well its like dealing with a problem child 😉
ive had to switch my attention to smoke coming from the direction of R659/660 and the main filter caps, that were brand new, just occational whisps at full volume, strange, but i cant ignore it, this has to be priority for now
Not sure if it has ever been driven that high TBH, it might just be a bit of glue on a component burning off when getting hot
ive had to switch my attention to smoke coming from the direction of R659/660 and the main filter caps, that were brand new, just occational whisps at full volume, strange, but i cant ignore it, this has to be priority for now
Not sure if it has ever been driven that high TBH, it might just be a bit of glue on a component burning off when getting hot
Smoke doesn't sound good. I'd have to see them on the circuit to get an idea why they might burn. There are that many NAD 3020 variations I never know which we are looking at 😉
so it looks like 'follow the smoke'
very starange, took all 4 caps out because i think that is where the smoke is coming from
put them back in, and now the voltage isnt wandering anymore, but still have a little smoke, so im going to change those caps out as it might be a dodgy batch, or even the recifier could be faulty yet? but i think im looking in the right direction now
very starange, took all 4 caps out because i think that is where the smoke is coming from
put them back in, and now the voltage isnt wandering anymore, but still have a little smoke, so im going to change those caps out as it might be a dodgy batch, or even the recifier could be faulty yet? but i think im looking in the right direction now
Well done 🙂 So those resistors are just in series with the headphone feed to limit power to the headphones.
Two things would have to happen for them to smoke. Firstly they would need a path to ground or via the speaker load to ground. Bit weird because that should not happen. Look at the way the socket is drawn. When you plug headphones in then the plug pushes the switched speaker line apart and disconnects the speaker while connecting the headphone through the resistor.
Everything connected to that is in the socket. Who knows what might have happened. Could be some silver foil shoved up there or anything 😀
Two things would have to happen for them to smoke. Firstly they would need a path to ground or via the speaker load to ground. Bit weird because that should not happen. Look at the way the socket is drawn. When you plug headphones in then the plug pushes the switched speaker line apart and disconnects the speaker while connecting the headphone through the resistor.
Everything connected to that is in the socket. Who knows what might have happened. Could be some silver foil shoved up there or anything 😀
ok so an update.I dont think it was the resistors that were smoking, in fact it cant have been.I put in 4 new caps, a different make and no smoking, so it must have been a dodgy cap, not sure which one ,i just binned all 4.
Its still going now without any issues, and no smoking,although i have not put a load on it yet.
with regards to the headphone socket, it was full of some liquid and ive just stripped it all down and cleaned it, so we shall see if it was the socket iself when i put it back shortly, if not its on from there i guess,but im real close now(again 😉).This thing has had multiple things wrong with it, but its all good learning.
Socket been squirted with something perhaps. WD40 perhaps.
If you buy caps from reputable suppliers then you should have no problems. Lots of eBay offerings are dodgy and/or fakes. Do an image search. Here is a cap within a cap.
If you buy caps from reputable suppliers then you should have no problems. Lots of eBay offerings are dodgy and/or fakes. Do an image search. Here is a cap within a cap.
i meant to say it also cures that earth issue, so no matter what the reference point,chassis or caps, the grounding points on the components are all 0v
ok latest-its not the socket itself, i did have my doubts, so now we have a new trail to follow as when you put it back in it all goes mad again
ok latest-its not the socket itself, i did have my doubts, so now we have a new trail to follow as when you put it back in it all goes mad again
TBH,they do cost more but i only buy panasonic,nichion or other reputable makes, and from proper suppliers
so by removing the headphone socket it cures the issue ,but it isnt the fault
i checked R803/4/5
running out of ideas now
i checked R803/4/5
running out of ideas now
any idea what the 2 circled in green are supposed to be doing?
so senario
if you push a chopstick into the headphone socket and engage it, it stops going wild
so senario
if you push a chopstick into the headphone socket and engage it, it stops going wild
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ive got this thing working and its not distorted
only thing is one channel(the one i didnt recap) is a bit more dull sound wise(not as clear treble wise)
could this be some poor old caps causing this?
only thing is one channel(the one i didnt recap) is a bit more dull sound wise(not as clear treble wise)
could this be some poor old caps causing this?
Plenty much stuff like that, yes. Same for transistors (remarked to say something else) and same for IC's
Look at the other channel. They just go to the - and + 25 volt rail. The resistors for a potential divider to give a known voltage across C704 and C706. When the signal voltage on C702 exceeds the divider level then the signal is effectively 'soft clipped' and it can not increase any more.
So its all part of the soft clip feature.
One channel sounding dull is a perfect scope exercise. You could set the signal generator to feed both inputs (L and R) and then use both trace of the scope to show L and R speaker outputs. Sweep the generator up to about 25kHz and see if the audio level falls with frequency on the bad channel.
It is unlikely to be a faulty cap. More likely a wrong value if they have been swapped anywhere or perhaps a faulty bass or treble control, that kind of thing.
so in the end i thought i couldnt go anywhere else and i was proberbly chasing nothing at all, so i checked 2 other 3020's i have here and both are exactly the same, when you ramp them right up, i mean beyond 3/4 full volume then all go crazy on the centre, and it goes when you plug in headphones,strange i know but ive been using it for a while now and no distotion at all. so i recon i had it right around #92
im starting to lean now that when all does not seem well, may not nessesarily be the case.
i will try the scope tomorrow
im starting to lean now that when all does not seem well, may not nessesarily be the case.
i will try the scope tomorrow
god what an idiot(twice) that realy anoys me when i dont notice things like that, still all good learning when someone points out the VERY obvious😉
Ah... so it looks like a 'feature', a design fault 😀 It wouldn't surprise me and that is not to be negative about them... they are what they are, a budget amp that happened to excel sonically.
We all do that, it a happens all the time to me with things.
We all do that, it a happens all the time to me with things.
