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Lynx 1 on/off issue


ewokmic

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Glad you got it working. I really need to take my Lynx apart and have a good look at it, in the meantime if there is more than one flex circuit which one did you change?

 

 

Those measurements did not look right, for a start you should not have the same voltage going into and coming out of an inverter gate but then as the Lynx was not in one piece and you bodged the On condition instead of measuring it having pressed the power switch they are relatively meaningless as the circuit is no longer trying to operate in the way it was designed due to you bypassing the entire power circuit.

 

 

 

You're right, the flex circuit *should* have been used to test because bypassing it ruins the whole point of testing. I only did that because I wondered if possibly the U6 was burnt or maybe something else corresponding to it wasn't working properly.. well, at least now it's working.

 

 

As far as flex circuits in the Lynx II, there's only one main circuit that controls the buttons on the face of the unit like Power On, Option 1, etc. The other flex cable is for the LCD.

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  • 11 months later...

Hi guys

I found 2 dead lynxes I this week end. The were bads mosfet in both lynx, so I changed it. for one lynx it's ok : power on and works.

For the other same issue, didn't power on, just power when I bypass the new mosfet.

So I checked the voltage on U6 as Stephen moss said previously:

(I checked the voltage with the ground probe on the pin 7 of U6)

 

System OFF System ON

1 - 9V No change

2 - 0v

3 - 0v

4 - 9V

5 - 9V

6 - 0v

7 - 0v

8 - 0v

9 - 9V

10 - 9V

11 - 0v

12 - 0v

13 - 9V

14 - 9V

I also checked the resitor:

R56 ok around 120ohm

R842 around 100 kohms and a weird thing is if I invert the probe I have just 27 kohms!

R79 ok aorund 10kohms

the inductor L6 is ok around 0 ohms, but the lynx doesn't power up when I wire Tp16 to on end of L6

I also checked is there was an open connection between R79 and pin 1 and 10: connection were ok

I also check the voltage value on the other working lynx and I didn't have the smae valur as expected up on this thread:

System OFF System ON

1 - 9v 1 - 4,4V

2 - 0v 2 - 4,4V

3 - 0v 3 - 4,4V

4 - 9v 4 - 3,91v

5 - 9v) 5 -0v

6 - 0v 6 - 0v

7 - 0v 7 - 0v

8 - 0v 8 - 4,4V

9 - 9v 9 - 3,9v

10 - 9v 10 -0v

11 - 0v 11 - 8,39v

12 - 0v 12 - 8,39v

13 - 9v 13 - 0v

14 - 9v 14 - 8,39v

Not the same value but working!!

What can I have too check now for solve this fucking power issue ;)

thanks in advance

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bdio,

with regard to the unit that works only with Q11 bypassed the “off” state voltages of U6 appear to be as I would expect them but for the system “on” state you indicate no change, presumably on all pins as you have only stated it once.

The fact that the off logic states of U6 are correct would initially suggest that U6 is generally operational and that all connections are sound, if your system on readings were taken after pressing the On button and not on as a result of the Q11 bypass the problem may be that the On button press is not being registered by U6. To test this remove the Q11 bypass, locate TP17 & TP18 (Lynx 1, think is the same for Lynx 2) and briefly touch them together with a piece of wire, thereby simulating a press of the On button, if the unit turns on then the problem probably lies with either the On button or the flex circuit and their respective connections.

 

As for the other unit which appears to work and has the expected U6 “off” voltage but screwy U6 “on” voltages can you first double check your measurements as you appear to have one gate with the same input and output voltage and pins 5 and 9 at different voltages despite both being driven by pin 4! If you get the same reading as before then from your reading the power on/off latch part of U6 (Pins 10 – 13) are normal, thus the problem must lie with the other part of the power circuit. So I would be looking at Q13 (Q8 Lynx 2) a 2N3906, R57 (R74 Lynx 2) at 120R, D12 (D13 Lynx 2) a 1N5991B 4.3V Zener, R54 (R72 Lynx 2) a 4K7 and C37 (C43 Lynx 2) a 560pF and the remaining gates of U6.

Try measuring the voltage between U6 Pin 7 and TP15 and between TP15 and TP19 to determine if the +5V supply is correct. The reason for the strange voltages could be because the remaining gates of U6 are in oscillation in which case you are fortunate the unit functions at all. One potential cause of any oscillation could be a Base-Collector short of Q13 (Q8 Lynx 2) unfortunately unless you have access to an Oscilloscope or Timer Counter any oscillation cannot be verified. I cannot really see what the function of Q13 is although I do not think it would cause any damage if it was removed for a quick test to ascertain if the “on” state U6 pin voltages looked more as one would expect without it. Although you should first try measuring the resistance of the Base-Collector junction (try leads both ways round) to see if that provides a clear indication of any short.

 

 

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Hi stephen

Thanks for your time!

Just to be clear:
For the unit that works only with Q11 bypassed:
When I measured the voltage "on" state : I did it by pressing the on button (although I don't know if it did something seeing that nothing "visible" appear). I didn't measure anything on "on" stage when the I bypassed Q11.

I have tested to touch TP17 and TP18 with a wire , but it didn't turn on the lynx :(

What can I check now, do you have another idea to elucidate this mystery ? :)

For the working one:
I have checked again the voltage on U6 and I read that (no change on off state, 2 change on state pin 5 and 6):

System OFF System ON

1 - 9v 1 - 4,4V

2 - 0v 2 - 4,4V

3 - 0v 3 - 4,4V

4 - 9v 4 - 3,91v

5 - 9v) 5 -3,92v

6 - 0v 6 - 4,45v

7 - 0v 7 - 0v

8 - 0v 8 - 4,4V

9 - 9v 9 - 3,9v

10 - 9v 10 -0v

11 - 0v 11 - 8,39v

12 - 0v 12 - 8,39v

13 - 9v 13 - 0v

14 - 9v 14 - 8,39v

You said to check:
R57 (120R) , but I don't understand what do you mean by 120R? According to the schematics it's a 47Kohm , no?
read: R57 47k
R54 4,7k

on "on" state : U6 Pin7 and Tp15: 8,40V

Tp15 and Tp19 :0,60V

And I will check the other component later : Q13 , D12 , C37

What do you mean exactly by "and the remaining gates of U6."?

Thank you again for your precious knowledge and help :)

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Sorry, typo regarding R57 - should have been R56 which is 120 ohms (120R).

By "the reamining gates of U6" I meant the other Input/Ouput pins - U6 is comprised of 6 Interver gates (Logic 1 in = Logic 0 Out and visa versa) for the unit in question the two gates forming the power On/Off latch appear to be doing what they should be so the problem appears to be with the other half of the power circuit lagergly comprised if the remainng gates of U6 (pins 1 & 2, 3 & 4, 5 & 6, 9 & 8 ).

 

I think trying to cover both units in the same post will get confusing for both of us so lets concetraite on the non operational one for now.

Using a piece of wire to connect Pin 14 of U6 to Pin 11 of U6 for a second, does this make the states of pins 13, 12, 11 & 10 change from 9V, 0V ,0V, 9V respecivetly to 0V, 9V, 9V, 0V?

If not try soldering the wire from Pin 14 of U6 to Pin 11 of U6 if you cannot get someone to hold it there for you and measure the voltages of U6 pin 13, 12, 11 & 10 with that wire in place.

 

I have to select your posts in order to see your measurement values, I do not know how you are entering those however if it is via Cut & Paste try using the "Paste as Plain Text" option (middle of the three clipboard icons).

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Hi Stephen

 

I have checked the R56 resistor on both lynxes and it's ok : 120ohms

 

You are right it's probably a bit confusing to treat both lynxes in the same time.

 

So for the non operational one I did that:

 

Plugged an DC adaptor

Measured voltage between pin 7(U6) and (didn't use the on/off button):

 

10 - 9v

11 - 0v

12 - 0v

13 - 9v

 

 

Wired for a second pin 11 to pin 14 and after measured that:

10 - 0v

11 - 9v

12 - 9v

13 - 0v

 

The same that you have expected.

 

And yes I used copy and paste for my previous post, now i try to use "paste as plain text "as you said but i confess i don't understand well the difference :)

Thanks again for your time Stephen :)

I confess to not see well the difference

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If you use standard copy & past it can include text formatting that the forum has difficulty interpreting, pasting as plain text removes those issues.

 

Those are teh voltages I would expect to see and it seems to should that the part of U6 that forms the power On/Off latch is working, as you have not reported the unit turning on after touching 6U Pin 11 to Pin 14 there is still a problem elsewhere.

Repeat the previous test, when U65 pins 10 - 13 read 0V, 9V, 9V, 0V respectively (power "On state") what do pins 1 - 6, 8 and 9 of U6 read?

Edited by Stephen Moss
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Here are the read after wired for a second pin 11 to 14.

1 - 9v

2 - 0v

3 - 0v

4 - 9v

5 - 9v

6 - 0v

7 - 0v

8 - 0v

9 - 9v

10 - 0v

11 - 9v

12 - 9v

13 - 0v

14 - 9v

 

It seems that the pin 1 to 9 don't change before or after I wired pin 11 and 14. I don't know if it's good or bad news :)

thanks again!

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The fact that pin 1-6, 8 & 9 do not change is not good news as that is why Q11 is not being switched on. With no power source connected try measuring the resistance between...

Pins 1 & 10 of U6

Pin 1 of U6 and each end of R79

Pin 10 of U6 pin and each end of R79

Pin 1 of U6 and TP14? (the one at the junction of R56, the 1N5991B Zenner and the Base of Q13) and

The resistance of R79

Check it with the leads connected in both directions.

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I measured the resistance between:

pin 1 and 10 (U6) 10Kohms

pin 10 and R79 south 10Kohms (I wrote the polarity of R79 on the picture)

pin 10 and R79 north around 0,3ohms

pin 1 and R79 south around 0,5ohms

pin 1 and R79 north 10Kohms

 

After I measured between pin 1 and TP14 (that I assume it's the red poin t on the picture) : 20,2ohms

Tp14- R79 north 10Kohms

Tp14- R79 south 20,2 ohms

 

And It doesn't change the measure if I invert the probes

post-41873-0-20315200-1465404120_thumb.jpg

I hope it will tell you something :)

 

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The results tell me that the reason for pin 1 of U6 not going low does not appear to be caused by a bad connection or faulty R79.

The measurements from TP14 to R70 north are as expected, however the measurements between TP14 and both U6 Pin 1 and R79 south are much lower that I would have expected and would suggest that Q13 (2N3906?) may be shorted thereby keeping Pin 1 of U6 high.

 

​There are a couple of things you might want to do before changing Q13...

Remove Q13 and re-measure the resistance between its Base & Emitter and between its Base and Collector (leads in both directions), assuming I have the part number correct all the data sheets I have found only show it as a non surface mount TO92 package. If you cannot identify which pins are which from visually tracing the PCB tracks (Base to TP14, Collector to Pin 1 of U6/"South" end of R79, Emitter to TP15) you can measure the resistances, you should get close to 0 ohms when you make the correct connections.

 

If Q13 is shorted then a possible cause is a failure of the Zenner diode (D12?, possibly ZD1, a 1N5991B - replace with 1N5229B) so you might want measure the resistance of that as well.

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Stephen,

 

I removed the Q13 and measure the resistance between base-collector and base emitter.

I didn't find regard to the PCB which part is collector and which part is emitter: too tiny.

but if you kkep the orientation of my picture of yesturday:

base- right pin : around 0 ohm

base left pin: no connection

 

So Q13 is shorted, right?

If I understood well I may have to change the zener diode D12 or ZD1 (depends of my pcb version) , is that right?

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With Q13 removed I would not expect a read of 0 ohms across any junction, generally I would expect more than that with the meter leads connected in one direction and a no connection reading with them in the other, if you are getting a reading of 0 ohms with the meter leads connected in both directions then Q13 the I would certainly say that Q13 has a short and needs replacing.

 

The question is did Q13 fail on its own or did something else cause that?

I do not know how accrute such reports actually are over people just reporting what they have heard but the Zenner Diode failing is often reported as a problem with the Lynx. If that has failed it may have caused Q13 to fail so it is worth checking it for short/open circuit to attempt to establish if it is also faulty (or just replace it anyway to be sure) before inserting a replacemnt Q13 as you do not want to blow the new Q13 or potentially do additional damage to the Lynx circuitry by powering it while it has a blown Zenner.

 

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thank you stephen!

 

So i will try to replace the Q13 and the zener ZD1. Do you know by which part I can change the Q13 (To92?) ?

sorry but last thing :

You said "you should get close to 0 ohms when you make the correct connections.", and in your last post you said "With Q13 removed I would not expect a read of 0 ohms across any junction"

So I am a bit lost :)

Anyway, I will change Q13 and ZD1 and tell you if it will works after that!

 

thanks again!!

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You said "you should get close to 0 ohms when you make the correct connections.", and in your last post you said "With Q13 removed I would not expect a read of 0 ohms across any junction"

So I am a bit lost :)

 

 

Because I could only find a data sheet for Q13 that had showed the pins for a TO92 (through hole) package and from your photo it appears to be an SOT23 (surface mount) package I was suggesting that you identified the Collector and Emitter pins by measuring the resistance between the pins of Q13 and one of the other components those pins should be connected to, whereby the correct connection should measure very close to 0 Ohms.

When testing Q13 I would not expect you to be able to measure 0 Ohms across any junction of Q13 itself as that would indicate a short circuit in Q13, particularly if you can read it with the meter probes connected in in both directions (one direction could cause a junction to conduct but I would still not expect a reading close to 0 Ohms)

 

The schematics for both the Lynx1 and Lynx2 are a mess, inconsistancies make it look like different parts were done by different people and then cobbled together to form a complete circuit. Unfortuantly it looks like the PCBs may have gone the same way as although there is a ZD1 clearly shown in your photo there is only one Zenner clearly shown in the schematics and it is not referenced as ZD1, I cannot find any diodes in either schematic referenced as ZD1.

Therefore you might want to check the continuity to make sure that is the correct diode, you should get a reading of 0 Ohms when making the connection from its Cathode (end with stripe) and one end of R56 (R74 Lynx2), and a reading of 0 Ohms from its Anode to one end of R78 (R75 Lynx2) if you get those then you should have the right diode.

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  • 3 weeks later...

SO I have been a little busy lately.

But I try to change Q13 and the zener ZD1 that I took of a working lynx 1.

After this change I tried to power on the lynx and tada! The lynx switched on but the screen was weird (monochrome, and some parasite) and the lynx blocked on title screen game... :?

 

So I decided to do the 5V regulator mod, and now it works perfectly !! :-D

I assume that it are one or two components that I had to remove with the mod which were incriminate.

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