I read a great deal on these forums in search of the complete answer. Let me give you the history. It's a 1990 or 91 Bobcat 225G. It's been sitting since 1995 after Hurrican Opal hit NW FL, where I'm from. SN 903125. Duaneb55 seems to be an awesome troubleshooter. So all the posts I read with his and others help I performed the following, some will be in Duaneb55's own post words: Checked F1 and F2, both good. Checked the Flashing Diode D4, it was good. Unplug both brush leads (wires #24 and #33). With your meter set to "OHMs", check rotor winding resistance by placing one probe on each slip ring. Resistance should be approximately 22-26ohms. Check for continuity between each slip ring and chassis ground. All checked good. While at the capacitor with wire 33D disconnected and with the meter set on at least "20K OHMs" place the red meter probe on the (+) terminal and the black probe on the (-) terminal. The meter reading should climb steadily from a negative to a positive value. Reverse the probes and the reading should repeat. I checked the SR2 rectifier by the pdf page linked, it was good.I still don't have power or weld capabilities. What should I do next?Thank you.Ken
Reply:Welcome to the forum Ken. A couple clarifications:1) The 22-26ohms figure I posted was in error. That's an Onan generator rotor resistance. The Bobcat is more like 3-5ohms.2) The number you listed looks like the units' part number. The SN would start with KA (for a '90) or KB (for a '91).As for additional troubleshooting, check the engine harness Molex plug pin #3 (wires #31 & #A3) for a bad connection. Should have continuity between RUN/START switch terminal #4 (wire #31) and engine side of connector (wire #A3).If that checks out, with starter solenoid wire #A5 unplugged to prevent the starter from engaging, check for battery voltage between chassis ground and both sides of fuse F2, both sides of diode D4 and at input side of field voltage trim resistor R2 (wire #21) with RUN/START switch in START position.With Fine Current Control at maximum and RUN/START still in the START position, check for (+) voltage (less than full battery voltage) at Fine Current Control rheostat input wire #23 and positve rotor brush lead (wire #24).Start with the above and let us know what you find.MM200 w/Spoolmatic 1Syncrowave 180SDBobcat 225G Plus - LP/NGMUTT Suitcase WirefeederWC-1S/Spoolmatic 1HF-251D-1PakMaster 100XL '68 Red Face Code #6633 projectStar Jet 21-110Save Second Base!
Reply:Thank you Mr Duane for responding so fast . 1) Thank you aand I will recheck this and ty again.2) Dead on again =) KB033455.As for checking these today, I can't It's storming bad here at the moment =( and the rig is on the the trailer with no way to move it indoors right now.As soon as I do these checks, I'll be posting the results.Thank you again Mr. Duane, you're a life saver =).
Reply:Hi Again Mr Duane =).1) I have 3.5ohms between the slip rings.2) Continuity between the #31 & #A3 at the molex connector was good.3) Continuity between Terminal #4 at the switch to the engine side #A3 was good.4) Checked for voltage between Chassis ground and Both sides of F2, Diode D4, and Wire #21 of field trim resistor R2 had 11.4V. Battery had 11.6V. Run/Start in Start Position.5) With the Fine Current Control @max and Run/Start switch to Start, I had 0.0V at Wire #23 or #24. This isn't right is it?Thank you again =),Ken
Reply:Originally Posted by Skinny Kenny5) With the Fine Current Control @max and Run/Start switch to Start, I had 0.0V at Wire #23 or #24. This isn't right is it?Thank you again =),Ken
Reply:I have 2.6ohms checking as you said for the R2.I loosened the tap terminal strap and low and behold alot of rust an corrosion from sitting. I cleaned the spot and roughed it up a bit, fired the unit up and I have power =).But it still wont weld =(. I guess we should go to next step?
Reply:I just referenced this thread: http://weldingweb.com/vbb/showthread.php...ht=bobcat+225g and with no progress.I've checked the voltage and have all 110v and 220v recepticles have power, but still wont weld. Originally Posted by duaneb55I should have been a little clearer. Check for voltage between both brushes not each one individually.However, if you only got 12V on one brush (likely the positive brush) that indicates you're only getting initial flashing voltage from the battery system and nothing from the exciter circuit due to a problem there. If that's the case it could be one of the following:1) Bad connection anywhere in the rotor exciter voltage circuit. Working from the exciter output toward the brushes that would include wires #28, 29, 22, 21, 23, 24 & 33. Including a bad connection at fuse F1 holder as you indicated earlier or a bad fuse altogether.2) Bad bridge rectifier SR23) Bad control resistor R2 (rare long shot but check the tap strap connection)4) The wierd readings on the other brush (negative ??) could indicate a bad ground connection on wire #33
Reply:OK, the 120/240 auxiliary power output confirms you now have proper field current following fixing the trim resistor R2 tap strap connection.So now you need to check the contacts of the Weld Process and Coarse Current selector switches for being dirty/tarnished. After removing any grease and dirt build up, clean them with some medium sandpaper to remove any tarnish.Once that's done, check for OCV (Open Circuit Voltage) at the weld output studs in all modes with th eFine Current contol on "10". Readings should be approxiamtely:CC/AC - 80VCC/DC - 72VCV/DC - 33VCC readings should be the same on all Coarse Current settings and both polarity settings.You may have a CV/DC reading but no CC/AC or DC readings. If still no CC OCV readings at weld output studs, locate weld stator output leads #9 (reactor input) and #8 and check for an AC voltage there. The connection at weld stator output lead #9 and reactor input has been known to be bad.If you find CC/AC voltage but no CC/DC or CV/DC then the weld output rectifier or its connections would be suspect.Check the OCVs and we can go from there.MM200 w/Spoolmatic 1Syncrowave 180SDBobcat 225G Plus - LP/NGMUTT Suitcase WirefeederWC-1S/Spoolmatic 1HF-251D-1PakMaster 100XL '68 Red Face Code #6633 projectStar Jet 21-110Save Second Base!
Reply:Just checked for voltage at the brushes and only had 12v on one brush. So I checked to see if the battery charging system was working and it wasn't charging. Where is the exciter output so I can work from there toward the brushes to find that problem you mentioned in the earlier post.Sorry if I'm being a pain =(.
Reply:So auxiliary power at the 120/240 outlets wasn't full voltage? If it was/is, the exciter output should be there.One brush is (+) and the other is (-). For your voltage at the brushes test, was the Fine Current control set to maximum (10)?To answer your question, exciter voltage goes thru fuse F1 so check that and make sure it's getting good contact in its fuse holder. Exciter output voltage on wires #28 and #29 (#22 after F2) is AC and should be 50-55V.Then check for DC voltage at the (+) and (-) terminals (wires #21 and #33) which should be pushing 60V if bridge rectifier SR2 is good.. . .and you're not being a pain.MM200 w/Spoolmatic 1Syncrowave 180SDBobcat 225G Plus - LP/NGMUTT Suitcase WirefeederWC-1S/Spoolmatic 1HF-251D-1PakMaster 100XL '68 Red Face Code #6633 projectStar Jet 21-110Save Second Base!
Reply:Hi duaneb55, I enjoy reading your posts. I have zero electrical experience, but am working on a 225NT for a friend of mine. I have been looking at your post regarding the 225G. I was hoping that the numbers on the wires would match up with the NT, but it doesn't appear they do. Basically, the engine runs good, but I have no outlet power and no welding spark. Any help would be great. Thanks!
Reply:Got a unit SN? Do you have the wiring diagram on the inside of one of the side panels or the unit manual to follow?MM200 w/Spoolmatic 1Syncrowave 180SDBobcat 225G Plus - LP/NGMUTT Suitcase WirefeederWC-1S/Spoolmatic 1HF-251D-1PakMaster 100XL '68 Red Face Code #6633 projectStar Jet 21-110Save Second Base!
Reply:Wow,I remember reading this thread and did Skinny Kenny ever get it going?Drink a Guinness Draught....Millermatic 140Do you still rememberDecember's foggy freeze --when the ice thatclings on to your beard isscreaming agony.
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on't know. He never reported back and I don't recall him sending me a PM on the outcome.MM200 w/Spoolmatic 1Syncrowave 180SDBobcat 225G Plus - LP/NGMUTT Suitcase WirefeederWC-1S/Spoolmatic 1HF-251D-1PakMaster 100XL '68 Red Face Code #6633 projectStar Jet 21-110Save Second Base!
Reply:Hey duaneb55! Thanks for the reply. I was able to get the machine to weld by fixing a couple wires that a mouse had chewed through! The whole unit was a mouse nest, so I'm lucky they only ate the two wires. I dismantled everything in order to get it cleaned out. And just for good measure, I did some sand-blasting and painting.Also I cleaned the contacts on the process selector switch, and the coarse adjustment switch. I cleaned the slip rings and checked the brushes. The machine is welding good now, but the fine current control rheostat will need to be replaced due to some arcing across the wires. I am excited to have it working, and I think my friend will be happy with it. Thank you again.
Reply:Thank YOU for reporting back what you found. It may help someone else in the future. MM200 w/Spoolmatic 1Syncrowave 180SDBobcat 225G Plus - LP/NGMUTT Suitcase WirefeederWC-1S/Spoolmatic 1HF-251D-1PakMaster 100XL '68 Red Face Code #6633 projectStar Jet 21-110Save Second Base!
Reply:I hope so. I found this forum to very informative and fun to read. Hopefully I will be back in the near future. Thanks for the beer...root beer right?
Reply:Originally Posted by Whitey75...root beer right?
Reply:Hi Duane I've heard a great deal about you...I have a problem similar to Skinny Kenny....no weld and no aux. power.MIller Bobcat 225 Serial LC137614 I've check F1, rectifier bridge shows good, flash diode also shows good. I'm getting 3.8 OHM's at the sliprings I' m getting continuity from sliprings to chassis and the capacitors voltage climbs when metered. I tried checking the continuity between term#4 on the start switch but i do not fined numbers 31 and 3a. Am I missing something somewhere?
Reply:Moonguy, you say you do have continuity between the slip rings and chassis? Brushes off the slip rings?If yes to both, that's not a good thing.Did you check for continuity between exciter output wires #28 and #29?Did you check for battery voltage at the (+) brush lead #24?MM200 w/Spoolmatic 1Syncrowave 180SDBobcat 225G Plus - LP/NGMUTT Suitcase WirefeederWC-1S/Spoolmatic 1HF-251D-1PakMaster 100XL '68 Red Face Code #6633 projectStar Jet 21-110Save Second Base!
Reply:Ok...Brushes were of when I checked continuity between slip rings and had 3.8 ohms.Brushes were on when I checked continuity to chassis.I checked for voltage between #28 and #29 and had no voltage with machine running.And no I did not know about voltage to #24.
Reply:Battery voltage to #24 is necessary for initial rotor excitation in order to produce voltage output on #28 and #29 so exciter output can take over.I'm sure the rotor windings are OK with a resistance reading of 3.8 but a "short" continuity check would be from each slip ring to rotor shaft with the brushes off the rings for future reference.MM200 w/Spoolmatic 1Syncrowave 180SDBobcat 225G Plus - LP/NGMUTT Suitcase WirefeederWC-1S/Spoolmatic 1HF-251D-1PakMaster 100XL '68 Red Face Code #6633 projectStar Jet 21-110Save Second Base!
Reply:awesome...I will check that first thing and reply tomorrow...
Reply:Ok I checked voltage at #24 and I'm reading 48-50(this intermitts, sometimes it reads over 100) DC volts.I also checked continuity between each slip ring and the shaft without the brushes...No continuity.While machine is running sometimes I get over 100DC volts at the slip rings.Last edited by moonguy; 06-13-2012 at 10:15 AM.
Reply:After using a different meter for testing...I have 13.7 dcv at excitation field #23 A input and .5 dcv at #24 output...what output voltage am I looking for on #24?There are 2 terminals where the #24 wire connects(the left side off excitation field resistor)...1 terminal on the right where the# 23A wire connects...I connect the #24 wire on the inside terminal and all is working...is that safe??? will it be ok in the long run??? thanks again for the help.
Reply:You're referring to trim resistor R2 which should have a tap strap that allows "trimming" the field voltage. So, I'd have to say either the tap strap has lost contact due to corrossion or the resistor is open between two of the referenced terminals. Any chance you could post up a photo of the working setup?MM200 w/Spoolmatic 1Syncrowave 180SDBobcat 225G Plus - LP/NGMUTT Suitcase WirefeederWC-1S/Spoolmatic 1HF-251D-1PakMaster 100XL '68 Red Face Code #6633 projectStar Jet 21-110Save Second Base!
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k... hope i did it right. Attached Images
Reply:I used the information above to fix a bobcat 225G, the clamp for the wire on resistor was rusted and cleaned all contacts now it welds and has power to the plugs. Thanks for providing diagnostic info on the web.
Reply:Good to know. Welcome and glad you got it working again.
Reply:Thank you duaneB..Your technical knowledge is awesome. My 225D had a bad resister, several broken windings; I simple installed the tap from the other end to achieve the proper resistance. This portion of repair was a no-brainer. The #9 stator output to the reactor input had indeed failed. No type of solder,rosin or acid would take, so I simply drilled a 1/4" hole in the reactor winding and used a short 1/4" machine screw w/ fender washers to re-attach. Lots of weatherstrip adhesive to seal and insulate...everything works great now. Thanks again for your willingness to share knowledge.
Reply:Good job on the repair mechman53 and your resistor fix would have been my recommendation.The problem with soldering is likely due to the aluminum windings of the reactor which takes a special solder to achieve a bond but your solution obviously gets the job done.Thanks for posting your problem and repair for the potential future benefit of others.MM200 w/Spoolmatic 1Syncrowave 180SDBobcat 225G Plus - LP/NGMUTT Suitcase WirefeederWC-1S/Spoolmatic 1HF-251D-1PakMaster 100XL '68 Red Face Code #6633 projectStar Jet 21-110Save Second Base!
