Zener Diode Replacements

[GTretro87]

Hello all,

 

Ok.. After failed attempts of doing the regulator mod.. I've decided to turn my Lynx II back to stock.

 

Instead of using the stock zener diodes (which I still have)... I thought that *maybe* standard diodes could be used - 1N4001 for example.

 

 

Boy was I wrong.. I'm no electrical engineer, but anything is worth a shot.. Or schock..

 

Anyway, I am starting to believe that by just replacing the zener diodes every other year or so should more than suffice to keep our Lynx's lasting optimally. They worked for 20 some of years, so why not.

 

 

I have found that D13 is a 4.3V 500mW zener diode.

 

Now I want to find out what D9, D10 and D11 diodes are. I will be searching around, if anybody has this info - PLEASE do contribute to this thread.

[GTretro87]

Ok so.. without having to search for these on the forum, here's the part # and a link to an example.

 

 

 

D9 through D11 - 1N4001 (http://www.ebay.com/itm/1N4001-Zener-Diode-10-pack-/131474017225?pt=LH_DefaultDomain_0&hash=item1e9c764bc9)

 

D13 - 1N4148 (http://www.ebay.com/itm/1N4148-Zener-Diode-Texas-Instruments-10-pack-/131500719326?pt=LH_DefaultDomain_0&hash=item1e9e0dbcde)

[GTretro87]

Ok so.. without having to search for these on the forum, here's the part # and a link to an example.

 

 

 

D9 through D11 - 1N4001 (http://www.ebay.com/itm/1N4001-Zener-Diode-10-pack-/131474017225?pt=LH_DefaultDomain_0&hash=item1e9c764bc9)

 

D13 - 1N4148 (http://www.ebay.com/itm/1N4148-Zener-Diode-Texas-Instruments-10-pack-/131500719326?pt=LH_DefaultDomain_0&hash=item1e9e0dbcde)

 

 

Now that I've ordered both of these sets off ebay (I'm sure I could have gotten these elsewhere not on ebay).. I'll confirm if they work or not, and if I can return my Lynx II back to bone stock form.

[phoenixdownita]

Not sure why you thought that a Zener and a normal diode are interchangeable, even a simple look at a wiki would have told you that Zener are usually used in inversion (they are optimized for it) while normal diode are not (they break down in inversion and have pretty crappy and not very predictable patterns in inversion).

http://en.wikipedia.org/wiki/Zener_diode#Uses

Be as it may, glad you found replacements.

And I know "it's easy to be wise after the event"

Edited May 20, 2015 by phoenixdownita

[GTretro87]

Not sure why you thought that a Zener and a normal diode are interchangeable, even a simple look at a wiki would have told you that Zener are usually used in inversion (they are optimized for it) while normal diode are not (they break down in inversion and have pretty crappy and not very predictable patterns in inversion).

 

http://en.wikipedia.org/wiki/Zener_diode#Uses

 

Be as it may, glad you found replacements.

 

And I know "it's easy to be wise after the event"

 

 

Oh it's very easy to be wise after an event like that.. what a slap in the face that was for me.. and I've *known* better!

 

But I knew they weren't the same from the very beginning.. but it was one of those moments at 2 AM when you say... "screw it" ..yep.. that's when you know you have to put things down and take a break. Don't think I'm not kicking myself because of that and now wondering if anything was damaged.

 

Nonetheless, I'll clean up the Lynx II, repair the cut trace for battery + (from regulator mod) with either a circuit pen (electric paint) or jumping the terminal to wherever that goes (I'll have to read the schematics).. maybe add back the original zener diodes and test to make sure nothing was damaged with my multimeter and logic probe

 

 

As far as it seems, Zener diodes really aren't THAT bad at all. Just, they're not meant to last forever... but neither are 7805's, and that's why we service our equipment.

[+karri]

I am very sceptical of electronic paint. It is definitely resistive for power traces. Use copper and solder it.

[leonk]

!?! Why would you go back to that horrible design which will eventually fail and kill your Lynx? Not to mention the common overheating associated with it!! Push forward not backwards! If all else fails have someone else fix it for you.

[GTretro87]

Yes true but how bad can it REALLY be if I change the diodes every year or other just for the sake of maintenance?

 

I definitely had a sour taste in my mouth from my lynx 2 not booting up, and my Lynx 1 has a different version PCB compared to others and that german site.. So I'm not sure if I should bother with a regulator

[leonk]

No disrespect to you but if a mod is done correctly, using quality components, quality tools by a competent modder, the improvement to the system can be accomplished once and it will last for decades with no further intervention.

 

If you are not capable of doing these sort of fixes (and adapt when your system is not exactly the same as what some guy showed on the Internet) well maybe you shouldn't have attempted the mod in the first place.

 

Any good modder with a cheap multimeter should be able to trace out your system into schematics and figure out the specific changes required to get you back on track.

 

Again no disrespect but many people over estimate their capabilities online.

[7800fan]

The version at German site works just fine. Get rid of zener diode and transistor and use a real 5v regulator in its place.

 

The stock design does not prevent excess voltage from getting dumped into entire Lynx if the transistor or diode fails. With a real 5v regulator, if that one fails usually nothing will pass through and Lynx is protected from getting fried.

 

It is entirely up to you if you want the safe and easy way by using r5v regulator, or keeping it looking "stock" with replacement zener diode.

[GTretro87]

No disrespect to you but if a mod is done correctly, using quality components, quality tools by a competent modder, the improvement to the system can be accomplished once and it will last for decades with no further intervention.

If you are not capable of doing these sort of fixes (and adapt when your system is not exactly the same as what some guy showed on the Internet) well maybe you shouldn't have attempted the mod in the first place.

Any good modder with a cheap multimeter should be able to trace out your system into schematics and figure out the specific changes required to get you back on track.

Again no disrespect but many people over estimate their capabilities online.

 

 

 

No worries, no offense taken at all. I'm fully capable of modding etc, I've done enough projects to hold those bragging rights lol. Am I great? No, because at time I'm impatient. But I *can* do the job for sure.

 

So I re-did the mod.. Now it works fine (as long as I jump batt ground and headphone ground).

 

I traced everything out, mounted the regulator out back instead of on the PCB, use he zeners on D10 and one on L14, removed D13 and Q8. I initially tested with a 7805 just to make sure that the PCB wasn't fried, and then with the R785 which definitely does the job (a lot cooler than a 7805, of course).

 

It plays great so far, LED light works.. Just the damn Power On, Off and Backlight don't work.. However, option 1, pause, and option 2 (and restart and flip) all work.. So that must be the flex circuit.. I hope... I mean the MOSFET on Q12 is outputting about +5v through the legs.. So it can't be the MOSFET.

 

I guess I'll post this on my other thread just for the sake of keeping record.

 

 

 

 

The version at German site works just fine. Get rid of zener diode and transistor and use a real 5v regulator in its place.

 

The stock design does not prevent excess voltage from getting dumped into entire Lynx if the transistor or diode fails. With a real 5v regulator, if that one fails usually nothing will pass through and Lynx is protected from getting fried.

 

It is entirely up to you if you want the safe and easy way by using r5v regulator, or keeping it looking "stock" with replacement zener diode.

 

It's too bad the zeners really aren't reliable. But one question, with the zeners in L14 and D10, if they blow and full current flows through them.. Not that I memorized the schematics, but will the regulator catch this current specifically from these??

 

Also, do you recommend another way to replace the zeners for the mod?? And perhaps another way to add a power and cut off switch in case the flex or something else is damaged?

[GTretro87]

Here are some pics

 

 

[+karri]

GTretro87:

It plays great so far, LED light works.. Just the damn Power On, Off and Backlight don't work.. However, option 1, pause, and option 2 (and restart and flip) all work.. So that must be the flex circuit.. I hope... I mean the MOSFET on Q12 is outputting about +5v through the legs.. So it can't be the MOSFET.

 

 

The whole board is at +5V when it is off. The job of the MOSFET is to connect the ground - not the VCC. So it can be the MOSFET.

Edited May 21, 2015 by karri

[GTretro87]

 

The whole board is at +5V when it is off. The job of the MOSFET is to connect the ground - not the VCC. So it can be the MOSFET.

 

Ohh.. Well maybe then. I'll upload some pics to show you my readings

[GTretro87]

Well, it's working now.

 

The MOSFET ended up being fine, probably the two others I've swapped were too. But nonetheless, I installed a new flex circuit from Best-Elecs. and it now finally powers on and off well with the buttons! http://atariage.com/forums/topic/238372-help-regulator-mod-gone-wrong/

 

..on to my Lynx I and other II now

Edited May 22, 2015 by GTretro87

[leonk]

I'm confused. Did you decide to use regulator or revert back? Personally I use a modern switching regulator (costs about $5) but supports up to 35V input and it runs cold without the need for a heat sink! Did similar mod on my sega nomad as the original sega regulator was overheating after long game play using new lcd screen.

[GTretro87]

I'm confused. Did you decide to use regulator or revert back? Personally I use a modern switching regulator (costs about $5) but supports up to 35V input and it runs cold without the need for a heat sink! Did similar mod on my sega nomad as the original sega regulator was overheating after long game play using new lcd screen.

 

 

 

Yes I decided to push through and use the regulator. I think my major concern was making sure that the battery positive track was cut through enough to actually make the mod work. It would be so much easier if all we had to do was swap the zener diodes for the regulator, no cutting or removal of anything.. But nonetheless, I got it to work.

 

When I re-tried the mod and checked all my points (voltage and continuity), the mod successfully worked with a 7805 as a test. THEN I swapped in the RECOM R785.0-1.0 [1412]. 6.5 to 18v max input range.

 

This is what I used for now: http://www.mouser.com/Search/m_ProductDetail.aspx?R=R-785.0-1.0virtualkey56830000virtualkey919-R-785.0-1.0

 

The R785 (switching reg) definitely runs cold compared to the 7805 which runs HOT.

 

Which was the regulator that you used?

 

Was it this? http://www.mouser.com/Search/m_ProductDetail.aspx?Murata-Power-Solutions%2FOKI-78SR-5-15-W36-C%2F&qs=uJpRT2lXVNXJP%252bo08dQqJQ%3D%3D

[leonk]

Yes. That's the one I use. For these sort of application (where's not a drop in replacement for a standard 7805) I de solder the pin header and solder the wires to the thru holes. I then use automotive grade double sided foam tape to attach to pcb.

[7800fan]

If you have a multimeter you can quickly check if the battery + trace is cut properly. Set it to ohms, put one probe on battery + terminal and another probe on the + pad where the regulator output pin goes (where the junction that 2 removed diodes used to connect). If you get infinity, it's a clean cut. If you get anything below 100 ohms, you may have not cut it cleanly.

 

It is a bit hard to cut it without damaging neighboring traces so power tool like dremmel is out of question. A very sharp xacto knife (new blade preferably) and some patience is the best way.