsch55]

Post a pic of your meter too so we can see what you have...

 

[LarryD]

Now flip your leads with Black (Negative) on base red (Positive) on collector. You know that all your transistors are not bad so you should be able to see a difference if you find a bad one. Your first set you kind of jumped around (Highlighted in red). Stay consistent. Do all of them one way, then all of them the other way. Check them thouroughly... Ie...

Red collector Black base all of them
Red collector Black emitter all of them
Red to emitter black to base all of them

SWAP LEADS AND DO IT AGAIN

Black collector red to base
Black to collector red to emitter
Black to emitter red to base

That's 6 checks per transistor

You will see a pattern, you will see your failure if you are consistent and thorough. If you make yourself a drawing, you can easily keep track of reading. Don't let the drawing confuse, one lead is red (+) one is black(-) but you can see there is 6 ways to check each transistor. This transistor shows 3 pins (you can use this on your control board) but your backplane transistors have 2 pins and the case is considered a pin. The results you see in the diagram may not be your results. They are examples. They will change from an NPN to a PNP tranny


View attachment 23483

Ok, Will do!

 

[LarryD]

pics


Thanks guy's. I have to get up at 3:00 am and drive 4 hours. Be back Friday. And thank you Perry for giving me another chance!
RED TO COLLECTOR/ BLACK TO EMITTER SHOWN AND OPEN.

 

[laatsch55]

Were you testing with the pointer on the scale where it was in the pic? And there is a diode test function on that meter. You should be testing using the diode test function. If your meter didn't have it we would go with ohms, but the diode test takes a lot of guessing out of it. I have a Craftsman meter very similar to that one. Good little meters actually. I test it against my Fluke 179 and they are actually pretty close if there are no high frequencies involved....

 

[laatsch55]

See ya Friday, we'll all be here....

 

[LarryD]

See ya Friday, we'll all be here....

Well still up ! Yes there is a diode test on the meter. I will switch to it and redo all readings. The very first post of findings I was trying to show what was out. This was before Perry told me to check all one way then move on to the next. I sometimes get in a hurry and do not read your reply completely, Sorry I will slow it down so not to miss anything you or Perry are asking. And Thanks for the help!