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VECTREX WITH PROBLEMS

Ok. So back to basics...

The first thing is to monitor the stability of the +5V ANA and -5V ANA power supply rails with your oscilloscope to ensure they are nice and stable with no noise on them. If there is any noise on these power supply rails we will never get a good picture.

Dave
 
daver2 said:
Ok. So back to basics...

The first thing is to monitor the stability of the +5V ANA and -5V ANA power supply rails with your oscilloscope to ensure they are nice and stable with no noise on them. If there is any noise on these power supply rails we will never get a good picture.

Dave
Click to expand...
Ok Dave, thanks!
Where is the best place to take these measurements for you?
 
You tell me...

Use the Vectrex service manual schematic. Look for the “+5V ANA” and “-5V ANA” rails and look at which pins on which chips they go to. Bear in mind that some of the ICs on the schematic are different to your particular board.

IC306 (the device you have just replaced) has these supplies on two of the pins. Download the data sheet for the MC34001 and identify the two power pins.

Dave
 
Yes i have -4,94 V on IC306/304 pin 4 and + 4,89 V on pin 7.
Stable voltage lines on scope!
 
Ok,

I would suggest putting the diagnostic cartridge into your other Vectrex and scoping the outputs of IC304 and IC306 (pin 6). Note what the picture image looks like and the oscilloscope traces from the two operational amplifiers. Then, compare and contrast the image and oscilloscope traces from the current machine (with the diagnostic cartridge running) - and look for the differences.

I am assuming that both of your Vectrex machines have an IC304 and an IC306.

Dave
 
daver2 said:
Ok,

I would suggest putting the diagnostic cartridge into your other Vectrex and scoping the outputs of IC304 and IC306 (pin 6). Note what the picture image looks like and the oscilloscope traces from the two operational amplifiers. Then, compare and contrast the image and oscilloscope traces from the current machine (with the diagnostic cartridge running) - and look for the differences.

I am assuming that both of your Vectrex machines have an IC304 and an IC306.

Dave
Click to expand...
Dave, the other Vectrex has only ic304...MC34002 :(
 
>>> the other Vectrex has only ic304...MC34002.

So look at the datasheet for the MC34002 and look for the two outputs and scope them.

Either that, or go for the connector from the logic board to the power board (J301) signals X.AXIS and Y.AXIS. They exist on both machines!

Let’s get these measurements first before adjusting the potentiometers - but, yes, this might be what is required.

Dave
 
Ok Dave :)
So these are measures on this Vectrex ( j301):
First X and after Y

 
Well, I can see some large glitches on both the X and Y traces of post #330 but not on the traces of post #331.

We need to find out where those glitches are coming from.

Do you see the glitches yourself when you view your two videos?

Dave
 
daver2 said:
Well, I can see some large glitches on both the X and Y traces of post #330 but not on the traces of post #331.

We need to find out where those glitches are coming from.

Do you see the glitches yourself when you view your two videos?

Dave
Click to expand...
Yes i can see :(
A guy from Vectrex facebook group told me that i must replace logic board and power board caps....
but it's just a guess ... I learned from you that before coming to a conclusion i must first carry out tests, right?
 
>>> A guy from Vectrex facebook group told me that i must replace logic board and power board caps....

Rubbish! That’s why we scoped the power rails, and why we are going to work backwards to find what is sourcing the glitches.

Can you scope IC302 (4052B) pin 14 please. This signal is common to both of the final opamps. Again, we are looking for glitches.

Dave
 
That’s Ok.

Just because it is 0V doesn’t mean it is incorrect!

The important thing is that there are no ‘glitches’ on it!

Dave
 
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