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LYNX 2 On/Off Problems Need Help


sub2001zero

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Ok, I did some additionnal test.

 

Values are changing on U6.

11,42v when in supposed OFF position

10,50 when in supposed ON position with no other sign of life.

 

OTher point, wiring headphone neg to battery neg doesnt do anything.

 

Any idea??

Edited by Jaybezeone
additional testing
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I would not expect to see any change by shorting C38 as that would be to turn if off and your problem is that you cannot turn it on.

 

I am surprised you did not see an change in voltage from  by briefly shorting pin 14 of U6 (top right corner in image a few posted up) to C38, try the same thing but directly to pin 11 of U6,

If U6 is operating correctly then you should see a change at least in pins 10, 11, 12 & 13. Otherwise I would think that U6 is defective.

 

If you have access to a 5V power supply then with the lynx power unit/batteries detached you could attach it to C44 (just right and above U6) or R75, but make sure you get the polarity correct, in the image a few posts up the top of C44 & R75 should be 5V and the bottom 0V (GND). If lynx powers up that will at least confirm that the problem is with power stage.  

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3 hours ago, Stephen Moss said:

I would not expect to see any change by shorting C38 as that would be to turn if off and your problem is that you cannot turn it on.

 

I am surprised you did not see an change in voltage from  by briefly shorting pin 14 of U6 (top right corner in image a few posted up) to C38, try the same thing but directly to pin 11 of U6,

If U6 is operating correctly then you should see a change at least in pins 10, 11, 12 & 13. Otherwise I would think that U6 is defective.

 

If you have access to a 5V power supply then with the lynx power unit/batteries detached you could attach it to C44 (just right and above U6) or R75, but make sure you get the polarity correct, in the image a few posts up the top of C44 & R75 should be 5V and the bottom 0V (GND). If lynx powers up that will at least confirm that the problem is with power stage.  

Hello thank you for stepping in.

So no 5v directly now, I ll try.

I did try with 5v : nothing with R75 or C44. Do I need to power on with the button ? I tried but nothing as well.

For U6
once connected :

For pins 8 to 14 : 0 / 11,47 / 11,47 / 0 / 0 / 11,45 / 11,47

once C38 tracked to Pin 11 :

For pins 8 to 14 : 0 / 10,45 / 0,25 / 9,6 / 10,63 / 0,37 / 10,46

 

I really don't know how to interpret this as I am expecting 5/6v max...

Edited by Jaybezeone
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4 hours ago, karri said:

The first question that comes to mind... How can you get 12V readings out of a power supply that should have a maximun voltage of 9V?

 

When fixing a Lynx something around 6V would be more appropriate.

I  saw multiple feed saying a approx 12v on U6 is normal when off... don't know, I had same thought as you.

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23 hours ago, Jaybezeone said:

OTher point, wiring headphone neg to battery neg doesnt do anything.

I strongly advise again doing that as it results in those parts of the circuit that should be running at 5V to run at 9V. However, as you have already done so it does indicate that a blown MOSFET is not the issue, or at least not the sole issue.  

20 hours ago, Jaybezeone said:

So no 5v directly now, I ll try.

I did try with 5v : nothing with R75 or C44. Do I need to power on with the button ? I tried but nothing as well.

For U6
once connected :

For pins 8 to 14 : 0 / 11,47 / 11,47 / 0 / 0 / 11,45 / 11,47

once C38 tracked to Pin 11 :

For pins 8 to 14 : 0 / 10,45 / 0,25 / 9,6 / 10,63 / 0,37 / 10,46

 

I really don't know how to interpret this as I am expecting 5/6v max...

If the flex circuits were connect, a cartridge was inserted and you correctly applied the 5V DC supply then the Lynx should normally power up as soon as the power is switched on as connecting 5V to R75 or C44 essentially bypasses the entire Lynx power stage including the power buttons and provides 5V to everywhere that needs it. So if that did not work you might have a major problem, however going back to you indicated that it did come on while shaking it, which may suggest a bad connection/solder joint somewhere.

 

You should not expect 5/6V max here (except for maybe pins 8 & 9), if you look at the power stage section of the schematic components drawn to the left of the MOSFET are operating at approximately 9V (when Lynx is operating), and those to the right of the MOSFET (excluding U6 gates) are essentially at 5V relative to the primary 9V power rail (Zenner subtract 5V from 9, remaining 4V dropped across MOSFET) . Which is why you have to be careful where you put the COM lead of your DVM otherwise you get anomalous readings such as those parts of the circuit that are running with a 5V supply looking like they are at 9V.

 

Well from those readings it looks like pins 10,11,12 & 13 are changing logic states from their Off States to their On states, which is what I would expect. I am not sure why you reported no change before, may your probing remade a bad connection or you just made an error before.

Pin 14 does not change, but it should not being the power pin, but nor do pins 8 & 9 which should be toggling between high and low states. I suspect Q8 but if you can get the pins into that state (U6 pin 10 close to 0V) again with the COM lead of you meter on Pin 7 (bottom Left) of U6 can you measure the voltage on all pins of U6 and all pins of Q8  

   

18 hours ago, Jaybezeone said:

I  saw multiple feed saying a approx 12v on U6 is normal when off... don't know, I had same thought as you.

Unregulated (unstablized) power units like those for the Lynx, 2600 and other consoles that have internal voltage regulation use transformers that are under rated for current, over rated for voltage but approximately the same output power, i.e. a power unit with a rated output of 9V @ 500mA (4.5W) may use a transformer with an output of 12V @ 400mA (4.8W). Consequently, it is only when the unit is operating and drawing current that voltage losses in the transformer bring the output voltage down to approximately that of the rated output. 

This is a cheap pseudo from of power regulation that allows manufactures to use smaller cheaper transformers. The downside is that the transformer losses create heat (a 3 volt drop @ 500mA = 1.5W of additional heat) so the power units can get a little toasty after long periods of use.

 

It is easy to tell if a power unit is regulated to not, if the specified output voltage is 9V and you disconnect if from the console and measure the output voltage at 9V it is regulated, if you measure in the 12-14 volt range it is unregulated, regulated power units also tend to be bigger due to transformer size and voltage regulation circuitry.    

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Thank you for your help all. BIG THANKS serioulsy I learnt a lot.

Here is the update.

 

I checked the ground... Had pb there. FIXED

That changed lot of things.

 

Now

- ON / OFF : Not working

- Same measures on U6

- C44 + Gound with 5v : WORKKKINGGGGGG yeaah

- Changed screen by a LCD

 

NExt :

Two options :

A. Go 5v for life :

--> How can I feed 5v on the board in a more definitive way ?

 

B. Find what is not working with 9v..

- U6 behave as expected

- MOSFETs seems to return values...

- Something blocks the ON OFF operation somewhere....

--> Any Idea knowing that I tested the shortage a C38 without success ? 

Edited by Jaybezeone
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On 11/11/2020 at 12:45 PM, Stephen Moss said:

Well from those readings it looks like pins 10,11,12 & 13 are changing logic states from their Off States to their On states, which is what I would expect. I am not sure why you reported no change before, may your probing remade a bad connection or you just made an error before.

Pin 14 does not change, but it should not being the power pin, but nor do pins 8 & 9 which should be toggling between high and low states. I suspect Q8 but if you can get the pins into that state (U6 pin 10 close to 0V) again with the COM lead of you meter on Pin 7 (bottom Left) of U6 can you measure the voltage on all pins of U6 and all pins of Q8 

After joy, back to work.

 

So I did this what you advised Stephen.

 

Measure on Q8 are anti-clockwise : 10.45v / unstable 6-11v / 10.50v

 

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21 hours ago, Jaybezeone said:

- C44 + Gound with 5v : WORKKKINGGGGGG yeaah

Hopefully is a good indicator that the Lynx is fundamentally working and the only problem lies with the power stage. 

4 hours ago, Jaybezeone said:

Measure on Q8 are anti-clockwise : 10.45v / unstable 6-11v / 10.50v

Cannot be certain but I don't think that is quite right, unfortunately I cannot compare to  working Lynx as it is at work and I been sent home for the duration of the Covid lockdown.

 

Use a piece of wire to again pins 14 and 11 of U6 for a couple of second so that it latch changes to the On state, confirm by measuring close to 0V on pin 10. Then...

1) Measure the voltage on all pins of U6, except for 7 and 14, as you have not previously asked I presume you know this but just to be sure Pin 1 is top Left and count increments in an ant-clockwise direction so Pin 7 is bottom Left, Pin is 8 bottom Right and pin is 14 top Right.

2) Remeasure the voltage on the pins of Q8 (located immediately to the right of the TP18 text, reference the measurements to the top Left (Base), Bottom Left (Emitter) and Right (Collector) pins.

3) Measure the voltage on the pins of Q12, reference the measurements the the Bottom (Drain), Top Left (Source) and Top Right (Gate)

4) Measure the voltage across the labelled A & K pins of D12.

  

 

 

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2 hours ago, Stephen Moss said:

Hopefully is a good indicator that the Lynx is fundamentally working and the only problem lies with the power stage. 

Cannot be certain but I don't think that is quite right, unfortunately I cannot compare to  working Lynx as it is at work and I been sent home for the duration of the Covid lockdown.

 

Use a piece of wire to again pins 14 and 11 of U6 for a couple of second so that it latch changes to the On state, confirm by measuring close to 0V on pin 10. Then...

1) Measure the voltage on all pins of U6, except for 7 and 14, as you have not previously asked I presume you know this but just to be sure Pin 1 is top Left and count increments in an ant-clockwise direction so Pin 7 is bottom Left, Pin is 8 bottom Right and pin is 14 top Right.

2) Remeasure the voltage on the pins of Q8 (located immediately to the right of the TP18 text, reference the measurements to the top Left (Base), Bottom Left (Emitter) and Right (Collector) pins.

3) Measure the voltage on the pins of Q12, reference the measurements the the Bottom (Drain), Top Left (Source) and Top Right (Gate)

4) Measure the voltage across the labelled A & K pins of D12.

  

 

 

So measures ground taken from Pin7 :

1) U6

11 / 0 / 0 / 11 / 11 / 0 / PIN7 

0 / 11 / 0.2 / 10 / 11 / 0.2 / 0.1

 

So measures ground taken from main ground :

2) Q8

Base : 0

Emitter : 0.1

Collector  : 0.1

 

3) Q12

Drain : 0

Source : 11

Gate : 11

 

4) D12

A : 0~0.1

K : 0.8~0.9

 

 

 

 

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On 11/13/2020 at 5:15 PM, Jaybezeone said:

So measures ground taken from Pin7 :

1) U6

11 / 0 / 0 / 11 / 11 / 0 / PIN7 

0 / 11 / 0.2 / 10 / 11 / 0.2 / 0.1

What is the pin order here? If 1-7 then 9-14 then there must be an error as pin 14 should be 11, not 0.1.

 

Also what do you mean by "main ground", I think I know but I need to be certain to understand the voltages you have provided that were refenced to that.

Sorry, I should have specified to measure all voltages with respect to pin 7 of U6, but I can correct in my head as necessary once I know where your "main ground" point was. 

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3 hours ago, Stephen Moss said:

What is the pin order here? If 1-7 then 9-14 then there must be an error as pin 14 should be 11, not 0.1.

 

Also what do you mean by "main ground", I think I know but I need to be certain to understand the voltages you have provided that were refenced to that.

Sorry, I should have specified to measure all voltages with respect to pin 7 of U6, but I can correct in my head as necessary once I know where your "main ground" point was. 

I'll Redo the measuring.

 

 

 

For U6, I took Pin7 as "fixed" point. The order is 1-2-3-.... anticlockwise.

 

I used the ground for all others (Q8, ...)

 

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23 hours ago, Jaybezeone said:

I'll Redo the measuring.

 

 

 

For U6, I took Pin7 as "fixed" point. The order is 1-2-3-.... anticlockwise.

 

I used the ground for all others (Q8, ...)

 

Hi there :

So before connecting U6 Pin14 and Pin 11

From Pin1->14 : 12.6 / 0 / 0 / 12.6 / 12 / 0 / PIN7 / 0 / 12.6 / 12.6 / 0 / 0 / 11.35 / 12.6

 

After connecting U6 Pin14 and Pin 11

From Pin 1->Pin14 : 12.6 / 0 / 0 / 12.6 / 12 / 0 / Pin7 / 0 / 11.1 / 0.2 / 10.45 / 11.7 / 0.35 / 11.36

 

  

 

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Definitely something wrong there as pins 1 to 6, 8 & 9 should be alternating when pin 10 is 0V.

 

With the power unit disconnected and your multi-meter on its 1K or 2K resistance range could you measure the resistance between the pins of Q8 as follows...

Top Left & Bottom Left (Base - Emitter)

Top Left & Right (Base - Collector)

Bottom Left & Right (Collector - Emitter)  

 

I need two measurements for each pair of pins, the first with the COM lead of your Multi-meter to the first pin mentioned in each pair, the second with the COM lead of your meter to the second pin of each pair. 

 

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  • 2 weeks later...

I was hoping so see a clear indication that Q8 was dead, hopefully I will be back at work on Thursday and can compare those measurement with my Lynx.  

 

I was hoping to see clear evidence of a short or open circuit between two junctions on Q8 as I suspected an issue there given the previously reported voltage readings, nonetheless the reading you provided did not look right to me, but I wanted to double check with my Lynx to be certain. On my Lynx, with no power source connected and no cartridge inserted, for Q8 I get...

 

Top Left (Base) - Bottom Left (Emmitter) = 112R / 112R, to be expected as it is reading across R74 @ 120R

Top Left (Base) – Right (Collector) = -- / 20M (over range on the 2K resistance range I requested you used),  

Bottom Left (Emmitter) - Right (Collector) = -- / 20M 

 

Your virtually identical readings (if correct) in both lead directions for two of the measurement suggests a possible short between two junction although the only way to know for certain if Q8 has a short is to remove it and remeasure its junction resistances while it is out of the circuit but if it was my Lynx Q8 that would be my top suspect. 

 

If you wanted to make further checks to eliminate any other possibilities/additional problems then...

For D13 I measure around 3000 ohms but it varies as capacitors are charged/discharged, however if there is an issue with Q8 it may alter that reading much more than those of Q7 & Q12

 

For Q7, I measure...

Top (Base)- Bottom (Emmitter) = 99K / 99K
Top (Base) – Right (Collector) = 15M / 27M
Bottom (Emmitter) - Right (Collector) = 50K+ / 50K+
 

For Q12, I measure...

Top Left (Source)- Bottom (Drain) = 99K / 99K
Top Left (Source) – Top Right (Gate) = 15M / 27M
Bottom (Drain) – Top Right (Gate) = 50K+ / 50K+
 

Edited by Stephen Moss
Added additional information following comparison measurements
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