Hi,
Problems with my VR machine again..
The problem I have affects the logic system, which is mostly controlled by a 74LS139 (2line- 4 demux)
I notice that its getting the correct signals in, but giving nothing out.
So I changed the chip..
Same problem.
One of the issues is I get very quiet, but heavily distorted audio.
What I tried, is remove the chip from the socket, so to be able to check the voltage going to it.
Upon machine boot-up, I got fully working audio.
But when I put my meter on the pins to check the voltage, I only got about 1.8v, instead of 5, and it dropped over about 3 seconds to less that 0.5v
Also, at the time of contact, I lost the audio back to the distorted - so I guess that the audio voltage is dropping too.
Any ideas why I`m getting a voltage drop, especially when I use the meter.
And seemingly completely when the IC is in place.
Simon
Problems with my VR machine again..
The problem I have affects the logic system, which is mostly controlled by a 74LS139 (2line- 4 demux)
I notice that its getting the correct signals in, but giving nothing out.
So I changed the chip..
Same problem.
One of the issues is I get very quiet, but heavily distorted audio.
What I tried, is remove the chip from the socket, so to be able to check the voltage going to it.
Upon machine boot-up, I got fully working audio.
But when I put my meter on the pins to check the voltage, I only got about 1.8v, instead of 5, and it dropped over about 3 seconds to less that 0.5v
Also, at the time of contact, I lost the audio back to the distorted - so I guess that the audio voltage is dropping too.
Any ideas why I`m getting a voltage drop, especially when I use the meter.
And seemingly completely when the IC is in place.
Simon