Lynx power issue

[thefred]

I have started to repair a few of my broken Lynx.

I have a Lynx 2 that would power on once batteries are installed into the system. It also powers on once the power brick is connected.

I figured it was a short in the flex cable, I have replaced it and the same thing. It even does it with the flex cable disconnected, I replaced the power circuits thinking one of them was shorted and the same thing. It does not power on with the game out. 

What is the next thing to check? I changed the diode, mosfet, and the two transistors and still have the same result, I don't see any shorts on the controller connector.

Thanks

[thefred]

I also have a Lynx 1 with the same issue, that one looks like it was worked on before I got it, Looks like some traces may of been bridged. I'm holding off on that one till last.

I also have a Lynx 2 that won't power on, I hooked voltage to the bypass cap and it did power on, but has no display or sound.

I have a Lynx 2 that had an issue, but I was working with Crossbow a little while back, Looks like the issue is the cart connector, I just desoldered the old one, Going to install the replacement one and that one should be fine.

I bought a few Flex cables and speakers from Best Electronics and they worked out great on a few others I had issues with. I also installed BennVenn screens on 2 of them. It is easy to do with the rev5 and with the rev6 coming out you will have the dial to control the brightness.

These old systems aren't too bad to work on. Installing the power rebuild circuits are a little hard to see but are doable. Colsole5 has them for a good price.

I have some work ahead of me for the next few weeks.

Any suggestions on my original post would be great. I cant figure out why it is powering on as soon as power is applied.

[+-^CrossBow^-]

The one you mentioned that you have replaced everything and it powers on by itself even with the flex removed would likely be a faulty U6 as that is basically a flip/flop for turning the power on and off. Might be it is stuck ON since the Lynx shouldn't power on normally without pressing the ON button, or if you bypass the power stage as I described for testing.

 

[+Stephen Moss]

For those Lynx's that power on as soon as a power source is applied, if you have a DMM measure...

The voltage between pins 7 & 10 of U6, it should measure around 9V DC

Also Measure the voltage between pins 7 & 8 and between pins 6 & 7 of U6, which should measure about 0V DC

If you do not get those values then the issue probably lies with U6 and associated components as CrossBow said, if you do get those values then someone may have bypassed Q12 or Q12 may have a Source-Drain short.   

[thefred]

Thanks guys, I will check that out this afternoon. One thing to note, the lynx 1 would power off when you hit the off button but the lynx 2 wouldn't.

[thefred]

Pins 7-10 is 9V, and 6-7 is 5V and 7-8 is 9V.

That would mean the U6 is bad then? Anything else to check?

[thefred]

I revisited the Lynx 1, I gave misinformation on my second post, if I provide power to the bypass cap it comes on. It does not come on by the power button. I think that one is a broken trace on the power on button line. It seems to play correctly with the bypass cap powered. 

I think I am working on too many at the same time.

[+Stephen Moss]

13 hours ago, thefred said:

Pins 7-10 is 9V, and 6-7 is 5V and 7-8 is 9V.

That would mean the U6 is bad then? Anything else to check?

Well you have not made any errors it looks like there is definitely something wrong there as not only are pins 6 & 8 the wrong voltage for when the lynx should be off the should be connected and so at the same voltage.

Powering the lynx from the batteries or its ac adaptor I would measure the voltage from pin 7 of U6 to all the other pins, those reading may help to determine if U6 alone is the problem, also try pressing the off button to see if it will turn off or is permanently on once the power source is connected 

11 hours ago, thefred said:

I think I am working on too many at the same time.

Yes, just work on one at a time, it is easier for you and anyone trying you help you to know where you are an not be talking at cross purposes in regard to different lynx's. Also what you learn from working on one you can then apply to working on the others which may make it easier and quicker to locate the problem.

[thefred]

From pin 7 voltages

1-4.2

2-5

3-5

4-3.5

5-3.3

6-5

8-8.2

9-.3

10-8.5

11-7.6

12-.5

13-3.5

14-5

 

The system does not turn off with the power off button.

[+Stephen Moss]

Those readings are all kinds of wrong.

With the Lynx on it is essentially a switching supply and do the exact reading for pins 1 to 6, 8 & 9 depend on the meter being used but I would expect them all to be about the same yet...

4 & 5 are a little lower then the rest and 5 should be the same as 9, could that be typo and you meant 3.3 as pin 5, in not that is very wrong.

I would expect 8 & 6 to be the same as they are connected together yet that are not.

11 & 12 should essentially be the same but they are not.

You have the supply pin at 5V and pins 8, 19 and 11 above that which is not possible.

 

At the moment I would be leaning towards either a bad U6 or just a bad solder joint on either pin 7 (GND) or 14 (Vcc), most likely pin 7. However I like to get as much accurate information as possible so... 

Do you know which pins are which on U6? Some people are unaware that 1 is top left and increase sequentially down the left side, then up the right which can result in misleading readings as values are ascribed to the wrong pins. 

I need to establish if the power rail voltages are correct in case an incorrect voltage could explain those readings, were you using an external 9V power source or a fresh set of batteries when making the measurement?

What is the voltage measurement across (one meter probe each end) D11 (top edge, left of VR1) and C52 (below U6).

What is the voltage across either D12, C44 or R75 (below VR1 and right of TP19)?

Does U6 get hot? 

With all power sources disconnected what is the resistance measurement across the Source (indicated on PCB and Drain (large tab on bottom edge) of Q12, make the measurement with the meter leads connected in both directions.

 

[thefred]

I think I must of been reading the pins wrong then. 1-7 should be right but the rest 8-14 are reversed. I was reading them 1 and 8 on the top. Wasn't thinking. Heading on a trip for work till Sunday. Wasn't getting hot.

[+Stephen Moss]

23 hours ago, thefred said:

I think I must of been reading the pins wrong then. 1-7 should be right but the rest 8-14 are reversed.

If that is the case then the values make more sense with the exception that the voltages for pins 10, 11, 12 & 13 are those for the on state as so that at least in part explains why the Lynx is on.

Possible causes are a fault with U6, a stuck On button , a problem with C38 or possibly a problem with Q7.

 

First disconnect the button (narrower) flex circuit from its socket, if the Lynx still immediately powers on when the AC adaptor or batteries are inserted we can eliminate a stuck "On" button.

 

If you have a small piece of (preferable solid) wire (i.e. a paper clip) use it to connect pin 7 of U6 to either Pin 11 of U6 or the bottom end of R70 (right of U6) for a couple of seconds, that should be enough to switch the Lynx off. If it does, does the Lynx remain off when the wire is removed or does it only remain off while the wire is in place?

 

If the Lynx remains off with the wire removed does using the wire to link pin 14 of U6 to either Pin 11 of U6 or the bottom end of R70 turn it on again?

[thefred]

18 minutes ago, Stephen Moss said:

If that is the case then the values make more sense with the exception that the voltages for pins 10, 11, 12 & 13 are those for the on state as so that at least in part explains why the Lynx is on.

Possible causes are a fault with U6, a stuck On button , a problem with C38 or possibly a problem with Q7.

 

First disconnect the button (narrower) flex circuit from its socket, if the Lynx still immediately powers on when the AC adaptor or batteries are inserted we can eliminate a stuck "On" button.

 

If you have a small piece of (preferable solid) wire (i.e. a paper clip) use it to connect pin 7 of U6 to either Pin 11 of U6 or the bottom end of R70 (right of U6) for a couple of seconds, that should be enough to switch the Lynx off. If it does, does the Lynx remain off when the wire is removed or does it only remain off while the wire is in place?

 

If the Lynx remains off with the wire removed does using the wire to link pin 14 of U6 to either Pin 11 of U6 or the bottom end of R70 turn it on again?

The lynx powers on with the flex circuit unplugged, I will try your suggestions on Monday and let you know what I find out. I am traveling with work the next few days. Thanks again for your help.

[thefred]

On 1/28/2021 at 5:38 AM, Stephen Moss said:

If that is the case then the values make more sense with the exception that the voltages for pins 10, 11, 12 & 13 are those for the on state as so that at least in part explains why the Lynx is on.

Possible causes are a fault with U6, a stuck On button , a problem with C38 or possibly a problem with Q7.

 

First disconnect the button (narrower) flex circuit from its socket, if the Lynx still immediately powers on when the AC adaptor or batteries are inserted we can eliminate a stuck "On" button.

 

If you have a small piece of (preferable solid) wire (i.e. a paper clip) use it to connect pin 7 of U6 to either Pin 11 of U6 or the bottom end of R70 (right of U6) for a couple of seconds, that should be enough to switch the Lynx off. If it does, does the Lynx remain off when the wire is removed or does it only remain off while the wire is in place?

 

If the Lynx remains off with the wire removed does using the wire to link pin 14 of U6 to either Pin 11 of U6 or the bottom end of R70 turn it on again?

The lynx does not power off when pins 7-11 are shorted.

Sorry for the delay, I have been busy with work.

[+Stephen Moss]

Don't worry about the delay, the all that other things that take precedence from time to time.

Measure the voltage on pin 10, 11, 12 & 13 of U6, from earlier test think you will read 0, 9, 9, 0 respectively, if that is the case what does it read after you have shorted pin 7 & 11 of U6 for a couple of second and removed the short?

If you still read 0, 9 ,9, 0 and have a second person with a steady hand available (or can solder in the pin 7-11 short what voltages do you get on those pins with the short in place?

 

Also measure the voltage between pins 10 & 13 (one meter lead on each).  

 

Would still be helpful to also know... 

What is the voltage measurement across (one meter probe each end) D11 (top edge, left of VR1) and C52 (below U6).

What is the voltage across either D12, C44 or R75 (below VR1 and right of TP19)?

With all power sources disconnected what is the resistance measurement across the Source (indicated on PCB and Drain (large tab on bottom edge) of Q12, make the measurement with the meter leads connected in both directions.