[Paul[_13_]]

This one was not powering up, so I cracked it open.

The on-board fuse was still good. There was 120 AC,
and about 330 DC on the first rectifier. But
there were no DC voltages going to the next board.

So it's most likely a power supply issue, but as you
know, modern switching power supplies are very
complex, and are difficult to troubleshoot, especially
without a proper schematic.

Any advice is appreciated.

[Scott Dorsey]

In article , Paul wrote:
This one was not powering up, so I cracked it open.

The on-board fuse was still good. There was 120 AC,
and about 330 DC on the first rectifier. But
there were no DC voltages going to the next board.

So it's most likely a power supply issue, but as you
know, modern switching power supplies are very
complex, and are difficult to troubleshoot, especially
without a proper schematic.

Get the datasheet for the PWM controller. Likely most of the power supply
will be copied right off the datasheet, or at least enough for you to
figure out what is going on.

If the big switching fet isn't shorted, if there is power on the big
primary-side capacitor, and you don't see physical damage, and it's
not kicking on briefly or crowbarring, then change out the kickstart
capacitor (which will be one or two MFD and right near the PWM controller
chip). If it doesn't fix the problem, it's still the first step toward
diagnosing why the PWM oscillator won't come on.

I wrote an introduction to repairing switching supplies without the manual
in AudioXPress a couple years ago, and the article is probably worth digging
up.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Paul[_13_]]

On 8/1/2019 2:30 PM, Scott Dorsey wrote:
In article , Paul wrote:
This one was not powering up, so I cracked it open.

The on-board fuse was still good. There was 120 AC,
and about 330 DC on the first rectifier. But
there were no DC voltages going to the next board.

So it's most likely a power supply issue, but as you
know, modern switching power supplies are very
complex, and are difficult to troubleshoot, especially
without a proper schematic.

Get the datasheet for the PWM controller. Likely most of the power supply
will be copied right off the datasheet, or at least enough for you to
figure out what is going on.

If the big switching fet isn't shorted, if there is power on the big
primary-side capacitor, and you don't see physical damage, and it's
not kicking on briefly or crowbarring, then change out the kickstart
capacitor (which will be one or two MFD and right near the PWM controller
chip). If it doesn't fix the problem, it's still the first step toward
diagnosing why the PWM oscillator won't come on.

I wrote an introduction to repairing switching supplies without the manual
in AudioXPress a couple years ago, and the article is probably worth digging
up.
--scott


I found your article:


https://www.audioxpress.com/article/...power-supplies

Thanks much. I will read this and let you know what I find.

P

[Phil Allison[_4_]]

Paul wrote:


I found your article:


( dangerous article link deliberately snipped )


Thanks much. I will read this and let you know what I find.



** Better make sure your life insurance is paid up and you have updated your will.

Wot a ****ing idiot.


...... Phil

[Paul[_13_]]

On 8/1/2019 4:29 PM, Phil Allison wrote:
Paul wrote:


I found your article:


( dangerous article link deliberately snipped )


Thanks much. I will read this and let you know what I find.



** Better make sure your life insurance is paid up and you have updated your will.


**** you, numbnuts. I've worked in the electronics field for
decades, so I know basic electronics safety.

Don't project your own ignorance and stupidity on others.

Wot a ****ing idiot.


You're a ****wit! Go **** on your Momma's grave!




..... Phil

[Phil Allison[_4_]]

Paul the Lunatic wrote:

-------------------------

Phil Allison wrote:
Paul wrote:


I found your article:


( dangerous article link deliberately snipped )


Thanks much. I will read this and let you know what I find.



** Better make sure your life insurance is paid up and you have updated your will.


**** you, numbnuts. I've worked in the electronics field for
decades, so I know basic electronics safety.


** You made that bull**** claim before.

You know SFA about safety when working on live mains equipment.



Wot a ****ing idiot.


You're a ****wit!


** FYI to all:

This poster is clearly schizophrenic with a death wish.



Go **** on your Momma's grave!


** Brainless POS like him would not be missed by anyone.



..... Phil

[Paul[_13_]]

On 8/1/2019 2:30 PM, Scott Dorsey wrote:
In article , Paul wrote:
This one was not powering up, so I cracked it open.

The on-board fuse was still good. There was 120 AC,
and about 330 DC on the first rectifier. But
there were no DC voltages going to the next board.

So it's most likely a power supply issue, but as you
know, modern switching power supplies are very
complex, and are difficult to troubleshoot, especially
without a proper schematic.

Get the datasheet for the PWM controller. Likely most of the power supply
will be copied right off the datasheet, or at least enough for you to
figure out what is going on.

I found the PWM chip. It's a 1271A, PTAC. So it's this one,
if I am not wrong:

pdf.datasheetcatalog.com/datasheet/on_semiconductor2/NCP1271-D.PDF

I have confirmed that I am getting AC and DC off the first main
rectifier, and there appears to be nothing on the secondary of the main
transformer.

I was NOT able to see a 65kHz driving signal on the driver pin 5,
but I assume this is because the oscillator is still off.


If the big switching fet isn't shorted, if there is power on the big
primary-side capacitor, and you don't see physical damage, and it's
not kicking on briefly or crowbarring, then change out the kickstart
capacitor (which will be one or two MFD and right near the PWM controller
chip). If it doesn't fix the problem, it's still the first step toward
diagnosing why the PWM oscillator won't come on.


Is the kickstart capacitor either C6 or C7 on page 18? One of the
1.2nF caps?


I wrote an introduction to repairing switching supplies without the manual
in AudioXPress a couple years ago, and the article is probably worth digging
up.
--scott

[Scott Dorsey]

In article , Paul wrote:
I found the PWM chip. It's a 1271A, PTAC. So it's this one,
if I am not wrong:

pdf.datasheetcatalog.com/datasheet/on_semiconductor2/NCP1271-D.PDF

I have confirmed that I am getting AC and DC off the first main
rectifier, and there appears to be nothing on the secondary of the main
transformer.

I was NOT able to see a 65kHz driving signal on the driver pin 5,
but I assume this is because the oscillator is still off.

Right. For the oscillator to turn on, you have to have good voltages at HV
and Vcc to run the oscillator. The ground has to be good.

AND... on a cursory reading of the datasheet:
pin 3 (CS) has to have less than 1V on it. If it has more, it will
shut down for overcurrent.
pin 2 (FB) has to be less than 3V.
pin 1 (skip/latch) has to be lower than 8V.

If all of these things are true, and the pwm chip is good, it should oscillate.
If it's not oscillating, check voltages and if voltages are out of range look
for bad electrolytics before you look for bad resistors.

And yes, the chips fail.
--scott


--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Paul[_13_]]

On 8/2/2019 10:49 AM, Scott Dorsey wrote:
In article , Paul wrote:
I found the PWM chip. It's a 1271A, PTAC. So it's this one,
if I am not wrong:

pdf.datasheetcatalog.com/datasheet/on_semiconductor2/NCP1271-D.PDF

I have confirmed that I am getting AC and DC off the first main
rectifier, and there appears to be nothing on the secondary of the main
transformer.

I was NOT able to see a 65kHz driving signal on the driver pin 5,
but I assume this is because the oscillator is still off.

Right. For the oscillator to turn on, you have to have good voltages at HV
and Vcc to run the oscillator. The ground has to be good.

AND... on a cursory reading of the datasheet:
pin 3 (CS) has to have less than 1V on it. If it has more, it will
shut down for overcurrent.
pin 2 (FB) has to be less than 3V.
pin 1 (skip/latch) has to be lower than 8V.


Pins 1 and 3 had 0 Volts.

Pin 2 had 1.3 Volts.

Pin 6 has about 2 Volts.

Pin 8 has about 320 Volts on it, coming off the first rectifier.
Is that normal?


If all of these things are true, and the pwm chip is good, it should oscillate.
If it's not oscillating, check voltages and if voltages are out of range look
for bad electrolytics before you look for bad resistors.

And yes, the chips fail.
--scott

[Phil Allison[_4_]]

Paul wrote:

This one was not powering up, so I cracked it open.

The on-board fuse was still good. There was 120 AC,
and about 330 DC on the first rectifier. But
there were no DC voltages going to the next board.

So it's most likely a power supply issue, but as you
know, modern switching power supplies are very
complex, and are difficult to troubleshoot, especially
without a proper schematic.

Any advice is appreciated.



** Give the job to someone who knows what they are doing and has the needed safety and test equipment.

Yours is definitely a case of " fools rushing in where angels fear to tread".

FFS ignore Scott Dorsey, the guy is a dangerous idiot.



...... Phil



..... Phil

[Paul[_13_]]

On 8/1/2019 3:32 PM, Phil Allison wrote:
Paul wrote:

This one was not powering up, so I cracked it open.

The on-board fuse was still good. There was 120 AC,
and about 330 DC on the first rectifier. But
there were no DC voltages going to the next board.

So it's most likely a power supply issue, but as you
know, modern switching power supplies are very
complex, and are difficult to troubleshoot, especially
without a proper schematic.

Any advice is appreciated.



** Give the job to someone who knows what they are doing and has the needed safety and test equipment.


I have the test equipment....haven't you been paying attention to my
posts?

Yours is definitely a case of " fools rushing in where angels fear to tread".

Yours is definitely a case of "I've got my head up my ass!"




FFS ignore Scott Dorsey, the guy is a dangerous idiot.


Look in the mirror if you wanna see an idiot!

[Phil Allison[_4_]]

Paul wrote:

On 8/1/2019 3:32 PM, Phil Allison wrote:
Paul wrote:

This one was not powering up, so I cracked it open.

The on-board fuse was still good. There was 120 AC,
and about 330 DC on the first rectifier. But
there were no DC voltages going to the next board.

So it's most likely a power supply issue, but as you
know, modern switching power supplies are very
complex, and are difficult to troubleshoot, especially
without a proper schematic.

Any advice is appreciated.



** Give the job to someone who knows what they are doing and has the needed safety and test equipment.


I have the test equipment....haven't you been paying attention to my
posts?


** I bet you have not got a iso-transformer or any clue of how to use it.

Amateurs should NEVER touch a mains switcher supply.


Yours is definitely a case of " fools rushing in where angels fear to tread".

Yours is definitely a case of "I've got my head up my ass!"





** You just proved beyond any doubt you are a bull****ting nut case and an asshole.

Make my day - go ahead, electrocute yourself.

[Paul[_13_]]

On 8/1/2019 7:18 PM, Phil Allison wrote:
Paul wrote:

On 8/1/2019 3:32 PM, Phil Allison wrote:
Paul wrote:

This one was not powering up, so I cracked it open.

The on-board fuse was still good. There was 120 AC,
and about 330 DC on the first rectifier. But
there were no DC voltages going to the next board.

So it's most likely a power supply issue, but as you
know, modern switching power supplies are very
complex, and are difficult to troubleshoot, especially
without a proper schematic.

Any advice is appreciated.



** Give the job to someone who knows what they are doing and has the needed safety and test equipment.


I have the test equipment....haven't you been paying attention to my
posts?


** I bet you have not got a iso-transformer or any clue of how to use it.

Amateurs should NEVER touch a mains switcher supply.


Yours is definitely a case of " fools rushing in where angels fear to tread".

Yours is definitely a case of "I've got my head up my ass!"





** You just proved beyond any doubt you are a bull****ting nut case and an asshole.

Make my day - go ahead, electrocute yourself.


Make my day - GO **** DOWN YOUR MOTHER'S THROAT!