What some people would do is replace all the semiconductor components.
That does not fix the problem if there is still a bad resistor or capacitor.

So why not replace all the components?
That still does not fix the problem if there is a short on the board or a broken track.

True....
What about lifting resistors to the bulb goes dark like JoeJester suggested earlier? Where would i start..

I will order components...

 

On a large computer board with hundreds of chips being powered from a common power rail, it becomes challenging to find a short across the power rails. Sometimes the only strategy available is to cut the power traces at strategic locations.

With discrete components such as this amplifier, we have the opportunity to lift components, usually the two push-pull transistors across the power rails.

 

Order some components from digikey.

I will add some zener diodes just so i have if i will need.

Will this be the correct part for D411?

https://www.digikey.com/product-det...6A-TR-PBFREE/1514-1N756ATRPBFREETR-ND/4807382

 

They will work but I don't think you need 10,000.

1N756A
1N5237B

Going by our past efforts at fixing this, I think we still have a long road ahead of us.
You may want to see what spares you have on hand and what else you should buy in one order to save time and shipping costs.

After I get a chance to look over the circuit diagram and review where we're at, I am going to suggest that we disable the LEFT channel and focus on one channel at a time.

 

Hehe... 10,000 might be too many

Yes, i will look over what i would need.
Okey, might be a good idea to disable.. what should i remove?

 

I recommend a building block method as well, One channel at a time. Isolate the sections as well, and start re-establishing the power supply loads one by one, to keep the surprises to a minimum. It's time to be methodical and slow.


The isolating resistors are shown in the power supply section for ease of referral.

You can't isolate L and R via resistors. However you isolate them by removing components.

The first section I recommend going back to load the is the low voltage X6xx Extended Servo Section. That would ensure you have all the low voltages and high voltages.

 

I guess you want me to remove some components to isolate the channels @JoeJester ?
But you need to tell me which one i will remove

I looked through what i have and what i would need, order many of parts that have gone bad earlier and lately, if no new ones smoke i will have the parts to put it together. just have to go from there

 

No, not unless we have to. But till the power problem is solved, we can't look at anything else.

Fixing the power problem is primary. Then we can start checking the other stuff.

Isolating the various sections is a quick way to find out where we need to look. Right now we KNOW the x4xx and the x5xx are causing their isolating resistors to burn up.

Is the power normal, all of the voltages with the two lamps disconnected? I think it was at one point, but where are we today?

Your were looking at a very small current flow through that one bulb that energized, way less than indicated by the main lamp shining brightly. That is why I am suspicious of more than that one area has problems.

So, disconnect one end of the two lamps, turn on the power and see if the main lamp de-energizes. or goes very dim, if it does not, there are other problems to solve before proceeding to the specific sections.

 

Sorry for being a little slow.. i'm a happy amateur, i think i get what you are trying to explain me.

So disconnected one of the 21W bulbs (R506) and the 100W bulb almost de-energized totally.
See pics.

 

Jumpers J121 and J220 take the +ve power from R505 and feed the LEFT and RIGHT channels.
J121 is for LEFT Channel
J220 is for RIGHT Channel

The same cannot be said for J116 and J219. These take -ve power from R506.
J219 is for LEFT Channel
J116 is for both LEFT and RIGHT Channel

If you cut J121 and J219, this will remove power to the Q4xx stages on the LEFT Channel.
Then your 21W bulbs should not be lit.

 

I'll assume the bulb you disconnected was the one that was slightly energized.

Which resistor was that .... so the troubleshooting effort can be directed there, IF you measure the two 60V supplies and they are normal.

thanks MrChips, my schematic doesn't have jumpers labeled.

 

I'll assume the bulb you disconnected was the one that was slightly energized.

Which resistor was that .... so the troubleshooting effort can be directed there, IF you measure the two 60V supplies and they are normal.

Yes, i disconnected the one that was glowing a little bit, R506

 

Okey, so you want me to cut J121 and J219, connect the bulb again and see if the 100W bulb shines?

 

Mr Chips already gave you better instructions on how to isolate the sections further.

 

Okey, so you want me to cut J121 and J219, connect the bulb again and see if the 100W bulb shines?

That would be reasonable.

 

Yes. If you cut J121 and J219 this ought to remove power from the LEFT channel Q4xx section.

Now you should be able to work on the RIGHT channel while waiting for parts to arrive.

Edit: BTW, I can only go with what I have to work with, that is, a circuit schematic and the photos of top and bottom sides which you have provided.
There is always the possibility that I have misread what I can see from the photos.

 

Okey.. i cut jumpers and connected the bulb, it worked...

 

Excellent!

Now you can focus on the RIGHT channel.
Notice that all the components in the RIGHT channel end in EVEN numbers (bottom section in the schematic diagram).

I don't know what components are off the board but a first test would be to measure the voltages at the two pins on TP502 with respect to GND.

 

I noticed R402 as being blown to pieces on that picture showing J121 as cut. That is part of the input circuitry of the R channel in section x4xx.

Not necessary to fix that until your ready to apply a signal to the right channel.

 

I noticed R402 as being blown to pieces on that picture showing J121 as cut. That is part of the input circuitry of the R channel in section x4xx.

Not necessary to fix that until your ready to apply a signal to the right channel.

I never could understand what would cause R402 to get blown away.
Can you?