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09-19-2014, 03:55 PM | #1 |
Not Yet Wild
Join Date: Sep 2014
Posts: 8
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26984 Total Charge III voltage has me stumped
Newbee needs help: Using Lester procedure transformer voltages are good with and without cap (91 & 62V). Diodes check good with two different meters in diode mode. Connect diodes and no load output is only 41V. Any ideas?
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09-20-2014, 07:15 AM | #2 |
Gone Wild
Join Date: Aug 2014
Location: Duncan Corners
Posts: 905
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Re: 26984 Total Charge III voltage has me stumped
This may help?
http://www.lesterelectrical.com/serv...e/35827_A1.pdf Charger does not "power up" until attached to cart. |
09-20-2014, 07:51 AM | #3 | |
Techno-Nerd
Join Date: Jun 2011
Location: West Virginia
Posts: 19,654
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Re: 26984 Total Charge III voltage has me stumped
Quote:
If one of the diodes was open, or if they had a lousy front to back ratios, you also might get something in the neighborhood. Could be a resistive path between the positive and negative output wires. (What does the ammeter read?) Try measuring the DC voltage between the heatsink the diodes are on and the ammeter terminal with the two wires from the transformer on it. If you still get 41VDC, unplug the Red and Black wires going to the control board. Here is a schematic and manual for a TC-III. Also, check the battery in your DMM. |
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09-20-2014, 07:59 AM | #4 | |
Techno-Nerd
Join Date: Jun 2011
Location: West Virginia
Posts: 19,654
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Re: 26984 Total Charge III voltage has me stumped
Quote:
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09-20-2014, 01:56 PM | #5 |
Not Yet Wild
Join Date: Sep 2014
Posts: 8
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Re: 26984 Total Charge III voltage has me stumped
JohnnieB,
Thanks for the reply, info and humor. I read many of your replies and actually got the Lester transformer test procedure from one of your posts. I'm far from perfect and should have provided more detail. I measured the 41V with 2DMM's in case one was bad and purposely tried measuring AC volts as well. The control board is bypassed and relay wires are jumpered. Voltage readings are from the diode heat sink to the center tap wire at the ammeter. I got the same forward bias numbers when I check the diodes, but they may be lousy as you say. I'm going to hook up a set of external 1N4004's and check no load voltage; that should tell me if it's a diodes or connection. Might take a few days, but will post results. Thanks again, |
09-20-2014, 02:36 PM | #6 |
Techno-Nerd
Join Date: Jun 2011
Location: West Virginia
Posts: 19,654
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Re: 26984 Total Charge III voltage has me stumped
You are getting about 90VAC between the wire that connect to the diodes, when they are disconnected from the diodes.
Try measuring the AC voltage on the same wires when they are connected to the diodes. If it is still about 90VAC, and you only get 41VDC between the heatsink and the ammeter, the diodes are sick. 1N1184 will work, or any power rectifier rated at 35A or above and 100V or more. (Just bore holes in the heatsink to mount them if the originals are press-fit) Be careful with a 1N4004, it is only 1A and might explode if there is a hidden load on the circuit. |
09-20-2014, 07:32 PM | #7 |
Gone Wild
Join Date: Jan 2014
Location: South Georgia
Posts: 1,120
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Re: 26984 Total Charge III voltage has me stumped
PD, Since you are familiar with the charger innards and bypass test procedures it would be a interesting experiment to disconnect both diodes and reconnect one diode at a time and measure the difference if any in the output voltage. If one were bad or weak the output voltage would be different. Usually bad power supply diodes are either open or shorted. If you have a handful of 1N4004 diodes you might want to parallel a few to get more current rating but one substituted for each power diode should tell you what you want to know.
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09-22-2014, 12:45 PM | #8 |
Not Yet Wild
Join Date: Sep 2014
Posts: 8
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Re: 26984 Total Charge III voltage has me stumped
Disconnected transformer wires from the diodes and measured front to back again; both show 0.5V forward bias and open in reverse. Then I measured open circuit output voltage from the transformer again just to make sure and it reads 91VAC. I removed the center tap connections from the ammeter; re-crimped them and cleaned the terminals just in case. I started thinking the diodes are failing when voltage is applied so I found a couple of 40A/600V diodes in the workshop and hooked them up; still only 42VDC no load. Now I’m really scratching my head. Will check AC volts with the diodes connected tonight and let you know.
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09-22-2014, 01:37 PM | #9 |
Techno-Nerd
Join Date: Jun 2011
Location: West Virginia
Posts: 19,654
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Re: 26984 Total Charge III voltage has me stumped
It depends on how your DVM handles the 120Hz ripple of the unfiltered output from the full-wave rectifier, but it ought to read either 82VDC (Average) or 91VDC (RMS), with 91VAC applied.
The 42VDC you are getting is roughly the output voltage from a half-wave rectifier with 91VAC applied. Make sure the heatsink the diodes are mounted on, isn't grounded to the charger chassis. ---------- Measuring the VAC on the wires connected to the diodes ought to tell the tale. If it is less than 91VAC, disconnect the wires going to the charger's output cable and the wires going to the control board. Also, check the AC input voltage to charger. ------------- I'm scratching my head too. This is a strange one, but we will figure it out. |
09-22-2014, 02:05 PM | #10 |
Gone Wild
Join Date: Jan 2014
Location: South Georgia
Posts: 1,120
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Re: 26984 Total Charge III voltage has me stumped
I know you ran the test to check the capacitors with the voltage test with it in and out of circuit. If you can put your hands on another capacitor I suggest you try it. The only golf cart charger I ever worked on almost whipped me because it would only charge at 8 amps. I finally substituted a AC run capacitor used in air conditioners of the approximate value and presto the voltage came up to normal and charge rate was normal 20 amps. I used a fluke meter with the capacitance measurement feature and measured the capacitance of the suspect and it was about 60 % of the correct value. It even had the capitance kick when I put my old analog meter on it.
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26984, low voltage |
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