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

KingBudda,

I just found this thread. I have much respect for anyone you dives in to this type of repair work.

I have an SA9500 that exhibits a hum in the right channel. I have often considered doing the repair work myself. However, I am a complete novice and I am concerned about doing repair work to such a nice piece of equipment such as the 9500.

I will follow your progress with interest.
 
Mark, your advice is heeded and I'll forget about a pre test and just move on with the project. Rkran, thanks for the encouragement and support. I don't know if I'll end up with a smoking heap, but I'm sure going to try my best to be careful, methodical and try my best to learn everything I can from this experience. It's a shame it had to be this amp that I screwed up because it has always been my favorite, but it was just sitting in a pile of parts for two years. It wasn't doing me any good that way other than to gnaw away at me. Time will tell.
 
9500 ll

This Sat., my 9500 ll awf 024 board is going to be operated on. It is entrusted to a friend (telecomms tech), who hopefully has a much steadier hand than me with a *iron*. Mark gave me a list of trans, resistors, and caps to replace to try & bring back to life the right channnel phono inputs. In the meantime, I purchased a second 9500ll which is fully operational. Have the parts to do both sides. Hopefully all goes well. :thmbsp: :scratch2: Guess I dont know how to do just a partiall quote.

{I have to say that I am surprised that more people have not visited/posted in this thread. It may be that not to many AKers have the 9500II. All comments are welcomed here. I'll keep this thread updated as I progress.}[/QUOTE]
 
Thanks for the post moermusic2. Having two of these would be a blast, literally.

Just a minor update. I had tested resistors on the AWH-052 board and some showed as bad. They are not. The problem was the use of my old meter that does not autorange. Operator error. New resistors will go in those spots anyway.Today I tested them with my Fluke after removing them and they were still good. I remember something about the right tool for the right job. Hmmmmm!

I picked up a selection of Bourne multi turn pots today and one of them fits as a perfect replacement and I have lots of 100ohm spares. I have turned them to full resistance but wonder if I should be better off to start with them at around 50ohms. Any opinions on this from the members?

Well, back to reassembly on the amp boards.
 
My soldering skills leave much to be desired. The left amp board is complete and checked. Unfortunately I damaged two traces slightly. Pioneer has very thick traces compare to the Onkyos I have worked on. This factor saved me.

I used a magnifying glass to inspect for flaws in my job. A few of the early solder joints seemed to raise up like a Hersey's Kiss, I turned the iron down and that seem to help with the issue. I am set around 48 watts. It might still be a little hot, I'll have to experiment carefully. Any suggestions here would be very appreciated. I'm also going to start a soldering thread.

I did not get done today what I thought I would, Maybe tomorrow will be better.
 
Getting the iron adjusted is not always that easy.
You want it to be warm enough so you don't need to be on the joint for an extended time. But by the same token if it's too hot what you experienced will happen.

Just hot enough so you can heat both the pad and part and have time to cover both completely.
Practice, Practice, Practice
 
KingBubba said:
Thanks for the post moermusic2. Having two of these would be a blast, literally.

Just a minor update. I had tested resistors on the AWH-052 board and some showed as bad. They are not. The problem was the use of my old meter that does not autorange. Operator error. New resistors will go in those spots anyway.Today I tested them with my Fluke after removing them and they were still good. I remember something about the right tool for the right job. Hmmmmm!

I picked up a selection of Bourne multi turn pots today and one of them fits as a perfect replacement and I have lots of 100ohm spares. I have turned them to full resistance but wonder if I should be better off to start with them at around 50ohms. Any opinions on this from the members?

Well, back to reassembly on the amp boards.
Click to expand...

On THIS type of bias circuit, you start at 0 ohms for minimum idle current. More ohms is more idle current, and you could accidentally be dialed in for TOO much idle current. It could go class a on you.....:D
 
Thanks Mark, saved my ignorant a** again. I made an assumption that more resistance on the Bourne pot was the way to start. Would this be true of other Pioneers, as the time to also do my SX 1250 and SX 1280 is nearing? Also, many thanks for your time applied to the mouser order #s. It made it so easy to copy and paste the order #s right to the Mouser site. Thanks.

The Mouser order went in today and in addition I added the stuff for my Onkyo TX 4500 and 4500mkII to kick back on shipping. Hopefully the backorder mentioned will be for the TX stuff.

Not much else got done today, but we'll see what I can do this evening. Keep the comments and suggestions coming folks; they are welcomed.
 
KingBubba said:
Thanks Mark, saved my ignorant a** again. I made an assumption that more resistance on the Bourne pot was the way to start. Would this be true of other Pioneers, as the time to also do my SX 1250 and SX 1280 is nearing? Also, many thanks for your time applied to the mouser order #s. It made it so easy to copy and paste the order #s right to the Mouser site. Thanks.

The Mouser order went in today and in addition I added the stuff for my Onkyo TX 4500 and 4500mkII to kick back on shipping. Hopefully the backorder mentioned will be for the TX stuff.

Not much else got done today, but we'll see what I can do this evening. Keep the comments and suggestions coming folks; they are welcomed.
Click to expand...

You need to check the manaul. Other amp circuits can be different. Like the NSA amplifiers. Doing something wrong there can be really bad news.
 
I only have one NSA amp that I know of, the SX 3800. I set bias and offset on that with no issues, but then again I did not dig into it very far, having read some of your posts about the 3800/3900 units. I guess in the future I'll figure what needs to be by setting the old pot where the manual suggests and taking a ohm meter reading on it.
 
Last edited:
good strategy.

the gotcha would have been on the earlier 3600's etc - they use something called a Vbe multiplier for bias control - a COMPLETELY different animal...
 
Just an update. The right side AWH-052 board is completed. Following Echowar's suggestion of sliding the iron away from the work, not lifting, and turning the iron down just a tiny bit more I find my solder joints look pretty good. Now I wait for the Mouser order to arrive and I will continue with the recap. My temptation is to go ahead and remove them all now, but I won't. I have found it is easier on the brain to remove and replace one cap at a time. It is probably a safer habit when it comes to assuring I reinstall the new caps with the correct polarity orientation. I have all the pics to refer to in case I have a memory issue or a discrepancy between the board marks, the schematic, and what was actually installed.

I also have considered retouching all solder joints, but the solder joints on the 052 boards look so good, I think if it ain't broke I'm not going to try to fix it. I'll have a good look at the power supply board and make my decision about that one later.
 
The operation on the 024 board went pretty good. All 10 transistors and most of the electro caps replaced. We also replaced my stranded wire bridge with a solid wire. ( All due to me breaking the trace awhile back when replacing 2 burnt resistors. About an inch & a half of wire.) After reading the soldering threads, without all the washing,washing , what might be readily available for the ave. consumer to touch up all the new flux? Then see if I can member how to reassemble. Then ask if just plug in and see if all the inputs work.
Doug
 
Mark: replaced all 10 trans., C1,2,17,18,21,22,31,32,&35 on Awf 024. forgot to do C9&10. But those cant be critical as both tape play, tuner, & aux work. Now, neither channel from both phono inputs work. Reoxied function sw. Tracks all look silvery vs the unused portions of the wafers. Am not or can not hear any signal thru spkrs by touching/jiggling C1,2,21 or22. Where do you think I go from here? thanks
Doug
 
KingBubba said:
I have been considering adding bypass caps to the filter caps on this unit. Any opinions on this?
Click to expand...


it's worth a try, these

5989-100V1.0-F 1 100

are about 50 cents apiece... and a sa-9500ii I did the phono amp and these was well received by the owner.
 
In another thread, Mark answered my inquiry about a replacement relay for this unit. Here is his response:

"from my records:

----------------------------------------------------------------------------------------
----------------------- my4-02-dc24 pcb pins no ears -----------------------------------
----------------------------------------------------------------------------------------
---- 4PDT ------------- omron my4-02-dc24 mouser part number 653-my4-02dc24 ------------
----------------------- 4pdt 24v yes flash suppressor no indicators --------------------
---- PCB -------------- mounted by PCB pins - no arrangements on case ------------------
----------------------- pcb pins (narrow) ----------------------------------------------
----------------------------------------------------------------------------------------
----------------------- possible substitute 769-HC4-HP-DC24V ---------------------------
----------------------------------------------------------------------------------------

you will have to cut away the row of normally closed contacts, as there are no solder pads for them.
should be an exact fit...

edit: mouser has about 40 in stock at slightly less than 6 bucks apiece... "

Echowars also added this info:

"According to the SM, it looks to be a 4PDT 24V PC-mount relay. Mouser and Digikey both sell Omron replacements." http://www.audiokarma.org/forums/showthread.php?t=90275
 
As far as the bypass caps. I had some spare 2.2uf metalized polyester film caps left from a previous Mouser order. I used them. We'll see how this thing sounds when it is complete. (Fingers crossed). :yes:
 
Just an update. All caps have been desoldered but remain in place for one at a time replacement. The new relay has been ordered and the old one has been removed. With the spaghetti of wiring that accompanies every move and board, I am surprised that I only nicked one piece of insulation with the desoldering iron. The iron is awkward and a bit of a PITA to use, but I am getting better.

The two transistors on the PS board have been removed, resiliconed, tested and resoldered. They obviously get quite hot because the aluminum heat sinks have actually turned a purple color, as if they were anodized. It is quite unusual and remarkable. The PCB is slightly browned but only slightly; so it appears that the heat sinks are doing their job. I have some old chipset heat sinks. I was considering cutting one in half and JB Welding it to the original heat sinks. Anyone have any thoughts on this?

Now I await the arrival of the parts.
 
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