VOGONS


First post, by rfsapiens

User metadata
Rank Newbie
Rank
Newbie

Hello people,

I'm building a new super socket 7 retro pc based on the motherboard DFI K6Xv3+/66 and an AMD K6-III 450 and everything was fine. Then I left the motherboard on for half hour and I found that the cpu fan just stopped. After that when I rebooted the machine the beeper became too quiet and almost unoticable. But the motherboard is fine never had any other kind of bug and the cpu is stable and the fan always working... Anyway, so after swaping the beepers and also trying with another cpu and the result being the same I decided to purchase an amplifier to connect to the speaker's output on the motherboard, so I went ahead and purchased the LC LM386 amplifier:

http://www.ebay.co.uk/itm/221946480854

which helped a lot this although it's not still at a very good sound level. The problem is that when I plug the hdd drives on my system, the noise of them spinning also goes to the speaker and I don't know why.... 😒 I fed the amp with 12V directly from a molex of my PSU and connected the ground to black wire of the molex. the other two pins on the amp (In and Ground) I connected directy to the motherboard. The speaker I connected to the output pins of the amps.
Now my question is what can I do to amplify the sound coming from the speaker but avoiding these kind of unwanted noise.
I attached two photos of what I'm talking about so you can see exactly what I installed in my pc to try to overcome the issue of a low beep sound (which I still don't know why my motherboard is doing so)

Thank you in advance for your kind help and support.

With the best regards,

Rfsapiens.

Attachments

  • 20170405_093034.jpg
    Filename
    20170405_093034.jpg
    File size
    1.68 MiB
    Views
    328 views
    File license
    Fair use/fair dealing exception
  • 20170405_093102.jpg
    Filename
    20170405_093102.jpg
    File size
    1.33 MiB
    Views
    328 views
    File license
    Fair use/fair dealing exception

Reply 1 of 1, by SSTV2

User metadata
Rank Oldbie
Rank
Oldbie

Toss that amp out.

First thing you need to do is figure out why exactly you get a weak signal from speaker header. There should already be some sort of driver/buffer on the motherboard for speaker as square wave generating timers output is too weak to drive it.

Try to trace speaker header signal pin back into motherboard, it should be connected to a bipolar transistor (which does all the amplification) collector pin, once you've found it, check if you get right voltage drops between B-E, B-C and if it's not shorting, also check if it gets power at all.