Need help to repair two phase 400 amps

[laatsch55]

With no outputs in the sockets you should only have to desolder the end of the one that is soldered exclusively to the 3 tab terminal strip. Leave that one alone, but test all of them again when you have the two desoldered.

 

[LarryD]

Yes, those are the ones we were talking about. Those diodes are affected by components on the backwall and by components on the driver board.

Diodes will have some designation to identify the cathode and anode end. A majority will have a black band on one end. The cathode end is "negative" and the anode is "positive" for testing purposes. You have to desolder one end of these to be sure they are good/bad. So pick the end easiest to desolder and resolder.

Lee I am trying to get this pos iron working. I am going out to the garage and get my other pos! LOL! Oh and one question. If I stay on this thread without leaving it , when you reply I do not see it. I have to go out to forums and look to see if there was a reply. That's not normal right? Be right back

 

[laatsch55]

On the main forum index page, to the right of the "Latest Topics" box is a small double arrowed box. If that tab is enabled There will be another long box that says " New Forum Posts". That is much handier to see if you or I have posted as opposed to hitting the refresh button. You can bounce between the main forum page and your thread by use of that box too.

 

[laatsch55]

Lee I am trying to get this pos iron working. I am going out to the garage and get my other pos! LOL! Oh and one question. If I stay on this thread without leaving it , when you reply I do not see it. I have to go out to forums and look to see if there was a reply. That's not normal right? Be right back

Yes that is normal. You have to reload the page to see a new post. See there, read your mind....As I had posted the above before reading your latest post.


You can also scroll down to the bottom of the main page and click on the "users online" and that will take you to a listing of where folks are in the forum at that moment.

 

[LarryD]

Ok I unsoldered the one I showed you a pic of. It now measures open/541.

 

[LarryD]

Yes that is normal. You have to reload the page to see a new post. See there, read your mind....As I had posted the above before reading your latest post.


You can also scroll down to the bottom of the main page and click on the "users online" and that will take you to a listing of where folks are in the forum at that moment.

Ok thanks

 

[LarryD]

Lee, I have to run to the store for food for my cat. He is yelling at me! And that was a prime example of why some components need to be removed.! I will try to be back asap!

 

[laatsch55]

There are 4 brown-green-brown resistors on the bottom row of sockets, did you check all 4?

 

[laatsch55]

No worries mate, the cats must be fed.....

 

[LarryD]

There are 4 brown-green-brown resistors on the bottom row of sockets, did you check all 4?

yes sir we did, those were the ones I missed the decimal on but I will check them again and send you the results. I will be back soon. Thanks for taking time with me. I will be gone for about 45 to one hour.

 

[laatsch55]

I may be in bed by then or maybe not. Post your results anyway....

 

[LarryD]

Finally , Ok here is what I have. I believe that should have a decimal like this 16.6 ohms.

1 166/179
2 167/167
3 166/166
4 165/164

 

[laatsch55]

They are 150 ohm resistots. Download and print out a resistor color code...and while you're at it a capacitor designator sheet.

 

[LarryD]

I may be in bed by then or maybe not. Post your results anyway....

Ok I have downloaded the charts. I will practice on the resistors and see if I can get it right. Thanks

 

[laatsch55]

Old resistors , like those in that amp , will drift over time so 160 or so could be the right reading for them.

Also. I need pics of the board wiring to the backwall. We need to be able to document the individual wire runs between the bboard and backwall. In your pics we need to see where they start and where they end. You will have to cut the small cable ties that hold the bias transistor (q6) bundle (3 wires,red,black, brown ) from the rest of those wires. CAUTION, those wires are old and stiff and too much flexing will break them. Trace the bias tranny wires from the board to the backwall, you'll see them attached to an aluminum P-Strap heatsink. Let me know when you've done this and we'll proceed.

 

[LarryD]

I may be in bed by then or maybe not. Post your results anyway....

Ok I have downloaded the charts. I will practice on the resistors and see if I can get it right. Thanks

 

[laatsch55]

Did you read my last two posts?

 

[laatsch55]

You gave me the same answer to two different posts of mine...

I was hoping for a different response after the explanation of old resistors drifting in values...

 

[Northwinds]

This is like doing heart surgery over a phone

 

[WOPL Sniffer]

I'm all for it.