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Old 24th January 2012, 10:17 PM   #1031
Zen Mod is offline Zen Mod  Serbia
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Quote:
Originally Posted by Tiroler View Post
........ preamp schematic for DIYers?
balanced BA3 FE is certainly worth of trying
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Old 31st January 2012, 07:09 PM   #1032
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Since today my UGS Preamp does not work anymore

I found that it is a problem of the uC Board.

When uC PCB is not connected to the supply - I measure 9Volt.
However when the uC PCB is connected the main supply drops to around 4Volts and that leaves too less voltage for the 7805 5V Voltage regulator on the uC.

Could you help me what to measure and test - to find the faulty part ?
Not sure if it is Atmega64 itself, 7805, Transistors,.....or too weak supply.

Schematic is the first one in the pdf:
http://psykok.homelinux.org/diy/prea...urs/Atours.pdf

Thanks,
dsdjoy
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Old 31st January 2012, 08:46 PM   #1033
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dsjoy, I would disconnect the relay boards and concetrate on the µ-controller board. First check the external supply, then the regulator at the bottom plate. Next step could be checking the voltages at the BS 170. That transistor should bring your µconroller board back to life... I upload measurements of my board and hope that it will probably help you to check your board and find the bug.
I experienced that there was quite an inrush when I turned the power supply on. As I fearded for all the chips, I have added a delay for the mains power which works nicely.
It is good to replace the 4,7R resistor at regulators e.g. up to 15R 2 or 3W.
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Old 31st January 2012, 09:14 PM   #1034
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Schrack relay, Brrrrr (exchanged too many)
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Old 1st February 2012, 12:43 PM   #1035
Tiroler is offline Tiroler  Austria
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Jacco,
I did not choose this relay on purpose, I just bought what I could get in the regional store. Thanks, now am prepared to probably exchange this part one day. What brand would you prefer? Glad that you like my heatsink/clamp assembly.
I do not have the Unimat drill/mill accessory.
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Old 1st February 2012, 06:58 PM   #1036
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Quote:
Originally Posted by Tiroler View Post
dsjoy, I would disconnect the relay boards and concetrate on the µ-controller board......
Thank you. I will check as per your suggestions in the weekend.

Checks I already did:

Disconnected all cables and VFD Display from uC board - only power cable connected.
Power Supply checked ok - delivers 9Volts for uC logic behind the 7809 in UGS - and also 24Volts for Relais.
When uC board is connected, voltage drops to 4.2 Volts behind 7809 in UGS.
Further voltage drop occurs behind the 7805 on uC board.
So the uC board gets only 3.9 Volts instead of 5.
When VFD and other cables are connected further voltage drop occurs and uC is not powering on.
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Old 4th February 2012, 12:33 PM   #1037
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I did several checks, but still have the same problem. 7805 and BS170 Transistor on the uC was checked and is not the problem.

The uC board get's current from a 7809 regulator on the main board.
I inserted a 10Ohm Resistor in the 9V Supply line that feeds the uC board.

On the 10Ohm Resistor I measure 0.10 Volts - that means uC board consumes only 10 milliAmps ?

Even with such low current the 9Volt supply voltage drops from 9Volt to around 5 Volt.

This would indicate a failure either in the power supply or a defective 7809 on the main board - which feeds the uC board ?
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Old 4th February 2012, 06:33 PM   #1038
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Quote:
Originally Posted by dsdjoy View Post
Since today my UGS Preamp does not work anymore

I found that it is a problem of the uC Board.

When uC PCB is not connected to the supply - I measure 9Volt.
However when the uC PCB is connected the main supply drops to around 4Volts and that leaves too less voltage for the 7805 5V Voltage regulator on the uC.

Could you help me what to measure and test - to find the faulty part ?
Not sure if it is Atmega64 itself, 7805, Transistors,.....or too weak supply.

Schematic is the first one in the pdf:
http://psykok.homelinux.org/diy/prea...urs/Atours.pdf

Thanks,
dsdjoy
Did you properly cooled the reg?
Depending on the Voltage provided at the output of the tranny (did you measure?) it can turn to heat a lot ...
It will almost shut off when becoming to hot! (protection)


Manu
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Old 4th February 2012, 07:32 PM   #1039
dsdjoy is offline dsdjoy  Germany
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Quote:
Originally Posted by Manu View Post
Did you properly cooled the reg?
Depending on the Voltage provided at the output of the tranny (did you measure?) it can turn to heat a lot ...
It will almost shut off when becoming to hot! (protection)


Manu
Manu - thanks for your help. It is very much appreciated !

The regulator is properly cooled - I followed the guidelines on HCFR.
My UGS amplifier worked for more than 1 year without problems - and then....from one day to next the uC did not work anymore.
I think that either one of the integrated circuits on the uC board is defective - or I overloaded the power supply for a long time and now the components are at the end of lifetime.

Might be that Atmel CPU has a short circuit, but I have no possiblity to verify/check that.
However I believe there is also a design flaw in the power supply.

The Transformer delivers 24Volts AC, 8 VA - max 315mA per side.
One side feeds the 7809 regulator - supplying power to the uC board.
The 7809 regulator on main PCB has very high dissipation loss: (26V input - 9V output) * output current.

So for every milliAmp used by uC Board there is even higher dissipation loss.
The power consumption of Atmel plus VFD Display might have consumed too much current from the transformer - exceeding it's specs.
Could it be that too high current draw has damaged the transformer ?

I continued my investigation with 7809:

I soldered a new 7809 regulator today - a no-name type. After a few seconds it gave a cracking noise and then the 7809 was dead.....
Maybe this no-name type did not like 26V input - or current draw was too high.
I will try again with a quality regulator from ST Microelectronics and put as well a Fuse between main board and uC to limit the current.
If the fuse blows....then it is strong indicator for a short circuit within the Atmel Microprozessor (or one of the other ICs).

BTW: I am willing to build a uC board from scratch. If someone has a uC board for UGS for sale......please let me know.

Last edited by dsdjoy; 4th February 2012 at 07:36 PM.
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Old 4th February 2012, 08:29 PM   #1040
Manu is offline Manu  Europe
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Quote:
Originally Posted by dsdjoy View Post
Manu - thanks for your help. It is very much appreciated !

The regulator is properly cooled - I followed the guidelines on HCFR.
My UGS amplifier worked for more than 1 year without problems - and then....from one day to next the uC did not work anymore.
I think that either one of the integrated circuits on the uC board is defective - or I overloaded the power supply for a long time and now the components are at the end of lifetime.

Might be that Atmel CPU has a short circuit, but I have no possiblity to verify/check that.
However I believe there is also a design flaw in the power supply.

The Transformer delivers 24Volts AC, 8 VA - max 315mA per side.
One side feeds the 7809 regulator - supplying power to the uC board.
The 7809 regulator on main PCB has very high dissipation loss: (26V input - 9V output) * output current.

So for every milliAmp used by uC Board there is even higher dissipation loss.
The power consumption of Atmel plus VFD Display might have consumed too much current from the transformer - exceeding it's specs.
Could it be that too high current draw has damaged the transformer ?

I continued my investigation with 7809:

I soldered a new 7809 regulator today - a no-name type. After a few seconds it gave a cracking noise and then the 7809 was dead.....
Maybe this no-name type did not like 26V input - or current draw was too high.
I will try again with a quality regulator from ST Microelectronics and put as well a Fuse between main board and uC to limit the current.
If the fuse blows....then it is strong indicator for a short circuit within the Atmel Microprozessor (or one of the other ICs).

BTW: I am willing to build a uC board from scratch. If someone has a uC board for UGS for sale......please let me know.
Before suspecting that there is something wrong with the atmel, I would insvestigate a little bit further in the PSU direction.
Did you measure the voltage at the output of the PSU (before first reg)? 24V is specs but most of the time in reality it is much more (up to 40V depending on the load ...), sometimes exceeding the rating of the regs.
And on the other side if the trafo is underrated it can be now damaged ...
You could try to replace it ...


Quote:
The 7809 regulator on main PCB has very high dissipation loss: (26V input - 9V output) * output current.
You could put another regulator between the two to spread the effort on more devices ...


Manu
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