What is the mobo or system model no. pray tell? You haven't given us much info to go on.....

Wasn't someone saying the other day that the speaker works ass backwards, it goes to 5V and the signal is more groundy... though that makes you worry more about probing than doing it with ground... try a low voltage maybe? Or through 1K resistor? Would still come through faint I would think.

Typically of this type of model what I would expect is the speaker built into the front panel board.

Caluser2000 wrote on 2021-08-12, 01:50:

What is the mobo or system model no. pray tell? You haven't given us much info to go on.....

I don't know the system model and the motherboard is an OEM design. I only know that it's a Compaq because of the splash screen at boot up. I googled around to figure out what the mystery ribbon connector was.

Kahenraz wrote on 2021-08-12, 03:45:

Caluser2000 wrote on 2021-08-12, 01:50:

What is the mobo or system model no. pray tell? You haven't given us much info to go on.....

I don't know the system model and the motherboard is an OEM design. I only know that it's a Compaq because of the splash screen at boot up. I googled around to figure out what the mystery ribbon connector was.

The mobo should have Compaq part number it...

If it's a SiS 5595/530 chipset, it could be a Presario 5340. Then the connector (J5?) for the CAC should occupy this - game port and 2xUSB front bracket. You can find more info here: https://www.elhvb.com/ctechinfo/msgs/5300.pdf

Any chance of a decent picture of the motherboard with nothing connected to it? It looks like that front panel just has a couple of USB ports and a gameport, so probably no speaker signal. I had a look at a service manual for the Compaq Presario 5000(ish) and that has a troubleshooting section including a fault of hearing no beep on POST, for which it says that an external speaker must be connected and the volume turned up. I take that to mean that Compaq routed the PC Speaker signal through the onboard audio, so you'd need to have amp + speakers connected to the line out and check if there's a software mixer setting for a speaker input.

And yes, as I understand it, the PC Speaker works by having one side of the speaker at +5V, then the other side is either floating or pulled to ground. Whenever there's a change it causes the speaker cone to produce a click, and when done repeatedly and fast enough we hear a note. Don't know why it was designed that way, but I'd guess it allows for higher currents.

Looks like Compaq also optimistically did away with a reset switch on the front panel. Obviously nothing was ever going to crash.

According to that PDF:

An external speaker must be installed into the speaker output connector to hear audible beeps during POST.

I tried this thinking the same thing. Let me try again with the volume cranked all the way up.

Definitely no beeps. I have the I/O bracket so I know that I connected the speaker to the right socket.

Very odd.