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Returning to Complete Repair of an SA 9500II: an Old Friend

All pots and switches have been cleaned with Deoxit and are drying. Tomorrow I will apply a bit of Faderlube. I considered Mark's method of cleaning, removal from the PCB and disassembling, but decided that this amp is not the one to try a new thing on. I'll just trust that I'll get the Deoxit in the appropriate places and it does its job.

I'm trying to keep this thread alive, but it seems there is still not much interest. I seem to be all alone. :tears: :D I still hope that the contents of this thread will be of use to someone, either as a witness to my failure or my success in this project. More to come in the near future. :banana:
 
Hope yours turns out better than mine. The more I *fix* seems the broker it gets. Have now got no phono output. both channels both sets of inputs. I used to have only right channel gone, before redoing the awf024 board. aux & tuner ok.
you are a hell of a lot braver than me to rip apart this whole thing. good luck!
 
I'm either brave or stupid, Doug. BTW, I visited your thread and it brought up an issue with a question for Markthefixer.

In Moermusic2's thread Mark had indicated a change of cap type for the phono preamp. He said:

"I had the recent opportunity to rebuild a sa-9500ii phono preamp recently, and the owner mentioned that he had heard detail in his vinyl that he had never experienced before..

I did 2 things differently from yours, if you find yourself ordering parts:

use 647-UKL1H010KDDANA 1uf 50v LOW LEAKAGE UKL capacitors
instead of the UPW1H010MDD caps.

and I put in four 5989-100V1.0-F capacitors ($0.53 ea), one across EACH of the 4 big can capacitors in the power supply.

Those are easily added later by popping the bottom cover.

I apologize for not catching the 1uf phono cap's low leakage status sooner. Changing it probably will result in a slightly quieter background. It will not affect the "transparency or detail" at higher frequencies because that 1uf cap is bypassed by the 0.47 uf metallized mylar cap which will dominate the tonal structure."

My questions to Mark are, is it worth it for me to wait to reorder the low leakage cap? Keep in mind that I am not really a vinyl person and rarely use my turntable. Would I be just as satisfied with the standard cap's performance. The second question is; is the 2.2 uf cap I used for the bypass still suitable? Thanks for your attention to these questions when you have time.

Doug, don't give up yet. The more you keep after this problem, the more you will learn. Look for the simple things like a transistor or cap in backwards. If you still plan to buy another amp, always check on the AK classifieds.
 
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The 2.2's are just fine.

The low leakage caps will just make the background noise a bit quieter in the phono stage. If it doesn't bother you, meh...


moermusic2: I was hoping you would get into your own thread with the questions, mixing two repairs in one thread is extremely confusing when handling multiple repair threads. That's why I don't troubleshoot by PM , email or mixes of them and the forum- gathering and separating the information just makes it all the harder, frustrating and disheartening for me. In the past I had been giving the WRONG instructions to the wrong people.
That's when I put my foot down, and ignore hijackings.
I don't mind conversations between the OP and others, just not two different fixes - even if initially related - in the same thread. Every fix deserves it's own thread.

I will violate this only once, right now: double check the lead layouts of every transistor you replaced, and then check them against the symbols on the board. After that we look at the dc power where it is common to both channels coming into the board.You might have to prove to me they are correct photographically, if somebody else can't look at that aspect with fresh eyes. We ARE blind to our own errors.... spellcheckers save my tukus a lot, and when I'm in a hurry, I make the same old spelling errors, no less the key typo's ...
 
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The majority of the components arrived today so the recap will start tonight. I have printed out the foils side images of the individual boards and circled the caps being replaced. When I am ready I will place the correct caps on the correct spot on the diagram. All I have to do is remember that the foil side shot is backwards. I will replace all the caps one at a time and double check myself as I go. I'll install the caps and bend the wires so they can't fall out. When all have been installed, I'll turn the board over and clip and solder.

I know I am narrating this thread like a "See Spot Run" book but I hoping that maybe my description of method will help others who are thinking about doing this; plus I am sort of double checking myself at the same time. In school, I had a habit of rushing through things to get it done. I always made a lot of stupid errors. I'm trying to fight that tendency and simplify my actions to keep the errors at bay.

I'll be finishing another project, a Onkyo TX 4500MkII, after this one and I'll try to finish my thread about that one in the same fashion as this. I have already rebuilt the Amp board and replaced the outputs on that project. All that is left is the PS board. That thread will also include a parts list that I try to make similar to Mark's method of listing.

Just trying to be of assistance to other AKers. :yes: :D
 
Tone control, phono preamp, and the two amp driver boards are complete. The power supply board is tomorrows project minus the relay, which has not arrived. :thmbsp:
 
Just Checking Again

The following caps:

AWS-109 C7 0.68 35 CSZA-R68M 35 667-ECQ-V1H684JL 0.68 50
AWS-109 C8 0.68 35 CSZA-R68M 35 667-ECQ-V1H684JL 0.68 50
AWS-109 C9 0.22 10 CSSA-R22M 10 598-DSF050J224 0.22 50
AWS-109 C10 0.22 10 CSSA-R22M 10 598-DSF050J224 0.22 50

show to be polar in the schematic, but the replacement caps are non-polar. I don't know about whether that is acceptable. Mark, I would assume that it is; or you would not have recommended the film caps in the first place. I am going to run on that assumption that this is okay to do, but if I could get a confirmation from Mark or others that this is suitable, before I fire this thing up in a few days, that would be appreciated.
 
I have discovered an issue on the power supply card that appears in a strange location, in the tape monitor loop. Here is a blowup of the foil diagram from the SM.

OverheatedTraceSA9500II.jpg


The trace between pins 12/13 and pins 4/5/6 gets very very thin at one point. At this point there is signs of overheating. The trace has lifted very slightly in one small place and a good 1/2" to 3/4" of the trace is brown and burned looking.

My gut instinct is to solder a jumper between pin 12 and 4 just to have a backup and to take up some of the slack in the current flow at that bottleneck. If anyone cares, would that be a reasonable safety precaution? One of the solder joints, on the second switch in, looked a bit stressed from heat; so I have touched and refreshed it.

This appears to me to be a bit of a PCB design flaw. The trace is just so tiny that it cannot handle the load that is expected of it. It also has a very sharp bend in it. I know, from house wiring, that bends in the wire will heat up first.

By the way.......The recap is complete and I am now just doing a double check and full visual check of all boards. :banana::banana::banana:
 
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mtf here at Robie's at the Chicagoland get together..

Yes, solder in a jumper for the burned trace.

Try to follow the original path, watch out for ground traces in between lines that act as shields for crosstalk. THAT could be a ground trace... I can't look closer now...

The caps are non polar and will never need to be replaced. No preferred lead orientation. They are superior substitutes.
 
Mark, thanks for sticking with me. I appreciate you. The matter of whether to add the jumper became a moot point when I started to clean up the resin from soldering, the trace floated up with the alcohol. I tried my best to follow the path; a pretty tight squeeze.

Tonight I recheck all solder joints on all cards and check all orientations on all caps that I replaced. This is tedious as hell to me, but I already found one backwards cap and two solder points that I missed; so it is necessary.
 
Well at long last the unit is going back together. Aside for a couple of iffy solder joints and one spun cap the overall job double checked just fine. One issue reared its head, but I knew it would. Due to the constant repositioning of the chassis, a number of wire wraps took a beating and had to be soldered. All of them were on the phono preamp. The soldering on the wraps looks a little haggard, but the connections now seem to be solid enough.

I have the inner faceplate on and the bottom attached. The phono preamp, the tone control board and the power switch and light are reinstalled. The bottom plate is on, which is good because it gives the chassis a good bit of stability. With all the plates removed, the power supply board was constantly in danger of damage. It got through okay. I was as gentle as I possibly could be.

Tomorrow I will reinstall the amp boards onto the heat sinks and reinstall the new output transistor with their accompanying brackets onto the heatsink. At that point it will be, drag out the dim bulb tester and see if I did a good job. I feel reasonably confident that I did everything correctly. I just have to put the PNPs and the NPNs in the right spot. To make that easy on myself, I marked the heatsink 2 years ago when I pulled the outputs. I also pencil marked the new output transistors with PNP or NPN when I received them a few days ago. I located and counted my micas, which I stored 2 years ago and they are all still present. I cut down the old Batwing Micas to fit the TO-220 transistors outline.

I'm once again keeping my fingers crossed. :yes:
 
I'm Skeered!!!!:eek: I started with a 25 watt bulb in the dim bulb tester and it acted normal. I switched to a 60 watt bulb and the bulb oscillated about three time up and down and then settled down. Right now I am sitting with the 100 watt bulb in it. The 100 watter did the same thing, a few minor oscillations and now it is stable. The relay has not kicked in and the on light is glowing ever so slightly.

I am afraid to go on. Should I look for a higher wattage bulb to see if the relay will kick; or should I just jump in with both feet?

I have been running with the 100 watt bulb for at least 10 minutes. I'm guessing if something was gonna blow, it would have done so by now.

Should I go on? Is the symptomology sounding correct to anyone else. I guess I am just a wimp.:nerd:
 
Well, I'm not a wimp, but it fired it up and blew a fuse. I'm waiting for the caps to discharge and then I'll see which fuses went. Pooey! :thumbsdn:
 
Sometimes you just have to take a leap of faith. I had the same fears a little while back when I repaired my 3800. DBT with 100 watter with no issues and then it was time to go for broke. This was after I checked, doubled checked and triple checked my solder joints and a repair job for a pin that snapped off. Yeah, I was sweating bullets but she is singing in my living room and sounds great.
 
It was fuse one only that blew. At this point, I'm not sure where to start and right now is not the time to do it. I will take a day off and come back on Tuesday refreshed. Any hints would be appreciated. Thanks. :tears: First glance at the foil diagram and it appears to be an issue on amp board left, AWH-052 L.
 
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Q2, the former 2sc1903 150v 50mA 1watt 150hfe 130mhz?

what replacement did you use?

Actually, please list them all, and I HOPE that the 1116 and 1616 aren't in that list, except for the final transistors in the protection circuit, i.e. current dump and relay drive...
 
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I used these, as per your comment on page 1 of this thread:

(more powerful to-220 replacements for the batwing transistors...
512-FJP1943OTU pnp to-220 bce 230v 15a 80w 30mhz 80-160hfe $1.21
512-FJP5200OTU npn to-220 bce 230v 15a 80w 30mhz 80-160hfe $0.85

I replaced the drivers with:

863-MJE15033G pnp to-220 bce 250v 8a 50w 30mhz 70hfe $0.87
863-MJE15032G npn to-220 bce 250v 8a 50w 30mhz 70hfe $0.87

All other transistors on the AWH-052 boards were tested ans found to be okay.
 
KingBubba said:
I used these, as per your comment on page 1 of this thread:

(more powerful to-220 replacements for the batwing transistors...
512-FJP1943OTU pnp to-220 bce 230v 15a 80w 30mhz 80-160hfe $1.21
512-FJP5200OTU npn to-220 bce 230v 15a 80w 30mhz 80-160hfe $0.85

I replaced the drivers with:

863-MJE15033G pnp to-220 bce 250v 8a 50w 30mhz 70hfe $0.87
863-MJE15032G npn to-220 bce 250v 8a 50w 30mhz 70hfe $0.87

All other transistors on the AWH-052 boards were tested ans found to be okay.
Click to expand...

Ok, Then it was an original transistor.
 
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