Generators and Motors
[Home] - [HELP] - [Forums] - [Articles] - [Photo Gallery] - [Groups] - [Chat] - [Classified Ads] - [Subscribe] - [Links] - [Books] - [Sponsors] - [Tools]

Go Back   SmokStak > SmokStak® Vintage Electrical Equipment > Generators & Motors General Discussion > Onan Generators
Forgot Password? Join Us!

Notices

Onan Generators Restoring, operating and maintaining vintage Onan generators.

Onan Generators

Need Help with 7.5JB-3CR/2442AB Genset


this thread has 9 replies and has been viewed 2850 times

Reply
 
Thread Tools Display Modes
  #1  
Old 08-07-2006, 11:55 AM
mi002le mi002le is offline
Registered-I
 
Join Date: Aug 2006
Location: Stamford, CT USA
Posts: 11
Likes: 0
Liked 0 Times in 0 Posts
Question Need Help with 7.5JB-3CR/2442AB Genset

Help!

One of my colleagues dropped off an old (circa) 1980 Onan Genset and asked me to look at it. The model number is 7.5JB-3CR/2442AB and the serial number is J790459440. It was pretty hard to read, but I think I got it right.

The first thing I noticed was that it wasn't all there. The output panel with meters and plugs is gone! He said he was able to hook it to his gas grill tank and get it started, but he had to hold the start switch on to keep it running...then he said something appeared to burn up...he wasn't sure what was burning. Now when I move the switch to the start position, nothing happens. I don't see anything obviously burned.

Does anyone know where I might obtain a wiring diagram and operating manual for this unit?
Reply With Quote
Sponsored Links
  #2  
Old 08-07-2006, 02:54 PM
Jim Davis Jim Davis is offline
Registered-III
 
Join Date: Oct 2005
Location: USA
Posts: 313
Likes: 2
Liked 20 Times in 14 Posts
Default Re: Need Help with 7.5JB-3CR/2442AB Genset

http://ebay.com/Onan-JB-JC-Service-Manual

Service manual above.

jamesdavis7@cox.net email me and I will reply with a PDF parts manual
Reply With Quote
  #3  
Old 08-21-2006, 10:22 AM
mi002le mi002le is offline
Registered-I
 
Join Date: Aug 2006
Location: Stamford, CT USA
Posts: 11
Likes: 0
Liked 0 Times in 0 Posts
Default Re: Need Help with 7.5JB-3CR/2442AB Genset

Jim;

Thank you for the parts manual and the direct to the operating manual. I purchased one.

I've cleaned out the mouse nests, made repairs to the starter solenoid, the ignition relay and rigged up a fuel line. This weekend, I got the engine running on gasoline...it runs pretty good!

As for the generator, I think I mentioned the output panel is missing. I tested for voltage across both sides of the line...At first I got less than 20 volts...then the voltage came on @ about 150volts per leg and the battery ammeter indicated the system was charging the battery. Then suddenly, it went back to less than 20 volts per leg and the battery is no longer charging.

I'm thinking voltage regulator. Any ideas anyone?
Reply With Quote
  #4  
Old 08-22-2006, 03:20 AM
BTPost's Avatar
BTPost BTPost is offline
Moderator
 
Join Date: Jan 2005
Location: Excursion Inlet, Alaska USA 99850-0090
Posts: 4,651
Likes: 515
Liked 1,715 Times in 1,132 Posts
Images: 1
Talking Re: Need Help with 7.5JB-3CR/2442AB Genset

from the Spec, it looks like you have a YD Genend 240/120Vac. I would look
at the Regulator for sure and since the genend is brushless there are no
brushes to check.

Bruce in alaska
Reply With Quote
  #5  
Old 09-06-2006, 04:46 PM
mi002le mi002le is offline
Registered-I
 
Join Date: Aug 2006
Location: Stamford, CT USA
Posts: 11
Likes: 0
Liked 0 Times in 0 Posts
Default Re: Need Help with 7.5JB-3CR/2442AB Genset

Bruce in Alaska;

I had a chance to open up the unit last night...there is no flywheel side generator on the unit and I'm kind of at a loss as to where to look for a regulator.

I started it again this afternoon...it's discharging on the DC side and about a 20V output on the AC. It doesn't seem to be getting voltage to the terminal block that supplies power to the PC board.

Any ideas? Anyone else who might be able to help is wecome to chime in.
Reply With Quote
  #6  
Old 09-06-2006, 04:52 PM
Steve Dawkins Steve Dawkins is offline
Registered-III
 
Join Date: Feb 2005
Location: Virginia Beach, VA USA
Posts: 321
Likes: 31
Liked 16 Times in 12 Posts
Default Re: Need Help with 7.5JB-3CR/2442AB Genset

Do you have a printed circuit board located under a square metal cover on top of the generator? If so, this is your automatic voltage regulator.
Reply With Quote
  #7  
Old 09-06-2006, 05:01 PM
mi002le mi002le is offline
Registered-I
 
Join Date: Aug 2006
Location: Stamford, CT USA
Posts: 11
Likes: 0
Liked 0 Times in 0 Posts
Default Re: Need Help with 7.5JB-3CR/2442AB Genset

Steve;

Yes I do. What I don't have is a schematic, wiring diagram or anything that let's me know what it's supposed to do. Thsi thing came totally without info and without some of the parts.
Reply With Quote
  #8  
Old 09-08-2006, 01:02 AM
BTPost's Avatar
BTPost BTPost is offline
Moderator
 
Join Date: Jan 2005
Location: Excursion Inlet, Alaska USA 99850-0090
Posts: 4,651
Likes: 515
Liked 1,715 Times in 1,132 Posts
Images: 1
Talking Re: Need Help with 7.5JB-3CR/2442AB Genset

What you NEED is the YD Generator & Controls Service Manual...
Onan # 900-0184 available from your local Cummins/Onan Dealers
Parts Department. This is the Gold Standard for ALL YD Genset
Service and Repairs. It also has all the Schematics for all the Control
Systems for any Genset that has a YD Genend. From the sound of
things, your problem is in the Exciter portion of the AVR, as your Output
Power is jumping around, at the same time as the DC Charging Voltage.
Since these windings are both Fixed in the YD, I suspect that you have
a problem in either the Exciter portion of the AVR or in the Fixed Exciter
Winding of the Genend. YOu should try Flashing the Fixed Exciter Winding,
and see if that cures, or temperarily solver the problem.

Bruce in alaska
Reply With Quote
  #9  
Old 09-08-2006, 10:19 AM
mi002le mi002le is offline
Registered-I
 
Join Date: Aug 2006
Location: Stamford, CT USA
Posts: 11
Likes: 0
Liked 0 Times in 0 Posts
Default Re: Need Help with 7.5JB-3CR/2442AB Genset

Bruce;

Thank you for the information. I'll see if we have a dealer around here I can get the manual from. I used the info from a previous thread and determined the charging circuit is wired correctly...now if only it will work again...I ain't giving up yet!

Michael
Reply With Quote
  #10  
Old 10-09-2006, 07:06 PM
mi002le mi002le is offline
Registered-I
 
Join Date: Aug 2006
Location: Stamford, CT USA
Posts: 11
Likes: 0
Liked 0 Times in 0 Posts
Smile Thanks for Help with 7.5JB-3CR/2442AB Genset

I got the unit generating electricity on Sunday! I bought the YD Manual from Cummins MetroPower and used the troubleshooting guides to determine the regulator board was malfunctioning. Bought a new regulator board from Cummins and installed it. Started the unit and adjusted the regulator board as per the instruction in the manual. Was able to get a balanced 124 volts with no load and less than 1 volt drop with 1500 watts on each leg of the output.

I was amazed to see how well it took load and maintained engine speed...it seemed like it could run indefinitely. Now I'm going to outfit it with a protected output panel and then test it to see how much load it can handle when it's hooked up to my house.

Thanks to all for your help and encouragement. I certainly learned a lot.
Reply With Quote
Reply


Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

F o r u m Jump

Similar Threads Chosen at Random
Thread Thread Starter F o r u m Replies Last Post
Help ID Genset richmc Generators & Motors General Discussion 5 10-21-2014 08:27 PM
OTC 5BH Genset John Hennig Onan Generators 3 03-23-2005 08:56 AM
VW Genset jdunmyer Generators & Motors General Discussion 4 11-03-2004 08:07 PM
My M5 Genset Jim Dunmyer Generators & Motors General Discussion 3 09-15-2004 03:47 PM
HOL-GAR Genset Mike Ledbeter Generators & Motors General Discussion 0 04-04-2002 07:31 PM


All times are GMT -4. The time now is 05:10 PM.

Smokstak and Enginads site search!


All use is subject to our TERMS OF SERVICE
SMOKSTAK® is a Registered Trade Mark
A Community of Antique Engine Enthusiasts
Copyright © 2000 - 2014 by Harry Matthews
P.O. Box 5612 - Sarasota, FL 34277