If anyone has time to share some thoughts, it would be much appreciated.
The 317 mkII stopped working. Cutting to the chase, I opened it up and did some checks. The following thread was most helpful.
http://audiokarma.org/forums/index.php?threads/sansui-au-317ii-troubleshooting-help-requested.412472
But my checks showed that more components appear to have failed on my amp, so it would be great if someone with the sort of knowledge shared on that thread would let me know how much further I need to go before replacing components.
Before the amp blew, I had inadvertently connected it to 4 Ohm speakers (back panel warns against anything less than 8 Ohm). I assumed that this would have been the cause and that, with luck, the damage might be confined to the output transistors. However, there appears to be a number of related components that have failed.
The immediate sign of failure was blown fuses (the ones supplying the output stage). I checked the output transistors to find that TR17 and TR19 are conductive C-E. The thread above contained the following advice:
I did the checks described (components in place).
I found that TR13 and TR15 were conductive C-E (~150 and 3 Ohms, respectively), whereas their counterparts on the other channel measured as an open circuit.
The related resistors R49 and R51 were about 130 Ohms and 3.5 Ohm, respectively, whereas their counterparts on the other channel measured at the correct 220 Ohms.
The other resistors all measured within ~5% of correct value (noting that the 0.33 Ohm resistors are hard to accurately measure) save for R17, which was 75.8 Ohms - about 10% over the correct value of 68 Ohms.
At this stage I would prefer to replace what I need to. These are
The questions I would like to ask are:
The 317 mkII stopped working. Cutting to the chase, I opened it up and did some checks. The following thread was most helpful.
http://audiokarma.org/forums/index.php?threads/sansui-au-317ii-troubleshooting-help-requested.412472
But my checks showed that more components appear to have failed on my amp, so it would be great if someone with the sort of knowledge shared on that thread would let me know how much further I need to go before replacing components.
Before the amp blew, I had inadvertently connected it to 4 Ohm speakers (back panel warns against anything less than 8 Ohm). I assumed that this would have been the cause and that, with luck, the damage might be confined to the output transistors. However, there appears to be a number of related components that have failed.
The immediate sign of failure was blown fuses (the ones supplying the output stage). I checked the output transistors to find that TR17 and TR19 are conductive C-E. The thread above contained the following advice:
I would check the following before refitting the outputs -
TR13, TR14, TR15, TR16 ( these are the driver transistors for the outputs). Check them in circuit using the same testing principles as with the outputs, they should measure the same for both channels (TR13/TR15 in one channel, TR14 and TR16 the other channel).
R47, R48, R53, R54 shoud be 82 ohm
R49, R50, R51, R52, should be 220 ohm
R33, R34, R43, R44, should be 680 ohm
R55, R56, R61, R62, should be 6.8 ohm
The above are "fuse" resistors and are known to drift high in value over time.
Also check R37, R38, R59 and R60< should measure almost short circuit as they are 0.33 ohm.
And while you are at it, also measure R17 an R18 on the Control Amp F2752 board, these are also fuse resistors (not marked as such in the schematic) These can be measured from the solder side of the board (refer to the board layouts in the service manual).
TR13, TR14, TR15, TR16 ( these are the driver transistors for the outputs). Check them in circuit using the same testing principles as with the outputs, they should measure the same for both channels (TR13/TR15 in one channel, TR14 and TR16 the other channel).
R47, R48, R53, R54 shoud be 82 ohm
R49, R50, R51, R52, should be 220 ohm
R33, R34, R43, R44, should be 680 ohm
R55, R56, R61, R62, should be 6.8 ohm
The above are "fuse" resistors and are known to drift high in value over time.
Also check R37, R38, R59 and R60< should measure almost short circuit as they are 0.33 ohm.
And while you are at it, also measure R17 an R18 on the Control Amp F2752 board, these are also fuse resistors (not marked as such in the schematic) These can be measured from the solder side of the board (refer to the board layouts in the service manual).
I did the checks described (components in place).
I found that TR13 and TR15 were conductive C-E (~150 and 3 Ohms, respectively), whereas their counterparts on the other channel measured as an open circuit.
The related resistors R49 and R51 were about 130 Ohms and 3.5 Ohm, respectively, whereas their counterparts on the other channel measured at the correct 220 Ohms.
The other resistors all measured within ~5% of correct value (noting that the 0.33 Ohm resistors are hard to accurately measure) save for R17, which was 75.8 Ohms - about 10% over the correct value of 68 Ohms.
At this stage I would prefer to replace what I need to. These are
- Output transistors TR17 and TR 19
- Driver transistors TR13 and TR15
- Resistors R49 and R51
The questions I would like to ask are:
- Does this pattern of failure suggest that more checking is needed?
- Should I replace the counterparts on the channel that have not failed?
- TR13 and TR15 are shown in the manual as 2SD357 and 2SB527, respectively. Any recommendations for replacements (or should I just look on line)?
- I have already obtained On Semi output transistors. I ordered MJ21193 and MJ21194 (as recommended in another AK thread) but received MJ21193G and MJ21194G parts. Is this an issue?
