Sony TA-5650 v-fet matching and 1N4148 diodes
- Thread starter Jeff W.
- Start date
ilimzn
Well-Known Member
Hold on, my copy of the service manual is horrible. But i do have a 5650 driver board somewhere here, I'll look at it.
In any case, the 6-pin connector is missing the -47.7V supply.
Can you measure the larger connector next to it? Pins from top to bottom - it says in the manual the wire colors go like this:
Violet?? (not sure)
Black
Black
Brown
Orange
White
Red
Blue
Green
Violet
In any case, the 6-pin connector is missing the -47.7V supply.
Can you measure the larger connector next to it? Pins from top to bottom - it says in the manual the wire colors go like this:
Violet?? (not sure)
Black
Black
Brown
Orange
White
Red
Blue
Green
Violet
ilimzn
Well-Known Member
OK, you are missing the main supply from the channel closest to the large connector.
The pins on this connector go like this:
Violet?? (not sure) = temperature sensor, connects to violet wire across the driver board. Voltage seems OK
Black = power ground left channel = 0V OK
Black = power ground right channel = 0V OK
Brown = main power supply = 47.8V OK
Orange = positive bias supply = not OK, should be round +80V. See note below.
White = output left channel = not OK, should be 0V, see below
Red = output right channel = 0V OK
Blue = negative bias supply = not OK, should be around -80V. See note below
Green = speaker protect out = voltage is ok but it should not be present because left ch output is not 0V
Violet = main power supply = not OK, should be -47V
The 6 pin connectors on the sides of the board are wired in parallel, that means pin 1 on the right connector to pin 1 on the left, etc, until pin 6 on the right to pin 6 on the left. Your previous measurement shows that there is something wrong or you have skipped a pin.
Here is what I do know:
1) The 47.5V positive main voltage is missing from both channels or is intermittent. The wire going to the bottom pin on the long connector on the side is probably broken or has a bad contact. you are measuring 19.7 or so V and it should be -47V. Check that the wire from the power supply board to the driver board is working, or that the connectors have good contact - this comes from connector (51) pin 6 on the rectifier board (mounted on the two large main capacitors).
2) The bias supply is working correctly but because the main -47V supply is missing, the circuits are pulling it down. This can be seen from the fact that the difference between the bias supplies is still around 160V (37.9V+131.3V) but it is not symetrical.
3) The speaker protect circuit (driver board, Q501, Q502) is not functioning properly. It should not let the relay click. Either there is a bad contact on pin 1 of the large connector on the side of the driver board or some of the components in the circuit are faulty.
4) The LEFT channel (the one with 18V on the output) is likely working properly. The right channel, the one with 0V on the output is not. The circuit cannot output 0V with the negative power supply missing.
5) C307 is likely installed backwards. Also check that R319 (1k) has not smoked. Also check C357 and R369 on driver board (same function as C307, R319 but other channel). It is VERY strange that C305 is damaged, SOmething may be wrong with other components around it, including transistors.
6) C408, C416 may be installed backwards but also their failing may be because of the boad voltage overload. Check R414 for signs of overheating! Also, there is a design problem with the bias supply in that the positive and negative bias supplies influence each other depending on load. This can be fixed by replacing diode D405 with two diodes of the same type in series, and connecting the connection point of the two to ground.
7) does your amplifier use wires wrapped directly to the connectors on the sides of the driver board, or does it use white female connectors? At some point it will be required to isolate the power supply for the right channel. The 6-pin connectors on the driver board are a 'bridge' that can originally be removed, early versions had female connectors here. However, it was later discovered they can be unreliable and if the contact of a bias supply fails, destroy the amplifier, so they started using directly connected wires. Tell me what is on yours and I will see how this can be solved.
The pins on this connector go like this:
Violet?? (not sure) = temperature sensor, connects to violet wire across the driver board. Voltage seems OK
Black = power ground left channel = 0V OK
Black = power ground right channel = 0V OK
Brown = main power supply = 47.8V OK
Orange = positive bias supply = not OK, should be round +80V. See note below.
White = output left channel = not OK, should be 0V, see below
Red = output right channel = 0V OK
Blue = negative bias supply = not OK, should be around -80V. See note below
Green = speaker protect out = voltage is ok but it should not be present because left ch output is not 0V
Violet = main power supply = not OK, should be -47V
The 6 pin connectors on the sides of the board are wired in parallel, that means pin 1 on the right connector to pin 1 on the left, etc, until pin 6 on the right to pin 6 on the left. Your previous measurement shows that there is something wrong or you have skipped a pin.
Here is what I do know:
1) The 47.5V positive main voltage is missing from both channels or is intermittent. The wire going to the bottom pin on the long connector on the side is probably broken or has a bad contact. you are measuring 19.7 or so V and it should be -47V. Check that the wire from the power supply board to the driver board is working, or that the connectors have good contact - this comes from connector (51) pin 6 on the rectifier board (mounted on the two large main capacitors).
2) The bias supply is working correctly but because the main -47V supply is missing, the circuits are pulling it down. This can be seen from the fact that the difference between the bias supplies is still around 160V (37.9V+131.3V) but it is not symetrical.
3) The speaker protect circuit (driver board, Q501, Q502) is not functioning properly. It should not let the relay click. Either there is a bad contact on pin 1 of the large connector on the side of the driver board or some of the components in the circuit are faulty.
4) The LEFT channel (the one with 18V on the output) is likely working properly. The right channel, the one with 0V on the output is not. The circuit cannot output 0V with the negative power supply missing.
5) C307 is likely installed backwards. Also check that R319 (1k) has not smoked. Also check C357 and R369 on driver board (same function as C307, R319 but other channel). It is VERY strange that C305 is damaged, SOmething may be wrong with other components around it, including transistors.
6) C408, C416 may be installed backwards but also their failing may be because of the boad voltage overload. Check R414 for signs of overheating! Also, there is a design problem with the bias supply in that the positive and negative bias supplies influence each other depending on load. This can be fixed by replacing diode D405 with two diodes of the same type in series, and connecting the connection point of the two to ground.
7) does your amplifier use wires wrapped directly to the connectors on the sides of the driver board, or does it use white female connectors? At some point it will be required to isolate the power supply for the right channel. The 6-pin connectors on the driver board are a 'bridge' that can originally be removed, early versions had female connectors here. However, it was later discovered they can be unreliable and if the contact of a bias supply fails, destroy the amplifier, so they started using directly connected wires. Tell me what is on yours and I will see how this can be solved.
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Ok now new values. The violet wire was cut off.
-47,4
0
0
47,7
64,4
,055
0
-98,4
-47,7
-47,8
R414 is ok
There is a wire wrap in this amp
Here is allso vfets voltages from left to right
39/0,057/47,7
38,5/0,056/47,6
-83,7/0,055/-47,7
-83,7/0,055/-47,8
-82,4/0,005/-47,6
-81,3/0,004/-47,7
38,1/0,005/47,8
38/0,005/47,8
I chekced all those what you told but everything seems to be ok as far as i can say. I havent change the C307 because it is the same way that the opposite one and shows same measurement allso.
And now the relay really clicks
Is There is still something?
-47,4
0
0
47,7
64,4
,055
0
-98,4
-47,7
-47,8
R414 is ok
There is a wire wrap in this amp
Here is allso vfets voltages from left to right
39/0,057/47,7
38,5/0,056/47,6
-83,7/0,055/-47,7
-83,7/0,055/-47,8
-82,4/0,005/-47,6
-81,3/0,004/-47,7
38,1/0,005/47,8
38/0,005/47,8
I chekced all those what you told but everything seems to be ok as far as i can say. I havent change the C307 because it is the same way that the opposite one and shows same measurement allso.
And now the relay really clicks
Is There is still something?
Last edited:
ilimzn
Well-Known Member
Much better. Still, the bias voltages are not symmetrical, perhaps changing those capacitors on the power board (C40x)? Something is still not right with the right channel, this may also be the reason for the bias voltage problem.
Can you check the voltages on the collector of Q354 (this is also one side of R362 and the D353), and Q355 (this is also one side of D352 and R364). It might be a problem getting to the collectors (middle pin of the transistors) but might be easier to get to the resistor pins. R364 and R362 are under the bias trimmer, and are green (second and third resistor under the trimmer). The relevant pins are further from the edge of the board.
Oh yes - one more thing - check that the bias trimmers are turned to minimum (fully anti-clockwise)
Can you check the voltages on the collector of Q354 (this is also one side of R362 and the D353), and Q355 (this is also one side of D352 and R364). It might be a problem getting to the collectors (middle pin of the transistors) but might be easier to get to the resistor pins. R364 and R362 are under the bias trimmer, and are green (second and third resistor under the trimmer). The relevant pins are further from the edge of the board.
Oh yes - one more thing - check that the bias trimmers are turned to minimum (fully anti-clockwise)
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ilimzn
Well-Known Member
Eh you misunderstood. Keep measuring as before, (-) of instrument on ground, (+) at the point where I said.
Do not understand what the megaohms should be??? These measurements make no sense and in fact do NOT make resistance measurements before at least 5 minutes have gone since turning off the amp because there will be remaining voltages in the capacitors which make the measurement nonsense - such as negative ohms! - and could in fact damage your meter.
What I need is voltage between ground (0) = minus terminal for speaker to:
1) R362 side closer to center of board
2) R364 side closer to center of board
For comparison it is possible o do measurements for the same pins on R312 and R314 but this may not be needed, depending on what is found in measurement 1) and 2).
I am sorry to keep going like this but it needs to go step by step, and what step is next, depends on what the previous measurement is.
If transistors need to be checked, it will be done differently - if your measuring instrument has a diode checker, this is where it will be used. But we are not at that stage now.
The problem here is that the left channel has 55mV on output which is sort of marginal offset voltage (it would be better if it is lower but this is not excessive, so not indicating a fault, but what one would expect from a working circuit which still has the original semiconductors installed). It is possible, but EXTREMELY improbable that you would get EXACTLY 0mV on the output, so the right channel is suspicious. I think there is something wrong there, and the measurement above is at a point where the front end of the amplifier and the driver stages are connected, you could say where the front and rear half of the amplifier circuit are connected. Depending on what is found in these measurements, I can then decide if the fault may be in the front or the rear half.
These points on the resistors are the ends of 2 diodes connected in series (one of them is the VD1221 or replacement) which generate the voltage drop from which the bias is derived. The difference between these voltages should be around 2V but it is of more interest at which voltage relative to zero these points are. This tells us what the front end is trying to do in order to get the driver to produce 0V at the output, and by that, if it is doing the expected thing for such a circuit.
Do not understand what the megaohms should be??? These measurements make no sense and in fact do NOT make resistance measurements before at least 5 minutes have gone since turning off the amp because there will be remaining voltages in the capacitors which make the measurement nonsense - such as negative ohms! - and could in fact damage your meter.
What I need is voltage between ground (0) = minus terminal for speaker to:
1) R362 side closer to center of board
2) R364 side closer to center of board
For comparison it is possible o do measurements for the same pins on R312 and R314 but this may not be needed, depending on what is found in measurement 1) and 2).
I am sorry to keep going like this but it needs to go step by step, and what step is next, depends on what the previous measurement is.
If transistors need to be checked, it will be done differently - if your measuring instrument has a diode checker, this is where it will be used. But we are not at that stage now.
The problem here is that the left channel has 55mV on output which is sort of marginal offset voltage (it would be better if it is lower but this is not excessive, so not indicating a fault, but what one would expect from a working circuit which still has the original semiconductors installed). It is possible, but EXTREMELY improbable that you would get EXACTLY 0mV on the output, so the right channel is suspicious. I think there is something wrong there, and the measurement above is at a point where the front end of the amplifier and the driver stages are connected, you could say where the front and rear half of the amplifier circuit are connected. Depending on what is found in these measurements, I can then decide if the fault may be in the front or the rear half.
These points on the resistors are the ends of 2 diodes connected in series (one of them is the VD1221 or replacement) which generate the voltage drop from which the bias is derived. The difference between these voltages should be around 2V but it is of more interest at which voltage relative to zero these points are. This tells us what the front end is trying to do in order to get the driver to produce 0V at the output, and by that, if it is doing the expected thing for such a circuit.
ilimzn
Well-Known Member
Well, I am trying to do my best
Hm, this looks OK for the front end if a bit towards the negative and points to a possible problem in the driver section.
So next steps:
1) If there is a voltage selector on the back of the amp, is it set to 240V? If not,set it to 240V (main voltage i slightly on the high side)
2) Are the bias set trimmers fully anti-clockwise (minimum bias)? If no, turn them to minimum.
3) Check the opposite sides of the resistors above. The other side of each of this resistor is the actual bias voltage to the driver section, as set by the trimmers.
5) Now turn the trimmers to maximum (fully clockwise) (you should NOT do this with VFETs installed! ).
6) Repeat measurement as in step 3. The voltages should be higher now. If not, the trimmers are not good.
Hm, this looks OK for the front end if a bit towards the negative and points to a possible problem in the driver section.
So next steps:
1) If there is a voltage selector on the back of the amp, is it set to 240V? If not,set it to 240V (main voltage i slightly on the high side)
2) Are the bias set trimmers fully anti-clockwise (minimum bias)? If no, turn them to minimum.
3) Check the opposite sides of the resistors above. The other side of each of this resistor is the actual bias voltage to the driver section, as set by the trimmers.
5) Now turn the trimmers to maximum (fully clockwise) (you should NOT do this with VFETs installed!
).6) Repeat measurement as in step 3. The voltages should be higher now. If not, the trimmers are not good.
ilimzn
Well-Known Member
In the previous step you measured voltages on the legs of resistors R362, 364, 312, 314 that are closer to the center of the board. Now measure the same resistors, but legs on the other side of the resistor, closer to the edge of the board. Two measurements are needed, once for the bias trimmer fully anticlockwise (minimum bias) (step 3 above) and once for fully clockwise (maximum bias) (step 6 above, because I forgot to put in step 4 ),
),
ilimzn
Well-Known Member
Still seems OK.
Now with the trimmers still in the clockwise position, please measure the bias supply voltage, and voltages on the VFET gates.
Both measurements are easily done by measuring on R339/R342 and R389/R392. These are the large green resistors, 3.3k (orange, orange, red, gold color code). The legs towards the edges of the board are the bias supply voltage, and the legs closest to the center of the board are the VFET gate voltage.
Sorry for being this slow but I am working so can't always read the answer immediately.
Now with the trimmers still in the clockwise position, please measure the bias supply voltage, and voltages on the VFET gates.
Both measurements are easily done by measuring on R339/R342 and R389/R392. These are the large green resistors, 3.3k (orange, orange, red, gold color code). The legs towards the edges of the board are the bias supply voltage, and the legs closest to the center of the board are the VFET gate voltage.
Sorry for being this slow but I am working so can't always read the answer immediately.
ilimzn
Well-Known Member
Absolutely, especially C416 - this might be the reason the bias supply voltage is not symmetrical.
It is very strange C307 has failed, but change it anyway and we will see what to do about it.
The manual you sent is very helpful, mine looks like it was sent through a very old telefax machine
Let me have a look on fixing this asymmetry issue on the power supply board...
It is very strange C307 has failed, but change it anyway and we will see what to do about it.
The manual you sent is very helpful, mine looks like it was sent through a very old telefax machine
Let me have a look on fixing this asymmetry issue on the power supply board...
ilimzn
Well-Known Member
OK this is getting better. Now you need to re-measure with the bias trimmers in the fully anti-clockwise position (minimum bias).
It is still asymmetrical but at least it is the same on both channels. I have looked at doing the symmetry fix on the power board but it is not as simple as it is on the 4650 amp
There is one more test we can do which has to do with the inputs. Did you manage to get shorting plugs for the main in (power amp) inputs?
Oh yes - one more question, what rank are your VFETs?
It is still asymmetrical but at least it is the same on both channels. I have looked at doing the symmetry fix on the power board but it is not as simple as it is on the 4650 amp
There is one more test we can do which has to do with the inputs. Did you manage to get shorting plugs for the main in (power amp) inputs?
Oh yes - one more question, what rank are your VFETs?
