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Onan Generators Restoring, operating and maintaining vintage Onan generators.

Onan Generators

Onan 7.5 JB-5DR/174440AA


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  #1  
Old 11-14-2017, 09:25:58 PM
RETCPO RETCPO is offline
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Default Onan 7.5 JB-5DR/174440AA

Looking at a generator and could use some help.
ONAN 7.5 JB-5DR/174440AA
Serial NO E770237484

What does the 5DR stand for? (3 phase?)
Manufactured MAY 1977
SPEC AA

Any other information that can be gained from the collective mines?

Respectully
Keith
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  #2  
Old 11-14-2017, 09:30:21 PM
Wayne 440 Wayne 440 is offline
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Default Re: Onan 7.5 jb-5dr/174440aa

https://www.smokstak.com/forum/showthread.php?t=119313

120/240 3 phase, 4 wire
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Old 11-14-2017, 09:32:43 PM
Chas183 Chas183 is offline
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Default Re: Onan 7.5 jb-5dr/174440aa

Voltage codes are here.
https://www.smokstak.com/forum/showthread.php?t=119313

Looks to be 120/240 3 phase 4 wire.

Just little further down Kevin K has a nice PDF for download.

chas183
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Old 11-15-2017, 02:28:05 AM
Ray Lynch Ray Lynch is offline
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Default Re: Onan 7.5 jb-5dr/174440aa

Spec AA is a YD gen end.
Ray
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Old 11-15-2017, 07:01:25 AM
MBB MBB is offline
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Default Re: Onan 7.5 jb-5dr/174440aa

I believe you have 1 to many 4s in the model number. Here is the build sheet for the unit. Very desirable. 4Wire. B150 extended Stack. (Had to go back and check I never saw a 4 wire with extended stack. Usually they are 12 wire.) No need to de-rate for single phase. It also has a meter panel and Housed providing its all there.
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Last edited by MBB; 11-15-2017 at 07:39:23 AM.
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Old 11-15-2017, 09:25:49 AM
RETCPO RETCPO is offline
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Default Re: Onan 7.5 jb-5dr/174440aa

MBB you're right!
7.5 JB-5DR/17440AA
Serial NO E770237484
Fat fingers and not proof reading strikes again...
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Old 11-15-2017, 09:56:36 AM
MBB MBB is offline
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Default Re: Onan 7.5 jb-5dr/174440aa

Don't know the condition or price but it's a good one.
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Old 12-03-2017, 09:07:18 PM
Max Thompson Max Thompson is offline
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Default Re: Onan 7.5 jb-5dr/174440aa

I had been watching this one for a month or more, but do not need another Onan, and since I was "cured" of the Green Disease some time ago I saw no need to even call about it.

Then RETCPO gives me a call: he would like to have this one for his mother's place, about 20 miles from me. How could I say no, it is for his "mother".

The story so far is below and pictures are here https://www.smokstak.com/forum/album.php?albumid=1546

Got the JB home Monday, got around to looking it over about Wed. Got the bulk of the mouse nest and trash vacuumed and blown out.

Contrary to the ad, the motor was not free. Water in both cylinders. I blew it out and added a cup of PB Blaster to each and let it sit a day or so. With a little persuasion it broke loose and seemed smooth rolling over. Just checked and showing #135 on no. 1 and #130 on no. 2 cylinders, so I do not think the water did any serious damage.
Made wiring repairs that “had to be done”, cut the outlets loose and removed the VR board, ”temporary” new oil and filter(cheap straight 30 wt. and a FL1 A filter). After a little fight with the points she came to life on carb cleaner. Hooked up a boat tank and she runs on her own. Let it run till she smoothed out and I was sure it was a runner then put the VR back in, makes good power.

Now I know it is a keeper, so will proceed with replacing control box wiring and relays, the relays are in sad shape. I may hook the load bank up and let it run an hour or so before I tear into the control box.

It is a 12 lead gen-end, wired “down” to 4 tagged leads. I will rewire to single phase before load banking it.
Sunday:

Today:

Changed out the 30 amp twist lock receptacle for a 4-wire 50 amp and reconfigured T-leads to 120/240 single phase. Replaced oil # gauge, the old one was sluggish. Greased the gen-end bearing. Rigged up a temporary exhaust.

Fired it up and let it warm for 15 min, plugged in the load bank and loaded it up to about 30 amps per leg. Ran for ½ hr. or so and seemed good but Hz were at 58 so after tweaking the carb to get the maximum Hz. I gave the governor about ¼ turn. No load = 61.6 Hz, full load 59.5 Hz @ 237 volts, recovery is very good from 6 amps to full load. I think this is close enough. It ran under full load for 2 ¼ hr. and never faltered. I think this one is a keeper.

While the JB was running, I moved 2 JCs from the floor of the shop to the loft in the barn and the trailer mounted JC to the barn with the other trailer mounted RJC. My help will be proud of me in the morning to see a little more floor space in the shop.

Shut the JB down at 4:30 and let it cool, then gave it a bath, won’t make it run any better, but more pleasant to work on. It is parked in the back of the shop until I get to the control box..
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Old 12-10-2017, 07:43:34 PM
Max Thompson Max Thompson is offline
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Default Re: Onan 7.5 jb-5dr/174440aa

Made some progress this week. My conscience would not let me put new relays and controls in the old mouse hotel so I sand blasted and painted the inside and bottom leaving the front original to match the rest of the set.

Replaced the rectifier and heat sink, start / stop switch, both relays and any wires or terminals that were “suspect”.

Starts, runs and now charges the battery.
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Old 12-10-2017, 08:32:15 PM
nothingbutdarts nothingbutdarts is offline
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Default Re: Onan 7.5 jb-5dr/174440aa

MAX,

You TRULY are one of the Kindest Gentleman I know!!!!!
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