4230 problems

[Vintagecasey]

Here is my jumpers.

 

[dankik]

(Right side board looking at it from the front )
J715 Orange
j721 red
j713 white and purple
j707 black
j708 Black
j714 white and gray
j716 gray

(Left side looking at it from the front )
J715 Brown
J713 white and green
j707 black
j708 black
j714 white j716 blue
J722 red
J716 blue

From internet site: Marantz 4230 Receiver Restoration
Looks like the wire colors match.

__

 

[Vintagecasey]

I replaced all the caps and transistors on the burnt board, 7 resistors and the output transistors. Bright bulb! Removed it again, rechecked orientation of caps and transistors, checked for bridging. I didn't find anything. Rechecked transistors, they check good. I didn't remove all the resistors but I did check them for dead shorts and none show dead shorts. Anything I can do to test the board before I put it back in again?

 

[Davron94]

Have you lifted a leg on all diodes and tested them? Check the ones behind the coupled caps and the R737, R738.
That R713 and R717 look like they got a bit toasty. Just because they read good on an ohm meter does not mean they will handle load properly under stress. The emitter resistors and drivers are usually the first to go if you had any blown outputs. Have you completely disconnected the outputs and tested those, as well as testing the driver transistors out of circuit? Ensure that you are testing forward and reverse bias, plus E-C voltage drop being open, on the diode setting of your DMM.

 

[dankik]

OK, I did a quick visual check of the components. Here is what I would like you to check:

1. R712 s/b 47k but it looks burnt and I see a black color code stripe - replace
2. R713 s/b 1.5M but looks burnt on the right end
3. R755 s/b 820 Ohms but color bands do not look like R756 - replace
4. Can't tell polarity of C707, C708, C702 - verify correct polarity
5. Probably should replace the 4 diodes.

 

[Vintagecasey]

I'm guessing those are no longer available, is there a good substitute that you could recommend? I think I'll replace all of them on both boards.

 

[dankik]

NLA, I don't know of an equivalent Ge diode. Maybe someone else can help out. Your DMM test seem to look OK. Maybe you can try some of those on eB.

 

[Vintagecasey]

I'm not very familiar with these type diodes, ( forward and reverse?) 1N60?

 

[Vintagecasey]

Would BAT41 or BAT46 be good substitutes for the 1N60 diodes?

 

[dankik]

Looks like a BAT43 will work. Digikey has them in stock.


The BAT43 and BAT46 are obsolete.
Mouser has the BAT43-TAP in stock. (see below)
(HINT: Since they are only 50 cents ea, might as well buy 10 to reduce the price to 0.306.

 

[Vintagecasey]

I may as well change the output resistors, can I use wire wound (that's what they look like to me) or metal foil or something else ?

 

[dankik]

I would advise not to just start changing parts for the heck of it. You need to diagnose the problem then determine what is causing the problem and repair it.
You still didn't answer my questions about the circled parts in Post #25 and polarity of the 3 electrolytic caps. If you still have one good board, I would start by measuring the ECB voltages of each transistor then compare those against the measured voltages of the shorted board.

 

[dankik]

Check the solder joints pointed to by the 3 pink arrows. (Image is reversed to match SM)
Make sure that the heatsink for H005 is not shorting anything on the PCB.

 

[Vintagecasey]

Those 3 capacitors are bi-polar. I have polars on order (my mistake getting the bi-polars by accident). My understanding is they will work fine, is that correct? The resistors that look (smokie) tested good, but I did add them to my new order. I'm not very impressed with the factory soldering on this unit, ALL boards have questionable solder joints. (Almost as bad as mine )

 

[Vintagecasey]

I was hoping not have a lot of time in this and just get some practice but after looking closer at the board not just trying to fix what was burnt, this thing had a rough life.

 

[Davron94]

If it were mine, I would reflow every one of those solder joints. It looks like someone did some messy repair work. I had to do the same thing to mine, along with replacing all the old, corroded wire-wrap leads to the outputs. These are tricky boards to deal with, being complementary dual amp boards.

Be very careful with those SV-3a varistor diodes also at J723-726. If the leads are broken, it's a whole other issue to solve!

 

[Vintagecasey]

Yeah, I'm trying my best not to move them. It's a mess, and I know there has been work done, gobs of solder, multiple boards and a burn hole.

 

[dankik]

What kind of soldering iron do you use? Temperature controlled, small tip. When you touch up the old solder, it is sometimes better to remove the old solder with a solder "sucker" or braid, then clean the pad with isopropyl alcohol and a Q-tip and apply some flux (I use a flux pen) and new 60/40 or 63/37 (lower melting point) solder. That will give you a good solder bond. Apply the soldering iron tip to heat up both the PCB trace and component lead at the same time, then apply the new solder. Wait a few seconds, then remove the iron. If you have any jumper wires, make sure that you scrape off the solder resist until you see bare copper, apply flux, then solder. The new solder should look "shinney" and smooth when it cools. If not, then you did not apply enough heat.

Here are some examples (no affiliation with sellers). You may already use all of these, but just making sure.