29 Ekim 2020 - YouTube
hi friends, at 1:20 some tims it come strong some times not and some times repeat it self.
any one have idia why this noise happen and how can i fix it?
and is it normal first 2 tube light normal and after that 2 tubes light low.
thank you for answers.
hi friends, at 1:20 some tims it come strong some times not and some times repeat it self.
any one have idia why this noise happen and how can i fix it?
and is it normal first 2 tube light normal and after that 2 tubes light low.
thank you for answers.
Welcome to Tubes / Valves!
Perhaps someone in Instruments & Amps will know more about your Guitar Amplifier.
Many European built 12A_7 and similar tubes are known for Very Bright filaments when the power is first applied, and then they settle down to low or normal light levels when they are warmed up and running.
Perhaps someone in Instruments & Amps will know more about your Guitar Amplifier.
Many European built 12A_7 and similar tubes are known for Very Bright filaments when the power is first applied, and then they settle down to low or normal light levels when they are warmed up and running.
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You have to take the amp apart and find the bad solder joint or faulty caps. If you are not used to hivoltage tube amp find a repair shop.
Hi thanx for answers. This amp burn current limit resistor 390r. İ change it and i see some leaking caps i change thats too. Amp working but this noise coming out.
There was 2 caps i dont change after bridge diode. 47uf 500v. but they look ok.
This noise maybe coming from caps or tubes?
There was 2 caps i dont change after bridge diode. 47uf 500v. but they look ok.
This noise maybe coming from caps or tubes?
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You will have to scope it to find where that noise is coming from.
First speaker out, then power amp input, to at least split amplifier into 2 working blocks: Power Amp and "everything else".
Divide and conquer.
And you should have posted this in "Musical Instruments" which has a separate section of its own for a reason, things are done in a way different than regular Hi Fi.
First speaker out, then power amp input, to at least split amplifier into 2 working blocks: Power Amp and "everything else".
Divide and conquer.
And you should have posted this in "Musical Instruments" which has a separate section of its own for a reason, things are done in a way different than regular Hi Fi.
İ dont have scope ☹️. İt not look like cap fail. But i dont fix before tube amp. İ ask for just to be sure its coming from tubes or not. Ty
You can use an analog AC voltmeter, costing about $25. Get one with 2 VAC & 20 VAC scales, although you can tell some things with a 50 vac scale on a cheaper meter. Put a .047 uf 400 v cap in series with the negative lead, they will read DC voltages on the aC scale without. Use alligator clip lead on the probe not used, you don't want 400 v from unit under test flowing from one hand to the other and stopping your heart. Wear no jewelry on hands wrists or neck when testing unit powered up.
Reason analog voltmeter, inexpensive DVM produce random numbers on AC not at 50 or 60 hz. Expensive fluke RMS DVM (~$160) which will read accurate music voltage, misses everything above 7000 hz, which means it would miss an ultrasonic oscillation problem. Waste of money IMHO.
Or you can use a sound probe, which is another amplifier speaker (preferably cheap) with at least 2 vac sensitivity, and a overvoltage protector on the input. Overvoltage protector is .047 400 cap series 2000 ohm resistor both plus and minus. Behind those put two red LED's back to back across the two input, to clamp the voltage to 2 vac max. Behind the LED's comes the input & ground of the amp/speaker. Music above 2 v will sound clipped, which is kind of nasty like a siren, but different hopefully than the random sounds you are tracking. If you can turn down the gain of the probe amp to less than 2 v sensitivity you can reduce the effect of the clipping when probing the higher voltage stages.
Of course you'll need music going into the amp to test for bad noises. I use a $3 pocket radio turned down out the earphone jack (which will produce ~6 vac, too much for PA amps) but a guitar amp you'll need to use a guitar or a much lower voltage input device than a radio.
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thank you for suggestions. i change filter caps too finaly i find them in my country. but nothing change still that things happen. i take out tubes and shake in my hand slowly and one of them some thing making noise insde. that mean tube in bad condition? that tube el84.