I got this kit from ebay.
13W*2 6P14/EL84 Push-pull HiFi Class AB Stereo Tube Integrated Amplifier DIY KIT | eBay
I put it together and i got stuck. When I turn the power on I get a loud high pitch noise, the actual audio if I get any is very little. I double checked the soldering I cant find where I made a mistake. The noise is on both channels. If i disconnect the negative feedback from the speakers output the noise goes away but there is no amplification of the audio signal. I am a NOOB. I must have made a mistake but I do not know where to look. I have enough knowledge to follow the markings on the PCB and to solder but I have no idea where to look for my mistake.
The build and schematics for this you can find it on
DJ100 Assembeld Manual_免费高速下载|百度网盘-分享无限制
Any suggestion will be greatly appreciated.
13W*2 6P14/EL84 Push-pull HiFi Class AB Stereo Tube Integrated Amplifier DIY KIT | eBay
I put it together and i got stuck. When I turn the power on I get a loud high pitch noise, the actual audio if I get any is very little. I double checked the soldering I cant find where I made a mistake. The noise is on both channels. If i disconnect the negative feedback from the speakers output the noise goes away but there is no amplification of the audio signal. I am a NOOB. I must have made a mistake but I do not know where to look. I have enough knowledge to follow the markings on the PCB and to solder but I have no idea where to look for my mistake.
The build and schematics for this you can find it on
DJ100 Assembeld Manual_免费高速下载|百度网盘-分享无限制
Any suggestion will be greatly appreciated.
There is a 6? part build series from this guy: Vacuum Tube Push-Pull Amplifier Kit - Part 1 - YouTube
It might help you see where you went wrong.
S.
It might help you see where you went wrong.
S.
I found the video while waiting for the kit. I look over it and i did not find any clues on where to look for my problem.
Sounds like the wiring of the output transformers.
By the looks of the pictures on the auction listing, they are ultralinear, meaning the screens of the output tubes have a seperate connection to the OPT. If you get the phase of the output wrong, by swapping the screen and plate connections, then you will get the loud howling you heard with the feedback. It is also important that the loudspeaker ground is attached to the amplifier ground.
Can you show the instructions you have for wiring the transformers? Maybe some pictures?
By the looks of the pictures on the auction listing, they are ultralinear, meaning the screens of the output tubes have a seperate connection to the OPT. If you get the phase of the output wrong, by swapping the screen and plate connections, then you will get the loud howling you heard with the feedback. It is also important that the loudspeaker ground is attached to the amplifier ground.
Can you show the instructions you have for wiring the transformers? Maybe some pictures?
Making some progress. I should have looked on the electrical diagram, the pictures are very poor. The output transformer 0 pin now is to the ground and also the black speaker post is to the ground( had the 0 transformer output directly to the black speaker post). The high pitch noise is gone.
Now this is very weird, when I plug the 110V power cord i can hear very faint sound out of the speakers, if i take the power plug out then suddenly is loud (i guess is from the power source capacitors charge).
I do have a multimeter and I checked the power supply output and seems ok.
This is the weird one. If I plug the power plug I get the loudness, if i use the power switch (which is only on the hot side of the power input) i don't. I thought perhaps is the ground from the power outlet side, i disconnected that and did not work. I also switched the neutral with the hot wire to the power transformer, still no luck. I also switched around the 370V power transformer output, still no luck. I must have something wired wrong but I this point i am out of ideas where to look.
there are 2 output voltage, one is listed at 300V and the other one listed at 350V. At the beginning the voltage is higher at 400V and then stabilizes, the 350V stabilizes at about 350V, the 300V actually reads 350V even after a while. The input to the power supply is at about 290V(on the transformer is marked at 275V)
Could be the power supply the problem? If this is the problem where should I look for a wrongly placed or defective part in the power supply?
View attachment Power supply.pdf
View attachment Amp schematics.pdf
Could be the power supply the problem? If this is the problem where should I look for a wrongly placed or defective part in the power supply?
View attachment Power supply.pdf
View attachment Amp schematics.pdf
Take out the fedback R5 first. Often this FB - that the connection is from the secondaries - can be connected the wrong way.
Severe oscilation can happen.
But your two ways of disconnecting the mains i dont understand.
Severe oscilation can happen.
But your two ways of disconnecting the mains i dont understand.
You have to 'start' some where...
Have you made any measurements as requested by astuffer (post #5)?
Start by checking the voltages circled in red. Tell us what you get.
P1 (ECC85) Pins 1, 3, 6 and 8.
P2 (EL84) Pins 3, 7 and 9.
P3 (EL84) Pin 7.
The pins are counted clockwise from the gap.
Have you made any measurements as requested by astuffer (post #5)?
Start by checking the voltages circled in red. Tell us what you get.
P1 (ECC85) Pins 1, 3, 6 and 8.
P2 (EL84) Pins 3, 7 and 9.
P3 (EL84) Pin 7.
The pins are counted clockwise from the gap.
Attachments
It seems a power supply problem indeed. There may be a wrong connection to the EL84 screen grid power supply. Check the voltage at pin 9 of the EL84 socket. You may also temporarily bypass the solid state stabilized power supply. Disconnect/remove the wire that feeds the 300V (stabilized g2 supply) from the power supply board to the amplifier board, and connect a 180 ohm 5W resistor between the 350V and the 300V on the amplifier board input connector.
The input circuit is rather complex.
Make sure the inputs are not accidentally shorted / mis-wired.
Use your meter on the Meg ohm range (or 200kΩ range if it has one) and measure the resistance from the outer gold ring of the RCA (input) connectors to the centre connector of the RCA. Turn the volume pot to maximum.
You should get about 50kΩ if all is correct. Low values indicate a problem with the wiring.
Make sure the inputs are not accidentally shorted / mis-wired.
Use your meter on the Meg ohm range (or 200kΩ range if it has one) and measure the resistance from the outer gold ring of the RCA (input) connectors to the centre connector of the RCA. Turn the volume pot to maximum.
You should get about 50kΩ if all is correct. Low values indicate a problem with the wiring.
The voltage is definitely off.
ECC85
Pin 1 121V ( should be 104V)
Pin 6 252V (should be 210V)
Pin 8 124V (should be 106V)
Pin 3 2.0V, possibly ok (should be 1.6V)
I do not know tubes at all. Are those voltages making the tube not working? Did I damage the tubes by applying this higher voltage?
I am guessing when I pull the power cord out the voltage decreases and the tubes voltage decrease to the function level, is this correct thought?
I apologize for probably stupid questions, I am trying to understand what am I doing.
I started testing the power supply.
I tested all the diodes and they are OK and soldered the correct way.
I think i might found the cause of the higher voltage for the 300V output. I think is the 2SC3150. When 2SC3150 is soldered the voltage for the Zenner diodes output is about 330V, if i take 2SC3150 the final output for those Zenner is correct at 300V. I tested 2SC3150 with my multimeter in the diode test mode and is not working correctly as far as I can tell. i rechecked the capacitors and they are soldered the correct way.
Is any other areas i should check while I am waiting for the 2SC3150 replacement?
When I turned on first time the power supply I could hear couples of cracking noises, after a couple of turn on and off it went away. There was no smoke and both of those LED light up, i figures the power supply is fine, it looks I was wrong.
Eliad said:
Yes they are all a little higher than you want, but they should not harm the valves (ECC85). The plug pulling thing makes no sense to me though...
Did you measure the EL84 voltages?
I did not measure the EL84 voltages since the ECC85 voltages were off. In the installation instruction they say first you plug in the ECC85 and if the voltages are correct then plug in and measure the EL84.
I will get back to you guys when I get the power transistor for the power source replaced. Hopefully this transistor was the cause of the 300V power supply being off. The 350V looks to me it comes directly from the first 4 rectifying diodes.
I really appreciate the help of this forum, you guys are awesome.
I will get back to you guys when I get the power transistor for the power source replaced. Hopefully this transistor was the cause of the 300V power supply being off. The 350V looks to me it comes directly from the first 4 rectifying diodes.
I really appreciate the help of this forum, you guys are awesome.
My guess is since the middle stage is dc coupled from the first, the voltage is wrong and keeping the tube cut off. The voltages fall when the plug is pulled allowing the tube to conduct briefly.
This is what I was thinking it happens when I pull the plug.
As I mentioned in my prior message it looks the power transistor in the power supply got fried somehow. I unsoldered and checked all the diodes and made sure are soldered the correct direction. I double checked the electrolytic capacitors to make sure are in the correct direction. Is anything else that I could have done to fry that power transistor or was just a bad one? I ordered 2 transistors just in case i fry another one.
The way i understand the power supply schematics there is not much that I could have done to fry that power transistor. I can unsolder the resistors to make sure they are the correct ones, is one resistor especially that could have caused this?
As I mentioned in my prior message it looks the power transistor in the power supply got fried somehow. I unsoldered and checked all the diodes and made sure are soldered the correct direction. I double checked the electrolytic capacitors to make sure are in the correct direction. Is anything else that I could have done to fry that power transistor or was just a bad one? I ordered 2 transistors just in case i fry another one.
The way i understand the power supply schematics there is not much that I could have done to fry that power transistor. I can unsolder the resistors to make sure they are the correct ones, is one resistor especially that could have caused this?