Hello all - I have a Kenwood DP-SG7 CD Player which won't power on.
I've opened it up and first port of call is a board with a transformer. I have 240v going in and on the ribbon cable that connect to the main board I am getting a reading of 13-14v. According to the service manual, if I am reading it correctly it should be more like 10v - see pin 1 below.
Is this in itself an issue?
I have also had a poke around the main board with a multimeter and I have found a FET which is giving an open circuit (beeping) when I test across Gate and Source in diode mode. The FET is still on the board though, does this indicate damage?
Also I have broken the ribbon cable connector that provides power to the main board - anyone know what type of connector this is:
This is where is plugs:
This is the service manual:
https://www.recambiosyaccesoriosonline.es/despieces/kenwood/dpsg7/Kenwood_DPSG7_Despiece.pdf
Thanks in advance for any feedback.
I've opened it up and first port of call is a board with a transformer. I have 240v going in and on the ribbon cable that connect to the main board I am getting a reading of 13-14v. According to the service manual, if I am reading it correctly it should be more like 10v - see pin 1 below.
Is this in itself an issue?
I have also had a poke around the main board with a multimeter and I have found a FET which is giving an open circuit (beeping) when I test across Gate and Source in diode mode. The FET is still on the board though, does this indicate damage?
Also I have broken the ribbon cable connector that provides power to the main board - anyone know what type of connector this is:
This is where is plugs:
This is the service manual:
https://www.recambiosyaccesoriosonline.es/despieces/kenwood/dpsg7/Kenwood_DPSG7_Despiece.pdf
Thanks in advance for any feedback.
It will be normal as that is a raw unregulated supply.
You need to check these voltage rails, If any are missing check the fusible resistors arrowed. The -30v supply is for the VFD vacuum fluorescent display)
Your best bet for the broken plug is to just hardwire and solder the lead directly. Those connectors are fairly common in equipment but I've never some across them as a generic spare part.
You need to check these voltage rails, If any are missing check the fusible resistors arrowed. The -30v supply is for the VFD vacuum fluorescent display)
Your best bet for the broken plug is to just hardwire and solder the lead directly. Those connectors are fairly common in equipment but I've never some across them as a generic spare part.
I think I've trashed this player.
I soldered some wires to the pins which broke at the connector. I powered it up and had the 13-15v as before at +B and GND - so all seemed ok. I then tried to check the voltage at the Q2 transistor, I put the red probe to either side - now when I check the voltage at B+ and GND as it leaves the power supply I'm only getting 1.8-2v.
Might be for the trash now I guess - might be more than my skills set to fix.
I soldered some wires to the pins which broke at the connector. I powered it up and had the 13-15v as before at +B and GND - so all seemed ok. I then tried to check the voltage at the Q2 transistor, I put the red probe to either side - now when I check the voltage at B+ and GND as it leaves the power supply I'm only getting 1.8-2v.
Might be for the trash now I guess - might be more than my skills set to fix.
The board is really tricky to access because it is mounted component side down and the screw will require some fiddling about as there is not enough room for a screw driver. But I think I have located IC1 - circled below?
Using my DMM i diode test mode it appears to be not open - no beep. what about the other component there - the KBP02ML-6127
Using my DMM i diode test mode it appears to be not open - no beep. what about the other component there - the KBP02ML-6127
I've successfully replaced the IC1 on the power supply board - I now am back to 13v which is great. Incidently, when i power off the meter slowly counts down from the 13v displayed, presumably that is the large capacity at play?
I now want to check the voltage on the 3 points suggest in post #2, I've attached 3 photos showing Q1, Q2 and Q3 - can I get some advice on where to test for the voltage readings as I'm struggling a little to map the schematic to the actual physical board.
I think that I blew that IC1 initially when I was poking around previously without properly identifying the points on the board.
Thanks in advance.
I now want to check the voltage on the 3 points suggest in post #2, I've attached 3 photos showing Q1, Q2 and Q3 - can I get some advice on where to test for the voltage readings as I'm struggling a little to map the schematic to the actual physical board.
I think that I blew that IC1 initially when I was poking around previously without properly identifying the points on the board.
Thanks in advance.
Measuring the voltage on R106 that links Q2 and Q3 will tell you if the +7 volts is present. You should see it on both sides of the resistor.
To measure the +5 volts on Q3 collector (which is most likely the middle leg) will need you to locate the print and measure the voltage anywhere on that line. That also goes to the positive end of C109 so that could be an easy place to measure.
To measure the +5 volts on Q3 collector (which is most likely the middle leg) will need you to locate the print and measure the voltage anywhere on that line. That also goes to the positive end of C109 so that could be an easy place to measure.
That doesn't sound good. Look at the diagram in post #2. It looks like the regulated supplies are all high, the 7 volt supply certainly is if you have 12 volts on R106. The regulated voltage is determined by the regulator IC1 and the resistor values of R7 and R8 and a a quick calculation shows the service manual appears correct and it really is 7 volts you should have there.
The next even bigger problem is that if you have 12 volts on the middle leg (the collector) of Q3 then you have effectively got 12 volts across all the 5 volt circuitry (all the processors and logic stuff) which will almost certainly have caused damage.
Ultimately I suspect this one is beyond economic repair
The next even bigger problem is that if you have 12 volts on the middle leg (the collector) of Q3 then you have effectively got 12 volts across all the 5 volt circuitry (all the processors and logic stuff) which will almost certainly have caused damage.
Ultimately I suspect this one is beyond economic repair
Thanks - that's disappointing to learn. Whilst I bow to your superior judgement and I do hear what you say, I've come this far so for the sake of a few quid I might just pick up a replacement IC1 and IC2 and in the feint hope that something is still salvageable - if nothing else i might learn something.
I have hope because I have been messing around with an old games console that requires 9v and 12v which I plugged in didn't fry anything.
While I am at it, are there any other components worth changing that could be suspect.
I have hope because I have been messing around with an old games console that requires 9v and 12v which I plugged in didn't fry anything.
While I am at it, are there any other components worth changing that could be suspect.
The only way you can attempt this is to fix the power supply first. The only thing I have to go off are the measurements you provide and tbh it is unlikely both IC's are faulty. Q2 and Q3 are much more likely failure points although again it is hard to see that both would be faulty. Accidental short circuits of the rails could possible do this.
I would begin by rechecking your measurements. Make sure you are using a correct and good ground point for the readings. If the 7 volts is high and still showing 12 volts then I would begin by replacing Q2.
Data sheet for for IC1 and 2
M5237L
and tbh it is unlikely both IC's are faulty. Q2 and Q3 are much more likely failure points although again it is hard to see that both would be faulty. Accidental short circuits of the rails could possible do this.I would begin by rechecking your measurements. Make sure you are using a correct and good ground point for the readings. If the 7 volts is high and still showing 12 volts then I would begin by replacing Q2.
Data sheet for for IC1 and 2
M5237L
I'm taking the ground from "2" on the connector WH1 (see post #2). I have a crocodile clip on the wires which I soldered to fix the connection - presumably this is a correct place.
BTW - "to fix the power supply first" - we are referring to the voltage that is incorrect on this board - not the actual PSU board (X14-4760-21 - post #1). Presumably we can assume this is fine since I am getting 12v on pin 1 which. Issue is likely one of those transistors that should regulate the power supply to the 7v presumably?
BTW - "to fix the power supply first" - we are referring to the voltage that is incorrect on this board - not the actual PSU board (X14-4760-21 - post #1). Presumably we can assume this is fine since I am getting 12v on pin 1 which. Issue is likely one of those transistors that should regulate the power supply to the 7v presumably?
That is the correct ground point and usually such a point is the same electrically as the metal chassis and the ground part of any output sockets and so on. When a lot of voltages seem incorrect you should double check you have the correct point and that that point really is what you think it is.
The three circled voltages in that image should all be correct. A good check is to measure the voltage across the appropriate capacitors which are C9 (5 volt rail), C6 (7 volt rail) and C3 (-30 volt rail). There is an error in the marked polarity of C3 in the diagram and such errors are not uncommon unfortunately. Plus end of cap will go to ground as that is a negative rail.
The three circled voltages in that image should all be correct. A good check is to measure the voltage across the appropriate capacitors which are C9 (5 volt rail), C6 (7 volt rail) and C3 (-30 volt rail). There is an error in the marked polarity of C3 in the diagram and such errors are not uncommon unfortunately. Plus end of cap will go to ground as that is a negative rail.