Quick question, can 2 opts have slightly different output gains? The oscilloscope shows me that one channel has a difference with the other, I exchange them and it changes
If you have multiple secondaries, make sure that you wired them correctly.
I heard this problem with made in china OTPs, sometimes they forget to wind an primary layer.
What means slightly different?
I heard this problem with made in china OTPs, sometimes they forget to wind an primary layer.
What means slightly different?
I only have an 8ohm output, the opt is custom made, by an expert from my country, who was recommended to me
I don't know exactly, keep in mind that I am new to everything, it is my first amplifier, I lack knowledge with the oscilloscope and my function generators are a cell phone, but the difference is seen, in addition to being heard
Swap the probe connections to make sure the transformer is the problem, not the scope or probe.
Best test is to swap the OT between channels.
The amplifier parts before the transformer can have differing gains.
Best test is to swap the OT between channels.
The amplifier parts before the transformer can have differing gains.
Last edited:
Make sure the fine vertical controls are both at the max value.
As @rayma said, hook the probes both to the same point, to verify that the scope channels are the same.
If there is a difference, increase the time base so you can see clearly, then use the vertical position controls to get the difference in vertical scale marks.
You want to make sure you have an issue before chasing ghosts.
Jan
As @rayma said, hook the probes both to the same point, to verify that the scope channels are the same.
If there is a difference, increase the time base so you can see clearly, then use the vertical position controls to get the difference in vertical scale marks.
You want to make sure you have an issue before chasing ghosts.
Jan
No need to connect both transformers to the same point - don't complicate it unnecessary!
Just pick one amp, feed it a signal and connect both probes to it - done.
If there is no difference then the probes are the same.
A further refinement if the OP has an AC multimeter - feed both amps the same signal and measure the output at the transformers to see if there is a difference that way.
It's really a no-brainer.
Jan
Just pick one amp, feed it a signal and connect both probes to it - done.
If there is no difference then the probes are the same.
A further refinement if the OP has an AC multimeter - feed both amps the same signal and measure the output at the transformers to see if there is a difference that way.
It's really a no-brainer.
Jan
If I place the 2 tests on the same channel, they show the same waveform.
If I exchange the probes, there is a channel that is always lower, it goes from top to bottom on the oscilloscope, due to how the probes are installed.
Is the difference you see significant?
Swap all the valves from side to side, and it's the same
If I exchange the probes, there is a channel that is always lower, it goes from top to bottom on the oscilloscope, due to how the probes are installed.
Is the difference you see significant?
maybe this?
Swap all the valves from side to side, and it's the same
Got a small power transformer? Doesnt have to be anything special, just something you can safely apply some fixed AC to your OPT with. As long as it’s output voltage is LESS than what is expected on said OPT.
Can you post the complete amplifier schematic?
We don't even know if it is single ended or push pull, or if there is global feedback.
We don't even know if it is single ended or push pull, or if there is global feedback.
I guess you could also use a test tone from Youtube or some phone app through an external solid state amp.
classic 6v6 pp dynaco
https://diyaudioprojects.com/Schematics/DIY-Push-Pull-PP-6V6-Tube-Amplifier/
i found the problem;
I made a mistake when assembling the amplifier, I exchanged the 470k resistor (grounded at the input) with the 47k resistor, which I don't really know what it does, but it messes with the output of the 6v6.
I detected it by placing the oscilloscope from the beginning of the amp to the end looking at the differences.
Thanks for the advice guys
Good work. Always be systematic and make no assumptions.
If the transformer inputs are different, their outputs will also be different.
If the transformer inputs are different, their outputs will also be different.
Last edited:
Good work! What the 47K resistor did was to reduce the input impedance of that channel by a factor of 10, thereby loading down the source and reducing the gain. Congrats on solving the problem!
Excellent, even if you switch the transformers problem stays the same, you said in the first post that it "changes".
Happy listening!
Happy listening!
You just passed the first class in "Oscillocope course" Gratulations.
For this kind of problems a scope is of great value. And you have started getting used to it.
One word of warning: even as the 10:1 proble is marked 400 or 500 volt, <dont use it on the
power tubes plates as there may easily be much more then that. You can get 100:1 probes for higher
voltages on ebay.