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#1 2006-08-09 13:31:58

aempee
Bloody beginner
Registered: 2006-08-09
Posts: 9

groundloop?

Hi
Im new to the forum and
Im having problem with my C64. I just bought this amazing prophet64 and i tried it at my friends c64 and it worked. Now that I tested it with my on computer  I couldnt hear almost anything because of the terrible buzzing sound. Could it be ground loop that makes that buzzing noise? I bought new cable for the c64 video port that I can get audio and video separately. The picture is nice but I cant get the audio properly. Can anybody please help me?

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#2 2006-08-09 13:40:23

KONEY
PROPHET64 GURU
From: VENICE - ITALY
Registered: 2006-07-08
Posts: 1062
Website

Re: groundloop?

Try by connecting it to a telly with the RF out. If the buzz goes off, then is you cable, if its' still there, you have problems with the SID or its circuitry.

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#3 2006-08-09 16:06:22

aempee
Bloody beginner
Registered: 2006-08-09
Posts: 9

Re: groundloop?

I hope it works with 8-bit nintendos rf cable because I dont have regular rf-cable. The cable that splits audio and video that I have has ofcourse 5-din on the oher end and 4 rca on the other end. Whats that one extra rca if one of them is video and two of them audio. I hope I havent screwed up my sid or something

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#4 2006-08-09 16:12:47

KONEY
PROPHET64 GURU
From: VENICE - ITALY
Registered: 2006-07-08
Posts: 1062
Website

Re: groundloop?

the RF cable is the simplest you'll ever see. Just get a male RCA and a antenna connector and wire them respencting the ground.

That's it.

Hey I have one idea. Basically there should be a total of 2 RCA coming from. The othet 2 should be AUDIO in and LUMINANCE. Is it possible that you plugged something in the AUDIO in? Any signal fedback on it would be instantly audible on the regular OUT:...

Try connecting ONLY the audio out, as a test...

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#5 2006-08-09 17:05:22

aempee
Bloody beginner
Registered: 2006-08-09
Posts: 9

Re: groundloop?

I have to get regular rf cable tomorrow. I tried to find the audio cable from those 4 rcas.  theres red, black, yellow and white rcas and the red one is video out. I got audio from the yellow rca but there was this buzzing noise again but it was not that awfull that it was the first time. I think this noise has got something to do with my other electronic devices. I have only two sockets in the room where most of my equipment are. Now that I think I had quite similar problem last spring when I got my self a pair of active nearfield monitors. I could hear my macs harddrive from the monitors and as soon as I changed the monitors to other socket the noise stopped. I have to get some extra cables to try my commodore 64 in other room.

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#6 2006-08-09 17:54:40

KONEY
PROPHET64 GURU
From: VENICE - ITALY
Registered: 2006-07-08
Posts: 1062
Website

Re: groundloop?

Exotic problems...

However good luck, and let us know wink

Last edited by KONEY (2006-08-09 17:55:03)

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#7 2006-08-09 18:05:46

AxiMaxi
PROPHET64 GURU
From: The Netherlands
Registered: 2006-07-09
Posts: 548
Website

Re: groundloop?

I bought myself a Samson Powerbright PB11, a while back.
I didn't have any groundloop problems, and it might also be psychological, but I have the impression that my gear is quieter now.
The PC and mixer are all connected to the same socket, but there's no interference whatsoever.


If everything is under control, you're not going fast enough.

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#8 2006-08-09 19:03:24

Slorrin
PROPHET64 GURU
Registered: 2006-07-09
Posts: 871

Re: groundloop?

You don't need a "regular RF cable" because a regular RF cable in our modern age is a COAXIAL cable.  What you need is an RCA cable, and then an RCA female to COAXIAL (f type) MALE converter.

THy sell them on atariage, but you can get them at radioshack for 2$.

YOu connect a standard RCA cable to the RF out of the commodore, and then plug it into the coaxial input of any video monitor, tv, or converter box, or vcr, etc..

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#9 2006-08-10 12:12:06

aempee
Bloody beginner
Registered: 2006-08-09
Posts: 9

Re: groundloop?

I tried two of those nintendo rf adapters and i coulnt get good picture but i heard sounds of the games I tried.

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#10 2006-08-10 12:19:24

Jaicen
Centipede
Registered: 2006-07-14
Posts: 461

Re: groundloop?

Why are you using those?? The C64 has an internal modulator, you just plug a coax cable from the C64 into the aerial port of  your tv.
I use this which gives much cleaner audio: http://pinouts.ru/Multimedia/AudioVideoC64_pinout.shtml

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#11 2006-08-10 16:56:12

aempee
Bloody beginner
Registered: 2006-08-09
Posts: 9

Re: groundloop?

I think my sid is broken because when I start the prophet64 it says SID revision N/A quite often. couple of times there was 8580 but I got buzzing and sounds were barely audible. I also tried rf cable with rca on the other end and coaxial on the other and I got good picture but not sounds at all. Shouldnt that rf-cable bring both audio and video ?

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#12 2006-08-10 17:43:47

KONEY
PROPHET64 GURU
From: VENICE - ITALY
Registered: 2006-07-08
Posts: 1062
Website

Re: groundloop?

YEs, audio and video on th RF.

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#13 2006-08-10 23:24:52

Slorrin
PROPHET64 GURU
Registered: 2006-07-09
Posts: 871

Re: groundloop?

sounds like the sid isn't necessarily broken, but possibly, the sid2sid isn't in the greatest shape.

Troubleshoot the following, in the following order

Check all the connections to make sure they are good, including the wire to pin 6 or 7 of the cartridge slot (can't rememer)

make sure there are no short circuits with that wire

make sure there are no solder splashes on the c64 motherboard

once that is done, do the following

make sure your wire wrap socket inserts firmly and fully into the dip socket on the c64 main board.  the wire wrap pins are wide, and it requires some force, or you can bend the sockets insert points a little with the tip of a needlenose plier.

if it is fully inserted, about .8 CM (about the length of the sid pins) then make sure all the pins are inserte, that none have been bent out

test it again

if it works, good

if not ,do the following

remove the first sid, replace it with a different sid (say, the 2nd)

test it

if it works, good

if not, do the following

take ouyt the sid2sid board entirely

insert the sid into the board mounted socket directly

you will possibly have to press down on it to get a good conetion, as the socket on the baord will have its inputs expanded by the wide wire wrap socket pins

does it work?

if so, the sid is fine, something is wrong with the wire wrap socket (the wire wrap socket merely connects the sid into the motherboard vicariously, so if it works on the board, but not in the wire wrap, it means it's not making a connection from the wire wrap socket to the motherboard... that's wher ethe problem lies)

however, if i am not mistaken, that sort of problem will not allow the C64 to boot.  Sid errors disable the computer, generally, and removing the sid is how you trouble shoot that.

IF the sound is garbled, do the following, connect using alligator clips 2 probes to the ground and audio portion of a 1/4" audio jack

hook up a cable from the audio jack to your computer or mixing board or plug in earphones or something.

then, turn on the c64, play the sound, and try testing the audio directly from the pins on the sid, the gnd pin and the auio out pin (pinouts are online).

if say, the first sid sounds fine and the 2nd one sounds fine, FROM THE CHIP, then problem is with the sid2sid's amplification circuit for the 2nd sid.


i guess i'm trying to cover too much at once.

Clearly define the entire problem.

You have a sid2sid installed, do you have 2 sids installed?

When you have toruble with the audio, is it both sids?  1 sid? 

have youy attempted the first steps of the troubleshooting procedure?  which is to check all connections, check for short circuits, and ensure that everying is plugged in fully?

have you tested the sid outside the sid2sid, independant of the wire wrap socket?

if so, does it?

once you have inserted that wire wrap socket, you will need to accomodate the connection between sid and motherboard by pressing down on it with your finger, or it won't necessarily connect well.

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#14 2006-08-10 23:42:23

Slorrin
PROPHET64 GURU
Registered: 2006-07-09
Posts: 871

Re: groundloop?

aempee wrote:

I tried two of those nintendo rf adapters and i coulnt get good picture but i heard sounds of the games I tried.

The NES adaptor adapts something to RF.

Your C64 already outputs RF, so it would never work.

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#15 2006-08-11 00:45:18

Slorrin
PROPHET64 GURU
Registered: 2006-07-09
Posts: 871

Re: groundloop?

i have no idea.. none

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#16 2006-08-11 09:38:16

aempee
Bloody beginner
Registered: 2006-08-09
Posts: 9

Re: groundloop?

amigatrash wrote:

That's strange. Why in the world would mine work then?

Is there something wrong with my c64 or am I the chosen one?

My friend tried also that nintedo rf-cable and it didnt work properly.

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#17 2006-08-11 13:12:45

www.DOGMATECH.info
Bomb Jack
Registered: 2006-07-08
Posts: 36
Website

Re: groundloop?

Do you get better sound if the video isn`t connected?


Join the Nintendohardcoreacidkamikazesamurai army!!!
http://www.myspace.com/dogmatech

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#18 2006-08-11 13:59:37

aempee
Bloody beginner
Registered: 2006-08-09
Posts: 9

Re: groundloop?

No I dont. Its the same buzzing sound and very thin sounds some where in backround. I gave up with that particular C64 and Im going to get new one soon. I hope that the problem was with the sid chip and not the groundloop that I first thought.

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#19 2006-08-11 19:13:12

Jaicen
Centipede
Registered: 2006-07-14
Posts: 461

Re: groundloop?

If it's anything like the old breadbox I have, the background noise you're hearing is coming from the address lines attached to, and adjacent to the SID Itself. If you turn off the picture (using the Space bar), the noise should change in pitch and be slightly reduced. If this happens, then there's not much you can do without isolating the SID using a buffer, which I think has been discussed here previously.

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#20 2006-08-11 21:02:41

AxiMaxi
PROPHET64 GURU
From: The Netherlands
Registered: 2006-07-09
Posts: 548
Website

Re: groundloop?

Aempee, can you send us an audio recording of the noise to hear if there's something unusual about it?


If everything is under control, you're not going fast enough.

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#21 2006-08-26 16:19:47

AlphA
Gianas Sister
From: STL
Registered: 2006-07-13
Posts: 26
Website

Re: groundloop?

Does it sound like this?
http://www.bigmech.com/misc/GroundLoopHum.mp3
If so, it may have more to do with the wiring in your house. Test this theory by using your gear without using power-cord ground pins via adapter:
http://www.epanorama.net/documents/grou … heater.gif
or cheep 2 pin extension cord. THIS IS JUST FOR TESTING PURPOSES!
If the hum goes away, it's your wiring. Don't make the elimination of the ground pin your solution! That pin helps keep your gear and yourself safe!
One way to permanently reduce ground loop hum is to put your C64 and your mixer/recorder on separate house circuits (EG: your c64 is not using the same breaker/fuse as your recording device).

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#22 2006-08-26 18:02:55

tuluseabaska
Dan Dare
From: warsaw
Registered: 2006-07-10
Posts: 77

Re: groundloop?

I had the same problem some time ago. Very loud buzzing and very very silent sound, almost no sound at all. Then I just got this stupid idea. I've wired audio out to ground and ground to audio out. guess what. It works! perfectly. I have no idea why but it seems that it should be soldered that way. Every C64 I've tested works well with this cable, tried it on a few C64C and a C64G. Concluding from your description it might be it.

I am using soundcraft compact 4 mixer, but when i connect audio to TV it does work the regular way, not reversed. I dont' know what's going on but I can assure you there's nothing wrong with my mixer inputs. weird

Last edited by tuluseabaska (2006-08-26 18:03:45)

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#23 2006-08-29 15:47:38

aempee
Bloody beginner
Registered: 2006-08-09
Posts: 9

Re: groundloop?

hi

it wasnt about groundloop and I dont know what was wrong with my c64. I got my self another one and its working. I had to change the cover from my broken c64 because some one had messed it up really badly. my new c64 was full of dust and I would like to know how I could clean the  motherboard? Thank you very much for your help.

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#24 2006-08-29 16:07:55

basil faulty
Dan Dare
Registered: 2006-07-19
Posts: 73

Re: groundloop?

aempee wrote:

hi

it wasnt about groundloop and I dont know what was wrong with my c64. I got my self another one and its working. I had to change the cover from my broken c64 because some one had messed it up really badly. my new c64 was full of dust and I would like to know how I could clean the  motherboard? Thank you very much for your help.

detergent and water? and dry it well before you plug it in???

Seriously, I use a flux and PCB cleaning solvent -in an aerosol can.

(although I am sure that water won't harm a board - unless it's plugged in? I have got equipment wet before, and it has been fine once THOROUGHLY dry)

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#25 2008-02-03 00:35:55

Kartoshka
Pac-Man
From: israel
Registered: 2007-08-22
Posts: 208

Re: groundloop?

AlphA wrote:

Does it sound like this?
http://www.bigmech.com/misc/GroundLoopHum.mp3
If so, it may have more to do with the wiring in your house. Test this theory by using your gear without using power-cord ground pins via adapter:
http://www.epanorama.net/documents/grou … heater.gif
or cheep 2 pin extension cord. THIS IS JUST FOR TESTING PURPOSES!
If the hum goes away, it's your wiring. Don't make the elimination of the ground pin your solution! That pin helps keep your gear and yourself safe!
One way to permanently reduce ground loop hum is to put your C64 and your mixer/recorder on separate house circuits (EG: your c64 is not using the same breaker/fuse as your recording device).

No idea why but suddenly this hum appeared out of nowhere... it was perfectly ok a week ago, last time i plugged it in.
Any ideas why? i'm using 220v european 2pin socket

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