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SA-9500 rebuild complete but fuse blew when testing, please help!

Well I finally received the fuses, it did not pop the fuse with the original outputs re-installed. So there is deffinately a problem with one or more of them. Thanks again AU-9900 from hell.

Now the problem, the relay is not kicking in, grrr. Is it possible that the shorted outputs caused something else to short or blow? I was incredibly careful when I installed the transistors and checked them 5 or 6 times each, at least. It is possible that one snuck by me, but still.

The only thing I was unsure about, was the two ksa940tu transistors in the power amp board that I substituted for MJE15033g. I never received an answer as to if it was okay though. I used it because it is listed as a sub in an old thread.

Now I guess I have to take the tops off again and go through each bloody board. I knew I should not have put the screws in until it was working.
 
Segasonic91 said:
Well I finally received the fuses, it did not pop the fuse with the original outputs re-installed. So there is deffinately a problem with one or more of them. Thanks again AU-9900 from hell.

Now the problem, the relay is not kicking in, grrr. Is it possible that the shorted outputs caused something else to short or blow? I was incredibly careful when I installed the transistors and checked them 5 or 6 times each, at least. It is possible that one snuck by me, but still.

The only thing I was unsure about, was the two ksa940tu transistors in the power amp board that I substituted for MJE15033g. I never received an answer as to if it was okay though. I used it because it is listed as a sub in an old thread.

Now I guess I have to take the tops off again and go through each bloody board. I knew I should not have put the screws in until it was working.
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Did you check DC Offset at the power amp output pins? It could be off enough the protection won't engage the relay. And did you set the BIAS current? Changing transistors will change everything.
 
I did not not do the bias yet, I did not want to leave it on too long without the relay kicking. Did that on my 7500 and then BANG! Pop went a cap that was in the wrong way around. Have not been able to get it to work since.

But anyway, I am embarrased to say that when I was taking it apart and inspecting the boards again tonight, I found two caps on the control board that were wrong. I somehow put a 100uf were a 4.7uf should have been (because I was 5 short on the WIMAs, need some caps in there until more arrive), and also have a cap in backwards. Sheesh. This is what happens when I do this work tired. I will change them in the morning and check the rest of the boards for any mistakes.
 
Wow, I do not know WHAT I was doing with that board! Can't sleep, so I decided to fix those two caps now. I discovered that beside each of the 1uf WIMAs, I installed 100uf 25v instead of 33uf. Fixed those, plus the other two but still no joy. I will thoroughly go through each board tomorrow to see if I can find anything else. Once I am happy that all caps and transistors are installed correctly I will tune bias and voltage. This will teach me not to check the amp after each board. D'oh! It is too difficult to get the stepdown out to where I was working on tue amp, so I did not do it.

I made little baggies of all the caps for each board ahead of time, so I must have been incredibly tired when I did that board.... Keep telling myself not to do these things while being over tired from no sleep!
 
nicholas2381 said:
Keep at it - you'll get it up and going soon!
Click to expand...

Thanks man! Appreciate it!

Starting a new job today, so I have been busy and have not looked at it again as yet. Will probably look tonight IF I AM NOT TOO TIRED! Haha!! If I am, I will wait until tomorow.

Edit: Should mention the MJE15033g again. Is this okay to use in the power amp board instead of the ksa940tu? If not, that could be the problem right there. It was in a substitute list for Sansui, but I figured it would not any different in another brand of amp.
 
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Segasonic91 said:
Thanks man! Appreciate it!
Edit: Should mention the MJE15033g again. Is this okay to use in the power amp board instead of the ksa940tu? If not, that could be the problem right there. It was in a substitute list for Sansui, but I figured it would not any different in another brand of amp.
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It's not the "brand" that matters, it is the circuit design that matters. If you replaced the PNP transistor, you should always replace it's compliment NPN transistor so their characteristics play well together. In this case, the NPN should be MJE15032G.
The MJE are a 30MHz minimum ft.
The NEC originals are 40/45MHz "typical"
The KSA940 is only a 4MHz
The MJE are the better suited substitute for this circuit design.
 
Skywatcher said:
It's not the "brand" that matters, it is the circuit design that matters. If you replaced the PNP transistor, you should always replace it's compliment NPN transistor so their characteristics play well together. In this case, the NPN should be MJE15032G.
The MJE are a 30MHz minimum ft.
The NEC originals are 40/45MHz "typical"
The KSA940 is only a 4MHz
The MJE are the better suited substitute for this circuit design.
Click to expand...

Ahhh, should be 32, not 33.... Thanks very much! I will swap them out. Would that be something to stop the relay kicking in?
 
Segasonic91 said:
Ahhh, should be 32, not 33.... Thanks very much! I will swap them out. Would that be something to stop the relay kicking in?
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I am surprised the smoke didn't fly if you put a PNP where an NPN belongs. They are opposite polarity. And there could be unknown collateral damage because of it anyways. And yes, the relay wouldn't kick in.
2SB536 is a PNP and gets replaced with the MJE15033G.
2SD381 is an NPN and gets replaced with the MJE15032G.
2SA and 2SB are PNP
2SC and 2SD are NPN.
KSA (and KSB) is PNP
KSC (and KSD) is NPN
 
It was the 2SB536 that I replaced with the MJE15033G, because I did not have the KSA940TU which was listed in the thread I was looking at with per board item subs. Did I say 2SD381 instead of 2SB536? As tired as my brain is, it would not suprise me. But I am not quite silly enough to put a NPN in place of a PNP or vice-versa :) I hope so, anyway!

EDIT: Ahhh, I think it is because I mis-read your post and replied with "ahhh, it is 32, not 33. I will swap them out". Sorry for the confusion!

I should be putting the MJE15032G in place of the 2SD381 so they match is what I get from your post. It currently has the KSC2073TU, so yeah, in need of changing to match. At least this time there will be no damned glue to worry about on the heat sinks, it was very tough.
 
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Finally got back to looking at this yesterday, and everything was correct, but still no luck. I installed 32Gs as well. There was a wire that had disconnected from a wire wrap which I fixed, but still nothing! I double checked the connections on the board I had lifted traces and pads on and everything seems to connect so I am very stumped. Also very annoyed. That one damned board was the only one to have problems.

I may go to the plan of setting the voltages to see if that helps. I just do not want to leave it on too long with the protection not kicking in. Just in case there is something I missed. I still don't have my DBT back and I also still have not found adaptors so I cannot use it anyway. I have not checked voltages yet, which I really should.
 
I tried to set the bias yesterday on this amp, but it would not set. On VR1 it kept climbing and jumping around, it would not steady. Same for VR3. VR2 and 4 did not respond at all.

Would this indicate something is wrong in the power amp section? Or just that there IS a problem? I discovered another wire that broke off from the idiot wire wrap yesterday. Hoped that was the missing link, but nope. I am thinking that over the weekend, I will pull the power amp section out again and uninstall and re-install all the transistors. Just to make sure they are all in correctly. The board is different to the SA-9500, so I cannot compare photos to see if everything is in correctly like I could with the other boards.

I still think there may be a problem with the control board which is where the traces lefted and pads fell off. That was the one and only board that had a problem. The board gives solid connectivity with my DMM though, so it SHOULD be good. I checked all the wirewraps to make sure there were no other missing wires and they seemed okay. I tried soldering the wraps to secure them, but the solder refuses to melt to the wire.
 
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