Apple /// Plus no sound

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Apple /// Plus no sound

So my Apple /// Plus which I thought was working apparently is not. It will not put out any sound at all. I have tried a known good speaker and according to the apple /// service manual :

https://mirrors.apple2.org.za/ftp.apple.asimov.net/documentation/apple3/service_reference_manual/Apple%20III%20Service%20Reference%20Manual-OCR-1982.pdf

 

Page 326 states you can try replacing LM380 (U103) . I did swap out the IC from a known working Apple /// and it still plays no sound. Where should I look next guys?

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The Apple /// has two

The Apple /// has two different sound modes. There is the simple "beeper", just like on the Apple II. This is implemented with basic logic ICs. And there is a 6bit DAC for more advanced sound control - which is implemented through the 6522. Do any of the two modes work? You can test them with the sound test on the dealer disk.

If both don't work, then the fault is likely in the analog part amplifying the signal for the speaker. In this case, plug some active PC speakers to the audio jack at the rear and see if you get sound there. The audio connector gets its signal directly from the digital part - before the amplifier.

It could also be a simple connection issue with the audio jack itself. The audio jack has contacts which disconnect the internal speaker when something is plugged. If the contacts were corroded, the audio signal could be interrupted permanently.

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Macfly, the /// Plus doesn't

Macfly, the /// Plus doesn't have the audio out jack that came on the standard model ///. Dont know why but they did away with that connector.

 

And no sounds at all play through any of the tests via the dealers diag disk.

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Verault wrote:Macfly, the ///
Verault wrote:

Macfly, the /// Plus doesn't have the audio out jack that came on the standard model ///. Dont know why but they did away with that connector.

Ok, didn't know that.

As I said, the beeper and the DAC are implemented separately. Both are tied via a resistor to produce the common audio out signal. Even if one of the two failed, the other would still produce a signal. When both don't work, then issue must be in the final bits around the LM380. See if it is correctly powered (12V supply). Also, check whether you can see the audio signal at the LM380's input pin. Even if you had no oscilloscope, every "beep" should result in see some "activity" even when measuring with a simple multimeter.

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Ok I will check for voltages

Ok I will check for voltages and see if there is any output on the lm380

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The /// plus is meant to have

The /// plus is meant to have the audio jack on the back. It's not mounted directly on the motherboard, but mounts on the metal panel above the video jack. It then plugs in to a header on the motherboard. Maybe yours is missing this jack?

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Yes It would seem mine is

Yes It would seem mine is missing. I have the pins  on the board and I have a hole on the plate, but it wasnnt labeled and I didnt think much of it. Shame.

 

Anyone know where I can get that connector so I can wire it up myself?

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Anywhere... ;-)

Both connectors are pretty much standard - better electronics online shops should them. A 3 pin connector like this  (or with wires) and a 3,5mm audio connector, mono, with a switch like this. Or ebay, AliExpress or whatever your preferred source...

For now, you could just wire up a make-shift connection of the two connector pins toward the rear (the brown and red wire in rjustice's photo above) to enable the internal speaker. That's the two pins which would be connected when no audio connector is plugged. The audio signal connects to the internal speaker "amplifier" then...

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Ok I havent tested on the

Ok I havent tested on the board yet (I will I just had to work on firewood for the winter), but hear me out. I know on the Apple IIgs if the audio out jack is oxidized or dirty you get very poor, low, or no sound via the internal speaker. Could that be the case with this adapter? What I mean is mine is missing so is that preventing sound out through the internal speaker?

 

So do you want me to jumper the 2 rearmost pins together and test the internal speaker again or connect the internal speaker to those two pins?

 

 

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Verault wrote:What I mean is
Verault wrote:

What I mean is mine is missing so is that preventing sound out through the internal speaker?

Yes, without the connector, the internal speaker is disconnected. The (missing) audio connector at the rear contains a switch. When nothing is plugged in the audio jack, then the audio signal would be switched through to the internal speaker. But when the whole connector is missing, then there cannot be any sound from the internal speaker - since the switch is missing.

See my post above: simply connect two pins of the empty audio connector (see description above) and you should get sound from the internal speaker.

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Ok Sorry for the late

Ok Sorry for the late response but I did what you said MacFly (jumper across the two rearmost pins on the ext connector block) and low and behold sound works perfectly fine now. All I need to do is buy the parts to make a new connector (which I already ordered). So thanks MacFly and Rjustice. I didnt even know there was supposed to be an adapter and since I have never seen an Apple /// Plus schematic, those connectors just never crossed my mind.

 

Now to get back to trying to make the floppy drive work reliably on this machine .........

 

I do have one more question and let me know if you think I should start a new thread. I have the /// Plus dealers diags which runs the clock tests. The machine came with the battery pack harness with some old corroded AA batteries. Luckily there was no damage except for the battery harness terminals which I have soaking in vinegar.

I dont know much about the clock circuit but it fails ALL the tests for the clock circuit when I run them (without the battery pack). Can the test only be run with batteries installed or am I missing some part of the circuit? Again this is the /// Plus board.

 

 

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