SUCCESS!!! Just repaired Stihl 045/056 Bosch electronic ignition!!!!!
- Thread starter foggysail
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I might loan you one
I thought i was buying two Capacitors!......Duh, Listing was for two packs of ten!... Now i have twenty of the things!...PM me your details and I'll send you one.
Foggy,
IDK if you've had time to look at Stihl's-Bosch patent on post #96, but what's the purpose of the optional RLC circuit at the bottom of the schematic? Are they trying to limit voltage based on RPM?
The original capacitor is a known quantity! If the guys here in the forum are offering one to you.......TAKE IT! The caps I provided the pointer to last night should work but they are not pulse rated, I also did not check the mechanical dimensions so they might be the same size or larger physically.
Foggy
EDIT:
Ruger22 found some on EBay that I missed.........of course if someone on the forum gives you one, that's even better.
http://www.ebay.com/itm/10-NEW-Phil...00102&prg=20140212121249&rkt=4&#ht_2390wt_617
Sure, I will try to explain the circuit....from memory, I don't don't have the schematic in front of me. Notice first the flywheel. It contains 3 magnets, two of which are placed on the body with their magnetic poles in series + on one magnet connects to the - on the other. The third magnet is oriented just opposite with its polarity - to +.
The two magnets in series are used to charge the capacitor that we focused on during the repair. As this pair of magnets rotate near the charging coil.....NOT THE COIL THAT HAS THE SPARK PLUG wire attached, it develops a sine wave. That will generate a current that will flow into the charging capacitor. But remember a sine wave changes for 0 to its positive high and then falls back to 0 and continues to a negative high and then back to 0.
This wave form charges the energy storage capacitor... the same one we replaced. Now remember, I said the current goes + and then -. The designer has placed a diode in series with the charging capacitor to prevent the negative voltage from allowing a negative current that would then discharge the just charged capacitor. So that energy capacitor retains its charge until something can discharge it.
Notice there is a switch (SCR) in the circuit that when turned on, discharges the energy storage capacitor allowing current to flow from it and through the high voltage transformer and back to the capacitor completing the circuit. Now the capacitor has to wait until the next revolution of the flywheel to recharge.
OK, but WHAT TURNS ON THE SWITCH???
That third magnet forces a current through the capacitor/resistor pair thereby charging that capacitor. Note that a capacitor can be thought of as a bucket into which electrons can flow. Electrons can also flow through the resistor obeying the equation I= V/R. But the capacitor has no V at teh start of the charging so no current flows through the resistor at the start. The resistor controls the time it takes for the capacitor to charge along with magnet. When the charge on the capacitor reaches about 1-2 volts it provides the 'trigger' to fire the SCR--- turns it on as a switch. The resistor will allow the capacitor to completely discharge for the next cycle to repeat the SCR firing. If I remember correctly there is also a diode in the charging loop here to prevent the magnet from discharging the trigger capacitor, the resistor does that as I just mentioned.
A little complicated but hope this helps.
Foggy
Thanks for the reply, the schematic is attached in post #96, you can pull it up if you are logged in. I understand the SCR & cap functions just fine, but not the RLC circuit at the bottom. The RLC are normally used for harmonics, and a chainsaw's RPM are all over the place..
Where do you see an RLC circuit at the bottom??? What I see is a zener diode (19) in series with diode (18) . In parallel with the zener is a dotted combo of a variable resistor (20) and capacitor (21). The dots mean those components may or may not be in the circuit. And the ignition I ripped apart does not have them.
Foggy
Thanks, that's the one. Now I see/understand that it's an option.
So either the Zener(19) or the RC(20,21) in parallel.
Sure glad we have smart guys on here to help us out. Good explanation foggy I even understand it I think.
AND THANK YOU FOR THE 4 ATTABOYS!!!
Foggy
Hello new to the forum joined because I found this fix. So here is the story behind my saw bought a very nice 056 hardly used thing ran for 5 min overheat then died. Took it apart not knowing this was a common problem with these saws found a bad shut off wire replaced it thought all was good and reassembled. Same thing so started researching and found this was a problem on these. Bought a used bosch ignition off ebay and the guy said he was sure it was good installed the thing only had very weak spark would spark across my ignition tester but not the plug. Sent that ignition back. Then found and tried the fix foggysail came up with on my original bosch ignition every thing looked great when I was done, I was so confident that would fix it I reassembled saw pulled it a couple times took off run for about 15 sec then it was like I shut the switch off. Now it wont spark across the plug but will spark across my ignition tester but looks like a weak spark. Disassembled the saw and cannot find a problem. Wondering if the capacitor could have got burnt up and if so how to test it or if there is any other ideas to try. Thanks for any advice and thanks to foggy for spending so much time on fix and sharing it.
Anything is possible in wonderland! This is always true although I doubt the capacitor crooked unless you installed the voltage rating is less than 400 vdc. Did you use the specified capacitor?
Here are things I believe you should look for. The first is that stinking switch wire AND THE SWITCH itself. If you notice the pictures you will see that I went to lengths to replace the switch wire. After replacing the wire I found the switch is open and the saw does not shut down. Now of course, that is the opposite of your problem.
It appears you have to pull the ignition apart again. I will not suggest what to do with the shut off switch because of implied safety concerns. I cut the wire right out of the circuit at the ignition block. No more problems from that. You can thank German environmentalists for that junk wire. At least one high end German car manufactured around 1997-98 used that supposed "green"wire for the engine wiring. The wonderful environmental BS has resulted in major costly repairs. The wire self destructs in a heated surrounding. My saw shuts down fast using the choke.
Further suggestions .... make sure your soldering is sound and done EXACTLY as shown in my pictures. Make sure the spark plug wire is retained in the coil.
Now because you need to pull the ignition apart.............. I WILL GIVE YOU MY GUESS AS TO WHAT YOUR PROBLEM IS and in the king's English, I DOUBT IT IS ELECTRONIC RELATED!!!!!!!!!!! Now of course I could be wrong but beeeeen there dooone that!
I am going to guess your problem is the shaft key..forgot what the name for those half moon keys is. But could you pull the flywheel and get back to the forum and let me know if the key is sheared or bent even a tiny bit? If you do not have the flywheel REALLY TIGHTENED, THAT KEY WILL SHEAR. Sometimes when you pull on the starter rope, the saw's piston doesn't even move.
In summary--
1. Make sure you have the right capacitor
2. Make sure your spark plug wire is firmly mounted into the HV pulse transformer
3. Can't tell you what to do with the switch wire, just told you what I did to mine
4. Check the half moon shaft key
5. Let us know how you're making out
Foggy
EDIT: I should have read your entire post. I see that you have pulled the saw apart. How does the key look???? General comment on a weak spark. When you crank by hand, you possibly can have a weak spark. The faster the magnets pass through the pole pieces, the higher the charge voltage will be resulting in greater spark. But the saw should start fine even with what seems to be a weak spark
Getting ready to try this "fixed" ignition module out on an 041 Super series. Bench tested fine on an 045 chassis while spinning the crank with a variable speed drill, so the SCR is still working! Forgot to check the shut off switch though... Hope it won't blow my muffler & intake cover off like Foggys!
Foggy, keep up the good work!......Your efforts here are appreciated by many!!
http://www.ebay.com/itm/10-NEW-Phil...00102&prg=20140212121249&rkt=4&#ht_2390wt_617
This is the capacitor I bought on ebay it was a different link then what you posted but I read over it comparing it to yours and it seemed to be the same thought they just created a new auction because they were charging a dollar more for them.
The kill switch wire is a new one and I have checked for continuity between it and the body of the ignition and all over the saw could not find any.
I will try to look at the saw more today if I get some time. thanks for the help
This is the capacitor I bought on ebay it was a different link then what you posted but I read over it comparing it to yours and it seemed to be the same thought they just created a new auction because they were charging a dollar more for them.
The kill switch wire is a new one and I have checked for continuity between it and the body of the ignition and all over the saw could not find any.
I will try to look at the saw more today if I get some time. thanks for the help
k_kindig11
ArboristSite Operative
I've been in contact with the seller of the replacement parts. Here's what he said:
Do you absolutely require 400 volts? I do have the Arcotronics 1uF 250 volt polypropylene caps.
I will check with my suppliers and see if I can get any more of the 1uf 400V polypropylene. Is polypropylene mandatory? Do they have to be Philips brand?
Let me know how I can help and I'll do my best.
Do you absolutely require 400 volts? I do have the Arcotronics 1uF 250 volt polypropylene caps.
I will check with my suppliers and see if I can get any more of the 1uf 400V polypropylene. Is polypropylene mandatory? Do they have to be Philips brand?
Let me know how I can help and I'll do my best.
k_kindig11
ArboristSite Operative
I guess a few questions from him that maybe the creator of the thread can answer. It's way over my head...
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.
Paul Brodie
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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?
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