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Kohler 12.5RCOP63 Spec. 96603C Serial 010774

Rjvega

Registered
Hi All,

I am searching for a schematic, parts list, troubleshooting/operators manual for this setup. I have a paper copy of the Maintenance Manual if someone needs something from there. Nowhere in the manual does it describe the controller box at all.

This GenSet was new in 1979. I hope it is old enough to interest this group.

Some wires near the start switch burned and I am hoping to rewire it and to understand why it burned. I have photos





Here are some specs that I feel fairly confident on:

On TAG
DPA 3248F990
Serial # R42372ZT
Model # PH30/500/9/188

Model # 12.5RCOP63
12.5 kVA
R - Remote control Start/Stop
C - Push Button Start at plant 12 V Electric Start?
O - Diesel
P - Perkins Engine
6- ?
Last number 3 - Marine

Kohler Generator Set (Discontinued)
Model # 12.5RCOP63
Spec: 96603C
Serial # 010774
KW 12.5 PHASE 1
KVA 12.5 HERTZ 60
VOLTS 120/240 RPM 1800
AMP 52 PF 1
WT #BATT 1
150-350cca

I tried to include these photos:
https://www.dropbox.com/s/clqxrho92agh5yi/Control Box Front.pdf?dl=0

https://www.dropbox.com/s/gfks153cacca7dg/Control Box Inside Right I would like to schedule a showing for this listing. I prefer to be at the home at damage.pdf?dl=0

The original receipt for this set " ES-795, 12.5RCOP63, Spec 96603L"
 

Zephyr7

Registered
That selenium rectifier may have failed. Classic problem with the old sets. You can replace it with a silicon bridge rectifier. Note that other things often fail when those old rectifiers fail so you need to check the rest to be sure.

Bill
 

Rjvega

Registered
That selenium rectifier may have failed. Classic problem with the old sets. You can replace it with a silicon bridge rectifier. Note that other things often fail when those old rectifiers fail so you need to check the rest to be sure.

THANK YOU for the reply. Do you know how I spec the new bridge rectifier? or where to acquire it?
 

Zephyr7

Registered
All the bridge rectifiers are cheap. I’d go for a 25A or larger, 1000 PIV unit. It’ll probably be maybe $5 max. You can get 35A and 50A sizes too. Larger won’t hurt for ampacity. Good sources are digikey, mouser, and all electronics. Jameco is another option.

Bolt the rectifier to the metal chassis somewhere inside the control cabinet. The metal box will help with heatsinking for the rectifier.

Remember that when the rectifier fails, it often takes other parts with it so you need to check the components connected to the rectifier too.

Bill
 

Rjvega

Registered
Great. I have both reviewed the FAQ (thanks jack0) and checked into a replacement rectifier THANK YOU Zephyr7. As recommended by the FAQ, I wrote to a distributor asking for the wiring diagram based on the info I had in my post. I will post what I receive.

I will need the schematic diagram to check what downstream damage might have been done. I'm hoping I receive something from the distributor.

In the meantime, I will test the Selenium Rectifier to see if it has failed. Will the increased efficiency of the new rectifier cause me any issues?

Is reworking this controller the optimum path? Are there aftermarket controllers that could work?
 

Zephyr7

Registered
Replace the selenium rectifier even if it still checks good. They’re all timebombs just waiting to fail. I doubt the better efficiency will cause you any problems, but check the generator output after you replace the rectifier since you’ll probably need to adjust the voltage.

I don’t have schematics for your particular genset, but it shouldn’t be too difficult to just trace the wiring from that rectifier to check connected components.

Bill
 

Rjvega

Registered
I wrote to Colburn Power Systems (service@colburnpower.com), provided the info I had about the GenSet and received the schematic within 12 hours. This indicates that I have Controller D-268950

https://www.dropbox.com/s/mcswf9hvebuv2lx/20190206075013386.pdf?dl=0

I also found this article about Selenium Rectifiers that seemed really good. I read that the addition of a 100 Ohm resistor to a replacement rectifier will get the output voltage very close to what the Selenium Rectifier was.

https://www.dropbox.com/s/af0je3k7gdwbtk6/RBSelenium2.pdf?dl=0

Happened across this Service Bulletin describing the replacement of relays from available service kit. The 233180 relay is used twice and the 233059 is used once in my controller.

https://www.colburnpower.com/mwdownloads/download/link/id/118/
 

Rjvega

Registered
It appears that the wire for the start switch, both in the control box, and in the remote panel burned. The one on the remote panel burned from the start switch to a remote voltage meter. Does this point to the Selenium Rectifier?
 

Vanman

Subscriber
Last Subscription Date
07/10/2019
The selenium rectifier is used to supply power to the auxilliary field winding, in proportion to load current. To do this it is in series with a transformer and the line. The load current then passes though the secondary, consisting of a few heavy turns.

This is why it is critical that the rectifier not go open circuit. If it does, the transformer develops a very high voltage, destroying itself.

The lower voltage drop of the silicon rectifier will merely make the output voltage *slightly* higher under load. Extra resistance is not needed here, and would introduce another potential failure point.

The control wiring is not interconnected with the auxilliary field circuit, however, on my set, it was unfused and found with similar issues to yours when I got it. I added fuses to key places during the overhaul.

Do NOT add a fuse or anything else in series with the auxilliary field, it's rectifier, or it's transformer.
 

Rjvega

Registered
Thank you Vanman for the reply. I am going to replace the rectifer although I'm not 100% on checking the Selenium Rectifier to verify its failed. The transformer spec is not in the diagram. Do you happen to know what it is and how to test it?

The three relays coil resistance varies widely. I would to source-like replacement relays for this unit. 233180 relay is used twice and the 233059 once. I found a spec for the 233059 that said it was a DPDT 10A 12V 120Ohm relay. (not close to any of my readings) I have not been able to find a spec for the 233180 relays. I measured coil resistance on the three relays and got ICR 475 ohms on CC 15 ohms and CR 64 ohms.

The wire to the start switch, both inside the controller and behind the remote panel (RV) burned.
 

Vanman

Subscriber
Last Subscription Date
07/10/2019
Wow, lucky it didn't burn down the RV. Scary. Definitely want to add a fuse or two as appropriate.

The rectifier may well still be good. Mine was. If it had failed open under load the resulting physical damage to it and the transformer would be readily apparent. This is the time to change them. Before their failure has ruined the transformer. :brows:

Odds are the transformer is good so long as it passes a visual inspection. Could verify that the windings are open circuit to the core. As per the schematic, two of the windings are connected internally at one end. The other should read open circuit to the joined pair.

It is a special transformer. Unlikely that anything off the shelf would be suitable. Another fellow on here had his destroyed when the rectifier failed. He had it rewound at considerable expense IIRC. :brows:

Can you post some photos of your set? :D

You can post photos directly to this site. Just scroll down below the reply field, and you will see the necessary places to click and so forth.

About Colburn Power. Before you order anything, I would call them and verify that they actually have the item that they list on their website. Took me a couple of months to get an order because of one item I ordered that they didn't actually have.
 

jack0

Registered
Age
60
Nice and with a Perkins. Pictures please.
I believe the relays in this plant are nothing special. 12v dc for coil clearing and crank-run. 120v ac for cr1. You could get them from McMaster-Carr, Graingers etc. Might be cheaper than going through Kohler.

It kind of sounds like there are some issues in the control wiring. I would go through everything and clean up the wiring. Relays are not expensive.
Now that you have a wiring diagram, should be straight forward.

There are some older posts by LWB250 on sequence of operation you might find interesting.

I find it kind of odd that the remote start switch and the meter are connected. You would think that the remote switch wires would run straight to terminals 3-4 on the generator terminal board.
 

Rjvega

Registered
Is the transformer spec known so that I can source a new one? I'm not sure exactly how to test the transformer in advance.

My overhaul plan consists of replacing the relays with new 10A octagonal base relays in sockets. The Kohler originals (without dust covers) appear to be discontinued. Of the three relays, there are two part numbers on these relays. Is there a spec for the relays that need to be adhered to?

I will rewire the entire control/relay section and put a 10A fuse in the control circuit. I have a 40A rectifier to replace the selenium rectifier with.

If I can figure out how to test the transformer I will. I'm hoping to source a replacement for the transformer while I'm at it.

Help testing the transformer and advice on the relay replacement would really help.

Thanks for your assistance.
 

Zephyr7

Registered
You’ll probably have to have the transformer rewound if it’s bad. You’d have to get very lucky to find a replacement since it’s not a normal transformer.

To test the transformer, you really need an impedance meter and then readings from a known good transformer for comparison. You could try checking for continuity (across windings should be good, and it should show open between windings and the frame), but I usually find burned transformers fail with shorted turns which a basic continuity check won’t see.

Bill
 

Rjvega

Registered
I've been looking at the schematic. It appears that the "High / Low" switch is for charging the start battery? My set has an alternator mounted on the Perkins so I'm not sure this is in use. Am I correct that this is the intended purpose? I see that the switch either employs one resister or another. Could anyone describe the application of this feature?

Ric
 

Vanman

Subscriber
Last Subscription Date
07/10/2019
In this instance, the transformer essentially functions as a current transformer. The end result is the current in the auxillary field winding is proportional to the load.

To approximately determine the turns ratio, I'd put a good load on the set, measure that load current accurately, then accurately measure the AC current before the rectifier.

Yes, most likely the high low switch is / was for battery charging.

Keith
 

Zephyr7

Registered
To approximately determine the turns ratio, I'd put a good load on the set, measure that load current accurately, then accurately measure the AC current before the rectifier.
Better to measure the voltages across the windings. Even in the case of a current transformer, voltages are still proportional. Current transformers care a lot more about the gauge of wire you wind them with though.

You still need to know the number of turns of one of the two windings. Voltages will just let you determine the turns ratio. If the transformer is shot, the best thing to do is to take it apart carefully and count the number of turns of each winding, and then use a micrometer to figure out what the wire gauge is (make sure to remove the enamel first). Remember too that enameled wire comes in both even AND ODD gauges, so yes, you might actually see something like 29 gauge wire.

Bill
 
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