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Sansui AU-317II troubleshooting help requested....

Uncle Bambi

Uncle Bambi

Funky Tut
I picked up a Sansui AU-317II recently that needs repair, and could use some guidance in how to proceed.

The first thing I did when I got it was to open it up and do a visual inspection. No obvious signs of fire/burning/physically damaged components, but the 5A main fuse was blown.

I replaced the fuse, put the unit on a DBT, and fired it up. The 100w bulb got very bright and stayed there, so I quickly shut it down. Obviously, something is pulling lots of current..... hopefully I didn't do more damage by doing something stupid.

I downloaded the service manual (which isn't much), and I'm in the process of pulling it apart to get a good look at everything. The output drivers are marked SONKEN 2SA981 and 2SC2261, and are socketed to the main board through a big heat sink.

I have limited troubleshooting experience, and most of that is confined to Pioneer silver series receivers. I do know how to read schematics, use a meter, remove/replace parts, etc., but lack the experience a lot of you seem to have.

So..... where do I begin? Is there a way to test these output drivers to see if one of them is bad? Can I fire up the unit without them in place to see if the DBT behaves better?

What's my next step?
 
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Uncle Bambi said:
I picked up a Sansui AU-317II recently that needs repair, and could use some guidance in how to proceed.

The first thing I did when I got it was to open it up and do a visual inspection. No obvious signs of fire/burning/physically damaged components, but the 5A main fuse was blown.

I replaced the fuse, put the unit on a DBT, and fired it up. The 100w bulb got very bright and stayed there, so I quickly shut it down. Obviously, something is pulling lots of current..... hopefully I didn't do more damage by doing something stupid.

I downloaded the service manual (which isn't much), and I'm in the process of pulling it apart to get a good look at everything. The output drivers are marked SONKEN 2SA981 and 2SC2261, and are socketed to the main board through a big heat sink.

I have limited troubleshooting experience, and most of that is confined to Pioneer silver series receivers. I do know how to read schematics, use a meter, remove/replace parts, etc., but lack the experience a lot of you seem to have.

So..... where do I begin? Is there a way to test these output drivers to see if one of them is bad? Can I fire up the unit without them in place to see if the DBT behaves better?

What's my next step?
Click to expand...

Diode check all the outputs. Out of circuit is best.
 
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sorry to correct you but these are the actual output transistors ..the drivers are the ones before them in the circuit ,, first off i would check them for short circuit after taking them out ...remember where they came from it may well help later on .. there are threads on ak on how to test transistors .use the search function .. if they test good then its a problem further back ..if they test bad then its likely you have more problems ..
 
Also - further to the above post re noting which position the outputs were in, if you find one or more with problems then knowing what position they were in will determine what channel was affected and what other components need to be checked. Be careful when removing these, if you haven't done this before - there are mica washers in between the transistors and the heatsink and these can be easily damaged.

There are some other common problems with the 317II that you can check for, but first you need to get the unit working.
 
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avionic said:
Diode check all the SANKEN outputs. Out of circuit is best.
Click to expand...

Ok - just rediscovered EW's helpful tutorial on diode checking transistors. Pulled the transistors and tested each one.

2SC661 #1:
+B -E = .28v
+B -C = .28v
-B +E = 1.92v
-B +C = 1.92v

2SC661 #2:
+B -E = .74v
+B -C = .74v
-B +E = 0v (open?)
-B +C = 0v (open?)

2SA981 #1:
-B +E = .68v
-B +C = .68v
+B -E = 0v (open?)
+B -C = 0v (open?)

2SA981 #2:
-B +E = .67v
-B +C = .61v
+B -E = 0v (open?)
+B -C = 0v (open?)

Looks like 2SC661 #1 is a problem?


petehall347 said:
sorry to correct you but these are the actual output transistors ..the drivers are the ones before them in the circuit ,, first off i would check them for short circuit after taking them out ...remember where they came from it may well help later on .. there are threads on ak on how to test transistors .use the search function .. if they test good then its a problem further back ..if they test bad then its likely you have more problems ..
Click to expand...

I appreciate the correction - that's how I learn. Looks like one of them is bad (see above).... unfortunately, I did not pay attention to its position, other than it was one of the two middle ones on the heat sink. It is unfortunate that I did not pay attention, if you say I may have problems further back. :(

Ok - what next?
 
its late here in fact past my bedtime .. you could try powering up on dim with them still removed .. if you had made note where they came from it would have saved you some time ..
 
petehall347 said:
its late here in fact past my bedtime .. you could try powering up on dim with them still removed .. if you had made note where they came from it would have saved you some time ..
Click to expand...

No worries - I'm not in a big hurry.

I made a mistake not making note..... I should have known better.

Just to re-verify before I do it.... I can power this up on a DBT without the outputs in place, without causing damage?
 
it should be ok as far as i know to power up on dim bulb with no outputs in circuit .
you really do need to check all transistors especially the drivers .and diodes .and emitter resistors and resistors around the biasing circuits . that should keep you busy for a while . if you come across something bad you have a good chance its in the bad channel .
just to add i am going away for a few days so if anyone wants to jump in i don't mind at all .
 
Thanks for checking in before you left for holiday!

I'll go ahead and power it up without the outputs, and report back. I may need a bit of hand-holding to check the biasing circuits, identifying which parts are in the paths I'm interested in.

Looking at the schematic, they list TR17 and TR18 as 2SC1403 and there are no 2SC2661's (what I have) listed. Since they are SC type, are shown as TO-3 (?) type big round cans that match what I have, and are directly coupled with TR 19 and TR 20 in the power amp circuit, I'm going to presume those are the one's I'm interested in.....
 
My schematic shows TR17 and TR18 as 2SC2261, sounds like you have the schematic for the AU317 and not the AU317II.

The serviece manual for the AU117II/217II/317II can be downloaded here

http://www.hifi-manuals.com/Download/Sansui/AU-317-Mk2-service-manual

You have to register to download, but it is free.

Be careful when using the manual to make sure you are on the pages dealing with the 317II.

If you have trouble let me know - I can email it to you.

Cheers

John
 
D'oh!

Skippy, thanks for that catch. sure enough, I have the wrong manual. I just downloaded the right one, thanks to your helpful link!



skippy124 said:
My schematic shows TR17 and TR18 as 2SC2261, sounds like you have the schematic for the AU317 and not the AU317II.

The serviece manual for the AU117II/217II/317II can be downloaded here

http://www.hifi-manuals.com/Download/Sansui/AU-317-Mk2-service-manual

You have to register to download, but it is free.

Be careful when using the manual to make sure you are on the pages dealing with the 317II.

If you have trouble let me know - I can email it to you.

Cheers

John
Click to expand...
 
OK - so, I fired it up on the DBT, with the outputs removed. Bulb went bright and then dimmed immediately, and the relay clicked immediately at power up... and then a few seconds later clicked again.

Subsequent power-ups get an immediate dim bulb on the tester, followed a few seconds later by the relay clicking closed and staying closed.

Does this tell me anything useful? What are my chances that the open output transistor was the only fault?

Can I check power reliably with the outputs removed?
 
I haven't tried firing up a 317II without the outputs fitted, but what you are seeing sounds OK.

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).

Let us know how you go.

Cheers

John
 
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just had chance to catch upon this . looks like everything is going well .+10 on above advice .. more detailed than i could do
 
Excellent - thanks a bunch guys! I'll report back when I get this latest advice accomplished.

Question - since we're going to replace the output transistors anyway, and the driver transistors can't cost too much, should I just go ahead and rebuild the whole driver output transistor chain?

Also - shouldn't resistors be measured out of circuit, or at least 1 leg up?
 
No problems in replacing the driver transistors as well, but its always nice to know what has failed.

Agreed the best method to measure components is out of circuit (one leg lifted), but in this case you should see the same result for each set of resistors of the same value (a comparison check of sorts), if anything the readings could be a little low due to the influence of other components but it should be consistant. In any event, my recommnedation would be to replace the 82, 220 and 680 ohm resistors with 1/2W metal film, as well as the two on the Control Amp board (68 ohm by the way), as whilst these may measure OK at the moment, they will eventually drift high in value. The 6.8 ohm are not normally a problem, but need to be checked in case the failure damaged one or more of them.

Cheers

John
 
skippy124 said:
No problems in replacing the driver transistors as well, but its always nice to know what has failed.

Agreed the best method to measure components is out of circuit (one leg lifted), but in this case you should see the same result for each set of resistors of the same value (a comparison check of sorts), if anything the readings could be a little low due to the influence of other components but it should be consistant. In any event, my recommnedation would be to replace the 82, 220 and 680 ohm resistors with 1/2W metal film, as well as the two on the Control Amp board (68 ohm by the way), as whilst these may measure OK at the moment, they will eventually drift high in value. The 6.8 ohm are not normally a problem, but need to be checked in case the failure damaged one or more of them.

Cheers

John
Click to expand...

Thanks - I'll be sure to check them to verify what has failed or survived.

Once checked, I will replace the whole set of transistors and resistors you specified. I did and advanced search and came up with some current transistor replacement part numbers - I have a couple, and a couple I need to buy. Might as well add them to the Mouser order, as long as I'm buying the outputs...

TR13,TR14 2sb527 - Mouser part# 512-KSA1220AYS
TR15,TR16 2sd357 - Mouser part# 512-KSC2690AYS

Also, on the metal film resistors..... Mouser shows two kinds: metal film, and metal film though-hole. Should I choose one type over the other?
 
Hi,

Should be metal film through hole (the others may be surface mount style).

I haven't checked the driver transistors subs (the KSA/KSC series aren't readily available down under so I'm not familair with them), make sure you check the pin outs when putting them in.

EDIT: those subs look fine

CHeers

John
 
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skippy124 said:
Hi,

Should be metal film through hole (the others may be surface mount style).
Click to expand...

Ahh.... another D'oh. :) "Through the hole"...... Duh.

Here are the results of my testing:

TR13, TR14, TR15, TR16 all check ok using EW's diode function test

R47, R48, R53, R54 should be 82 ohm - actual values 84, 83, 81, and 81

R49, R50, R51, R52, should be 220 ohm - actual values 219, 219, 220, 220

R33, R34, R43, R44, should be 680 ohm - actual values 676, 686, 679, 678

R55, R56, R61, R62, should be 6.8 ohm - actual values 6.9, 6.9, 6.9, 6.9

R37, R38, R59 and R60 should be 0.33 ohm - actual values .9, .2, .5, .5

R17 an R18 on the Control Amp F2752 - 88, 71

So far, it looks like only that one output transistor is the problem.....
 
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