Any movement or anything physical like that, and that causes things to happen is sure fire sign of either a bad joint or bad connection as you mention or something physically shorting in response to movement.
That's bad luck that there is still this underlying problem.
That's bad luck that there is still this underlying problem.
At least we know it is functioning as it should. Now to track down these loose connections/solder joints. When I get off work tonight I am going to flip it over and check all the wire connections into the power supply board as well as all the wire connections into the main boards
Started inspecting the left channel problem board. I have 2 blown transistors. Q701 and Q703. I mean the transistors had the backs blown right off of them. and I am just getting started. WOW
Those are odd ones to take a hit.
Look carefully at the diagram and check check check...
Q703 is to monitor overcurrent. The collector is connected to a high impedance area (the 47k) which can not deliver any destructive current. The base of Q703 is also isolated from possible high voltage (and so excess base current which would be caused by failure of the 0.22 ohm).
So I think we are left with something physical here.
Q701 is similarly isolated to a large extent. R720 would go up in smoke if a massive current flowed and so to R717
There just aren't the direct paths to supply rails that can cause really high current to flow here. That said I can see one possible failure route for Q701 but not for Q703. If Q701 turned fully on it would try and pass current through D705 and the Zener. High current could put a high voltage across the 10 volt cap C705 which then conducts massively and that current flows in the transistor. That is just a theoretical route that exists though, not that it happened.
I must admit your much more inteeligent than I when it comes to electronics and I agree with everything you said, So how the heck did these transistors basically split right in two. I haven't even had anything in that area of the board. I must admit it seems odd. I will get those replaced with KSC1845 and KSA992
Got the tranny's replaced. It still has an issue with a loose wire or component. If the power is on and I move the back of the amp just a little bit it goes into protection and the DBT gets very bright. I suspect there is more loose wires somewhere. There is so many wires all covered in the back of this amp it'll be a little difficult tracking it down but Im sure Ill find the culprit. I've already fixed and resoldered about 7 wires all going into the reg/prot board. I think at this point it would be prudent on my part just to go ahead and reflow all the wire connections on both the regulator board and power supply board
both either with or without. I need to qualify what is happening. The back panel of the amp is detached, you cant fully remove it with out disconnecting a bunch of cables. Not sure if you have work on a Nikko but you detach the back panel to get to the main boards. Any time I have reattached the back panel after thinking the issue was resolved and it was playing music just fine, I power down reattach the back panel power up thru DBT to confirm operation and I get a very bright light and no relay engagement. If I detach the back panel and pull it back just a little bit it works just fine although the left channel is not working now.
I've not worked on a Nikko but in any case this really sounds like a one off sort of issue. I would work without a speaker attached though seeing the fault occurs with and without one.
Perhaps try and fault find with the bulb lit bright. See if any rail stands out as very low. Even if say a -/60 volt rail falls to -/+15 volts with the fault look for any imbalance like -3/+15 and so on. Same for any other single rails. Are they lower than they should be compared to others.
Use low value resistors in the circuit to look for volt drops to see if you can find where the current is going. The 0.22 ohm resistors on the output stages are a good starting point. Is the current flowing in the output transistors or elsewhere.
Feel parts to see if any run hot when the fault occurs.
Perhaps try and fault find with the bulb lit bright. See if any rail stands out as very low. Even if say a -/60 volt rail falls to -/+15 volts with the fault look for any imbalance like -3/+15 and so on. Same for any other single rails. Are they lower than they should be compared to others.
Use low value resistors in the circuit to look for volt drops to see if you can find where the current is going. The 0.22 ohm resistors on the output stages are a good starting point. Is the current flowing in the output transistors or elsewhere.
Feel parts to see if any run hot when the fault occurs.
OK, Quick update. I found wire #18 on the reg board that goes to left main amp board was very loose. Resoldered the wire to the board and it was working ok, but then the old issue creeped in again. So back to looking for the culprit. feeling around for hot components. Carefully moving wires to see if it jumps out of protection.
Apologies are in order as I have been away from the work bench. Mother in law is coming back with the wife so I have to get a room ready which means moving one of my boys upstairs to an unfinished bedroom because mother in law cant climb stairs. SO been busy trying to get unfinished bedroom finished enough so he can stay in there for the time being. Yeah one of lifes little twist and turns. This is the first time I have been on the bench this week. Hopefully Ill be able to get in here more consistently.
Apologies are in order as I have been away from the work bench. Mother in law is coming back with the wife so I have to get a room ready which means moving one of my boys upstairs to an unfinished bedroom because mother in law cant climb stairs. SO been busy trying to get unfinished bedroom finished enough so he can stay in there for the time being. Yeah one of lifes little twist and turns. This is the first time I have been on the bench this week. Hopefully Ill be able to get in here more consistently.
No apologies needed, life often throws a curveball our way.
At least you seem to have found one definite issue... so maybe there are more lurking.
At least you seem to have found one definite issue... so maybe there are more lurking.
I am more confused than ever. Not coming out of protection now. I discovered that if I pressed down on the differential circuit module on the left channel main board it would dim the light and come out of protection. I desoldered the module and resoldered it back in. Upon doing that it now does not come out of protection and the light stays dim. If I reconnect the back panel to the frame it makes the light go bright and if i pull it away from the frame it goes dim. Very strange.And under no conditions does it come out of protection. It almost feels like a grounding issue??? Back panel touchs frame and light goes bright, back away dim. Maybe I will post a video so a visual can better explain.
All these things sound like physical issues. No amount of pressing or bending up to actually breaking something should cause any fluctuations at all.
If I need any more help with it I will holler at you. We know it works and very well. Just need to find the physical issue with it. It very well cant operate laying open on my work bench.
OK 👍
And remember when the bulb lights is the chance to see where the current might be flowing as I think I mentioned earlier. Some low voltages will still be present on the rails so look for imbalances and measure volt drops across any low value resistors and so on to see where it is flowing.
And remember when the bulb lights is the chance to see where the current might be flowing as I think I mentioned earlier. Some low voltages will still be present on the rails so look for imbalances and measure volt drops across any low value resistors and so on to see where it is flowing.