Heavy Sixer Image disapear after 30 seconds

[Avenger75]

I am currently repairing a sears heavy sixer.

I have plugged on it a simple composite mod (with 2 resistor and 1 transistor) as I was not able to retrieve an image with the RF output.

I am facing a strange problem, the image and the sound appears when I plug on the VCS and the image is clear and acceptable, sound is good.

But after at least 30 seconds, the image disapear, and it is not possible to have it coming back, except by switching off then on the VCS. THen the image is OK, but disapear after 30 seconds.

I have changed all the capacity of the switch motherboard, and also exchanged the TIA, CPU and RIO with the one of another NTSC VCS, but I'm not able to fix this problems.

 

What can be the root of this backs screen after 30 seconds ?

 

I have changed quite all component of the Switchboard card, even the regulator A101 .

 

[+-^CrossBow^-]

Are you using an original power supply or after market?

 

[Avenger75]

I'm using an after market power supply,  but it is a model that work well with my other VCS.

[+-^CrossBow^-]

19 minutes ago, Avenger75 said:

I'm using an after market power supply,  but it is a model that work well with my other VCS.

Well I'm only asking because something similar came up from someone else recently and I believe using a different PSU took care of the issue. Is your other VCS AV upgraded in the same manner?

 

 

[Avenger75]

yes, my other VCS is an ATARI heavy sixer,  and the current VCS I try to repair is a Sears Heavy sixer.

They have both a composite mod using 2 resistor (2.2 K and 3.3 K) and 1 transistor.

Is there a difference of power supply between Sears and atari unit ?

[Avenger75]

I made test with another power supply, and get same result, the screen turns black after 30 seconds.  😞

[+-^CrossBow^-]

From here you need to put it back to stock condition and see if the issue remains. If not, it might be an issue with the transistor on the composite amp board?

 

[Corby]

Heat sink?

[Avenger75]

On 12/16/2022 at 12:55 AM, -^CrossBow^- said:

From here you need to put it back to stock condition and see if the issue remains. If not, it might be an issue with the transistor on the composite amp board?

 

I have replaced the transistor of composite amp board and problem remained the same.

 

On 12/16/2022 at 12:56 AM, Corby said:

Heat sink?

I changed it also as I thought it was maybe involved, but the image still disapeared as before .

Thanks for helping anyway, as it convinced me that maybe TIA or 8507 processor had trouble.

 

I was guessing that maybe the TIA was not working correctly, and by swaping the TIA with the one of another VCS, the problem was solved !

Now I need to buy another NTSC TIA.