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Yesterday I took in a Soundcraft Signature 22 22-Channel Mixer that failed after a short-term Power Outage. I've never seen this model before. Unit is around 6 yrs old. The IEC Power Connector is on the inside space of the Tilt Block at the back of the board, and, there is NO Power ON/Off Switch. Plug it in and for get it...remains on as long as there's power.
Guess that changed with this power outage, as it hasn't powered back up. When I plugged it in on my Check-out Bench, I got no Power Consumption reading and saw the Pilot Light flickering at a slow rate, along with the signal activity lights on the stereo buss. Indicative of the SMPS trying to start but couldn't.
I pulled the bottom pan off, then extracted the SMPS from the pan. Nothing immediately obvious.
After writing up the work order and sending the client off, I checked all of the discrete semiconductors, which all tested fine. There are two SOIC packaged 8-pin SMD IC's... a UC3842A and a GPM8023.
This morning, I called Harman International to see if I could purchase a replacement power supply for the mixer. P/N 5071878-01.V Or, 5071878-02.V, being the latest revision. Back Ordered, not due in until early June, built in Hungary. $85.70 + tax/shpg. Placed the order for that.
I found I already had the UC3842 data sheet in my files, and had a couple on hand, but....they were 8-pin DIP. I then looked to see what I could find on this GPM8023. No such luck on that.
That part appears to be the 5VDC Regulator for the logic circuits on the mixer.
I connected a 300 ohm/5W resistor across the +/- 15VDC Outputs on the bottom side of the PCB, as I don't have any mating connectors for the 9-pin shrouded white header plug. Connected my DMM across the resistor which, if the supplies ARE +/- 30V, would yield 100mA. Plugged it into my switched outlet connected to my variac/power analyzer, and switched it on. I got 46VDC across the resistor spanning the +/- 15V terminals on the back side. AC Mains wattage was 14W. Turned it off, dug up a pair of EZ Microhook test leads, and clipped onto the 5V output and it's ground. Got 0.128VDC. Not a good sign. Clipped onto the +48V terminal, and got +48VDC. I tacked on a second 300 ohm resistor across the +/- 15V supply, and now got 40VDC ,pulling 16W. So, the front end of the SMPS IS working. Still no output from the 5V circuit. I loaded the +/- 30V supply with a pair of 40 ohm/50W power resistors in series, leaving the 300 ohm resistor in place, and now that dropped the bipolar supply voltage to 36VDC. So, I'd conclude each channel or group of channels have local +/- 15V Regulators. The 48V circuit remains steady.
But, the problem appears to be this GPM8023. Searching for this part has led me to a post in Gearspace.com, where the last page on the topic of problems with the Soundcraft Signature series mixer appears to be this unavailable GPM8023. No data sheet, no apparent direct-replacement for it, and has been the main problem with this product series.
No idea what is on the SMPS that I just ordered. I wasn't able to get onto Gearspace...perhaps due to my searching on an XP machine with Mozila Firefox browser. I was able to scroll the last page reading nobody having any success in finding these parts or substitute for them.
Anyone have a data sheet, details on the GPM8023 or a substitute for it?
Guess that changed with this power outage, as it hasn't powered back up. When I plugged it in on my Check-out Bench, I got no Power Consumption reading and saw the Pilot Light flickering at a slow rate, along with the signal activity lights on the stereo buss. Indicative of the SMPS trying to start but couldn't.
I pulled the bottom pan off, then extracted the SMPS from the pan. Nothing immediately obvious.
After writing up the work order and sending the client off, I checked all of the discrete semiconductors, which all tested fine. There are two SOIC packaged 8-pin SMD IC's... a UC3842A and a GPM8023.
This morning, I called Harman International to see if I could purchase a replacement power supply for the mixer. P/N 5071878-01.V Or, 5071878-02.V, being the latest revision. Back Ordered, not due in until early June, built in Hungary. $85.70 + tax/shpg. Placed the order for that.
I found I already had the UC3842 data sheet in my files, and had a couple on hand, but....they were 8-pin DIP. I then looked to see what I could find on this GPM8023. No such luck on that.
That part appears to be the 5VDC Regulator for the logic circuits on the mixer.
I connected a 300 ohm/5W resistor across the +/- 15VDC Outputs on the bottom side of the PCB, as I don't have any mating connectors for the 9-pin shrouded white header plug. Connected my DMM across the resistor which, if the supplies ARE +/- 30V, would yield 100mA. Plugged it into my switched outlet connected to my variac/power analyzer, and switched it on. I got 46VDC across the resistor spanning the +/- 15V terminals on the back side. AC Mains wattage was 14W. Turned it off, dug up a pair of EZ Microhook test leads, and clipped onto the 5V output and it's ground. Got 0.128VDC. Not a good sign. Clipped onto the +48V terminal, and got +48VDC. I tacked on a second 300 ohm resistor across the +/- 15V supply, and now got 40VDC ,pulling 16W. So, the front end of the SMPS IS working. Still no output from the 5V circuit. I loaded the +/- 30V supply with a pair of 40 ohm/50W power resistors in series, leaving the 300 ohm resistor in place, and now that dropped the bipolar supply voltage to 36VDC. So, I'd conclude each channel or group of channels have local +/- 15V Regulators. The 48V circuit remains steady.
But, the problem appears to be this GPM8023. Searching for this part has led me to a post in Gearspace.com, where the last page on the topic of problems with the Soundcraft Signature series mixer appears to be this unavailable GPM8023. No data sheet, no apparent direct-replacement for it, and has been the main problem with this product series.
No idea what is on the SMPS that I just ordered. I wasn't able to get onto Gearspace...perhaps due to my searching on an XP machine with Mozila Firefox browser. I was able to scroll the last page reading nobody having any success in finding these parts or substitute for them.
Anyone have a data sheet, details on the GPM8023 or a substitute for it?
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