Atmos excessive buzzing from speaker

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SpaceFlightOrange
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Atmos excessive buzzing from speaker

Post by SpaceFlightOrange »

Hi.

I haven't been on here in a while, sorry, been on other projects, and haven't used the Atmos since fixing it mainly because i had no software and hadn't gotten around to making the appropriate lead to load tap files from ISS's excellent Android loader app.

Anyway, I ordered an Erebus from Steve Gould which arrived a week or two ago, and everything works great, apart from Im hearing excessive buzzing coming from the speaker, regardless of whether the Erebus is connected or not.

Im using a new, modern 9v 1a PSU with it, but i've also tested it on my bench PSU to see if that makes a difference and it doesn't. Interestingly, I noted that the current draw is a fairly stable 0.66a without the Erebus, and it barely moves up to 0.67a with the erebus connected.

When i say excessive, it's audible in normal use, but nowhere near as loud as the keyclick sounds for example.

Difficult to describe, this.

Should i be worried about this?

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mikeb
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Re: Atmos excessive buzzing from speaker

Post by mikeb »

What kind of buzzing? Like 50Hz mains hum (poorly smoothed power supply)? Or other frequency? Do you mean the purring of a happy Oric, but louder? :)

Also, what do you have connected to the cassette port, as unwanted signals going into pins 4,5 (the non-cassette I/O pins) will be amplified and spat out of the speaker -- just checking there's not an odd/mismade/unsuitable lead.

SpaceFlightOrange
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Re: Atmos excessive buzzing from speaker

Post by SpaceFlightOrange »

mikeb wrote:
Thu Apr 30, 2020 4:19 pm
What kind of buzzing? Like 50Hz mains hum (poorly smoothed power supply)? Or other frequency? Do you mean the purring of a happy Oric, but louder? :)

Also, what do you have connected to the cassette port, as unwanted signals going into pins 4,5 (the non-cassette I/O pins) will be amplified and spat out of the speaker -- just checking there's not an odd/mismade/unsuitable lead.
Its definitely not mains hum, and as I mention, i've tested it on my bench PSU with no change. you know? Purring is a good description. Problem is I have no frame of reference, this being the first Oric i've ever used.

Nothing connected to the cassette port. only thing i have connected is the Erebus, but, again, there is no difference, regardless of whether its connected or not.

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HigashiJun
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Re: Atmos excessive buzzing from speaker

Post by HigashiJun »

I had the same problem, but after recapping my Atmos, everything went back to normal.

I think the capacitor concerned is the C1 near the ULA chip (mine was 16V 220µf). The bottom was cracked and it had started to leak.

It's worth trying it, as you only need to change 3 caps (C1, C8 and C21)...

Cheers.
HigashiJun

SpaceFlightOrange
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Re: Atmos excessive buzzing from speaker

Post by SpaceFlightOrange »

HigashiJun wrote:
Fri May 01, 2020 1:14 am
I had the same problem, but after recapping my Atmos, everything went back to normal.

I think the capacitor concerned is the C1 near the ULA chip (mine was 16V 220µf). The bottom was cracked and it had started to leak.

It's worth trying it, as you only need to change 3 caps (C1, C8 and C21)...

Cheers.
I have recapped it, but it's worth another look as i may have fitted a dodgy one... though i do test them all before i fit them

Thanks

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HigashiJun
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Re: Atmos excessive buzzing from speaker

Post by HigashiJun »

If you test your caps before fitting them, it then might be something else.

I still have a faint humming coming out from the loud speaker, but it is not the "whistling" it was...

As for the caps, I always use "good brand" ones (Nichicon, Panasonic, Toshin Kogyo, etc.) and not fake craps from Chinese Ebay sellers.

Cheers.
HigashiJun

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Lardo Boffin
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Re: Atmos excessive buzzing from speaker

Post by Lardo Boffin »

I have recently got my first Oric 1 and I’m sure the speaker was pretty silent when not in use but now makes an audible noise. Purring is a pretty good description! I replaced the caps but that made no difference. When I switch on it is quiet but as soon as it gets to the main BASIC prompt it is making the noise. Its a bit like the noise many BBC micros make but louder.

To be fair I have only recently started using it to any extent recently so I may have just not noticed before. My hearing is not the best...

It makes the noise with only the PSU connected. Its an original PSU.

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mikeb
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Re: Atmos excessive buzzing from speaker

Post by mikeb »

Purring is a happy Oric noise. It's a good sign!

When you power on the Oric, while the memory test is happening you get a more frantic whirring noise, then a "kerplink!" (part of which I think is the cassette relay open-closing during setup of the VIA chip), just as the screen wipes to grey and goes to the normal "Oric Extended Basic..." screen.

Purring begins straight after.

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Lardo Boffin
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Re: Atmos excessive buzzing from speaker

Post by Lardo Boffin »

Ah, all is well then thanks!

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6502Nerd
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Re: Atmos excessive buzzing from speaker

Post by 6502Nerd »

I like the term purring!

But what is the source and is it curable?

It seems to change if in low or high resolution, and how much 'stuff' there is on the screen, and even if the CPU is doing a tight loop. I notice that with interrupts disabled, the purring is almost inaudible.

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Re: Atmos excessive buzzing from speaker

Post by Godzil »

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.

As far as I know the "clic" some Orices make is also linked with that. I don't think the internal relay would be that audible, the "click" I have on some machine is clearly from the speaker. I don't remember ever hearing the relay moving when running a CSAVE/CLOAD command

Just got my atmos out to run a quick test now that I do have a working tape deck with remote input, I can't hear the relay (but it clearly work as it is set in "pause" mode by default, even when not powered up) so I doubt you hear the relay click while powering up, I don't think the ROM do anything about that. (why did I choosed to load a slow tape, been minutes and not done yet)

Edit: hmmm my remove cable was wonky. That's weird, unpowered the relay is position to block the tape, while the rom start it put the relay in play mode, they block again. that's a bit silly.

Though I still can't hear the relay on both my 1 and my Atmoses. (and yet it still make the faint bleep in some condition like ending the HIRES process) (and the 7905 heatsink is really not mean to power an Oric from 12V :D but that's the only power supply I had at hand, the thing get really hot.. And my (official) forth tape may have issue I need to have another tape deck to compare if it is the deck itself or the tape.. Hope, in a way, it is not the deck)

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mikeb
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Re: Atmos excessive buzzing from speaker

Post by mikeb »

Godzil wrote:
Sat Nov 07, 2020 4:24 pm
I don't think the internal relay would be that audible, the "click" I have on some machine is clearly from the speaker. I don't remember ever hearing the relay moving when running a CSAVE/CLOAD command
It depends on your hearing -- it's a high frequency "plink" and it *is* audible when it opens and closes. If you don't hear it when using CSAVE/CLOAD, you either have an unusually quiet relay, or don't have the golden ears ;)
Godzil wrote:
Sat Nov 07, 2020 4:24 pm
Just got my atmos out to run a quick test now that I do have a working tape deck with remote input, I can't hear the relay (but it clearly work as it is set in "pause" mode by default, even when not powered up) so I doubt you hear the relay click while powering up, I don't think the ROM do anything about that. (why did I choosed to load a slow tape, been minutes and not done yet)
I just got my bare "gold-board" out to check properly (it's a reference Oric with strange mods, chips in sockets etc to use as a comparison when fault-finding).

The plink I'm talking about is definitely the reed relay.

When ORIC is unpowered, the relay is normally open state (pause as you said). As soon as ORIC is powered it closes (confirmed with a continuity tester). At the end of the DRAM test, as the screen flips and reverts to BASIC, the relay opens again (this is the characteristic plink that I mean, when the reed relay contacts open, they twang like a tiny pair of tuning forks).

That's the source of the sound. To confirm it, disconnect one leg of the speaker, put your ear on the relay. Or, an old trick, put a short length of tubing in your ear and place the open end right over the relay. Not a joke, useful for finding capacitors/inductors that have started whistling! :)

Agreed, there are other noises from the speaker also occuring which may distract. But that relay plink has always been a perfectly normal part of Oric booting up.

I think the rate of the "purring" when it's running is linked to the rate at which the keyboard is being scanned (something to do with interrupts going on and off?) and remembering that although the sound "track" may cross the busses, the PSG/8912 chip is also being prodded as part of the keyboard scanning (providing I/O lines for one side of the keyboard matrix) so keyboard-scanning would possibly induce noises INSIDE the chip. Then there's whatever junk can get around on the voltage rail.

My question: Have any of the emulators thought to include this sound? And if not, why not ;)

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kenneth
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Re: Atmos excessive buzzing from speaker

Post by kenneth »

We can hear the ReedRelay continuously when playing with Road Race Game in the demo program.

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Re: Atmos excessive buzzing from speaker

Post by Godzil »

My hears are working fine, thanks for the concern.

Easy, no Oric I have here have a relay making any audible noises, and can't also be picked by a microphone put just on top of the chip. (and they are working)

I've also recorded directly from the HP the noise both from a 1 and an Atmos, and the "high pitch" blip is clearly part of the recording.

A relay should not make a "high pitch/frequency" noise when it open or close unless driven at a high frequency and it will not last long if that happen.



Warning pop & noises at high volumes!

My Oric 1 boot noise:
http://www.mirari.fr/dwQW?a=open
My Atmos boot noise:
http://www.mirari.fr/ZobC?a=open



(can't make the [media] tag to properly include these audio files)
The only thing I've done on these audio files is to reduce the pop noises from inserting/removing the power supply to be able to normalise the noise at a better level

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mikeb
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Re: Atmos excessive buzzing from speaker

Post by mikeb »

Godzil wrote:
Sun Nov 08, 2020 2:57 pm
no Oric I have here have a relay making any audible noises,
Then either they are not the standard reed relays, or faulty. :)
Godzil wrote:
Sun Nov 08, 2020 2:57 pm
A relay should not make a "high pitch/frequency" noise when it open or close unless driven at a high frequency and it will not last long if that happen.
Incorrect, it's normal for reed relays to do this, especially on opening, which is what is happening at bootup.

I can't do better than provide facts and measurements, and I realise you won't be convinced.

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