Jaguar repair help

[chrischuck]

Hi
     I have a Jaguar with perfect sound but messed up image. I get no image with rf but do get sound. I used a jag2gen converter on the av port to use both component and composite video cables for Sega Genesis model 2. Composite I get just sound again. Component I get perfect colors however it's a scrolling skewed messed up image. I attached an example. Any thoughts what parts I may look into. I already recapped the board reflowed cartridge pin and parts around the av connector. Turns on every time. I cleaned cartridge slot above and bellow a million times. Everything looks good and clean from when I got it. Maybe the video encoder? Since I do get the image and colors I assume nothing with the main chips.

 

[chrischuck]

Not sure if my actual text is coming through so typing this again. So I have a Jaguar with video issues as you can see in the images. I have reflowed cartridge slot. I have recapped the board. I have cleaned the cartridge slot top and underneath many many times. I have no image on rf but do have sound. I have no image with composite and so get good colors etc with component using a jag2gen adapter and genesis 2 cables. I soldered composite direct to the board and again get sound but no image. It looks like the composit signal is not working missing. My thought is possibly the video encoder. Anyone ever seen this or know if I can pull a composite signal from somewhere else on the board. Currently pulling it from the capacitor just behind the av port l6 I think it is .. 

[Stephen Moss]

It is difficult to fault find the video stages without an oscilloscope (which most people will not have/have access to) to see the actual signal.

1st, I would check the supply to U1 (Pin 1 = Vcc, Pin 11 - GND)

2nd, I would check the supply voltage to the Composite power stage, this can be found at several points and I would suggest trying them all, those points are TP5, Pin 1 of the RF modulator, the Collector of Q1 (if not sure which pin test all three) and one end of R17 (test both).

3rd, I would measure the voltage across R23, if it is static at 0V or 5V then there may not be any composite signal at that point, if the voltage is something other than either of those and particularly if it is varying that would suggest that a composite signal exist at that point, although whether or not it is a valid composite signal is another matter.

[CatQuartetGamer]

I think this behavior could happen if the console is PAL and your television is NTSC.  RF and composite wouldn't work because it is a completely different video standard.  But RGB which your cable converts to component, the colors would come through fine but it would be running at 50hz which would explain the scrolling.

[M2theCello]

If the power light is green it's PAL, this could also be a clock issue or something around that circuit if it's not 50 vs 60hz.

 

Can you share pics of the board model etc ( m vs k)

[chrischuck]

Hey 

Thanks so much for your response. I didn't know anyone had responded. Assumed I would get a notification. Anywayi went ahead and changed the video encoder. It went great but didn't make a difference. So what I do get is audio it works great. I am able to get a stable image with messed up colors by bridging l13 and l14. Weird I think I just grounded the blue signal. Anyway it's playable this way but obviously still missing the composit signal. Would be willing to do something else like sync on luma or something nif I can figure that out. Will go through voltages later tonight. 

[chrischuck]

Also it has a red light so should be NTSC. 

[chrischuck]

Also looks like there is no r23 on this board. 

[chrischuck]

Oops was looking at it the wrong way

[M2theCello]

Are the resistors above the video encoder good, can you jump straight from composite out of video encoder to the filter on the edge connector?

[chrischuck]

Have not gone through to check resistors etc. Does anyone know the pinouts of the video encoder. I started trying to map out the traces but it's a difficult taks

[M2theCello]

 

High quality schematics 

[chrischuck]

Ok well I finally got around to testing some things. 

 

Findings so far

Voltage across r23 is showing in mv so basically looks like 0. 

 

Testing of q1 

I believe the collector is the middle pin? If so it's at 4.92v the other 2 points are both about 2.2 

 

The rf modulator is 0 0 and 4.9 left to right looking at it from front of console

 

As far as r17 and tp5 I can not for the life of me find them on the board. I tested capacitor 17 just in case that was what you mentioned it is at 1.8 v

 

All other test points I could find

Tp1 2.45v

Tp2 2.55v

Tp3 2.66v

Tp4 2.8v

Tp6 5v

Tp7 2.3v

 

 

Any tips ideas thoughts would be much appreciated 

 

 

[M2theCello]

Check schematic and see values of resistors verify if all good,  if you swapped encoder maybe replacement encoder is not good? So you have RGB which doesn't need the encoder to output but somewhere in the circuit from encoder to DSP is issue

[chrischuck]

Hi. Thanks for the reply. I looked over schematic again and found tp5 and r17. 

 

Tp5 4.92v

R17 2.1v and 4.92 other end

 

Maybe I'll swap encoder again. I did have to get a few to buy them anyway. 

[chrischuck]

Just started checking around already have a few questionable resistors. 

 

R27 reads 120 instead of 100

R59 reads 75 instead of 100

[chrischuck]

On 8/11/2023 at 12:49 PM, M2theCello said:

Are the resistors above the video encoder good, can you jump straight from composite out of video encoder to the filter on the edge connector?

Do you think I can run a wire from pin 2 on encoder the composite out straight to the filter on the edge connector? I guess it would be 11b on the bottom side 

[chrischuck]

Or I guess actually to L6

[M2theCello]

Yes try a jumper to it yes

[Stephen Moss]

On 8/23/2023 at 12:00 AM, chrischuck said:

Findings so far

Voltage across r23 is showing in mv so basically looks like 0. 

Not knowing exactly what signal level should be coming out of U3 and considering that DVM's are not good with fast moving signals I will have to check against my Jaguar for verification, but for now I would say that could be a problem as that it may not be enough alter the base bias of Q6 to pass the component video signal through Q6.

UPDATE:

No R23 in the Jaguar I was using but the signal was 435mV which seems reasonable, by your original comment I assumed you were be getting about 1/10th of that.

 

On 8/23/2023 at 12:00 AM, chrischuck said:

Testing of q1 

I believe the collector is the middle pin? If so it's at 4.92v the other 2 points are both about 2.2 

If that is indeed the collector the Voltage looks right as it should the 5V supply, the others are not what I would expect if Q6 is always conducting but could be OK given there may be a fault and it is not always easy to know exactly what effect it may have.

 

UPDATE:

Looking from the Front of the Jag I measured...

0.478V Emitter (Top left Pin)

1.149V Base (Top Right Pin)

4.88V Collector (Bottom Pin) 

 

On 8/23/2023 at 12:00 AM, chrischuck said:

The rf modulator is 0 0 and 4.9 left to right looking at it from front of console

Sounds right to me.

 

UPDATE:

Left to Right I measured 0V, 1.01V (I think) & 4.88V

 

On 8/23/2023 at 1:50 AM, chrischuck said:

I looked over schematic again and found tp5 and r17. 

 

Tp5 4.92v

R17 2.1v and 4.92 other end

The 4.92V is what I would expect, 2.1 maybe OK.

 

UPDATE:

4.8v & 1.175V

 

On 8/23/2023 at 12:00 AM, chrischuck said:

All other test points I could find

Tp1 2.45v

Tp2 2.55v

Tp3 2.66v

Tp4 2.8v

Tp6 5v

Tp7 2.3v

Could be generally useful as a general reference but I don't think they will be with this particular issue as not really relevant to video circuitry.

 

On 8/23/2023 at 2:02 AM, chrischuck said:

Just started checking around already have a few questionable resistors. 

 

R27 reads 120 instead of 100

R59 reads 75 instead of 100

Resistors do not always read the correct value when measured in circuit as the test signal from the DVM can leak though parallel connection with of other components affecting the reading. Barring a major cockup during manufacture, a bad resistor will always read higher than its value, so R59 is probably fine as it is reading lower, R27 maybe a little off (should be 95-105) but again is probably OK. Again I will check against a Jaguar I have for confirmation.

 

UPDATE:

R27 = 101Ohms

R59 = 99.3 Ohms

 

On 8/23/2023 at 2:45 AM, chrischuck said:

Do you think I can run a wire from pin 2 on encoder the composite out straight to the filter on the edge connector? I guess it would be 11b on the bottom side 

I don't know what output signal level encoder produces but the intermediate circuitry is there to condition it to the correct voltage, but given that the intermediate circuitry (Q1, Q6 and associate resistors) looks like a Darlington pair configuration to give a lot of gain I doubt the signal output would be sufficient to dive a composite input directly.

Also, there is the possibility of damaging the comp out of Q3 and if you were to do that (I would not recommended it) then you should remove R18 & R67, because if there is an issue with the intermediate circuity leaving a connection back to it via either of those resistors could have a negative impact on the Q3 comp out signal, thereby rendering the whole point of making the direct connection futile.

[M2theCello]

Oh and I forget did you recap the console? Another shop had issues with a Jag due to high esr, lower quality, caps they got from console5 ( normally their cap quality is very good , but in this case it caused a delayed RSOD boot)

[chrischuck]

I did recap with console 5 caps. I had the issue before the recap as well though

[chrischuck]

Also I would think the caps are good. I am able to get it to play and it boots Everytime etc. Just no composite. 

[Stephen Moss]

I updated my previous post with the measurements from a Jag I have for comparison.

 

@chrischuck It looks like something is definitely not right with your Jag given the readings I took, I'll have a think about it over the next few days.

In the meantime perhaps retest the values for R27 & R59 (ensuring the power is off, and in both directions) in case you accidently measured the wrong one, particular the latter as maybe you were measuring R67 instead which is 75 Ohms.

 

Also check the voltage both sides or R18. 

[chrischuck]

For r18 I get 2.2v and 4.9v

For r67 120ohm

For r59 75ohm

 

Only had a minute to look at thinga this morning. Maybe I'll take a deeper look again tonight. 

 

I had asked over at the retrosix discord and he said sounds like sync is missing. No image on composite and messed up image with rgb