Mr. Johnson,
I was testing an old DYNACO ST-150 power transformer last night.
With all previous transformers I would get a clear trace on the 'scope but with this one there is lots of blurring - since I am new to using 'scopes I am not sure of the correct term for this.
This is a large EI transformer with a center tap though i will not be using the center tap. Approx 70 volts unloaded - not sure of the VA. Previously I have tested HAMMOND EIs in the 70 to 100 VA range and toroids of 300 VA. With these the display is clear and stable
Could what I am seeing be a characteristic of larger EI transformers? Or could it indicate a problem with the transformer?
Curious if this is to be expected or does it indicate I have done something wrong?
I was testing an old DYNACO ST-150 power transformer last night.
With all previous transformers I would get a clear trace on the 'scope but with this one there is lots of blurring - since I am new to using 'scopes I am not sure of the correct term for this.
This is a large EI transformer with a center tap though i will not be using the center tap. Approx 70 volts unloaded - not sure of the VA. Previously I have tested HAMMOND EIs in the 70 to 100 VA range and toroids of 300 VA. With these the display is clear and stable
Could what I am seeing be a characteristic of larger EI transformers? Or could it indicate a problem with the transformer?
Curious if this is to be expected or does it indicate I have done something wrong?
Every transformer I have ever connected to a v3 or v4 Quasimodo (or Cheapomodo) has produced a crisp un-blurred trace on the oscilloscope. If you ship me that transformer, and also send me enough money to pay for postage to ship it back to you, I would be happy to test that transformer, here, with my Quasimodo and my oscilloscope, in my laboratory in California USA. If you include a nice bottle of Champagne, I will perform the measurements more quickly than if you don't.
Another possibility is: you and your mentor can work on this problem together. A third possibility is: you can post photographs of your lab setup and photographs of your oscilloscope results, then see whether the collective expertise of diyAudio is willing (or able) to help you unfark your testing.
Another possibility is: you and your mentor can work on this problem together. A third possibility is: you can post photographs of your lab setup and photographs of your oscilloscope results, then see whether the collective expertise of diyAudio is willing (or able) to help you unfark your testing.
You sure do give unusual answers to simple questions.
I have no mentor. I have no idea what you are going on about there. My audio pursuits are singular locally though I do appreciate the help I get from many on the forums.
It had never occurred to me to send it to you. I don't think it is worth the time and money.
Simply wondering if you had ever seen a blurry trace testing a transformer and that answer is NO which is all I needed. I had not seen one either and at this point I have "snubbed" around twelve transformers.
I think am using the same RIGOL "scope you are.
I have two of these transformers. Haven't yet tried the other one. If it looks the same as the first I think I will consider them as nothing more than heavy objects. They are very old but were well made. I think HEYBOER made them. Maybe something has gone wrong with them or just the one I have tested.
Thanks,
I have no mentor. I have no idea what you are going on about there. My audio pursuits are singular locally though I do appreciate the help I get from many on the forums.
It had never occurred to me to send it to you. I don't think it is worth the time and money.
Simply wondering if you had ever seen a blurry trace testing a transformer and that answer is NO which is all I needed. I had not seen one either and at this point I have "snubbed" around twelve transformers.
I think am using the same RIGOL "scope you are.
I have two of these transformers. Haven't yet tried the other one. If it looks the same as the first I think I will consider them as nothing more than heavy objects. They are very old but were well made. I think HEYBOER made them. Maybe something has gone wrong with them or just the one I have tested.
Thanks,
Good luck with your testing. I suspect there are lots of threads here on diyAudio which discuss how to determine whether a transformer is bad or good. I further suspect that DIYA members recommend using a Dim Bulb Tester (aka Lamp Limiter), and I further suspect that people from Scottish Borders are actively involved in those threads.
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Rick. Run some waves thru it with a sigjenny and look with dso. Any verdict on my C1 value? I see it has 150 nF in one schema and 1 nF in the other.
Or sorry, now I went looking on the bags and there is one MMK BD9 that measures 1000 pF/1 nF. My bad, must be that one right?
I am using Mr. Johnson's suggested values and with the other transformers I get a result that looks like what he shows in his posted pictures.
I do not have a sigjenny. Have to admit it took me a moment to figure out what that was. I am new to trying to measure things! That is something I would like to have.
I have yet to measure the other transformer but I have the feeling there is something wrong with this transformer.
I do not know what QUASIMODO is telling me here but I think I should take it as an indicator of something wrong and for that I am grateful for QUASIMODO, yet, again.
I do not have a sigjenny. Have to admit it took me a moment to figure out what that was. I am new to trying to measure things! That is something I would like to have.
I have yet to measure the other transformer but I have the feeling there is something wrong with this transformer.
I do not know what QUASIMODO is telling me here but I think I should take it as an indicator of something wrong and for that I am grateful for QUASIMODO, yet, again.
Do you have a computer? NaTCH Engineering - SigJenny an Audio Signal Generator for Free
Or a smartphone, lots of apps out there
Or a smartphone, lots of apps out there
Well, QUASIMODO might not be good at detecting funny transformers but in my case it did detect a defective user.
Second transformer presented a steady result so I connected the first one again with no troubles.
One of these days, though i have been promising for a long while, I will do some further checking before crying WOLF.
Thanks Mr. Johnson and Stajo for your suggestions and Mr. Johnson for his skepticism I was having the problem I thought I was. Your experience is invaluable if your advice at times is rather cryptic! It does give you a aura of mystery, though. As Mr. Pass constantly reminds us, this is entertainment. Your DIYAudio persona does make for entertainment. Your contributions are among the best at DIYAudio. You do try to get us to think and, most importantly, DO something!
Take care,
Second transformer presented a steady result so I connected the first one again with no troubles.
One of these days, though i have been promising for a long while, I will do some further checking before crying WOLF.
Thanks Mr. Johnson and Stajo for your suggestions and Mr. Johnson for his skepticism I was having the problem I thought I was. Your experience is invaluable if your advice at times is rather cryptic! It does give you a aura of mystery, though. As Mr. Pass constantly reminds us, this is entertainment. Your DIYAudio persona does make for entertainment. Your contributions are among the best at DIYAudio. You do try to get us to think and, most importantly, DO something!
Take care,
I would like to know if the power mosfet NTD4906N part is equivalent with the IRLB8721PBF part (https://cdn-shop.adafruit.com/datasheets/irlb8721pbf.pdf).
Many thanks to Mark for this equipment device.
Many thanks to Mark for this equipment device.
Just, I found the post 175 with the requirements of mosfet.
I see that the IRLB8721PBF achieves these requirements, am I right?
I search, for the documentation of dip switch U3 on Rev.4 (through hole). Is there somewhere this information?
I see that the IRLB8721PBF achieves these requirements, am I right?
I search, for the documentation of dip switch U3 on Rev.4 (through hole). Is there somewhere this information?
I have only tried the devices listed in the Bill Of Materials. I have not tried other devices that are not listed in the B.O.M. You could do some experiments with non-BOM parts, and find out whether they do, or do not, work well on the QM V4 PCB. Remember that Cheapomodo manages to function properly using 3 crummy 2N7000s in parallel. This might provide a reason to be optimistic, that other types of MOSFETs may succeed too.
The DIP switch is listed in the BOM, see red box. Its web page is here.
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The DIP switch is listed in the BOM, see red box. Its web page is here.
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Hi Mark,
Thanks for the answer.
It was the only that I had for power mosfet, but it seems that works ...
https://www.youtube.com/watch?v=pxqrWACArzU
Sorry, for my bad English, as you see I am not speaking the English language natively.
..about the DIP switches: I meant that I can't find the appropriate information in pdf, how the DIP switches work on circuit.
Thanks for the answer.
It was the only that I had for power mosfet, but it seems that works ...
https://www.youtube.com/watch?v=pxqrWACArzU
Sorry, for my bad English, as you see I am not speaking the English language natively.
..about the DIP switches: I meant that I can't find the appropriate information in pdf, how the DIP switches work on circuit.
See Cheapomodo thread, posts #11 and #14. 99.9% of QM V4 owners set all four dip switches to open-circuit ("OFF") and never touch them again.
