Need guidance on Sansui AU-717 rebuild

Going out to test some voltages now. Not sure why no one is replying to my Transistor questions but I did some research and found out this info on polarity. My board is marked E-B. E = Emitter B= Base the non marked terminal is C for collector and that's always the middle terminal. I really need to look at my schematic way more than I am. It's slightly intimdating but I'm finding if I look at it long enough and compare to the PCB I end up figuring out were the path and connection points are on the PCB. Anyway I found this drawing on the schematic and it shows which terminal goes were.

TR.JPG


That left the question about the transistor symbol on the schematic. How did this correspond to the illustration? Turns out like this.

transistorPolarity.JPG


So I will check the TR09-12 on F-2663 that I replaced. I just went by my photo which was not the best and I couldn't see all 4. If I find a reversed one I'm not sure if this is the cause of my problem but at least I'll correct it whatever it does.
 
sruddy said:
Looking at the schematic for F-2663 Power supply circuit protection board I see three voltage test points. Two are 50 and -50V are these DC and are they the ones your talking about? One is at the connection of R05 and one leg of TR06 the other is at connection of R16 and one leg ot TR08. Hopefully I can get to them without pulling the board out. I also found +/- 32.4V on F-2723. and a single 32V on F-2720.
Click to expand...

You should have +/-32 on the F-2720 and the F-2723 boards - you need to measure these voltages coming out of F-2663 (PSU/Protector circuit board)

The above diagrams are for the parts originally installed in the Amp - if you have used equivalents for any they could have different pin configurations - possibly with 'Collector' leg not in the centre. If you are working to this level on a piece of equipment you should know very well how to determine which leg of a transistor is which.
 
Hyperion said:
You should have +/-32 on the F-2720 and the F-2723 boards - you need to measure these voltages coming out of F-2663 (PSU/Protector circuit board)

The above diagrams are for the parts originally installed in the Amp - if you have used equivalents for any they could have different pin configurations - possibly with 'Collector' leg not in the centre. If you are working to this level on a piece of equipment you should know very well how to determine which leg of a transistor is which.
Click to expand...

Unless I'm blind I only see one -32V on F-2720 nothing on F-2723. At least I can check that one. I will also check my replacement transformers for any difference in terminal orientation. Thanks John!!!
 
Just checked mouser and they don't say anything about the TR terminals on the TR's I purchased. They are ksc1845 and ksa992 which are NPN so they should be BCE. Let me know if I'm wrong.
 
The current pinout standard is "ECB" for TO-92 transistors; the datasheets for KSC1845 and KSA992 confirm the same.
 
Warning Will Robinson, those ksc and ksa transistors are available with different lead layouts depending on the suffix. Would you list the entire Mouser part number as printed on the transistor package?
example --- ksa992cyta
 
Overundr1 said:
Warning Will Robinson, those ksc and ksa transistors are available with different lead layouts depending on the suffix. Would you list the entire Mouser part number as printed on the transistor package?
example --- ksa992cyta
Click to expand...

I loved Lost in Space!!! Now I feel like watching one again!!

Here are the links.

http://www.mouser.com/Search/ProductDetail.aspx?R=KSA992FBUvirtualkey51210000virtualkey512-KSA992FBU

http://www.mouser.com/Search/Produc...FTAvirtualkey51210000virtualkey512-KSC1845FTA
 
Those transistors both look OK - centre collector ;)

Now we only have to be sure that you inserted them correctly when you replaced them ;)
 
Hyperion said:
Those transistors both look OK - centre collector ;)

Now we only have to be sure that you inserted them correctly when you replaced them ;)
Click to expand...

Yep! I'm going to check the polarity this weekend. Did you see I didn't get -32V at one of those points you asked me to test? see post #86. What does that tell us?
 
sruddy said:
What does that tell us?
Click to expand...

It tells us you (most likely) have a fault in the regulated power supply (on PSU/Protector board) which will disable all pre-amp and phono amp functionality.

However, things like wrongly installed or damaged components, misplaced connectors, cracked solder joints, broken or trapped wires or damaged pins, could also cause this.
 
Hyperion said:
It tells us you (most likely) have a fault in the regulated power supply (on PSU/Protector board) which will disable all pre-amp and phono amp functionality.

However, things like wrongly installed or damaged components, misplaced connectors, cracked solder joints, broken or trapped wires or damaged pins, could also cause this.
Click to expand...

I will be pulling that board this weekend as it's the only board I worked on so far. The last class lecture this week was on diodes and I learned that Zener Diodes are used for voltage regulation. Looks like I replaced ZD01/02 and ZD601/602 would these be a logical place to look? Also what does the Varistor Diode do? It's in D604 that's the one I had to solder two in series and the original was only a single and it was stock for sure so I'm still questioning that. See my photo in post #20 for photo of original diode and post #53 for my replacement series soldering and install job.

Hope you all have a happy thanksgiving!
 
Last edited:
sruddy said:
I will be pulling that board this weekend as it's the only board I worked on so far. The last class lecture this week was on diodes and I learned that Zener Diodes are used for voltage regulation. Looks like I replaced ZD01/02 and ZD601/602 would these be a logical place to look? Also what does the Varistor Diode do? It's in D604 that's the one I had to solder two in series and the original was only a single and it was stock for sure so I'm still questioning that. See my photo in post #20 for photo of original diode and post #53 for my replacement series soldering and install job.

Hope you all have a happy thanksgiving!
Click to expand...

You did a beautiful job of that - don't worry it is the standard fix for those unreliable 'red blob' dual diodes - just have to get them in the right way round - which it looks like you did.
 
Last edited:
Hyperion said:
You did a beautiful job of that - don't worry it is the standard fix for those unreliable 'red blob' dual diodes - just have to get then in the right way round - which it looks like you did.
Click to expand...

Thanks John but it actually replaced a single black with silver stripe diode seen in post 20. Still no worries?? Thanks!
 
D604 is a dual diode according to the schematic - which should have looked like a red blob ! - the diode you show (in post 20) does not look like a dual diode at all !! - where did it come from because it should not have been in D604 position.

I saw a picture of a dual diode replaced with 2 neatly soldered 1N4148 looking glass diodes - I thought it was in your thread but maybe not...

But perhaps more to the point, what have you got in D604 position NOW !?
 
Hyperion said:
D604 is a dual diode according to the schematic - which should have looked like a red blob ! - the diode you show (in post 20) does not look like a dual diode at all !! - where did it come from because it should not have been in D604 position.

I saw a picture of a dual diode replaced with 2 neatly soldered 1N4148 looking glass diodes - I thought it was in your thread but maybe not...

But perhaps more to the point, what have you got in D604 position NOW !?
Click to expand...

Sorry another mistake of mine. You're right it was a red ball with plastic insulator tubes on each leg so it sat up high on the board. I didn't get a photo as that monster cap replacement was laying over it and I forgot to take a photo when I removed it. Yes that dual diode replacement was mine here is the photo again. When I take the board out tomorrow I will take a photo of it as I failed to do that before I put reinstalled it. If I can't find an error maybe you or someone else may discover one.

Thanks.

IMG_0140.jpg
 
I finally got done checking all the parts I replaced on the power and circuit protection board. The last parts I checked were the following:
  1. TR11,12 - 2SA847 replaced with KSA992
  2. TR 9,10 - 2SC1708 replaced with KSC1845
Both were installed backwards. I installed them the same way as the old ones but I didn't know enough to check the data sheet to see if the emitter and collector were oriented the same as the original, they weren't. Do you think they are ruined or I ruined anything else as a result.? Also the capacitors I replaced I have no idea of the specs other than the uf and voltage. Is that enough or are temp specs important. They were C01,02,15, and 16.

Thanks!
 
Please advise the values/voltages of C01,02,15, and 16. - and what board they are on.

You might be lucky and have escaped damage to the transistors - but why not put in new ones anyway? - they are cheap.

The important thing is, do you now have +/- 33V at pins 17/19 - and 23/25 and also at pins 18/20 and 24/26 of the F-2663 PCB ?
 
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