Vectrex troubleshooting: faint sound

[norkusa]

I've got an extra Vectrex that I'm getting ready to put on the auction block, so I've spent some time cleaning it up today. I plugged it in for the first time in a couple years to test it out and I notice that there is a problem with the sound. It's very, very faint. When I turn the volume knob all the way up, I can just barely Minestorm. I remember when I first got it that it had this problem but after a few weeks though, the sound started working fine. Now its back to how it originally was.

Anyone know if this can be fixed easily? If so, can someone give me some help or direct me to someplace online that will tell me how to get it running tip-top again?

[christianscott27]

i dont know who your service provider is but go to your newsgroup section and subscribe to rec.games.vectrex. theres a hardcore tech scene out there, tap into their knowledge and you will never want for a working vec!

[norkusa]

i dont know who your service provider is but go to your newsgroup section and subscribe to rec.games.vectrex. theres a hardcore tech scene out there, tap into their knowledge and you will never want for a working vec!

Thanks for the tip. I completely forgot about that newsgroup. Those guys totally know their stuff!

[FABombjoy]

Do you hear any scratchiness in the volume control? Do you hear the typical Vectrex buzz at all?

[norkusa]

Do you hear any scratchiness in the volume control? Do you hear the typical Vectrex buzz at all?

No scratchiness heard in the volume control (my other Vec has a major problem with that though) It just goes from mute to barely audible when I turn the volume knob all the way up. I do hear the Vectrex "buzz" over the weak sound though. Any suggestions?

[FABombjoy]

I do hear the Vectrex "buzz" over the weak sound though. Any suggestions?

If the buzz is the same volume level as it's always been, then that should mean that the audio amp is still working within spec, but there is a problem with the audio output from the logic board.

Have you worked on a Vec before? You probably already know, but be careful of the high-voltage stuff on the inside.

1st thing that I would do is pull/sand/resocket (if they are both socketed, board may vary) both IC302 (4052B) & IC208 (AY3-8912), as well as the thin audio cable itself. Vec chips tend to build up a slight corrosion over the years, and a lot of problems like this are from that.

When you start the Vectrex, are the top/bottom/sides of both boxes on the start up screen parallel to each other? If not (if the inner box appears slightly rotated in relation to the outer), suspect IC302 as a possible cause of both the audio & vector issues.

It's doubtful that the audio pot is to blame, but measure it's resistance. The schematic puts lists it as a 10K pot.

If none of the above helps, you really need to be able to swap those two chips & see if anything improves. You don't happen to have a 2nd Vectrex, do you? If not, I'm not positive if the Vec will run with IC302 removed but you could at least try pulling it & seeing if the audio returns to normal. It should run without it, but I've never tried.

If you have a test/multicart, run the audio check & see if the volume on all 4 channels is the same.

All right, so all of that was assuming that the 'buzz' is still loud. If not, there are a few electrolytic caps in the audio amp, as well as the amp IC103 (LM386). Refer to the schematic in the service manual for details on that. The electrolytics in Vectrexes are getting very old, and more problems relating to them will probably begin to surface in the next 5-10 years.

Well, that should do it for now. Let me know if the chip thing helps.