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Phono Pre-amp fault
Phono Pre-amp fault
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Old 1st February 2018, 10:29 AM   #21
Dunk02 is offline Dunk02  Australia
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Hi thanks for the reply, can I ask how you identified the op amp just in case I need to replace with identical component?

I am confused about the configuration of the op amps - I have to admit. I assumed there was one for each channel. Are you saying that each op amp is inputting and outputting signal to each speaker?

My scope ground is connected to the back side chassis rubber and I probe each pin with the signal generator inputting to each channel per test, with the output RCA going to a resistive load. The scope dc coupled.

The outputs measured in the scope are:
..........OA R........OA L
Pin 1 : 4.7V ____ 2.2V 1kHz sine wave
Pin 7: 2.4V ____ 2.2V 1kHz sine wave

Last edited by Dunk02; 1st February 2018 at 10:32 AM.
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Old 1st February 2018, 11:32 AM   #22
Dunk02 is offline Dunk02  Australia
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Looks like ART can supply schematics upon request. I will post it if allowed, if I get one.
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Old 2nd February 2018, 06:50 PM   #23
Dunk02 is offline Dunk02  Australia
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Even though ARTs website states

Simply send an email to support@artproaudio.com. Be sure to include the model name! We'll send you an Adobe .pdf file with the schematic you requested. PLEASE NOTE: Schematics are not released for new products still under warranty. (e.g. Tubefire8)

My unit is out of warranty but they will not provide one.
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Old 5th February 2018, 01:32 PM   #24
Dunk02 is offline Dunk02  Australia
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Anyone?
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Old 5th February 2018, 01:37 PM   #25
Mooly is offline Mooly  United Kingdom
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Phono Pre-amp fault
Don't mind having a gander but we have to start at the beginning
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Old 5th February 2018, 01:49 PM   #26
Mooly is offline Mooly  United Kingdom
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Phono Pre-amp fault
Key things to know at the outset...

What devices are U2,3 and U4

Which device of those is the signal applied to for the right channel.

Assuming U2,3 and 4 are dual opamps, do they share left and right duties per opamp throughout the preamp or are any used exclusively for one channel.

Again, assuming duals, one must be shared if the other two are not.
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Old 5th February 2018, 07:01 PM   #27
Hans Polak is offline Hans Polak  Netherlands
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I have tried to follow your thread, but so far it has been very confusing.

1) That's why I have copied your Image below, now with inserted pin numbers.
That makes that no misunderstanding can exist where you are measuring.
2) From the data you provide it is unclear whether you mean AC or DC.
3) Using a 1KHz signal at the input is O.K. but 80mV is far above the 40mV max that ART specifies, so try to take this back to 14mV
4)Put the gain switch in the 0dB position, gain will now be 37dB, giving 1V output signal from the 14mV input, still below the 1.4V max out that ART specifies.

Now make a list for U2 to U4, specifying for all 8 pin numbers what you measure with the 14mV applied at the input.
Something like
U2: Pin 1: 14mV 1Khz, Pin 2: 5 Volt DC, Pin3: 0V DC, Pin 4: 500mV 1Khz, Pin 5: 100mV AC noise, etc.
U3: .......
U4: ........

With that table at hand will it be possible to help you in a much better way.


Hans
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Old 6th February 2018, 04:00 AM   #28
Dunk02 is offline Dunk02  Australia
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Thanks you Guys. I will get back to it over the next couple of days with answers and data. Please check back. Travelling for work at the moment.
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Old 6th February 2018, 07:27 AM   #29
Mooly is offline Mooly  United Kingdom
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Phono Pre-amp fault
And just to add to Hans list above, give both signal and the DC voltage for ALL pins of all three opamps.

Perhaps also do a second separate list of all opamp DC voltages with no signal applied.
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Old 6th February 2018, 09:02 AM   #30
Dunk02 is offline Dunk02  Australia
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Thanks will do. Get back you soon.
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