SUCCESS!!! Just repaired Stihl 045/056 Bosch electronic ignition!!!!!

[hotshot]

Hi,
I am the seller on eBay who had the capacitors you guys were using but I've run out of them. I do have many other caps available but you said they should be pulse rated and that limits things a bit. If you can provide me with more info about the ratings for the caps you need, I can try to get some for you, maybe some much closer to the original or even superior to the original. Unfortunately, .8uF is not a common capacitance at all but I'm sure I can get .68uF, if they will work. The voltage could be difficult. How important is the 400 volt rating? Will 250 volt caps work? Also, is physical size a factor? I believe you said that the ones I was selling on eBay were a bit larger than the original. Finally, do they have to be polypropylene or will polyester caps work?

Paul,

Welcome aboard, & thanks for posting.

Yes, they need to be 400 volt rated minimum, polypropylene, and 1.0 microfarad is fine. These need to be pulse rated caps, minimum of 250 cycles per second. The smaller the better, given the specs, as there isn't much room to mount them.

 

[foggysail]

Hi,
I am the seller on eBay who had the capacitors you guys were using but I've run out of them. I do have many other caps available but you said they should be pulse rated and that limits things a bit. If you can provide me with more info about the ratings for the caps you need, I can try to get some for you, maybe some much closer to the original or even superior to the original. Unfortunately, .8uF is not a common capacitance at all but I'm sure I can get .68uF, if they will work. The voltage could be difficult. How important is the 400 volt rating? Will 250 volt caps work? Also, is physical size a factor? I believe you said that the ones I was selling on eBay were a bit larger than the original. Finally, do they have to be polypropylene or will polyester caps work?

HEY!!!!!!!! I AM THE GUY WHO PUT THE FOCUS ON YOUR CAPACITORS!!! DO I GET A CUT :- ) ???

Seriously -- they need to be 400vdc and although they should be pulse rated for greater reliability it is possible that a plain Jane polypropylene metalized film will work. And yes I understand that a 0.8 is not a standard value but 0.82 is. When I gave the value of 0.8 uf it was meant only to establish a range.What I hoped to provide to the guys here in the forum was a simple repair procedure they could do themselves and have a high degree of confidence their repair works in their saws. You can view the repair pictorials a few pages back here in this forum thread to see what I am asking from these guys to do their repairs.

A 0.68uf MIGHT work. But if it does not the guy doing the repair won't have enough knowledge in electronics to understand the capacitor's stored energy was inadequate. They don't want to become technicians, they just want their tools to work, in this case the tool is a chain saw. Finally your question on size. Take a look at the pictures. There is little latitude with sizes.

I have not put a scope on the capacitor but my guess is the discharge time to develop the HV for the spark plug occurs in about 10-100 useconds. Of course this is determined by the leakage inductance of the high voltage pulse transformer and the discharge capacitor's capacitance. The saw can scream upwards to 12000 RPM or 200 pulses/second. Not a tough job for a polypropylene capacitor.

It becomes a guessing game as to whether or not polyester would work as well as polypropylene considering the higher dielectric losses in polyester.

Foggy

 

[Paul Brodie]

HEY!!!!!!!! I AM THE GUY WHO PUT THE FOCUS ON YOUR CAPACITORS!!! DO I GET A CUT :- ) ???

Seriously -- they need to be 400vdc and although they should be pulse rated for greater reliability it is possible that a plain Jane polypropylene metalized film will work. And yes I understand that a 0.8 is not a standard value but 0.82 is. When I gave the value of 0.8 uf it was meant only to establish a range.What I hoped to provide to the guys here in the forum was a simple repair procedure they could do themselves and have a high degree of confidence their repair works in their saws. You can view the repair pictorials a few pages back here in this forum thread to see what I am asking from these guys to do their repairs.

A 0.68uf MIGHT work. But if it does not the guy doing the repair won't have enough knowledge in electronics to understand the capacitor's stored energy was inadequate. They don't want to become technicians, they just want their tools to work, in this case the tool is a chain saw. Finally your question on size. Take a look at the pictures. There is little latitude with sizes.

I have not put a scope on the capacitor but my guess is the discharge time to develop the HV for the spark plug occurs in about 10-100 useconds. Of course this is determined by the leakage inductance of the high voltage pulse transformer and the discharge capacitor's capacitance. The saw can scream upwards to 12000 RPM or 200 pulses/second. Not a tough job for a polypropylene capacitor.

It becomes a guessing game as to whether or not polyester would work as well as polypropylene considering the higher dielectric losses in polyester.

Foggy

I would be concerned about heat buildup with polyester caps. I know that with most high frequency applications, polypropylene is much better and preferred over polyester. What would be best are polycarbonate capacitors, if you could find any. They are superior to polypropylene and used to be used in high heat automotive applications but are no longer manufactured.
I have been checking my sources but haven't had any luck finding anything appropriate. If I do, I'll post what I find. I just thought of a possible solution. You can use X2 rated or Y2 rated safety capacitors. They are usually rated 250VAC or 275V AC, which is equivalent to at least 400VDC, which is what the caps I was selling are rated. Since X2 safety caps are built to be extra robust and have to be able to sit across the power input of electronic equipment almost constantly, even though they are polyester, they might very well work fine in this application, especially since they are also self healing. I do have some high quality EVOX RIFA 1uF 250VAC X2 safety caps that are polyester but I only have 7 of them left and they are more expensive than the caps I was selling before and they are just a little bit larger. I usually sell these types in pairs. If it were me, though, I would want to be sure whatever I used was going to last. I would hate to have to go back in and repeat a repair job. Good luck on all your repairs!

 

[jeff taswelder]

just went to the shop and got me some more opcorn:

 

[foggysail]

Hi Paul-- (GUYS-- THIS IS POST SOMEWHAT TECHNICAL, please don't get awed if you read it)

First Paul, thanks for joining in and offering help to those here in the forum searching the elusive capacitor. Some who read these post have electronic experience, others could care only about getting their broken saws functioning.

I do agree that 250vac should be reliable at 400vdc. As to polyester... I have mentioned that it has a higher dielectric loss so it should not be considered. The only recommendation I can support is to use a capacitor that has a polypropylene dielectric rather than risk continued failures that the guys in this forum have experienced with this particular chain saw. If you checked the photos I submitted as a repair aid you will see the replacement capacitor is connected in an area that is exposed to the saw's cooling air stream so I doubt a polypropylene capacitor will ever see 105C which is the upper temperature limit for that material.

I really want to keep this as simple as possible for the guys who are trying to breath new life into saw that was once considered too problematic and expensive for repairs. Further, it is not me doing the purchasing/repairs. I am providing engineering guidance to them asking only "thanks" in return.

In post #120 I posted a pointer to some 0.82uf 400vdc capacitors for those interested.

Foggy

 

[ruger22]

Update, I removed the epoxy that I put in place of the potting where I soldered the yellow wire to the bus. It was a bit damp under the epoxy do to the flux I used so I cleaned that out with alcohol good, let it dry and this time sealed it with high temp silicone. I also went ahead and replaced the capacitor with a new one. I reassembled the saw and it started and run good, run it for at least 15 min under load which is way longer than it has ever ran. So far it looks like the fix is going to work! I hope to run it for a while in the weeks to come if I get time. I'm not sure what fixed it but at least its running for now.

Hats off to foggy for all his help thank you.

P.S. I would highly recommend trying this fix It may look a little difficult but its not to bad, especially if you have some one to help hold the wires while soldering. Thanks again foggy

 

[arrow13]

NO! DO NOT PURCHASE ANYTHING LESS THAN 400V! I didn't want to make my fix a big, ongoing project so I did not install a capacitor, spin the crankshaft and place my oscilloscope on the capacitor to see how high the charging voltage gets to. And sure, maybe a lesser voltage rated capacitor will work just fine until the dielectric finally fails. Further, the original Bosch ignition used a 400V capacitor. AND NO, THEY DO NOT HAVE TO BE MADE BY PHILIPS.

Some of the members here in the forum have spares from their purchases. Maybe you can work out a deal with someone.

But in the mean time... this should work OK.

http://www.ebay.com/itm/400V-0-82uF...823?pt=LH_DefaultDomain_0&hash=item484ff984bf

The issues with the cap are the voltage rating, physical size for the needed capacitance, capacitance value ranging from 0.8 to 1UF and dielectric losses. Polyproppylene dielectrics have less dielectric losses which result in less internal heating. Film capacitors are better for pulse current than metalized film. The difference here is with film, there are 2 aluminum films sandwiching the dielectric where as the metalized film is usually a metal sprayed onto both sides of the dielectric. Obvious advantage of the metalized film is smaller physical size. And pulse rating refers to the the rapid charging along with the rapid discharge currents.

Thanks foggysail! I've got an 056 that needs this fix. Sure glad your willing to share your talent with all of us. Much appreciated.

 

[foggysail]

Update, I removed the epoxy that I put in place of the potting where I soldered the yellow wire to the bus. It was a bit damp under the epoxy do to the flux I used so I cleaned that out with alcohol good, let it dry and this time sealed it with high temp silicone. I also went ahead and replaced the capacitor with a new one. I reassembled the saw and it started and run good, run it for at least 15 min under load which is way longer than it has ever ran. So far it looks like the fix is going to work! I hope to run it for a while in the weeks to come if I get time. I'm not sure what fixed it but at least its running for now.

Hats off to foggy for all his help thank you.

P.S. I would highly recommend trying this fix It may look a little difficult but its not to bad, especially if you have some one to help hold the wires while soldering. Thanks again foggy

Wondering what happen to you. Encouraging that you have the 'fix' working! The reason I wanted you to look at the half moon key is when I first started my saw after finishing the fix, I didn't have the flywheel tightened to where it should be. Result... my saw screamed to some very high rpm and then quit! You guessed it, I sheared the flywheel key.

Just a comment about your solder. I highly recommend solder that has self contained flux. Flux is acidic and can cause corrosion. But if you did a good job cleaning it with alcohol, you should be OK.

Good luck with your saw.......put that thing to work!

Foggy

 

[foggysail]

Thanks foggysail! I've got an 056 that needs this fix. Sure glad your willing to share your talent with all of us. Much appreciated.

Thanks Arrow-- try the fix. As Ruger just posted, it is not a difficult job. Just use a small soldering iron, electronic solder with self contained resin, not plumbing solder that Radio Shack should have. Take your time and you should be able to fix you saw.

Foggy

 

[DIYDoug]

Paul was selling these capacitors in batches of 10. I missed the opportunity before he sold out. Does anyone else have 9 extras (or at least one) that they would be willing to resell? PM me if you can help. Thank you!


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[hotshot]

"Paul was selling these capacitors in batches of 10. I missed the opportunity before he sold out. Does anyone else have 9 extras (or at least one) that they would be willing to resell? PM me if you can help. Thank you!"



I will have an extra one, once I run test "The Fix" CD module (see Post #114) on a saw in the next week or two. Have you already got your ignition cut open & need one right now?

 

[DIYDoug]

I will have an extra one, once I run test "The Fix" CD module (see Post #114) on a saw in the next week or two. Have you already got your ignition cut open & need one right now?

I haven't cut open my ignition module yet. I did find some other capacitors online and also found a used ignition module that I'll try first. This saw is consuming me. Oh, the additional effort associated with heating a house with wood.


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[olyman]

Oh, the additional effort associated with heating a house with wood.


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you wouldn't have it any other way................

 

[smdaugherty]

I applied this fix to my father-in-law's 045AV this weekend. Prior to the fix his saw would run well until it got hot and then had to cool off before she'd run again. It eventually gave up altogether. I found this fix via Google searching and am glad I did! The saw fired right up after installing the new capacitor. I don't have any hours on the fix yet as I'm waiting for the expoxy to cure. I'm feeling very confident about it though.

Thank you for the repair instructions Foggysail

I have extra MKP 378 capacitors left over from my order. Forum members: feel free to contact me if you are in need of one.

 

[foggysail]

For those interested-- I came across this part on EBay that should work. Now of course, we know the Phillips cap is the base line.

http://www.ebay.com/itm/WIMA-Polypr...SHIPPING-/111284517808?_trksid=p2054897.l4275. Again, quantities may be a problem. I do want to mention that there are numerous electronic suppliers that should be able to provide suitable replacements.

Good luck all--

Foggy

 

[DIYDoug]

I'm bought some capacitors to fix my ignition module. Somewhere I came across these, which are 400v, 0.82 uF. Other links point to a 1.0 uF. Will this .82uF work?
http://www.ebay.com/itm/310579397823


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[Riftweaver]

Thanks for all the info and hard work guys!

 

[foggysail]

I'm bought some capacitors to fix my ignition module. Somewhere I came across these, which are 400v, 0.82 uF. Other links point to a 1.0 uF. Will this .82uF work?
http://www.ebay.com/itm/310579397823


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I believe it will work. As to values, this application does not require high point precision values. Give it a try and report back to share your experience with others

 

[Harburmaster]

I need one of the capacitors for my 056. Is anyone willing to part with one of the originals specified by foggysail? The Phillips cap?
Philips 1uF 400V volt radial polypropylene MKP 378 AC & Pulse capacitors

 

[Harburmaster]

I applied this fix to my father-in-law's 045AV this weekend. Prior to the fix his saw would run well until it got hot and then had to cool off before she'd run again. It eventually gave up altogether. I found this fix via Google searching and am glad I did! The saw fired right up after installing the new capacitor. I don't have any hours on the fix yet as I'm waiting for the expoxy to cure. I'm feeling very confident about it though.

Thank you for the repair instructions Foggysail

I have extra MKP 378 capacitors left over from my order. Forum members: feel free to contact me if you are in need of one.

Would you sell me one of the caps, please?