Re-do an SA-6500ii?

Panamafred

Panamafred

AK Subscriber
Subscriber
Hey guys! Picked up an SA6500ii at a yard sale last weekend and seeing as how I'm loving the sound of the re-done 737, I kind of want to re-do this one. It already runs fine, but I do so enjoy having a project running in the basement.

It looks like there is a lot less going on in this unit than the 737. Was thinking of ordering the caps from this list http://www.audiokarma.org/forums/showthread.php?t=415827 , they are all ready to ship, have there been any changes to the list? Are there any problematic transistors in this one?

Cheers!
 
That will be a nice project. The list is not that old but I would PM the member who's thread you linked. Ask him if there is any thing he would do different?
I think you got the bug!!
Good link as well.
 
I took a cruise around the sa-6500ii

no problematic transistors
(don't like the way they did protect, no relay, deliberately blow main fuse - but that's another matter)
cap list is unchanged.

Have Fun!!
 
Thanks Mark, parts just arrived today and I was noticed that the filter capacitors are secured to the heatsink, I don't think that the replacements are going to fit quite like the originals. Cosmetically it's not a concern but will this affect the functioning of the receiver? Thanks!
 
For the record, replacements seem to have worked just fine without fastening to heat sink. Recap went well and everything checked out on the DBT but has not fared so well after bringing it up to the mother ship.

One speaker channel is pretty seriously distorted, have checked for loose solder joints and see none. Am thinking it could be the idle current. As per the service manual I measured between TP1 and TP3 and got 22mv between TP2 and TP4 0.00mv.

The service manual is instructing me to "cut the jumper lead" if the voltage is less than 10mv. I believe I've located the jumper lead but this seems extremely un-scientific and I am hesitant to just start clipping.

Well, at least the other channel sounds awesome!:thmbsp:
 
Panamafred said:
The service manual is instructing me to "cut the jumper lead" if the voltage is less than 10mv. I believe I've located the jumper lead but this seems extremely un-scientific and I am hesitant to just start clipping.

Well, at least the other channel sounds awesome!:thmbsp:
Click to expand...

Desolder one end and leave it hanging. Tape it if you're afraid of unintentional contact, or just snip the bare metal. Remember, you can always make a new jumper from some other wire. the same procedure was listed in the SX-780.
 
Okay, thanks. I just removed the jumper lead and the voltage between TP2 and TP4 still read as 0.02mv. Where to next, any ideas?
 
Finally got some time to give a little love to the 6500ii. Was double checking my work and I found 2 caps backwards. I corrected it and I am still getting a reading of basically 0mv between TP 2 and 4 whether I cut the jumper or not.

I noticed that each channel seems to be missing a capacitor. I have uploaded a picture and pointed out with red and yellow arrows where it is uneven between sides. The values of these caps are the same. I switched the position of the capacitor on the side of the bad channel to match the side of the good channel but this did not effect anything. I have now returned everything to it's original position.

Any ideas on how to proceed on trouble shooting this thing? Thanks in advance!


 
Did you do anythings else? Like change some transistors?
Look at C78 and C79 for any issues.
Pioneer will leave out caps on occasion, normally they solder over the holes (Not always).
 
All I did was replace capacitors. Will check C78 and C79. I'm just at a loss for how to even start troubleshooting.
thanks zebulon and everyone else
 
post voltages (ebc) on all the transistors in the power amp; q8, q10, q12, q22, q14, q16, q18, q20

then the base to base voltages of q14 to q16, and the q18 to q20

you can compare them to the corresponding transistors on the other channel.
 
Mark , I really appreciate the detailed help here, I'd be lost without it. Sorry it took so long to get the readings, I've had my "family man" hat on this weekend. Good to have my "AK' hat on this afternoon though!

Q8
E: .61
C: -39.5
B: .024
Q10
E: .59
C: -38.8
B: .029
Q12
E: -39.3
C: -1.13
B: -38.8
Q22
E: 33
C: 1.28
B: 32.5
Q14
E: -.51
C: -34.8
B: -1.11
Q16
E: .685
C: 34.9
B: 1.26
Q18
E: .015
C: -34.7
B: -.5
Q20
E: .016
C: 34.7
B: .685
Base to Base Q14/16: -2.4
Base Base Q18/20: 1.2

I measured all of these by securing the black probe to the chassis turning the power on and touching the red probe to the legs of transistors. All readings are VDC.
Do any of these jump out as strange to you? I gather the next step would be comparing the readings off of the opposite side of the board. Please let me know what you think, tanks alot!
 
Was about to start comparing to the other side and was measuring Base to Base voltage between Q17 and Q19. I guess the probes weren't insulated as well as I thought they were. :no:
Magic smoke from the back, blew FU3. Replaced FU3, blew it again. I guess that means a new set of output transistors, right? :no: Has got me wondering if it's even worth it.

There are a couple of reccomendations thrown around in this thread. http://www.audiokarma.org/forums/showthread.php?t=536051 is this a good start?
Let me know what you guys think, maybe there's a better replacement out there
 
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The parts aren't that expensive...

But there is a HUGE difference between the sa-6500 and sa-6500ii

you aren't anywhere near ordering replacement parts yet.
 
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Thanks for hanging in there with me Mark. Was I on the right track at least, measuring and comparing voltages from the opposite side of the board? Will I be able to do this without the outputs? I measured voltages on the output transistors after the short-out and they were damn near zero which doesn't seem right to me.

If I don't hear otherwise, the next chance I get I will read and post the readings from the corresponding transistors.
 
with the short - everything on that channel is suspect.

The parts are really inexpensive, we'll end up building pretty much two "new" power amp channels.
 
Alright, coincidentally the short occurred on the channel that was actually working. :bs:

I will keep poking around (with better insulated probes) and try to figure out what is going on on the original bad side. Thanks Mark, good morning
 
we were starting a search for a bad transistor or bad resistor.

new transistors on BOTH sides for symmetry and during replacement ALL resistors will be checked.
 
Okay, Mark. I have no idea how to find proper replacements for the transistors, I'm hoping it won't be too much trouble for you to put that list together.

If so I will begin to look into the absolute basics of replacing transistors. If I can figure that out I will absolutely run the list by you before even thinking about placing an order. Thanks you for helping this rookie out, I really appreciate it.
 
Just look into the installation of the replacement transistors...

I will be providing YOU with the list of replacement parts.

I have to reverse engineer it, not too hard because it is simple and straightforward.

I'm about halfway done, the biggest question is what are the output transistor's mechanical mounting constraints, i.e. space available between the "height" of the area available, as well as the "width" available between the two batwing mounts, or do I remember seeing some to-3p's / to-247 (larger transistors) mounted SIDEWAYS on a heat sink somewhere? (and covered the other "batwing" hole...)
 
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