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Atari 7800 No sound at all.


INTVCruise

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Hello, just got an NTSC 7800 console that plays fine except there is no sound at all, not when using a normal 7800 cart, pokey cart or 2600 cart. I tried adjusting the red cylinder that controls the sound frequency but no change. I think I've heard that the little clear caps on the board near channel select switch might be the cause but I wanted to be sure. Also if that is the case are the caps, that look similar, on a 2600 board compatible? Thank you for everyone's help!

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Just now, Jinks said:

Are you on the right channel?

Is your tv tuned properly? 

 

Hello, I believe so, I have a second properly working 7800 that work runs fine on the current television settings. Could the fact that I'm using a plasma television affect the results at all? All games play just fine, 2600 and 7800, there's just no sound at all, no hum, no static no anything. 

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I guess it's possible that the TV could be muting the sound when there's no sound carrier.  Do you have a multimeter?  If so, put it on AC and see if there's any voltage at C5.

 

Also, is the ferrite slug in your red tuner still in one piece, or does it look like it's crumbling?

Edited by ChildOfCv
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4 minutes ago, ChildOfCv said:

I guess it's possible that the TV could be muting the sound when there's no sound carrier.  Do you have a multimeter?  If so, put it on AC and see if there's any voltage at C5.

 

Also, is the ferrite slug in your red tuner still in one piece, or does it look like it's crumbling?

Hello, just tried the cinsole on a new tv. Its making looooouuud static. Also yes it is crumbling inside, should I replace that piece? Would a 2600 one work the same way?

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1 hour ago, INTVCruise said:

Not sure how visible it is but the little red cylindar definitly had some small chunks of grey and I flipped it over to spill them out. The grey cylindar still spins

15724063863931788295426.jpg

Then it's likely that you can't get it tuned to the proper frequency as is.  One thing you might be able to do though is completely remove what's left of the slug and buy a new replacement tuner.  You should use a hex wrench of the correct size so that you don't damage the new one.  Anyway, it may be possible to transfer the slug from a new tuner into the one that's still on the board.  I did that with the RF tuner on a 2600 of mine.

 

But yeah, the 2600 uses the same sound circuit so if you want to salvage one you could go that route.

 

If you want to try at least getting a slug replacement, try this:  https://www.mouser.com/ProductDetail/Coilcraft/143-16J12L?qs=%2Fha2pyFadugY9UaWdXf7wfS9qmHHaSWAY4T7Pj6baiBiWav1GEb1gQ%3D%3D

 

Warning:  Remove and insert slugs from the bottom.  The top is made to have a stop so that you don't twist it out completely.  Naturally that means you have to desolder it.

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2 hours ago, INTVCruise said:

Also I do have a multimeter, where would c5 be sorry for my ignorance. 

Those clear capacitors near Q1 and Q2 are C4 and C5.  Put the black probe on the metal RF modulator case and the red probe on any of those two capacitors with the setting on AC and see if you get any voltage readings.

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Just now, ChildOfCv said:

Those clear capacitors near Q1 and Q2 are C4 and C5.  Put the black probe on the metal RF modulator case and the red probe on any of those two capacitors with the setting on AC and see if you get any voltage readings.

Hello, on the 200 AC V setting they read at 10.0 each. 

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Just now, ChildOfCv said:

Those clear capacitors near Q1 and Q2 are C4 and C5.  Put the black probe on the metal RF modulator case and the red probe on any of those two capacitors with the setting on AC and see if you get any voltage readings.

Hey ChildOfCv, just replaced the little red cylindered frequency thing! Works like a charm! Thank you for your help, honestly I didn't know if that was it or not since it looked like it was in good condition upon inspection, repair literally took 30 seconds haha. I have a heavy sixer that had no sound too, looks like this might be the fix. God bless you sir!  

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10 hours ago, INTVCruise said:

Hello, on the 200 AC V setting they read at 10.0 each. 

That's an interesting reading, though the main point is to make sure they are oscillating, so nonzero.  If they weren't, then it would probably be the transistor that was the problem.  So just a note for future troubleshooting.

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20 hours ago, ChildOfCv said:

That's an interesting reading, though the main point is to make sure they are oscillating, so nonzero.  If they weren't, then it would probably be the transistor that was the problem.  So just a note for future troubleshooting.

Hello ChildOfCv, appreciate your insight, I have one more 7800 with a small problem, the flip flop chip is dead and I need a replacement, just wanted to be sure if the following chip is suitable. Thank you!

 

https://www.ebay.com/itm/5PCS-MC14013BCP-Dual-Type-D-Flip-Flop-new/123332810857?_trkparms=aid%3D111001%26algo%3DREC.SEED%26ao%3D1%26asc%3D40719%26meid%3Ddd609168794548f691e9808a4dd523ac%26pid%3D100227%26rk%3D4%26rkt%3D7%26sd%3D121407314080%26itm%3D123332810857%26pmt%3D1%26noa%3D1%26pg%3D2053904&_trksid=p2053904.c100227.m3827

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On 10/30/2019 at 2:34 AM, INTVCruise said:

just replaced the little red cylindered frequency thing!

For future reference, that thing is an RF tuning coil. It is *not* designed to rotate freely from stop to stop, like the color potentiometer. It's a completely different kind of thing. If it ever has to be adjusted, use a plastic hex wrench, as metal will affect the RF tuning that you're trying to dial in. Also - it should never be forced, or moved more than the very smallest amount in any direction - there are hair-thin wires wrapped around inside and they will break if twisted very much.

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4 hours ago, INTVCruise said:

Well, it would take about a month for that to be sent from Shenzhen.  If you're in the US, you could order from Mouser and get it sooner and from a more reputable source.

 

https://www.mouser.com/ProductDetail/Texas-Instruments/CD4013BE?qs=sGAEpiMZZMvxP%2Bvr8KwMwE%2FH01ykG3Igg0CFxBDqisc%3D

 

$0.50 each, but they do make up for it in shipping cost...

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Just now, ChildOfCv said:

Well, it would take about a month for that to be sent from Shenzhen.  If you're in the US, you could order from Mouser and get it sooner and from a more reputable source.

 

https://www.mouser.com/ProductDetail/Texas-Instruments/CD4013BE?qs=sGAEpiMZZMvxP%2Bvr8KwMwE%2FH01ykG3Igg0CFxBDqisc%3D

 

$0.50 each, but they do make up for it in shipping cost...

Oops lol, uploaded the wrong link, yeah I don't like waiting a month either haha, found a source in the U.S., just wanted to be sure that was the right chip. Thank you again. 

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