Pioneer SA -508

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Nidexx
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#1 erstellt: 02. Dez 2022, 14:25

Hallo
Pioneer SA -508
Sound ist bis auf unten gut

Habe einen Pioneer ergattert 12 euro
Bin ein Anfänger Entschuldigung wenn das blöd ist.
(Hat einen Luxman auf dem Boden
komme, wenn ich Zeit habe)

Alle Bedienelemente scheinen zu funktionieren
Ich habe Potentiometer mit Kontaktreiniger gereinigt.
Beim Einschalten der Spannung klingelt im Lautsprecher Volume Off -- verschwindet nach einer Sekunde
klingt abnehmend

Der Ton aus den Lautsprechern ist „im Bass verzerrt.
Bei beiden Lautsprechern gleich. nicht so viel, aber immer noch etwas, das behoben werden muss

Es existiert nicht
Verzerrungen beim Hören mit Kopfhörern.

Ich habe nichts weiter gemacht oder das Service Manual zu besorgen

Das Faszinierende an diesen Geräten ist, dass es manchmal 3 Minuten für 1 Euro dauert und manchmal praktisch unmöglich zu reparieren ist

Ich hatte einen Harman Kardon, bei dem es Filterkapazitans am Eingang gab, die Rauschen erzeugten
Leicht behoben

Also bitte, wenn das alles bekannt ist Ringing with Distortion
Bitte sagen Sie mir, wo ich anfangen soll zu suchen oder was es genau sein könnte.

Nochmals Entschuldigung, wenn dies zu einfach ist und ich zu schlecht gelesen habe.
Ich denke, dass Experten hier direkt sagen könnten, was das Problem ist

Rabia_sorda
Inventar

#2 erstellt: 02. Dez 2022, 15:34

Hallo,

Schreibst du evtl. mit einer Translation?
Schreibe deinen Text besser auch noch zusätzlich in deiner Sprache, denn ich verstehe deinen jetzigen Text kaum.

Nidexx
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#3 erstellt: 02. Dez 2022, 16:31

Ja Richtig .. Danke bin in Süd Schweden Lund
Soll es besser machen In English , -- I suppose Swedish wont help.

I am a beginner.
I have a Pioneer SA -508
Flea market a 12 Euro.
Everything seems to work .. Sounds good.but I have some distortion on bass notes.
Both channels -- Not that much but enough that it needs attention.
No distortion in headphones
I have cleaned the Potentiometers and knobs. Have not done anything else

When power on there is also a ringing / Oscillation in the Loudspeakers At all selector positions Phone / Aux/ Tuner Something is wrong there .That decreases and vanishes after about a second or two
The ringing is there without anything connected IN on those positions .

Sometimes the faults are simple and quick to repair other times Difficult.+ .Impossible
So I put it here without having done much ( Anything ) myself.
Can it be input Filter Capacitors
Please if this is known for the experts here give Info
Thanks Jan

Rabia_sorda
Inventar

#4 erstellt: 02. Dez 2022, 17:12

I don't know the device and I can't find anything under Pioneer SA-508 either. Is that the correct term?

If you don't hear any distortion with the headphones, but you can also hear a whistle on the speakers, then the power amplifier may well oscillate and destroy your speakers.
This oscillation should be viewed on the oscilloscope.

Dry electrolytic capacitors can be the cause, but also defective transistors.

A signal trace should also take place to find out whether the oscillation really comes from the power amp or already from the preamp section.

Since you got it from the flea market, it could already be "tinkered" or internally misaligned. To do this, you should first compare it technically with the service manual.

Have you checked everything for bad solder joints?

It would be best if you show some pictures with "img" here.

Nidexx
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#5 erstellt: 02. Dez 2022, 17:57

Thank You Sir -- That's the one there

https://www.hifiengine.com/manual_library/pioneer/sa-508.shtml

At the moment I haven't done anything Except cleaning the pots and tried with 2 tuners and
a CD player and Headphones. Was looking for the Quick fix .
Have not even downloaded the Service manual and measured anything or so.

If quick fix not available I have a Luxman that is before in the Pipeline.
But eventually ill get more info and take more actions.
But I don't have that much time at the moment.
Have paperwork about an estate to go trough :
Thanks Again -- .Jan

Rabia_sorda
Inventar

#6 erstellt: 02. Dez 2022, 18:15

Of course, switches and potentiometers can be dirty or oxidized, but then the error would also be audible with a headphone.

Also look for oxidized fuse holders FU2 and FU3.

The "triple" diodes (D105/106) in the output stage sector are often striking.
These can be replicated with 3 individual diodes connected in series.
Fuse resistors (e.g.: R127/R128) can also become highly resistive and should be replaced with flame-retardant resistors.

The DC-offset at the loudspeaker outputs should also be checked according to the service manual.

So far a start....

Nidexx
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#7 erstellt: 02. Dez 2022, 18:48

Thank you very Much Sir
This is why these types forums are good.
I will get back when I have had time to read the Service manual and do the tests according to your suggestions
Thanks Again Jan

Rabia_sorda
Inventar

#8 erstellt: 02. Dez 2022, 18:57

I am excited!

All the best ...

Nidexx
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#9 erstellt: 02. Dez 2022, 23:45

Hello
I got inspiration and opened the cover

Measured the Output DC
6.6 mV one side
2.1 the other side
So differed a bit

Measured the idle Voltage 5.6 mV and 5.4 Should be OK
There was mention of a Jumper Cable to be cut if problems and it was open .Someone has cut it .

I hooked up at dummy load gave it 50 % on the Volume to see if something was getting hot Could not notice anything

But something looks strange on the Output Capacitors Please give opinions

The Output capacitors is turned in opposite directions

On the top in picture the dot for Marking is at 3 o Clock
And on the lower it is at 9 o Clock
Does this look right to you gentlemen I Find it not being logic and I took a look at a Luxman I have open as works in progress. There the capacitors was both in the same direction.

Has someone mounted / installed it wrong ??
Thanks Jan

d_bolle
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#10 erstellt: 02. Dez 2022, 23:58

Good catch, a SA 508 for 12 bucks is very nice catch.

The filter caps (not output) having opposing directions is not unusual, might just make sense layout-wise. Board Layout and schematic will be different. Like on the schematic, a minus and a plus will connect. To do that on the board, you would arrange them that way.

You can usually tell on the backside if someone has soldered on them. Don't randomly turn them around, that might break the entire thing. Also, on the PCB pioneer often has a little "+"

I also got a Pioneer Sa 508 half a year ago, there the filter caps had issues, but the problems I had were different from yours.
But read on that forum, maybe you get inspiration.

https://www.hifiengi..._on_pio_sa-508.shtml

Rabia_sorda
Inventar

#11 erstellt: 03. Dez 2022, 00:00

The Output capacitors is turned in opposite directions

That is correct, because the two rail voltages are +/- to the zero point/GND.
A - voltage is therefore a "+ voltage" compared to the common zero point/GND.

Nidexx
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#12 erstellt: 03. Dez 2022, 03:01

Hello
Continued with the dummy load and 50 % volume

Noticed a resistor getting hot R15 ..cant hold the finger on it

I have -43 V on the right side it has the 1.5 k
But no Voltage On the left side. It is Zero Need to measure some more and think about it.
Feel free comment
mfg Jan

Rabia_sorda
Inventar

#13 erstellt: 03. Dez 2022, 12:19

With its 2 watts, the resistor R15 is dimensioned in such a way that it can get hot and it is therefore correct.

If a voltage is missing, then you should check its voltage path. Somewhere there are defective components.

CarlM.
Inventar

#14 erstellt: 03. Dez 2022, 12:25

Theother side of R15 ist connected to GND. Therefore it must be 0 VDC.

Nidexx
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#15 erstellt: 03. Dez 2022, 13:41

Thank You gentlemen
Helping a beginner .. Did not see it being to ground tonight
This can be tricky Qualitative rather than Quantitative.
Will measure some more I do have a computer Oscilloscope and a simple signal injector.
Ill get back.
I believe i will try again with the dummy resistor ( 1000 W 4 ohm ) see if something else gets hot or warms up uneven between the channels.Keeping it on for an hour or more later today.
Cranking it full on volume would that be stupid ?? Should the fuses prevent damage
Thanks Jan

Nidexx
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#16 erstellt: 03. Dez 2022, 19:56

Working on the potentiometers moving and lubricating
The function selector did not move so easy
Now it is stuck altogether
Taking it out servicing or bypassing
/ Jan

d_bolle
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#17 erstellt: 03. Dez 2022, 20:47

Weird that it's stuck. What did you use to lubricate it? An electrical contact cleaner? In Germany, "Kontakt 60" is commonly used.

Nidexx
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#18 erstellt: 03. Dez 2022, 20:54

It is called
Contact cleaner
PRF
TCC

It did not move without some force from the start. I suspect some other lubricant has been applied like sewing machine oil or so. Dont know

https://www.kopplat....-kontaktspray-520-ml

/ Jan

Nidexx
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#19 erstellt: 03. Dez 2022, 22:06

Took out the function selector some desoldering
And the outgoing axle was stuck
Gave it some light oil 5-56 And it came loose and out.

It was dirty and had a tight fit so maybe the contact cleaning solvent flushed more dirt in there and locked the axle.

The stiff movement form dirt in there from the start.
Not sure if it can be serviced yet .But this is mechanical that is something I have done many years.

I have had problems with these types potentiometers and selectors on many other HiFi Equipment
As well as on Old Motorcycles.
Not saying it is the case here.

/Jan

Nidexx
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#20 erstellt: 04. Dez 2022, 03:42

No Luck
Did get the selector fixed . Grinding off Oxide and lubricating.

Computer with the oscilloscope Crashed black Screen

The ringing on power on still there
As well as the distortion on bass notes.
Going backwards. ( the computer )
No quick fix ..Need to reevaluate and think it over..
Perhaps exit strategy. Perhaps capacitor replacement eventually.
/ Jan

d_bolle
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#21 erstellt: 04. Dez 2022, 08:53

That is some serious rust (and nice gear you have)

If the selector is so rusty, it means the amp was in wet conditions, like a damp cellar. Electronics hate humidity.

But I don't have much experience so I won't write any guesses here, other people on the forum actually know what they're doing

Nidexx
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#22 erstellt: 04. Dez 2022, 17:27

I can see that there are replacement kits out there
( that can have interest for others )
Ranging from capacitors a 30 Euro
And more complete to 160 Euro on the high priced end
feel free tell if you know of a good cheap vendor in Europe

Got the Oscilloscope installed on another computer.

https://www.ebay.com...7Ctkp%3ABFBMyI3o3pth

d_bolle
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#23 erstellt: 05. Dez 2022, 20:10

I'm not sure if complete recapping makes sense at this point, especially with the expensive kit of fancy caps.

You wanna know what's wrong with the thing first. If it's not the caps, you spend all that time and money and still have the problem.

Nidexx
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#24 erstellt: 05. Dez 2022, 21:53

Thank You
I am with you there . Been doing some measurement around the filter capacitors. Cant find any values . wrong there.
Been thinking --- since it is ringing in both channels at Power on I will try to look upstream in early stages.. Giving Same signal to both stages.
It is difficult to find a fault in circuit. For me as a beginner at least.
Extra difficult when not open circuit.
Maybe Oscilloscope. And signal Generator.
But the fault finding can be to difficult and time consuming -- then the component replacing is one way forward. But not necessary buying the whole kit.
But it can wait a while I find info on internet and Know one that is experienced I can ask. .
Will look more at the Circuit schematic.
Thanks again
/ Jan

Nidexx
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#25 erstellt: 06. Dez 2022, 01:20

Been Reading the manual

And it turns out there is a circuit for preventing ON / OFF
Sounds

A fair assumption can be that it is not working since there is oscillating at power on ? Maybe

It is close to the Hot resistor. R15

Will check there --- Feel Free comment if some component is obvious to suspect.
The Voltages seems to check out.
/Jan

d_bolle
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#26 erstellt: 06. Dez 2022, 17:03

All of this is beyond my skill.

Good luck, have fun and stay safe!

I will keep reading!

If you can't solve it, consider getting a professional look at it, or put it back on the bay (with an honest description) and get another one.

Poetry2me
Inventar

#27 erstellt: 07. Dez 2022, 18:41

For better understanding of the power supply and muting circuits I have marked the relevant parts here for you:

Pioneer SA-508 schematic detail power supply and muting circuit marked

See the muting circuit in green. It is basically implemented through one transistor Q3 and some additional parts.

During normal operation Q3 is shut and will not conduct between Collector and Emitter, thus nothing is muted.
Only if Q3 Basis-Emitter voltage becomes higher than 0.6V it will open and pull the voltage at regulator Q1 Basis down to ground. This will shut down the regulator output from 34V to 0V and the power amp will be muted.

It is important to understand that in normal operation, voltage at the Basis of Q3 is in balance at a negative voltage level, causing Q3 to remain shut. This is due to a voltage divider network out of R5 and R8. The balance point (Basis of Q3) is between these resistors. Should power from the transformer disappear, the negative voltage created through D6+D7 and C6 will stop pulling the balance point below 0V. Voltage there will become >0.6V and Q3 will open, causing mute.

I hope this helps to understand the circuit.

- Johannes

[Beitrag von Poetry2me am 07. Dez 2022, 18:48 bearbeitet]

Nidexx
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#28 erstellt: 07. Dez 2022, 20:35

Thank you very much Sir
I did continue investigating that circuit could not find any Voltage wrong after start-up when the ringing is over

Suspected the Q1 not having the right physics i started to measure and take out components Nothing found
R1 R2 R3 correct
Capacitors
C1 OK -- C4 C5 + 10 % ( Is that OK ? )

Measured in circuit C2 C3 Not displaying the same nor the 8000 uF

Talked to a shop today a senior Radio dealer ,High end , Good memory and
long experience .Where I sometimes buy components
He said he would take out C2 + C1 and measure out of circuit
He said the IC Circuits would he suspect
Then Capacitors
And Power transistors

not been able to find the R16 yet

Thank you again Sir .Will continue and read your description.
Thinking and measure.
Resistors around Q 3 and Q 2 among other

CarlM.
Inventar

#29 erstellt: 07. Dez 2022, 20:43

Testing the capacitors you only measured the capacity and not losses/leakage?

Maybe the meter shows 10% too much because there are losses.
I would replace these capacitors.

Nidexx
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#30 erstellt: 07. Dez 2022, 21:21

Thank You Sir
I only have a cheap tester

Tested the capacitors a couple of times again

marked 50 V 100 uF Nippor Chemi Con

1.
ESR 0.17 --0.29 U loss 1.3 %
108.3 uF

2. ESR 0.13 --0.27 U loss 0 .0 -0.1 %
109.7 uF

I dont know if these values are out of range or bad or not
But since they are out of the board and there is a suspicion malfunction there in that circuit
It makes sense to replace them

Nidexx
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#31 erstellt: 08. Dez 2022, 00:28

OK Gentlemen
The one large capacitor is gone finito
Even if it is a " Low Budget " device for measurement it cant be so big difference doing exactly the same measurement.
More thinking and reevaluation to do.
On line I have seen that some have had problems with these but the rest capacitors being fine
They replace all capacitors in this power supply circuit
One Spanish site had gone up to 10 000 uF allegedly getting better sound.
/ Jan

Rabia_sorda
Inventar

#32 erstellt: 08. Dez 2022, 16:58

If you now take new capacitors with 10,000 µF, then they will most likely only have 8000 µF.
You then have to take 12,000 µF to have around 10,000 µF.
Manufacturers exploit their tolerances (+/- 20%) at the expense of consumers.

Also consider 42V too low for the capacitors and you should choose the new capacitors with a higher voltage (50 V or higher).