BOM
hi mark,
could you please post the latest version of BOM for the supplemental kit?
many thanks and regards
hi mark,
could you please post the latest version of BOM for the supplemental kit?
many thanks and regards
Perhaps I can offer a few suggestions if you don't mind.
According to Nelson's schematic Q13 is a TL431 so if it is running hot then check the value of the associated resistors, R15, R17 and particularly R19 as this is the one supplying Q13 from the 28V rail. Also check the orientation of diode D1, making sure that it is reverse biassed from the 28V rail.
As to the LED close to Q13 remaining unlit then check also its orientation as this must be forward biassed to illuminate.
Ok I replaced Q13 again and problem solved>>>
Next issue: During second set of voltage checks I have the following
T6 T7 a little high at 7v
T2 24v T4 .9v
bias voltages seem to set up ok
Mostly concerned with T4
According to Nelson's schematic Q13 is a TL431 so if it is running hot then check the value of the associated resistors, R15, R17 and particularly R19 as this is the one supplying Q13 from the 28V rail. Also check the orientation of diode D1, making sure that it is reverse biassed from the 28V rail.
As to the LED close to Q13 remaining unlit then check also its orientation as this must be forward biassed to illuminate.
Ok I replaced Q13 again and problem solved>>>
Next issue: During second set of voltage checks I have the following
T6 T7 a little high at 7v
T2 24v T4 .9v
bias voltages seem to set up ok
Mostly concerned with T4
Afraid I can't help you.
7 volts between T6-T7 also quite high, it must be around 0V at initial settings.
Perhaps there are other parts defective, Q8, Q14 I don't know.
I just suggest to you to compare it to the other (seems to be O.K.) channel.
Regards,
Gyuri
7 volts between T6-T7 also quite high, it must be around 0V at initial settings.
Perhaps there are other parts defective, Q8, Q14 I don't know.
I just suggest to you to compare it to the other (seems to be O.K.) channel.
Regards,
Gyuri
I meant initial voltages between T6-T7 and between T8-T9 should be around 0V.
Yes that voltage between G and T4 is certainly wrong.
I thought there is a bad semiconductor perhaps T14 or Q8 or something else, I really don't know.
Yes that voltage between G and T4 is certainly wrong.
I thought there is a bad semiconductor perhaps T14 or Q8 or something else, I really don't know.
Do you know there is a typo in the article about R6 test points, which are not T9-T10 but T8-T9?
I have checked now:
"Now we are going to bias up the front end Mosfets. We will be looking at the voltage drops across R5 (T6 and T7) and R6 (T9 and T10) as well as the DC offset at T18 (relative to ground) while adjusting the trim pots P3 and P4"
"Now we are going to bias up the front end Mosfets. We will be looking at the voltage drops across R5 (T6 and T7) and R6 (T9 and T10) as well as the DC offset at T18 (relative to ground) while adjusting the trim pots P3 and P4"
Can anybody advise me on why I only have .9v on T4 all resistors are correct and all other test points are spot on. T2 is 24v
I would check Q8, Q14, D2 (without power) compared to the seems to be O.K. channel.
Do it with a DMM in diode checking mode.
Changed polarities as well.
And compare it to the other channel, I don't have a better idea.
Do it with a DMM in diode checking mode.
Changed polarities as well.
And compare it to the other channel, I don't have a better idea.
Maybe to expand on Variac's post, the page
Sony VFET Kit Status Page – diyAudio Store
Is where the link to the 'sign up' list for Essential kits (Vfets+PCB's+L-brackets) as well as Supplemental kits is located.
The list for the Third round of Vfet release has been open for sometime.
When the Vfets are ready (?? 6th Feb) emails will be sent out to the 1st, 2nd 3rd etc on the list offering kits for sale.
The list is still open.
I am told that the cost of the Essential kit will be US$155
Hope this helps
Sony VFET Kit Status Page – diyAudio Store
Is where the link to the 'sign up' list for Essential kits (Vfets+PCB's+L-brackets) as well as Supplemental kits is located.
The list for the Third round of Vfet release has been open for sometime.
When the Vfets are ready (?? 6th Feb) emails will be sent out to the 1st, 2nd 3rd etc on the list offering kits for sale.
The list is still open.
I am told that the cost of the Essential kit will be US$155
Hope this helps
Quick question: why did the modulated cascode get dropped in the kit vfet amp? I was reading the Zen articles, and I was getting the idea of what it's supposed to accomplish, and I'm wondering why it was eventually omitted here?
My guess, is simplicity, and minimising the risk to the completely irreplaceable parts here, but I thought it worth the question.
Thanks!
My guess, is simplicity, and minimising the risk to the completely irreplaceable parts here, but I thought it worth the question.
Thanks!
What's the proper way to test amplifier with square wave? This seems to be quite useful: Squarewave Testing
but not sure about testing conditions - at 1W output? No loading? Loading with a capacitor?
I'm not Nelson, but I'll offer a guess - the output stage regulators eat up about 8v of each rail and make the rail voltage approximately 20V, but offer the advantage of making the rail very quiet and being able to sequence the power up and power down as required to keep the Vfet happy. The cascode isn't necessary for safe Vfet operation.
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Rod's write up is great. In order to generate these waves, the advice I found was to start with a 1kHz sine wave with sufficient amplitude to generate 1v across an output dummy load (4R and 8R). Then, do a frequency sweep with your signal generator and watch the output wave forms on your scope. Next, adjust the input amplitude until you get 10v output across your dummy load and repeat. Use both sine waves and square waves. I have written up some of this in the Output Power & Waveform Testing section of my Aleph-X web page.
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