jefftheworld
Offline
Toronto, Ontario, Canada

So, I recently bought a 6581 from CMDR.  Upon arrival I switched out the partially working chip with the new one but I've yet to get it working in any way.  Before assuming that it's a totally bum chip, I thought I'd ask here what else it could be.

The thing that strikes me as a little odd is that the new chip makes absolutely no sound at all.  Even the background noise is completely gone.  Even my previous chip, with it's barely functioning one voice, would make a bit of noise when the computer was on (especially if video was turned on in Cynthcart).

Any ideas?

CMDR
Offline
brighton, uk

That chip I sent you should be fully working, I put it in a 6581 machine to test before I decided to fry it's ram chip.
Take a look at the internal fuse, it might be blown.

jefftheworld
Offline
Toronto, Ontario, Canada
CMDR wrote:

That chip I sent you should be fully working, I put it in a 6581 machine to test before I decided to fry it's ram chip.
Take a look at the internal fuse, it might be blown.

Checked that, yeah.  It still works with the other chip, even after several tests with the new chip.  So I'm not sure what it could be.

CMDR
Offline
brighton, uk

http://noname.c64.org/csdb/release/?id=33265

check out this guide

CMDR
Offline
brighton, uk

an online version too

http://www.devili.iki.fi/Computers/Comm … ce_Manual/

another troubleshooting link:

http://www.commodore.ca/manuals/Tips/c64_tips.htm

Last edited by CMDR (Dec 16, 2010 11:19 pm)

jefftheworld
Offline
Toronto, Ontario, Canada

Yeah, I've seen that guide before but it doesn't really mention audio problems of this sort.  Aside from saying "If you have no audio, check the 6581 chip."

I had previously changed several caps, but I checked those just now and they're all working.

It seems to me like the chip isn't getting power at all.  It emits no sound and doesn't get warm.  However, there doesn't appear to be any damage to any pins.  Aside from some cosmetic scratches on the bottom of the chip it looks perfectly fine.  So I'm still muddling through what it could be.

Last edited by jefftheworld (Dec 16, 2010 11:28 pm)

CMDR
Offline
brighton, uk

yeah sorry about those scratches, fumbling :x
A dead chip should always get power!

jefftheworld
Offline
Toronto, Ontario, Canada
CMDR wrote:

yeah sorry about those scratches, fumbling :x
A dead chip should always get power!

That's what's confusing me.  My other half-dead chip still emits that video noise when the video is turned on, but this chip makes no noise at all.  I tried cleaning off the pins & and socket but that's made no difference.

CMDR
Offline
brighton, uk

Have you checked the PN2222 NPN amp transistor?

And are you testing the audio through the RF connection or a line-out?

jefftheworld
Offline
Toronto, Ontario, Canada
CMDR wrote:

Have you checked the PN2222 NPN amp transistor?

And are you testing the audio through the RF connection or a line-out?

Line-out.  And no, I haven't check the amp transistor yet.  I'll do so now, but I doubt it'll be either of those things.  If it was a problem with those things, it would be affecting both chips.  Which it's not.

EDIT:  Can't seem to get it going yet.  I'm going to give up for the night cause I've got a bunch of work to finish.  Thanks for the help.

Last edited by jefftheworld (Dec 16, 2010 11:57 pm)

AdamGetsAwesome
Offline
Boulder, CO

Check the power supply. I had an issue with no sound and the AC fuse blew in the PSU. Replaced the fuse and all was well.

Edit: how was the other chip "partially" working?

Last edited by AdamGetsAwesome (Dec 17, 2010 12:04 am)

jefftheworld
Offline
Toronto, Ontario, Canada
AdamGetsAwesome wrote:

Check the power supply. I had an issue with no sound and the AC fuse blew in the PSU. Replaced the fuse and all was well.

Edit: how was the other chip "partially" working?

One voice worked, the other two did not.  Filters did not work.

It's a common issue.