600XL Noise Audio

[enito]

Hi there,

 

This week i installed sophia revb (works amazing) in my atari 600Xl ntsc. Too Antonia 4mb, all fine, but sound i get some buzz . I tryed using the RF output pin for audio and too the audio outoput from din area and same effect. I checked ground and all is fine. I know cable using for get the audio can be inadecuate, i attach a video. Im using pin1 of sophia (not used pin) for install the rca audio cable.

 

Regards and thx!!

 

Edited September 25, 2023 by enito

[macsonny]

I'd be interested to hear what other have to share as I have a similar problem.

[+scorpio_ny]

Hi @enito,

 

It looks like you picked up the audio from where the RF modulator was. I recommend trying picking it up from the pad for audio were the monitor port used to be was since there is circuitry there for filtering audio and see if that improves things. It sounds like there is noise picking up the circuitry. 

Edited September 26, 2023 by scorpio_ny

[enito]

Hi there thx for the reply tried too there in pad audio you mention but I have the same effect . Regards 

Edited September 26, 2023 by enito

[Beeblebrox]

Ground and centre pin connections on the rca jack around the right way? 

Edited September 26, 2023 by Beeblebrox

[enito]

2 hours ago, Beeblebrox said:

Ground and centre pin connections on the rca jack around the right way? 

Yep all correct in the right way , regards 

[+scorpio_ny]

Hi @enito

 

When I wired for audio, I usually use a separate wire apart from the video and a separate ground. I see you are sharing the same unshielded ribbon cable for both audio and video. Try wiring up an independent audio cable from the motherboard with its own ground. I recommend using shielded cabling for the new audio cable since that is such a long run directly from the motherboard.

Edited September 26, 2023 by scorpio_ny

[enito]

Hi thx for reply, but i soldered a better cable direct for test and same effect of noises..I attach a video, regards!

[_The Doctor__]

I don't see signal grounds connected, I don't see shield connected, if this is just for audio that might be ok, but

the red wire can also easily contact another pad

double check no caps are damaged

@enito  are you NTSC USA? That power supply looks like an ingot, they are death for Ataris, noisy, hum bar producing and eventually chip killing over volting boat anchors

Edited September 27, 2023 by _The Doctor__

[enito]

Hi , the red one is using to ground , i use multimeter and not contacting anything more. The blue one is + , i tested with multimeter to rca connector and all is fine. Ground to Ground and + to +,
 

Regards

 

[enito]

1 hour ago, _The Doctor__ said:

I don't see signal grounds connected, I don't see shield connected, if this is just for audio that might be ok, but

the red wire can also easily contact another pad

double check no caps are damaged

@enito  are you NTSC USA? That power supply looks like an ingot, they are death for Ataris, noisy, hum bar producing and eventually chip killing over volting boat anchors

Hi, yes is a NTSC USA 600XL, and i tested with two ones psu. One Atari and other "modern" one, same effect.

 

Regards!

 

[Overange]

Have you put it back to stock to double check you do not have a potentially faulty Sophia?

Whilst the Sockets are exposed/open maybe worth cleaning the sockets?

 

Have you replaced the main board electrolytic caps recently?

If not, may be worth trying that...

[enito]

Sound good replacing caps , but Wich one can be interfered with sound ? I try too soon uninstall Sophia and try . Thx for the tips 

[Beeblebrox]

37 minutes ago, enito said:

Sound good replacing caps , but Wich one can be interfered with sound ? I try too soon uninstall Sophia and try . Thx for the tips 

Can you post a hi res image of the 600XL's pcb and also some close ups of the caps. Do any of the caps look compromised, bloated, leaking, any holes? Also the solder points on any of them either side of the board cracked or dulled? 

[enito]

Hi there, i attach some photos hope the quality is good and clear. I replaced one cap look a bit badly, but the noise continue. thx !!!

 

[_The Doctor__]

I don't remember exactly but the caps near the op amp, 103? 102? etc...

Follow the traces in to and from the op amp to your lead!

Edited September 27, 2023 by _The Doctor__

[Overange]

5 hours ago, enito said:

Hi there, i attach some photos hope the quality is good and clear. I replaced one cap look a bit badly, but the noise continue. thx !!!

 

 

 

Looks like you have replaced all the audio caps, but not the power caps?

 

 

Just to be clear, you have the red on the Ground 0 Volt Plane and the Blue on the Audio Live output?

 

I do not know how you got it wired at the other end?

 

 

 

Anyone know what the diode bridging the Crystal is for, is it an NSTC Thing?

 

 

 

[Overange]

10 minutes ago, Overange said:

 

Looks like you have replaced all the audio caps, but not the power caps?

 

 

Just to be clear, you have the red on the Ground 0 Volt Plane and the Blue on the Audio Live output?

 

I do not know how you got it wired at the other end?

 

 

 

Anyone know what the diode bridging the Crystal is for, is it an NSTC Thing?

 

 

 

forgot to add

 

 

That wire is floating / unattached ?

 

 

And can you open up this part, so we can see what is going on? 

Thanks

 

 

Edited September 27, 2023 by Overange

[enito]

Hi , for doing a clean test i removed sophia card, and the trouble still continue. Noise continue, the cable distribution to rca is red to ground (case of rca plug) and blue to + (pig of rca).

 

Regards!

 

[enito]

The floating cable from sophia card is only a test cable for the first try for connect audio from there to pin1 of db9 and rca to monitor, but this one is disconnected.

 

[+scorpio_ny]

@enito,

 

Do you have any other speaker or monitor that you a connect the audio to to?

[enito]

Yes, im sure the speaker of monitor is good but i tested with another direct speaker..Same effect noise.

 

I attach a video, Regards!

 

[+Stephen]

That sounds a lot like a known transistor issue with some old Akai reel to reel players.  However, I think the transistors in question were germanium type.  If you have verified that the power supply is outputting a clean 5 volts DC (no noise or AC ripple), you may want to change the transistors in the audio output path.

[enito]

4 hours ago, Stephen said:

That sounds a lot like a known transistor issue with some old Akai reel to reel players.  However, I think the transistors in question were germanium type.  If you have verified that the power supply is outputting a clean 5 volts DC (no noise or AC ripple), you may want to change the transistors in the audio output path.

Sound good, i thinked the transistor is the 3 ones 2N3906 near of the area of sound. But you mention germanium style, i think i a bit confused .. Regards!

[+Stephen]

44 minutes ago, enito said:

Sound good, i thinked the transistor is the 3 ones 2N3906 near of the area of sound. But you mention germanium style, i think i a bit confused .. Regards!

Sorry - I mentioned the old type of transistor in the Akai units as being germanium.  All newer stuff since probably late 60s to early 70s has been silicon transistors.  But I have definitely heard "noisy" transistors like this before.  In my Akai reel to reel, as it warmed up, it would sound like someone was blowing wind into a microphone.