@pcan
i can only upload the pictures here.
The symptom: valves also light up and warm up, there is no noise of any kind towards the speakers (no hum) but no sound comes out of it.
Today I tried to measure the capacitors: the main condenser (replaced by a 120 uF 400V) and apart from a single bit (I didn’t take this out to measure it) all have normal capacitance.
I also tried to measure the voltage values.
300 + V can be measured at the main capacitor. That's because the multimeter is calibrated up to 300V. I saw a stable 310V on its display and a signal that the result was above the limit.
The pictures also show that I measured ~ 12V and (1000 uF 16V capacitors) ~ 8-9V at the indicated (X2) capacitors.
For all other capacitors, I measured practically 0 V, a couple of mV values.
I also checked the continuity at the points I could recognize with the multimeter, but what I examined was good everywhere.
IMG-20210204-184345 — ImgBB
mde — ImgBB
i can only upload the pictures here.
The symptom: valves also light up and warm up, there is no noise of any kind towards the speakers (no hum) but no sound comes out of it.
Today I tried to measure the capacitors: the main condenser (replaced by a 120 uF 400V) and apart from a single bit (I didn’t take this out to measure it) all have normal capacitance.
I also tried to measure the voltage values.
300 + V can be measured at the main capacitor. That's because the multimeter is calibrated up to 300V. I saw a stable 310V on its display and a signal that the result was above the limit.
The pictures also show that I measured ~ 12V and (1000 uF 16V capacitors) ~ 8-9V at the indicated (X2) capacitors.
For all other capacitors, I measured practically 0 V, a couple of mV values.
I also checked the continuity at the points I could recognize with the multimeter, but what I examined was good everywhere.
An externally hosted image should be here but it was not working when we last tested it.
IMG-20210204-184345 — ImgBB
mde — ImgBB
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Filament supply is present (tube filament lights up), so the primary and low voltage section of the power supply seems to be working. I would start by removing the tubes from the sockets and measuring the DC voltage between ground and anode of each tube. The EL84 anode is pin 7. If all of them are missing, then backtrace the circuit (measure on the + terminal of each filter capacitor) until you find the fault. Be sure to use a good multimeter probe because expected voltage is about 250V.
Hi, I took the measurement as you wrote, black on the ground, red on the positive leg. Well, I didn't know what I measured last time (330V between + and - leg on the sem capacitor the red and black pin) , because now the voltage is only 146V at the main capacitor, I couldn't even measure the value at the other capacitors with this method.
If the DC voltage between the + and - legs of the capacitor on the primary side of the switched mode power supply is low, then check the voltage between + and - of the bridge rectifier. If normal, check the thermistor between the bridge rectifier positive terminal and the capacitor positive terminal. It should measure a few ohms (usually 5). The measures are on the live part of the circuit, so precautions should be taken for safety.
Be aware that the main capacitor is not referenced to ground, because it is on the primary side of the transformer. The voltage applied across the capacitor on the primary side of the transformer must be measured at its + and - legs directly. If you measured zero volt between ground and the positive terminal of each one of the smaller high voltage capacitors on the secundary side of the transformer, then you should check the diode between the transformer winding and the first capacitor.
Be aware that the main capacitor is not referenced to ground, because it is on the primary side of the transformer. The voltage applied across the capacitor on the primary side of the transformer must be measured at its + and - legs directly. If you measured zero volt between ground and the positive terminal of each one of the smaller high voltage capacitors on the secundary side of the transformer, then you should check the diode between the transformer winding and the first capacitor.
The voltage between the + and - legs of the main capacitor is ~ 310V, this is the voltage between the + and - legs of the bridge rectifier too. While the resistance between the main capacitor + foot and the bridge rectifier + foot is ~ 27 Ohm.
I checked the diode: ~ 80 V voltage between the two legs. Now I have measured values on the other high voltage capacitors as well, black pin on the ground, red pin on the capacitors + feet: ~ 180V initially, but the voltage drops slowly. This is true of all of them. After about 1-2 minutes it is about 40-60V the measurable value only. I replaced the main capacitor with another, but the same phenomenon.
The voltage value between ground 0 and pin 7 of the EL84 socket is 0.
I checked the diode: ~ 80 V voltage between the two legs. Now I have measured values on the other high voltage capacitors as well, black pin on the ground, red pin on the capacitors + feet: ~ 180V initially, but the voltage drops slowly. This is true of all of them. After about 1-2 minutes it is about 40-60V the measurable value only. I replaced the main capacitor with another, but the same phenomenon.
The voltage value between ground 0 and pin 7 of the EL84 socket is 0.
And to complete the picture, in the meantime, another symptom arose: a sound that I had a hard time describing, but I would try. Somewhere a mixture of hum and sizzling. As soon as you get electricity, it starts right away, if not too loudly, but definitely audibly. (as if the hose was leaking on the bike). And even after unplugging, approx. half to 1 minute before it finishes and fades completely.
I'm 100% sure 
that all electrolytics are fakes and should be changed anyway , after that it could be fixed itself . I would check first the little one near the power IC radiator .
The sound is from an unhappy SMPS , not working right / shorted from the cause written above or other to be found ...
that all electrolytics are fakes and should be changed anyway , after that it could be fixed itself . I would check first the little one near the power IC radiator .The sound is from an unhappy SMPS , not working right / shorted from the cause written above or other to be found ...
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All capacitors have been replaced from factory capacitors to Panasonic capacitors ordered from Farnell (considered ergo original). "
Or one hasn't been replaced, and that is the "I would check first the little one near the power IC radiator" you also mentioned.
I have no idea why I missed this. I'll check it anyway.
Or one hasn't been replaced, and that is the "I would check first the little one near the power IC radiator" you also mentioned.
I have no idea why I missed this. I'll check it anyway.
There are only small developments: there is currently enough tension within the area marked with a blue frame. The two 47uF 350V Panasonic capacitors now have a value around 250V, but the voltage no longer goes to the next, ie the third (horizontal) capacitor. It's like stopping there at the inductor or capacitor. I have already replaced the capacitor with another for the duration of the test, but there is no change: 0V is the result.
Replacing the inductor may solve the fault. Or at least the DC goes further.
Replacing the inductor may solve the fault. Or at least the DC goes further.
An externally hosted image should be here but it was not working when we last tested it.
I don't know if there is a connection, but I found the following: when it is switched on, there is 300V in the main capacitor and in the bridge rect. However, after switching off, it will drop to 0V in about 10 seconds. While the other two larger capacitors within a blue frame still slowly drop Vt after a few minutes.
I had the same problem. Bought a used N3 that needed repair in 2018. Finally got around to repairing it in 2022. I found the problem ( no filament current and weak B+) to be a dead main filter cap (270uf x 400v). I also used a 100uf x 450v Nichicon 105c as a previous post because anything close to 270uf x 400v was WAY too big to fit. Replaced the 3 filament caps while in there ( 2 - 1000uf x 16v & 1-100uf x 16v ), Works great now!
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