SA-6500 II restoration

[Trw]

hifiengine (free registration) has the SA-6500ii service manual: https://www.hifiengine.com/hfe_downloads/index.php?pioneer/pioneer_sa-6500_mk2_service.pdf

The phono stage is not transistors, it is one integrated circuit : TA7136P1 per channel. Behind the tape monitor jacks.
Runs off of +21, -16v resistor derived from the Zener regulated + & - 24v power supplies

There is only one set of phono jacks, so they run directly (unswitched) INTO the phono preamp stage.
AWK-083 pins 3(L) & 4(R) are the Phono INPUT, while phono output is at AWK-083 pins 13(L) & 14(R)
Output is switched by function select ( PHONO, TUNER< AUX) rotary switch.

C1, C7, C21 left channel
C2, C8, C22 right channel
C1, C2 are tantalum, replaced with Nichicon UKL
Rest were low noise, also replaced by Nichicon UKL.

Not much to fail .

I'm getting some music but it has a crackle not disimilar to Sansui Au-101's common transistor fault hence suspecting the transistors

 

[Trw]

 

[Trw]

Not that i can make much sense of it! though i thought it may be of use to someone

 

[markthefixer]

Describe the crackle further: is the crackle occurring on both channels ? (L or R or both) If so, at the same time? IF so, the common power supply has a fault.

Or is it only on one channel (L or R) ? Does it overwhelm the music? Or is it just heard in the music? Can it be heard without ANY music going through the system?

Did you deoxit the switches?

 

[Trw]

Describe the crackle further: is the crackle occurring on both channels ? (L or R or both) If so, at the same time? IF so, the common power supply has a fault.

Or is it only on one channel (L or R) ? Does it overwhelm the music? Or is it just heard in the music? Can it be heard without ANY music going through the system?

Did you deoxit the switches?

It can be heard in the music,it comes and goes it seems to effect both channels (moreso the right channel i think i also sometimes suspect that the right channel is a little quieter) i haven't noticed it without a signal although i would say that it's quite a loud backgroud hiss (i'd expect quieter)

I've cleaned the selector although i've not disasembled it

 

[Trw]

I've reflowed the pcb tonight and it's made quite an improvement what i did notice was at low volume the bass seemed a little distorted i then engaged the loudness button and everything improved dramatically..i'm now suspecting a failing cap so i think assuming i can locate all the caps Mark mentioned i'll swap them out.

Many thanks everyone

 

[Trw]

Update..further testing from cold the issue seems to be in both channels at the same time which as Mark suggested is a common power supply issue.

Where do i start looking.. Caps?

 

[Spenser]

...crackling popping you know is a failing transistor symptom. Maybe try Conrad Hoffman's poor man's method (alternative to 'freeze spray' unless you have some of that), rubbing alcohol on a Q-tip technique (with extreme care of short-avoidance it's conductive), to help ID / rule out possible power supply transistor culprit?

I apologize I'm still in the middle of moving and haven't looked at the service manual.

Nice little amp and well worth the work.

 

[Spenser]

I do recall the problem with mine was bad transistor in one channel in the power amp. Embarassed to say never did figure out which one. Shotgunned.

 

[Trw]

One thing i have noticed is that both main ps caps have low capacitance circa 3800uf vs 6800uf so i think they need changing out regardless, i'm having difficulties finding suitable caps (width of terminals) the only ones i have to hand with suitable terminals are 10000uf

 

[Watthour]

20mm spacing on the leads?

 

[Trw]

25mm i think

 

[Trw]

20mm spacing on the leads?

25mm i think

 

[the_burmese]

I am currently working on SA-6500 restore (and repair) also
The main caps C57 and C58 are 20mm lead spacing
I have not found any direct match on Mouser for this, everything there is 10mm spacing.