I had a problem with my Arcam CD 5+ (no sound output) and I have been trying to locate the problem. I found that the +/- 25 Volt supply to the audioboard (supplied through a vertical 4 pin connector from the main PCB to the audioboard which sits on top) is only showing +/- 2V on my voltmeter.
The pinouts of the connector are:
4: -25 (ANNEG)
3: 0 (ANGND)
2: +25 (ANPOS)
1: Kill
However, if I take the audioboard off the vertical connecting pins and measure again then I see -18V between pins 4 and 3, and +27 volts between 3 and 2.
Now my beginners question is as follows: Is the pin 3 of this connector the same as GND and if so is GND referenced to the chassis of the unit? The reason I ask is because if I check the voltage between pin 4 and the unit chassis I see 0V, between pin 3 and the chassis I see 0V and between pin 2 and the chassis I see 4.8V. On another connector elsewhere which is labelled 5V, I see 5V when I measure between this pin and the unit chassis as I expected.
Why do I see 0V between pin 4 and the chassis, whereas I see -18V between pin 4 and pin3. Is there something wrong with this input voltage and could this be the reason I am only seen +/- 2V when it is connected to the audioboard???
Any assistance understanding this would be greatly appreciated...
Cheers
Sean
The pinouts of the connector are:
4: -25 (ANNEG)
3: 0 (ANGND)
2: +25 (ANPOS)
1: Kill
However, if I take the audioboard off the vertical connecting pins and measure again then I see -18V between pins 4 and 3, and +27 volts between 3 and 2.
Now my beginners question is as follows: Is the pin 3 of this connector the same as GND and if so is GND referenced to the chassis of the unit? The reason I ask is because if I check the voltage between pin 4 and the unit chassis I see 0V, between pin 3 and the chassis I see 0V and between pin 2 and the chassis I see 4.8V. On another connector elsewhere which is labelled 5V, I see 5V when I measure between this pin and the unit chassis as I expected.
Why do I see 0V between pin 4 and the chassis, whereas I see -18V between pin 4 and pin3. Is there something wrong with this input voltage and could this be the reason I am only seen +/- 2V when it is connected to the audioboard???
Any assistance understanding this would be greatly appreciated...
Cheers
Sean
Sean,
Disconnect the power! Measure the resistance between windings TA1,TA2 and TA3 on the transformer (TA1 to TA2 should match TA2 to TA3 and TA1 to TA3 should be twice this, all should be in the range of a few ohms). Disconnect the audio board and measure the resistance beween pins (4 and 3) and (3 and 2) on the 4 pin connector, then measure the resistance between pins 4, 3, 2 and the chassis. Report back on your findings.
Cheers,
Jon
Disconnect the power! Measure the resistance between windings TA1,TA2 and TA3 on the transformer (TA1 to TA2 should match TA2 to TA3 and TA1 to TA3 should be twice this, all should be in the range of a few ohms). Disconnect the audio board and measure the resistance beween pins (4 and 3) and (3 and 2) on the 4 pin connector, then measure the resistance between pins 4, 3, 2 and the chassis. Report back on your findings.
Cheers,
Jon
Hi Jon,
Here's the results of the measurements...
With the audioboard removed and the power disconnected:
Between pins 4 & 3 I see infinite resistance (or at least greater that the 2000k setting on my meter)
Between pins 3 & 2 I see and ever increasing resistance as though I was testing a capacitor (it rose from 64ohms upto 150Ohm before I removed the probe).
Between any of the pins and the chassis I see infinite resistance.
Between TA1 and TA2 (and between TA2 and TA3) I see about 5ohms and double that between TA1 and TA3 as you suggested...
Hope this provides a clue to what might be going on...
Cheers
Sean
Here's the results of the measurements...
With the audioboard removed and the power disconnected:
Between pins 4 & 3 I see infinite resistance (or at least greater that the 2000k setting on my meter)
Between pins 3 & 2 I see and ever increasing resistance as though I was testing a capacitor (it rose from 64ohms upto 150Ohm before I removed the probe).
Between any of the pins and the chassis I see infinite resistance.
Between TA1 and TA2 (and between TA2 and TA3) I see about 5ohms and double that between TA1 and TA3 as you suggested...
Hope this provides a clue to what might be going on...
Cheers
Sean
Sean,
>Between pins 4 & 3 I see infinite resistance (or at least greater that the 2000k setting on my meter)
Between 4 and 3 are R410 and C407. Measure across R410, it should be 10 ohms. If this checks out then suspect C407. This cap is an electrolytic. On top you will see a cross pattern in the aluminium can, this is a vent. The purpose of the vent is to relieve pressure inside the can in the event of failure (stop it exploding). Have any of the vents on the electrolytic caps opened up or are there any deposits around them (leaking electrolyte) ? If so they need to be replaced.
>Between pins 3 & 2 I see and ever increasing resistance as though I was testing a capacitor (it rose from 64ohms upto 150Ohm before I removed the probe).
You are testing a capacitor! Measuring C406 in series with R409 (in parallel with half of the bridge).
>Between any of the pins and the chassis I see infinite resistance.
Good.
>Between TA1 and TA2 (and between TA2 and TA3) I see about 5ohms and double that between TA1 and TA3 as you suggested...
So the windings on the secondary of the transformer haven't failed either.
Cheers,
Jon
>Between pins 4 & 3 I see infinite resistance (or at least greater that the 2000k setting on my meter)
Between 4 and 3 are R410 and C407. Measure across R410, it should be 10 ohms. If this checks out then suspect C407. This cap is an electrolytic. On top you will see a cross pattern in the aluminium can, this is a vent. The purpose of the vent is to relieve pressure inside the can in the event of failure (stop it exploding). Have any of the vents on the electrolytic caps opened up or are there any deposits around them (leaking electrolyte) ? If so they need to be replaced.
>Between pins 3 & 2 I see and ever increasing resistance as though I was testing a capacitor (it rose from 64ohms upto 150Ohm before I removed the probe).
You are testing a capacitor! Measuring C406 in series with R409 (in parallel with half of the bridge).
>Between any of the pins and the chassis I see infinite resistance.
Good.
>Between TA1 and TA2 (and between TA2 and TA3) I see about 5ohms and double that between TA1 and TA3 as you suggested...
So the windings on the secondary of the transformer haven't failed either.
Cheers,
Jon
I have just found that the resistors R409 and R410 are bad. They are reading 1800K and 90K respectively. The capacitors C406 and C407 are charging up OK when I measure the resistance and there is no sign of electrolite leakage..
I guess the next step is to remove the cicuit board and replace these resistors.. Is there anything else I should check in the meantime or should I replace these then work backwards if the voltage supply is still not showing 25V?
Thanks
Sean
I guess the next step is to remove the cicuit board and replace these resistors.. Is there anything else I should check in the meantime or should I replace these then work backwards if the voltage supply is still not showing 25V?
Thanks
Sean
Sean,
> I have just found that the resistors R409 and R410 are bad. They are
reading 1800K and 90K respectively.
Interesting, that would certainly explain the (uneven) volt drop! Are they
blackened or chard at all ? I'm guessing they are probably rated at 3Watt or
higher (quite chunky). They are mainly there to limit the current, although
with the associated capacitance they also create a 1st order filter.
So, if instead of measuring the 4 pin connector you measure across C406 and
C407 do you get +/-25V here ? Getting under the caps to measure will be
tricky but of course you can just measure between the AGND pin on the 4 pin
connector and the cap side of the resistors.
Regards,
Jon
> I have just found that the resistors R409 and R410 are bad. They are
reading 1800K and 90K respectively.
Interesting, that would certainly explain the (uneven) volt drop! Are they
blackened or chard at all ? I'm guessing they are probably rated at 3Watt or
higher (quite chunky). They are mainly there to limit the current, although
with the associated capacitance they also create a 1st order filter.
So, if instead of measuring the 4 pin connector you measure across C406 and
C407 do you get +/-25V here ? Getting under the caps to measure will be
tricky but of course you can just measure between the AGND pin on the 4 pin
connector and the cap side of the resistors.
Regards,
Jon
Jon,
Yes I get -22.4 V and 27V when I measure across the capacitors
so it looks like the resistors are the problem. There is no sign of discolouration or anything though, but I have rechecked and the resistances are way out as I said..
They are the metal oxide type (3W?) with colour code:
brown, black, black.... gold, violet
I don't know what the last colour (violet) refers to: is it a temperature coefficient (5ppm) or is it to specify that the resistor is flame proof?
Sean
Yes I get -22.4 V and 27V when I measure across the capacitors
so it looks like the resistors are the problem. There is no sign of discolouration or anything though, but I have rechecked and the resistances are way out as I said..
They are the metal oxide type (3W?) with colour code:
brown, black, black.... gold, violet
I don't know what the last colour (violet) refers to: is it a temperature coefficient (5ppm) or is it to specify that the resistor is flame proof?
Sean
Sean,
Is it easy for you to remove C407 and measure the negative voltage again ? I am puzzled why the positive and negative voltages are not the same. Also measure the voltages (AC not DC) across the output of the transformer if you can (between TA1 and TA2 and between TA2 and TA3).
Cheers,
Jon
Is it easy for you to remove C407 and measure the negative voltage again ? I am puzzled why the positive and negative voltages are not the same. Also measure the voltages (AC not DC) across the output of the transformer if you can (between TA1 and TA2 and between TA2 and TA3).
Cheers,
Jon
It's Fixed!!!!!!!!
I replaced the 10 Ohm resistors with 2W metal oxide versions (I couldn't get 3W from RS Components and Farnell wanted £20.00 minimum order. This was suggested by RS components as a suitable alternative - hopefully it will be OK.
Anyway as soon as I replaced the faulty R09 and R10 I got +/-29V on the appropriate connector pins. Upon reconnecting the Audioboard I saw 15V from the regulator. So I fetched my little Quad 306/Quad 34 and my mini mission M30s and plugged it in and hey presto - Beautiful clear sound.
Thanks again for all your help with this Jon, and thanks also to Arcammanaic......
I replaced the 10 Ohm resistors with 2W metal oxide versions (I couldn't get 3W from RS Components and Farnell wanted £20.00 minimum order. This was suggested by RS components as a suitable alternative - hopefully it will be OK.
Anyway as soon as I replaced the faulty R09 and R10 I got +/-29V on the appropriate connector pins. Upon reconnecting the Audioboard I saw 15V from the regulator. So I fetched my little Quad 306/Quad 34 and my mini mission M30s and plugged it in and hey presto - Beautiful clear sound.
Thanks again for all your help with this Jon, and thanks also to Arcammanaic......
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