Yamaha psr e403 low sound output from speakers

[samuel phillips]

HI been trying to solve this problem for while now can't seem to make any head room I've changed the volume control the power amp ic and still the same volume output can anyone give ideas as to what could be the problem.

Here's a link to the service manual
https://elektrotanya.com/yamaha_psr-e403.pdf/download.html

 

[kellys_eye]

Does the volume vary at all? Is there an external output port (headphone socket perhaps)?

 

[samuel phillips]

no the volume does not vary and there is output port to connect to an audio system, but I'm talking about the speaker output it's very low on half of volume you can hardly hear I tested the speaker both with a tester and on a mini audio system and the speaker are fine.

 

[73's de Edd]

Sir samuel phillips . . . . .

Since you now say that full familiarity with your equipment’s normalcy in the past, now confirms that the present volume is 1/2 or less than it used to be, therefore you remember that level as a reference of its prior capabilities.

I just prepped up the block diagram, as it seems to have all referencing output to the audio flow thru the system.

Originating, all the way from its point of origin over at pins 11/12 and 9/10 as the analog R and L audio outputs at the Digital Analog Converter IC.

Initially, can you confirm for us, that you have the full operational DC supply voltage at pin 5 of the IC551 AF out?

Also, can you confirm that IC 502 is properly receiving a proper +6 vdc at its pin 8?

You’re telling us of having NO volume control action is certainly suggestive of your problem being in the AF output stage.

Your headphone jack merely switches audio out between either the headphones or the speakers, with no intermediary lower drive level going exclusively to the headphones.

Did you get the identical decreased audio level effect with the old IC551 AF chip in circuit ?

An initial test requires a wire leaded ceramic-poly-paper capacitor of 0.01 thru 0.1 ufd range, such that its lead ends can bridge from pin 1 over to pin 12 of the IC551.

There is a 50/50 chance of a good result . . . . . . . . it’s all being in accordance to phase relationships.

If the unit is powered up and in normal working settings and conditions, when that cap is bridged between those points .

If the moon is in the right solar positioning . . .and you are LUCKY ! you then just might get the loudest tone coming from that unit that you have heard since all was last working normally.

If no luck, think about your having additional audio equipment , on which, we need a line level audio output from something that typically does that outputting thru a female RCA jack. Also we will need a shielded, male at both ends, RCA patch cord and that prior isolation capacitor that was being used.

AF sources . . .? . . . . . .CD player - - - - - a DVD players R or L audio output - - - - --VHS or BETA tape players and their AF output - - - - - - - another component system with Tuner AF output - - - - -tape output . .etc.

Standing by to further fill in and trade info . . . . .

Relevant Techno Referencing:

73’s de Edd

 

[samuel phillips]

Hi @73’s de Edd thanks for your response I tested the dc volts at the pins

Initially, can you confirm for us, that you have the full operational DC supply voltage at pin 5 of the IC551 AF out? at this pin of the power amp, IC I'm getting 5.66v dc.

Also, can you confirm that IC 502 is properly receiving a proper +6 vdc at its pin 8? at this pin I'm getting 5.98v dc

Did you get the identical decreased audio level effect with the old IC551 AF chip in circuit? yes same decreased audio level.

I also tested the other voltage regulators and their voltage output are good.
(An initial test requires a wire leaded ceramic-poly-paper capacitor of 0.01 thru 0.1 ufd range, such that its lead ends can bridge from pin 1 over to pin 12 of the IC551.)
If i do this test and it works what does that ?mean

 

[73's de Edd]

Sir samuel phillips . . . . .


BEEP . . . . .BEEP . . . . .BEEP .. . . . . RED flag going up.

Look to the right and the DC power input, which shows this unit having an option of using 6 D cells in series to get 9VDC as the power source OR the option of use of a 12VDC adapter which should drop 12VDC down to 9 VDC.

Sooooooo . . . . . you indicate that you were finding only 6VDC as the main power input to the POWER amp IC551 at its pin 5.

That should be on up around 9VDC, being only down at that 6VDC level after it has passed through IC151 for other lower level circuitry.

Now, which power source are you using, or if using batteries, could a couple of cells be installed backwards polarity and thus cancelling out some of the total series string voltage.

Parte deux . . . . on the audio testing aspects

IF that capacitive feedback DOES (remember the 50/50 chance aspect ) produce an oscillatory tone output, that is being GREATER than the prior audio level that you were hearing; that is indicative of that AF output amp stage being able to still produce that level of volume output.

Therefore, that is being suggestive of needing a greater level of audio input, such as would be acquired with the stage of buffering / amplification that is being provided by stage IC502. Maybe that stage is at fault, BUT the volume control should be working, if so.

Do you have any of the prior suggested sources of a test audio signal output ?

73’s de Edd

 

[samuel phillips]

@73’s de Edd im using a 12v adapter

 

[samuel phillips]

was doing some tracing and I'm getting full 11v at pin 4

 

[73's de Edd]

Sir samuel phillips . . . . .

OK on the power supply medium now.

You indicate that you were finding only 6VDC as the main power input to the POWER amp IC551 at its pin 5.

Ahhhh haaaa . . . . they mis labeled the power pin on that block diagram # 4 is the correct one instead of their marked # 5.
. Do you also find that 11 V comes up on the #8 standby pin when you power up?
Now how about any of those audo signal sources.

73’s de Edd

 

[samuel phillips]

Yes I'm getting 11v at pin 8

for some info I'm getting 5.65v at both out pins 5 & 3
6v at pin 9 and nothing on pins 11 and 12

 

[samuel phillips]

@73’s de Edd hi what do you think is the cause

 

[73's de Edd]

Sir samuel phillips . . . . .

Dang . . .they had that simplified block diagram marked in error on the AUDIO output pins ALSO . . . . The correct ones are 5 and 3.

At any rate since they are using two output stages that are normally working at a DC level of ½ of the supply voltage. With 5.65VDC being on the output pins, all is well, as the series 1000 ufd coupling capacitors will isolate the connected speakers.

No more voltage readings needed for now.

NOW

Let’s see if that power amplifier stage is AMPLIFYING, or if the problem is being in an earlier stage.

You now need to rig up that . . . . . anywhere from a 0.01 through a 0.1 ufd . . . . . capacitor, between pin 3 and pin 12 to see if a positive feedback will make that stage oscillate with a LOUD tone output.

Like I said, there is a 50/50 chance of this working, it’s all according to the phasing of that feedback signal.

Our last chance, if getting no TONE in that last test.

First, you have the volume set to max.

You keep using the pin 12 connection but the other end of the cap needs to get extended w a a a a y over (by a twisted on piece of hook up wire to one of the caps leads) . . . . to reach the IC502 preamp IC, to either the common shared junction of R503 and R507 or the common shared junction of R504 and R510 . One of those connections should get a strong tone . . . if the IC502 stage is good.

The VOLUME level of the tone should be right up there at the max volume of the unit, back in its old working state.

If none of these work we will have to be using one of the afore mentioned items, to use to get us a test audio signal source to then inject into the different points of the audio amplifier stages.


73’s de Edd

 

[samuel phillips]

hello @73’s de Edd I'm getting a loud pulse tone at the start then a few seconds later a solid tone when I connect the capacitor to pin 3 to 12.

 

[samuel phillips]

hi @73's de Edd as i said in my recent reply that i got the loud sound from what you told me to do, so should i try the next step in connect pin 12 to the common junction of the resistor you told me about.

 

[samuel phillips]

@73's de Edd

 

[samuel phillips]

it does sound a little louder than before when I connect pin 12 to the common junction of r503 and r507 so does that mean ic502 is bad

 

[73's de Edd]

Sir samuel phillips . . . . .



Be sure that your volume control is at max level, then try pin 1 of IC502 . . .then evaluate its volume level.

If it oscillates to make a tone, see if decreasing the volume pot causes a shift in frequency and finally a no oscillation state, and the tone stops.

That confirms that the pot is OK. Put the pot back at max volume.

Lastly, you were previously at R503-R507 junction, but, this time, try the R504-R509 junction.

Also check and see if ~ 5VDC is present at IC502 pin 8.

Since the block diagram was incorrect at two different places I am now making up a condensed full schematic, relevant only to our left channels audio signal flow path.



73’s de Edd

 

[samuel phillips]

@73's de Edd

I'm getting 5.97v at pin 8.
when connecting to pin 1 of ic502 the notes play loud but it's not affected by the volume control
also when holding the wire there's a hum and only when I touch pin 1 of 1c502 the hum stop and the keys play loud when pressed.
I get a static sound and at r504 and r509 but it's also not affected by the volume and its just notch louder than the current sound of the keyboard so only at pin 1 of ic502 there's no static and the keyboard plays as before like if there's no problem the sound is loud.

the volume control was what I also changed, its new.

 

[kellys_eye]

Is the volume control mounted on the circuit board?

If so, resolder the pins on it. Sounds like you might have one side of it open-circuit.

 

[samuel phillips]

it's mounted on it own PCB but I was just doing some digging after getting loud sound at pin 1 of ic502 I decided to test after capacitor c514 and I'm getting low sound as with out touch pin 1, does that mean this cap is the cause of the problem.

will resolder the pins but the volume control is working its just not working when i connect pin 12 to pin 1