@Buzzford: i did it everytime, but that day just hurry to show it up, and make it until late midnight, too tired maybe...:lol.
Anyway, i also work hard tonight but just only can bring back 1 channel to work, another got fired that i still don't know reason. but one channel is good enough to show you all about narrow bandwidth.
Following Images series is what i measured for that channel.
Power Max: 19VAC ~45W
1KHz at output 3.342VAC.
10KHz, output is 3.305VAC, slightly reduce
15KHz, output is 3.257VAC, more reduce
25KHz, output is 3.107VAC, reduce faster
40KHz,output is 2.876VAC, too much reduce, look at the OSC you can see the sinewave much smaller than 1KHz
So do you think that it has very narrow bandwidth?
Anyway, i also work hard tonight but just only can bring back 1 channel to work, another got fired that i still don't know reason. but one channel is good enough to show you all about narrow bandwidth.
Following Images series is what i measured for that channel.
Power Max: 19VAC ~45W
1KHz at output 3.342VAC.
10KHz, output is 3.305VAC, slightly reduce
15KHz, output is 3.257VAC, more reduce
25KHz, output is 3.107VAC, reduce faster
40KHz,output is 2.876VAC, too much reduce, look at the OSC you can see the sinewave much smaller than 1KHz
So do you think that it has very narrow bandwidth?
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I also did test with square wave.
1KHz, square wave is good
10KHz, i don't know it is good enough or not, but it can show up not good as HF
For Low Frequency, 100Hz
And 25Hz
So the Low Frequency is not bad.
This time do test i used 500VA transformer for 1 channel, so it should not the underpowered issue.
1KHz, square wave is good
10KHz, i don't know it is good enough or not, but it can show up not good as HF
For Low Frequency, 100Hz
And 25Hz
So the Low Frequency is not bad.
This time do test i used 500VA transformer for 1 channel, so it should not the underpowered issue.
25kHz is +-0.6dB ref 3.342Vac @ 1kHz
40kHz is ~ -1.3dB ref 1kHz.
Not great.
But, did you check your input signal?
Is it constant at those spot frequencies?
Or does it too vary as you sweep the frequency?
Square response is not good IMO, that much low frequency tilt is unacceptable ..
AndrewT: ofcourse the input constant as every frequency, i used it to do measured amp very often.
Ittien,
perhaps this might help
http://www.diyaudio.com/forums/pass-labs/206640-f5-turbo-problems.html
perhaps this might help
http://www.diyaudio.com/forums/pass-labs/206640-f5-turbo-problems.html
@ZM: I still have JFet that matched by seller from Japan.
With this F5T, I already tried try to replace all of other components. but not try another JFET. all of other changed can make the sound better, but F5T always get poor dynamic range and narrow bandwidth. So what the buzzford said the bad JFET also make sense. that's the only one that i can not change so far. i tried to bias from low (200mV) to high(450mV, used fan), does not help.
attached is some images of my JFET, i have both V and BL, see if you can point out it is the bad.
I will tried to double them tonight and will let you know.
thanks
With this F5T, I already tried try to replace all of other components. but not try another JFET. all of other changed can make the sound better, but F5T always get poor dynamic range and narrow bandwidth. So what the buzzford said the bad JFET also make sense. that's the only one that i can not change so far. i tried to bias from low (200mV) to high(450mV, used fan), does not help.
attached is some images of my JFET, i have both V and BL, see if you can point out it is the bad.
I will tried to double them tonight and will let you know.
thanks
Zen Mod: it so strange, after double JFET, although i set bias to 0, power on and can not bias any more for N channel, P channel is fine. remove all FET and Diode to check is all of N are dead, P channel is fine, all diode fine.
Check Jfet section only, all bias work fine, i can bias for more than 4V, nothing wrong with JFet section. mount new output FET and diode, check everything by ohm meter, all are good. 5K trim port both well, set them to minimum value. power on, and can not bias on N channel again. trim port 5K on N channel can not bias for more than 2V. then check all FET on N channel dead again.
.
I don't have any N channel FET any more to play with.
Check Jfet section only, all bias work fine, i can bias for more than 4V, nothing wrong with JFet section. mount new output FET and diode, check everything by ohm meter, all are good. 5K trim port both well, set them to minimum value. power on, and can not bias on N channel again. trim port 5K on N channel can not bias for more than 2V. then check all FET on N channel dead again.
. I don't have any N channel FET any more to play with.
Then i maybe not the lucky man, buy lot of jfets that are not good. Read in this forum, i saw lot of people buy a kit, and make it work without any problem. reviewed the sound and bandwidth very good. but me, and other DIYes in my country, no-one can make F5T work properly. sound bad and very easy to get fired at night or day, I also make F5 standard version, sound also not good either. we all buy jfet together from 1 seller. this should be the point.
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Just tried to order a TX 25V 1000VA from Antek, their website say EVERY TX in stock; availability is 0 ???
How could they be out of EVERY TX ? The phone number just rings and says no one is answering and then disconnects. Any Idea whats up? Last I heard they were training new employees....... sorta contradicts what their website and phone system is doing.
Ron
How could they be out of EVERY TX ? The phone number just rings and says no one is answering and then disconnects. Any Idea whats up? Last I heard they were training new employees....... sorta contradicts what their website and phone system is doing.
Ron
