• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

Pioneer SX-9 Where to start, if at all

that's a bump...

it's gonna take a while to get an answer from me, it's crunch time here for the next week or more meeting inflexible committments - I am painted into a corner and something's gotta give... and I'm probably gonna be snowed in too, for a while... posts are gonna suffer - there only so much of me to go around.

wewill try different nsa transistors or lowering the nsa thresholds a bit - since these are NOT the original output transistors.

THAT will take some thinking and figuring on my part.

The thresholds on the replacements are probably a bit lower than the originals. Millivolts, but they are enough in the wrong spot.
 
Weeber, sit back and chill awhile, and Mark can get you dialed in soon.

This thread is like a great Agatha Christie mystery. Gonna be cool when you have that thing rocking.
 
Chill, wish I could too....

When I started the AM alignment on the current SX-1980, the AM generator's internal 400hz oscillator wasn't working, so I had to fix THAT.

Now with all the snow, I gotta FINISH fixing my snowblower....

it never lets up.... sigh:
 
Found these output transistors in my saved parts pile they tested good if you can use them they are yours
 

Attachments

  • IMG_0775.jpg
    IMG_0775.jpg
    69.8 KB · Views: 44
Last edited:
sawdust said:
Found these output transistors in my saved parts pile they tested good if you can use them they are yours
Click to expand...

Wow, that's very generous. Thanks Sawdust, I'll keep that in mind.

By the way I think the wood cases you make look amazing! Are you back making them? I've got a RT-707 that's feeling a bit cold.
 
onwardjames said:
Weeber, sit back and chill awhile, and Mark can get you dialed in soon.
Click to expand...

I'm gonna chill like a penguin on an ice cube. :smoke:

In the meantime I have a couple questions I need to ask to satisfy my curiosity. These aren't just for MTF, anyone can chime in with knowledge on audio amps.

I notice the SX-8 produces 100 watts, the SX-9 makes 125.

The power supply and amp boards are practically identical, in fact I can't see any differences.

The rectifier board is different. The filter caps are smaller on the SX-8 and it only has 4 total output transistors, while the SX-9 has 8. But the SX-9 has transistors like those pictured in Sawdust's post, while the SX-8 uses the same Sanken types I've used as replacements in the SX-9. The board itself actually looks the same (even has the empty spaces for the extra transistors) just has different components.

My questions:
1) Is that where the extra output comes from, those 4 extra transistors?
2) Why change the type form SX-8 to 9, when everything else seems exactly the same?
 
two outputs per channel versus 4, plus somewhat higher unregulated voltages and the obligatory doubled (or more) heat sink area.


125w into 8 ohms is 32.62v
100w into 8 ohms is 28.28v

Read this

why do the sx-3800 versus the sx-3900
why do the sx-d500 versus the sx-d7000

compare them, there are downloadable manuals.
 
I decided to follow what this person did with their SX-3900: http://www.audiokarma.org/forums/showthread.php?t=540812&page=2

I replaced R138, R141 & R140, R142, all 220 Ohm resistors, with 240 Ohm resistors.

After this, the idle voltages on both channels fell to below 56mV, the starting point for adjustment. They started off around 42mV when first turned on and increased to about 51 after a few minutes before they stopped. I adjusted everything correctly and let it run for about 20 minutes, then repeated the procedure.

Once fully set I hooked up some speakers. The right channel sounded great, but the left channel was muted and scratchy :no: Disappointment! What now!

I noticed that both channels sounded fine when mono was selected however, which to me sounded like pre-amp issues, not power amp. So I hooked up my SX-3800 as preamp and BAM! perfect sound!

I hoped that all was needed then was a good De-Oxit job. Well, I gotta say, taking this thing apart to access the switches is a major pain! (Quaddriver knows what I'm talking about). De-Oxit job done, buttoned it all back up.

Well I'm happy to say ITS ALIVE!! :banana::banana::banana::banana::banana:
(been waiting a long time to use that banana)

Thank you so much Mark The Fixer for your help and tutelage, there's no way this could have happened without you guiding me and giving advice.
 
Oh, here's a pic!

4a6387bf49f660bde31f5c73326bb9f2.jpg
 
Excellent! Now dont forget to burn in the new capacitors!

I have not forgot about mine, I have my parts list but Im building it for my next order since its coming from 2 places - gotta dilute the shipping charges (Im trying to burn off some of the tube sets waiting - not literally - burn off means to me work on!)
 
Weeber, glad to see you were finally able to resurrect the amp! Now, how does it sound with the CS-99A's? I have a pair of those and love them!

Enjoy!
 
quaddriver said:
Excellent! Now dont forget to burn in the new capacitors!

I have not forgot about mine, I have my parts list but Im building it for my next order since its coming from 2 places - gotta dilute the shipping charges (Im trying to burn off some of the tube sets waiting - not literally - burn off means to me work on!)
Click to expand...
I'll be keeping an eye out for the rest of your thread. I'm interested in seeing how it turns out.

PLUS, if I ever want to torture myself again I'll have instructions on what to do. This amp in constructed like some kind of engineers mind puzzle. Crazy.
 
onwardjames said:
GREAT JOB, WEEBER!!!

I'd rock that amp. Looks cool.

How does it sound now??
Click to expand...

Thanks, onwardjames, I'm happy I can finally give you closure on this. :)

The amp actually sounds really good. Very clear with really deep bass. I'm surprised how much I like it given the amps fugliness.
 
rustycat said:
Weeber, glad to see you were finally able to resurrect the amp! Now, how does it sound with the CS-99A's? I have a pair of those and love them!

Enjoy!
Click to expand...

So far I've only tried it with my Polk Monitor 10s, which sound really good. I'll have to try it with the cs-99As for sure.
 
sawdust said:
Found these output transistors in my saved parts pile they tested good if you can use them they are yours
Click to expand...
Hi! do you still have this transistors ? I am looking for the same transistors trying to fix my two Pioneer A9 ? Please let me know if I can buy it from you.
 
Carguy1394 said:
Hi! do you still have this transistors ? I am looking for the same transistors trying to fix my two Pioneer A9 ? Please let me know if I can buy it from you.
Click to expand...

Sorry most of my old and spare parts got tossed when my shop got cleaned after my stroke
 
You must log in or register to reply here.
Back
Top Bottom