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Atari Lynx II: repair problem with blown capacitors


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#1 GuybrushThreepwood OFFLINE  

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Posted Thu Feb 1, 2007 7:41 AM

Hello to everyone! As you can see, I'm new here and I've found this forum very interesting! Having a place where we could speak about our beloved Lynx is a great thing!
I've a problem with two Lynx: the both of them won't power up anymore. I don't know their story but I'm sure that the both of them have two blown capacitors near the volume potentiometer (I've seen from the schematics that the Lynx I has only one capacitor in that zone: perhaps has it something to do with stereo sound?). The capacitors specs are: 470uF, 6,3V. I've bought some replacement capacitors and replaced them but the Lynx still doesnt' power up.
Any idea? Thanks in advance for your replies! :)

#2 Video OFFLINE  

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Posted Fri Feb 2, 2007 3:51 PM

Well, it may be that the button is bad itself, there's some other topics on here about that. I'm surprised someone hasn't already come by and talked to you het. But yeah, if the capacitor is blown it helps to replace it. However, if it blew, it may have taken something else out with it, or had another problem that caused it to blow in the first place. Maybe someone will get back to you to be sure though.

#3 GuybrushThreepwood OFFLINE  

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Posted Fri Feb 2, 2007 4:22 PM

Well, it may be that the button is bad itself, there's some other topics on here about that. I'm surprised someone hasn't already come by and talked to you het. But yeah, if the capacitor is blown it helps to replace it. However, if it blew, it may have taken something else out with it, or had another problem that caused it to blow in the first place. Maybe someone will get back to you to be sure though.


Thanks for your reply! :) I don't think that it's a button problem. The blown capacitors are the proof that something has happened, perhaps an electric surge, I don't know. And you're certainly right when you say that probably the capacitors have taken something else with them. Replacing them didn't help, that's why I was asking for help: I hope that it could be a common and well known issue (I'm quite sure of this because I own two Lynx with the same issue) and that someone could give me an hint. Have a good day!

Edited by GuybrushThreepwood, Fri Feb 2, 2007 4:27 PM.


#4 semicolo OFFLINE  

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Posted Sat Feb 3, 2007 7:57 AM

if the capacitors blew, it could be because they were powered in reverse.
I think there's a mosfet that tends to blow, you should search the forums for karri's posts, tripwood. I know he already explained that somewhere.

#5 GuybrushThreepwood OFFLINE  

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Posted Sat Feb 3, 2007 9:18 AM

if the capacitors blew, it could be because they were powered in reverse.
I think there's a mosfet that tends to blow, you should search the forums for karri's posts, tripwood. I know he already explained that somewhere.


Thanks for your reply! I'll make a search but I think that, if a mosfet is faulty, the replacement capacitors should have blown too, don't you think? Do you exclude an electric surge? It might have damaged the capacitors and something else (and I'd like to know what is this 'something else' to understand if there is something to do or not).
What do you think? In the meantime I'll make a search as you've suggested... Have a good day! :)

#6 GuybrushThreepwood OFFLINE  

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Posted Sat Feb 3, 2007 10:10 AM

@semicolo

I've made another search and it ended with the finding of this interesting topic that I've missed previously:

http://www.atariage....s...4&hl=mosfet

Here Karri speaks about a short circuit between the audio ground and the battery minus. Does this mean that I need to use batteries instead of the ac adapter? Could you tell me exactly how to behave? I don't want to make a mess... By the way, though the situation is almost like mine, here nobody speaks about the two blown capacitors and this makes me think that my situation is somewhat different.
Thanks again for your reply and excuse me if my questions could seem stupid but I'm not a technician.

Edited by GuybrushThreepwood, Sat Feb 3, 2007 10:11 AM.


#7 karri OFFLINE  

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Posted Sat Feb 3, 2007 1:13 PM

@semicolo

I've made another search and it ended with the finding of this interesting topic that I've missed previously:

http://www.atariage....s...4&hl=mosfet

Here Karri speaks about a short circuit between the audio ground and the battery minus. Does this mean that I need to use batteries instead of the ac adapter? Could you tell me exactly how to behave? I don't want to make a mess... By the way, though the situation is almost like mine, here nobody speaks about the two blown capacitors and this makes me think that my situation is somewhat different.
Thanks again for your reply and excuse me if my questions could seem stupid but I'm not a technician.


It does not matter if you have batteries or the AC adaptor. The wire just does the job that the MOSFET Q12 should do when you press the power on-button. That is: connect the ground of the electronics to the ground of the power supply.

You just take some wire and connect the battery ground (or minus) to the metal ground of the headphone connector. If the Lynx starts working normally then you need to buy a new Q12 component.

--
Karri

#8 GuybrushThreepwood OFFLINE  

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Posted Sat Feb 3, 2007 4:13 PM


@semicolo

I've made another search and it ended with the finding of this interesting topic that I've missed previously:

http://www.atariage....s...4&hl=mosfet

Here Karri speaks about a short circuit between the audio ground and the battery minus. Does this mean that I need to use batteries instead of the ac adapter? Could you tell me exactly how to behave? I don't want to make a mess... By the way, though the situation is almost like mine, here nobody speaks about the two blown capacitors and this makes me think that my situation is somewhat different.
Thanks again for your reply and excuse me if my questions could seem stupid but I'm not a technician.


It does not matter if you have batteries or the AC adaptor. The wire just does the job that the MOSFET Q12 should do when you press the power on-button. That is: connect the ground of the electronics to the ground of the power supply.

You just take some wire and connect the battery ground (or minus) to the metal ground of the headphone connector. If the Lynx starts working normally then you need to buy a new Q12 component.

--
Karri


@karri

Thank you very much for your reply! :) As soon as I've some spare time, I'll make a try and let you know. According to what I've read on the other topics, it seems that a faulty mosfet that causes voltages higher than the nominal levels to enter the circuitry can fry all. Do you think that it could be my case? There must be a cause for the blowing of the capacitors... Do you know what's the function of those capacitors?
Thanks again for your reply and have a good day!

Edited by GuybrushThreepwood, Mon Feb 5, 2007 10:08 AM.


#9 GuybrushThreepwood OFFLINE  

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Posted Mon Feb 5, 2007 10:21 AM

@karri

I've made as you've suggested and the Lynx powered up. The strange thing is that it powers up as soon as I insert the last battery and that any button (the on, off and the backlight) doesn't work. The power led is on and the screen is lit but it remains black (let's say grayish because the backlight is on) and I can't see nothing on it also when a game is inserted... Is it normal? I hope this is the proof that the Q12 mosfet has departed but everything else is ok though I fear that it isn't so... I remember that on another topic, someone was talking of a very similar issue and, on another (or perhaps the same), you were speaking about the replacement part for the Q12 mosfet too. I'll try to make a search and find it out.
Thanks in advance for your reply and for the help that you've already given to me! :)

Edited by GuybrushThreepwood, Mon Feb 5, 2007 10:29 AM.


#10 GuybrushThreepwood OFFLINE  

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Posted Mon Feb 5, 2007 11:17 AM

I've made some searching and I've discovered that:

Edited by GuybrushThreepwood, Mon Feb 5, 2007 11:32 AM.


#11 semicolo OFFLINE  

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Posted Mon Feb 5, 2007 12:08 PM

it's normal that the lynx powers up as soon as you insert the last battery since you jumped q12, it's a trick to bypass it.
If the lynx displays a picture when on, q12 is dead and the other components seem to be ok, if the screen remains blank, there's probably another chip that is damaged.

#12 karri OFFLINE  

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Posted Tue Feb 6, 2007 1:40 AM

The first thing I usually do after I get it to power up is to measure the voltage that goes to the Lynx. It should be around +5V. There is not much point fixing anything else before the power is ok.

If the voltage is much higher you have already fried some chips if it is much lower then some chip has sacrificed itself and it drains the power. In either case it is very difficult to fix the Lynx.

When the power is also OK and nothing happens I usually connect a wire at the cart connector (pin 31 to pin 33) to fool the Lynx that a cart is inserted. As there is no cart the Lynx should show the message INSERT GAME at startup.

If still no life then you could see if the crystals are oscillating at all with an oscilloscope.

If you have some extra time you could also resolder all connections.
--
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#13 GuybrushThreepwood OFFLINE  

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Posted Tue Feb 6, 2007 4:57 AM

The first thing I usually do after I get it to power up is to measure the voltage that goes to the Lynx. It should be around +5V. There is not much point fixing anything else before the power is ok.

If the voltage is much higher you have already fried some chips if it is much lower then some chip has sacrificed itself and it drains the power. In either case it is very difficult to fix the Lynx.

When the power is also OK and nothing happens I usually connect a wire at the cart connector (pin 31 to pin 33) to fool the Lynx that a cart is inserted. As there is no cart the Lynx should show the message INSERT GAME at startup.

If still no life then you could see if the crystals are oscillating at all with an oscilloscope.

If you have some extra time you could also resolder all connections.
--
Karri


Thanks for your reply! I will make a try with connecting the pins 31 and 33 of the card connector but I think it wouldn't change anything. I've inserted a game and it should have just started it. I think that the trick is useful only if you haven't any cart to test the Lynx with, isn't it? How could I measure the voltage? Excuse me for the dumb question but I'm not technician, I'm quite sure that I need a multimeter and I know how to use it but I don't know where to take the measurement.
For what concerns resoldering all the connections, I can't afford this: it would be too much time spending!
Have a good day!

Edited by GuybrushThreepwood, Tue Feb 6, 2007 4:58 AM.


#14 GuybrushThreepwood OFFLINE  

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Posted Thu Feb 8, 2007 5:23 AM

Hello again! I'm quite stuck because I haven't succeded in finding out what is pin 1 in the cart connector (and consequently I can't find pin 31 and 33). I've made an extensive research but have found only Lynx 1 schematics and a lot of other useless pages. I've found out that also many other people on various forums and newsgroups have this question...
As said, I don't know where to take the voltage measurement by a multimeter.
Please, give me some advice soon! Thanks and have a good day!

Edited by GuybrushThreepwood, Thu Feb 8, 2007 7:29 AM.


#15 GuybrushThreepwood OFFLINE  

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Posted Thu Feb 8, 2007 7:49 AM

I've made some, let's say, "reverse engineering". I was thinking that I've no way for understanding what's pin 1 on Lynx classic curved lip, flat and ridged carts because the connections to the pins are covered... Unfortunately, I own only those types of carts but I remembered that, on Atari Age, there are also carts scan and I went to see one of a cart with the green pcb:

http://www.atariage....areLabelID=2690

From this image, I've understood that pin 31 and 33 are, respectively, the fourth and the second on the left side of the image and I'll connect them on the cart connector of the Lynx accordingly. :cool:

I'll let you know if it has worked or not but I'm still waiting for knowing where to measure the voltages... Have a good day! :)

Edited by GuybrushThreepwood, Thu Feb 8, 2007 7:51 AM.


#16 GuybrushThreepwood OFFLINE  

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Posted Thu Feb 8, 2007 10:54 AM

I've tried also shortcircuiting pins 31 and 33 and, as I expected, nothing changed. At this point, it's obvious that those two Lynxes can't be repaired. By the way, I'd like to know how to measure the voltages, just to learn another thing.
Thanks in advance for your reply! :)

#17 semicolo OFFLINE  

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Posted Thu Feb 8, 2007 11:40 AM

well with you multimeter set to 20V continuous, you touch a neutral point with the black probe (for example the minus of the power supply) and with the red probe you touch the point you want to test, look the "useless" lynx schematic for a point where there should be 5V.

#18 GuybrushThreepwood OFFLINE  

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Posted Thu Feb 8, 2007 12:53 PM

well with you multimeter set to 20V continuous, you touch a neutral point with the black probe (for example the minus of the power supply) and with the red probe you touch the point you want to test, look the "useless" lynx schematic for a point where there should be 5V.


First of all thanks for your reply! :) I never intended to say that the Lynx schematics are useless: though all the Lynxes I own are mk2, I find it very interesting and, first of all, a piece of gaming history.
What was useless were the pages dedicated almost to the same issues (which very rarely were solved). I've found incredible that I didn't succeed in finding a page about the cart pinout (though many people asked for it).
I'll take a look to the Lynx I schematics and make a try ASAP. Thanks again and have a good day!

#19 semicolo OFFLINE  

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Posted Thu Feb 8, 2007 5:11 PM

the cart pinout is not so hard to find : here's some I found
1 GND
2 D3
3 D2
4 D4
5 D1
6 D5
7 D0
8 D6
9 D7
10 CARD/ (this is OE/)
11 A1
12 A2
13 A3
14 A6
15 A4
16 A5
17 A0
18 A7
19 A16
20 A17
21 A18
22 A19
23 A15
24 A14
25 A13
26 A12
27 SWCON/ (this is WE/)
28 A8
29 A9
30 A10
31 Vcc
32 AUDIOIN (I/O pin but not analog, digital, for 1MBcards used)
33 Vcc
34 SWVCC

Note: A12..A19 is connected to a 74HC164 to select block
A0...A10 is connected to a 4040 to select postion
A11 is __missing__
CARD/ is strobed on reads
SWCON/ is strobed on writes

The lower 11 bits of the cart address space come from a counter.

There are 3 different games out in the Lynx-market. Most old games
use only 9 bits of this counter (512 bytes/block). All the new games
use 10 bits (1024 bytes/block) and two or three games use all 11 bits
(2048 bytes/block).

All the other address bits are directly accessible through a 8-bit parallell
port.

Edited by semicolo, Thu Feb 8, 2007 5:12 PM.


#20 GuybrushThreepwood OFFLINE  

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Posted Fri Feb 9, 2007 2:43 AM

the cart pinout is not so hard to find : here's some I found
1 GND
2 D3
3 D2
4 D4
5 D1
6 D5
7 D0
8 D6
9 D7
10 CARD/ (this is OE/)
11 A1
12 A2
13 A3
14 A6
15 A4
16 A5
17 A0
18 A7
19 A16
20 A17
21 A18
22 A19
23 A15
24 A14
25 A13
26 A12
27 SWCON/ (this is WE/)
28 A8
29 A9
30 A10
31 Vcc
32 AUDIOIN (I/O pin but not analog, digital, for 1MBcards used)
33 Vcc
34 SWVCC

Note: A12..A19 is connected to a 74HC164 to select block
A0...A10 is connected to a 4040 to select postion
A11 is __missing__
CARD/ is strobed on reads
SWCON/ is strobed on writes

The lower 11 bits of the cart address space come from a counter.

There are 3 different games out in the Lynx-market. Most old games
use only 9 bits of this counter (512 bytes/block). All the new games
use 10 bits (1024 bytes/block) and two or three games use all 11 bits
(2048 bytes/block).

All the other address bits are directly accessible through a 8-bit parallell
port.


Thanks for the informations! :) I've found them too but the problem was that nobody said what was pin 1 on the cart or on the connector. By the way, now I know what is pin 1 (thanks to AtariAge for the cart scans!)

Edited by GuybrushThreepwood, Fri Feb 9, 2007 9:31 AM.


#21 semicolo OFFLINE  

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Posted Fri Feb 9, 2007 11:19 AM

you could also check with an ohmmeter on a lynx game to find the 2 pins connected together.

#22 GuybrushThreepwood OFFLINE  

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Posted Fri Feb 9, 2007 4:45 PM

you could also check with an ohmmeter on a lynx game to find the 2 pins connected together.


You're completely right! Thanks for the smart suggestion! Now that I don't need it anymore, I've a lot of ways to discover what are pins 31 and 33! ;) I've learned something for the next time!

#23 demolithium OFFLINE  

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Posted Tue Mar 13, 2007 10:44 PM

I've made some searching and I've discovered that:


Have you found where to purchase these mosfets? I've got a lynx 2 that I've been trying so hard to get running, and I hate having a wire hanging out that I twist together when I want to play (the bat- jumped to headphone gnd). I'm new here and not trying to step on toes but I cant seem to find parts.
thanks in advance

#24 semicolo OFFLINE  

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Posted Thu Mar 15, 2007 10:58 AM

Just try to find an equivalent model, from the datasheet, the stdn12N06 is an N-channel power mosfet
Max Vdss of 60V, typical Rds(on) of 0,1 ohm and a maximum drain current of 12A.
Shouldn't be hard to find something like that with the same layout.

#25 demolithium OFFLINE  

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Posted Wed Apr 4, 2007 7:43 PM

Just try to find an equivalent model, from the datasheet, the stdn12N06 is an N-channel power mosfet
Max Vdss of 60V, typical Rds(on) of 0,1 ohm and a maximum drain current of 12A.
Shouldn't be hard to find something like that with the same layout.


thanks alot! :) I found a shop walking distance from my work that just opened to the public but carries pretty much anything an electronics junkie could possibly want. I'll give an update tomorow on what I find.




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