MEP-003A Bridge Rectifier Assembly Board R1 Resistor value

[nonnieselman]

MEP-003A
Plate says to use TM 5-6115-585-12

I have a R1 Resistor Failure on the Bridge Rectifier board. Im looking at the wiring and i see the burnt resistor is attached to Location 5 and 6 on this board.
In the TM i find that 5 = P67A16 wire and 6 = P59G16.
P67A16 goes to A2 and im lost after that
P59G16 goes to Ground?

Trying to trouble shoot this and running out of ideas.
On the Bridge Rectifier board i have open circuit on 5 and 6 which should be P67A16 / P59G16

P59G16 does show good ohm reading to ground so i feel like that is correct.

Im not sure how to check P67A16 to see why this resistor blew.

Any ideas?

Thanks.
Here is the other thread from this morning i made when i found out about the set not putting out power after i turned the engine off to check oil level.

 

[nonnieselman]

MEP-003 AUX Fuel Solenoid

What is the point in the solenoid? Why not switch the pump on and off? Is it to prevent a siphon? Thanks to Hurrican Ida we have been running 80 hours on the MEP-003 and I've been using the AUX to fill the day tank "manually". I leave it in AUX until the day tank is full and turn it back to...

www.steelsoldiers.com

 

[Chainbreaker]

MEP-003A
Plate says to use TM 5-6115-585-12

I have a R1 Resistor Failure on the Bridge Rectifier board. Im looking at the wiring and i see the burnt resistor is attached to Location 5 and 6 on this board.
In the TM i find that 5 = P67A16 wire and 6 = P59G16.
P67A16 goes to A2 and im lost after that
P59G16 goes to Ground?

Trying to trouble shoot this and running out of ideas.
On the Bridge Rectifier board i have open circuit on 5 and 6 which should be P67A16 / P59G16

P59G16 does show good ohm reading to ground so i feel like that is correct.

Im not sure how to check P67A16 to see why this resistor blew.

Any ideas?

Thanks.
Here is the other thread from this morning i made when i found out about the set not putting out power after i turned the engine off to check oil level.

Not sure if this is any help however...I have a blown up D size schematic for MEP-003A/-002A although its really hard to read pin #'s due to poor reproduction quality. However it appears that P67A16 Pin 5 does go to the A2 VR Board and on into the Control Box to "T1" Transformer's X2 tap then it also runs into the Gen Head (via the two wire connector I think) where it connects into the rotating exciter field at F1. Pin 4 on the the A4 board ties to the other side of the exciter windings at F2. Also, P59G16 does indeed tie to ground.

I really don't have a clue how to troubleshoot those circuits, maybe someone like "TripleJim" has an idea since he builds a replacement VR card and may be familiar with how those circuits work.

 

[nonnieselman]

Not sure if this is any help however...I have a blown up D size schematic for MEP-003A/-002A although its really hard to read pin #'s due to poor reproduction quality. However it appears that P67A16 Pin 5 does go to the A2 VR Board and on into the Control Box to "T1" Transformer's X2 tap then it also runs into the Gen Head (via the two wire connector I think) where it connects into the rotating exciter field at F1. Pin 4 on the the A4 board ties to the other side of the exciter windings at F2. Also, P59G16 does indeed tie to ground.

I really don't have a clue how to troubleshoot those circuits, maybe someone like "TripleJim" has an idea since he builds a replacement VR card and may be familiar with how those circuits work.

Thanks
Thats another of my problems is finding legible schematic.

I emailed Mr Jim yesterday to see if he made a board for that. He replied no and I needed to find out why the resistor blew before replacing it.

 

[nonnieselman]

This is the best match to replace the resistor.

HS25 56R J Ohmite | Resistors | DigiKey

Order today, ships today. HS25 56R J – 56 Ohms ±5% 25W Wirewound Chassis Mount Resistor from Ohmite. Pricing and Availability on millions of electronic components from Digi-Key Electronics.

www.digikey.com

Im wondering if i can solder that resistor on the board so i can trouble shoot it better?

 

[Guyfang]

MEP-003 AUX Fuel Solenoid

What is the point in the solenoid? Why not switch the pump on and off? Is it to prevent a siphon? Thanks to Hurrican Ida we have been running 80 hours on the MEP-003 and I've been using the AUX to fill the day tank "manually". I leave it in AUX until the day tank is full and turn it back to...

www.steelsoldiers.com

OK, lets try and take this problem by problem.

The Aux solenoid is there so you can take fuel from a "foreign" source. Like a fuel drum, fuel can, truck fuel tank. The way it works is like this. When the S1, (Master switch) is in the Aux/run position, the gen set sucks fuel from a "foreign" Source, and sends it to the Gen set fuel tank. When the fuel tank is full, the S3, (fuel tank level switch) tells the Aux fuel sol to shut off. That way the tank is not supposed to over fill. If everything is working right, you do not need to turn anything off and on.

 

[Guyfang]

Thanks
Thats another of my problems is finding legible schematic.

I emailed Mr Jim yesterday to see if he made a board for that. He replied no and I needed to find out why the resistor blew before replacing it.

Download both the 002A schematics and 003A. They are interchangeable. You can use parts of both sets schematics to come up with what you think is the most readable. The below listed schematics are a combo of both sets, and should/maybe have the best readable schematics. But you need to look and decide.

 

[Guyfang]

MEP-003A
Plate says to use TM 5-6115-585-12

I have a R1 Resistor Failure on the Bridge Rectifier board. Im looking at the wiring and i see the burnt resistor is attached to Location 5 and 6 on this board.
In the TM i find that 5 = P67A16 wire and 6 = P59G16. (You do not need to write the last two numbers of the wire number. That is the wire size, and most folks do not write it, or say it. No need for it.)
P67A16 goes to A2 and im lost after that. (P67A goes to TB3-5 then goes in tow other directions. One of them is F1. TB4-4 is the other.)
P59G16 goes to Ground? (I can not find a wire P59G.)

Trying to trouble shoot this and running out of ideas.
On the Bridge Rectifier board i have open circuit on 5 and 6 which should be P67A16 / P59G16


P59G16 does show good ohm reading to ground so i feel like that is correct.

Im not sure how to check P67A16 to see why this resistor blew. (Lets not forget, that some of these gen sets are older then many SS members. If the R1 is burnt, replace it. I would buy two, in case it blows again. But it could simply be a case of "OLD".)

Any ideas?

Thanks.
Here is the other thread from this morning i made when i found out about the set not putting out power after i turned the engine off to check oil level.

Open to see comments.

 

[nonnieselman]

Thank you GuyFang.

I'm learning as I go. I now see the fine print as to the last 2 digits are wire size.

I'll double check the P59G. It's hard to make out on the wiring and the diagram.
I haven't opened your PDF yet tho.


I found some wire wound 56 ohm resistors and ordered the minimum of 10. So when they get here I'll attach with jumpers and test with meter.

The manuals only say to replace the resistor. No other info that I can find except that it's a 56ohm.
Testing the + side I got the same voltage as what was in the batteries. So I assume that circuit is ok and correct.

I have to get my dad's meter and check the diodes on that board. Mine isn't fancy enough to do diodes.

 

[nonnieselman]

This is the resistor that i ordered.

HS25 56R J Ohmite | Resistors | DigiKey

Order today, ships today. HS25 56R J – 56 Ohms ±5% 25W Wirewound Chassis Mount Resistor from Ohmite. Pricing and Availability on millions of electronic components from Digi-Key Electronics.

www.digikey.com

My dad was telling me to measure the Diodes and to get one the same size or larger if it was bad. So once i get all those tested ill see how that works out.

 

[nonnieselman]

HS25 56R J Ohmite | Resistors | DigiKey

Order today, ships today. HS25 56R J – 56 Ohms ±5% 25W Wirewound Chassis Mount Resistor from Ohmite. Pricing and Availability on millions of electronic components from Digi-Key Electronics.

www.digikey.com

This resistor replacing R1 on the Bridge rectifier board fixed my 003A generator.

 

[Guyfang]

Great! Thanks for closing the loop.

 

[nonnieselman]

Now i just have to find out how to permanently attach it to the board.
I just used some wire to rig it and wanted to test it before going through all that trouble of soldering it to the board and the problem be else were.

 

[Chainbreaker]

Now i just have to find out how to permanently attach it to the board.
I just used some wire to rig it and wanted to test it before going through all that trouble of soldering it to the board and the problem be else were.

According to the MFG's datasheet:

"Manufactured in line with the requirements of MIL 18546 and IEC 115, designed for direct heatsink mounting with thermal compound to achieve maximum performance.

Heat dissipation: Whilst the use of proprietary heat sinks with lower thermal resistances is acceptable, uprating is not recommended. For maximum heat transfer it is recommended that a heat sink compound be applied between the resistor base and heat sink chassis mounting surface. It is essential that the maximum hot spot temperature of 200°C is not exceeded, therefore, the resistor must be mounted on a heat sink of correct thermal resistance for the power being dissipated"

The resistor you selected is enclosed in a heat dissipating sleeve and thus designed to be mounted to a heatsink for shedding heat. With the eyelet type leads for attaching wires you could mount it off the PCB board on a close by metal surface (using the 2 screw holes it provides with some thermal paste) and then solder proper gauge wires into the circuit board after removing the old resistor, or clip old resistor leads near old resistor body leaving enough room to solder the wires to old resistor leads.

 

[Triple Jim]

The resistor has to dissipate about 24² ÷ 56 = 10.28 watts. It does this only when the switch is held in the start position. It's rated at 25 watts when properly mounted to a heat sink. It can handle 10 watts intermittently as it needs to in this application without being mounted to a heat sink. The problem remains that something caused the original to overheat, and the reason should be found and corrected. Maybe something stuck and left it active after the generator was running, or maybe it was something else.

Measure the voltage across the resistor after the generator is running and see if it's zero as it should be. If it's still near 24 volts, then something is causing it to remain active when it shouldn't be.

This derating graph shows that the resistor can handle about 13 watts full time without a heat sink:

 

[nonnieselman]

The resistor has to dissipate about 24² ÷ 56 = 10.28 watts. It does this only when the switch is held in the start position. It's rated at 25 watts when properly mounted to a heat sink. It can handle 10 watts intermittently as it needs to in this application without being mounted to a heat sink. The problem remains that something caused the original to overheat, and the reason should be found and corrected. Maybe something stuck and left it active after the generator was running, or maybe it was something else.

Measure the voltage across the resistor after the generator is running and see if it's zero as it should be. If it's still near 24 volts, then something is causing it to remain active when it shouldn't be.

This derating graph shows that the resistor can handle about 13 watts full time without a heat sink:

Thank you for the clarification on that. I've done alot of wiring and stuff on race cars but never dealt with anything like this so I'm learning.

But what your saying is that the resistor is only used during the engine starting process where this DC power is applied to the fields to excite them so the gen set starts producing AC power?
That's why my machine was producing AC power until I turned engine off.

If I have any voltage Across the resistor then I need to look back toward the starting circuit?

 

[nonnieselman]

So I left that resistor on the board and have used the generator several times as power goes out often.
No issues till today. Went out to crank the generator to let it warm up. Its main breaker was off and no wires attached to the taps.
Checked the oil and fired it up. After about 2 minutes I heard a pop and the resistor had blown.
Now time to figure out how to trouble shoot.

 

[nonnieselman]

Put a new resistor on it. Connected meter leads and it briefly showed 22 volts across it then went down to 3-5mV.
I had 221 volts on taps L1 - L3 and 110 volts on L1-L0.
Everything seemed fine so turned generator off and let it sit. Hooked leads back to the resistor and it showed 21.5 volts across it while cranking and went down to 4-6mV. Power output showed good again.

3rd time I cranked it was same as 2nd but this time I didn't have time to check voltage across the resistor before it popped.

I'm not exactly sure what to do now.

 

[nonnieselman]

Been looking at these wiring diagrams and when i get to the resistors and transisitors on the VR ASSY GEN section from wire P67 coming from Bridge Assy im lost.

Also Pin 6 on the bridge assembly shows P55 then follow it to the right it turns into P59?
This is getting confusing fast

 

[Triple Jim]

If it were mine, I'd attach a meter to the two ends of the resistor with alligator clips so I could read the voltage across it without having to get to it with probes. (You probably already did this.)

To cause that resistor to overheat so much that it make a popping sound in a few seconds would require making it dissipate WAY more than the 13 watts it's rated for. That would imply that somehow it's getting much more than 24 VDC across it. Something like a wire with bad insulation touching something with high voltage on it, as one wild guess possibility. This could be AC, so watching AC volts on the meter as well as DC might shed some light.