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Re: Atmos excessive buzzing from speaker

Posted: Sun Nov 08, 2020 7:20 pm
by kenneth
I remember a weird phenomenon, when the relay is activated, the tape recorder turns, and when the relay is deactivated the tape recorder does not stop anymore, you have to unplug and re-plug the jackremote to "unjam" the relay ... Maybe that the tape recorder had a too much big motor?

Re: Atmos excessive buzzing from speaker

Posted: Mon Nov 09, 2020 5:38 pm
by mikeb
kenneth wrote:
Sun Nov 08, 2020 7:20 pm
I remember a weird phenomenon, when the relay is activated, the tape recorder turns, and when the relay is deactivated the tape recorder does not stop anymore, you have to unplug and re-plug the jackremote to "unjam" the relay ... Maybe that the tape recorder had a too much big motor?
That's entirely possible -- reed relays can "stick" if allowed to arc, and a nice inductive motor stopping could indeed weld the tiny reeds together. Looking at the Oric schematic, there is nothing there to prevent this (e.g. a small capacitor across the contacts to provide a path for any inductive kick).

I guess a little kinetic adjustment of Oric (hit it!) would shock it apart!

Glad you can hear the plink noises too ... not sure why Road Race would do that (doing something unpleasant to the VIA chip? A conspiracy to wear out the relay! :roll: ).

I know my diag ROM/board works the relay open/closed a few times as part of testing, which makes a pinging noise if there's no sound -- normally buried by the sound from VIA/Timer 1/800Hz cassette output, passing through it on the way to the speaker input. :)

Re: Atmos excessive buzzing from speaker

Posted: Mon Nov 09, 2020 5:53 pm
by kenneth
mikeb wrote:
Mon Nov 09, 2020 5:38 pm

Glad you can hear the plink noises too ... not sure why Road Race would do that (doing something unpleasant to the VIA chip? A conspiracy to wear out the relay! :roll: ).
The game was offered by the factory... Maybe a planned obsolescence? :twisted: :mrgreen:

Re: Atmos excessive buzzing from speaker

Posted: Thu Nov 12, 2020 4:17 pm
by Lardo Boffin
Godzil wrote:
Sat Nov 07, 2020 4:24 pm
Orices are well known to chant the activity on the Data/Address bus.

If you look at PCB, you will see that the audio out track of the AY-3-8910 is crossing both data and address bus. As it is before the amplification stage, the noise ig get from these is amplified, and ending in the main HP noises.
Would it help reduce noise if the tracks were cut close to the audio out of the AY-3-8910 and the input to the amplification stage and replaced with shielded wire?

I have composite modded some early Atari 2600s and had to replace various wires with shielded in order to get rid of both audio and video ‘noise’.