need help on univolt converter

[sander17]

Originally Posted by FrenchBern

To anyone who might be interested,
My Univolt model 35 (1970 overlander and also a friends 1971 overlander) has a nominal output of 13.5 volts because of the series voltage regulator inside. If the regulator is shorted the output will be close to the winding voltage which is 17 volts and will cook and dry up any 12 volts battery. Simple check to find out condition. With or without a battery and with different loading, the univolt output should read about 13.5 volts which will never boil a battery unless the acid level is low nor will it overcharge. I have a picture of the regulator board but I am not able to paste it. Is a 98Kb pic too big?

That is surprising that the '70 and '71 univolts had a voltage regulator in them. My '79 just had a couple of diodes forming a half wave bridge on the secondary of the ferroresonant transformer and producing rectified, but unregulated power. I would be interested in your photo showing how they used a 3-terminal voltage regulator in the circuit. (V(un-reg), V(reg), Common)

[Lumatic]

The Univolt on my 73 seems to only be charging at 7-8 volts. Which will cause my 12 v system to eventually shut down until I charge the battery with the tow vehicle or a seperate battery charger. What is the likely cause and is it possible to, or worth repairing?

[sander17]

Originally Posted by Marshall

The Univolt on my 73 seems to only be charging at 7-8 volts. Which will cause my 12 v system to eventually shut down until I charge the battery with the tow vehicle or a seperate battery charger. What is the likely cause and is it possible to, or worth repairing?

Likely cause: Usually it is the capacitors that fail in these beasts.
Possible?: yes
worth repairing? usually $10 vs. $180 for a new converter

Now the big question: Are you confident working on electrical equipment with LETHAL voltages present? Are you experienced with soldering, riveting the case, using a VOM to test diodes and capacitors?

IF NOT, THEN DON'T DO IT!

A new unit will have a normal 115 VAC cord and the only wires to be hooked up are low voltage (13.5 or so volts).

[FrenchBern]

Please someone help me and tell me how to post my picture of the voltage regulator board in the Univolt for Sander17 and anyone else. Why can't I just copy and paste it in the text?

[thenewkid64]

Originally Posted by FrenchBern

Please someone help me and tell me how to post my picture of the voltage regulator board in the Univolt for Sander17 and anyone else. Why can't I just copy and paste it in the text?

Because it is a different file type........


After you have typed your post scroll down on the screen and you will see a box labeled Manage attachment. Then browse to the picture and upload. Wait for it to finish before closing the window. Once the files upload you can close the window and post.....

[FrenchBern]

God bless you Thenewkid64 for your help. I was using quick reply instead of post reply.

Here's the picture of the regulator board in the model 35 univolt built in 1970.

[Lumatic]

Originally Posted by sander17

Now the big question: Are you confident working on electrical equipment with LETHAL voltages present? Are you experienced with soldering, riveting the case, using a VOM to test diodes and capacitors?

IF NOT, THEN DON'T DO IT!

Thanks, I can handle the soldering and riveting. I'll try and find a volunteer who likes playing with electricity to help with the technical stuff.

Marshall

[Swanny]

Hello everyone. I'm now experiencing the joy of 12vdc operation .

Anyway, I charged my deep cycle battery a couple of weeks ago and put it in the AS. After working in the trailer for a few days and running lights, radio and fans, I noticed that when I turned on the 'final' interior light, the radio would turn off. Once I turned the extra light off, the radio would kick back on.

So here's an AS with a humming converter (the original by the looks of it) and I'm not sure which item is the problem. Per your great advice, I've already checked the fuses on the panel and they all seem to be okay.

Any direction you can provide would be awesome. Thanks again.

Mitch

[FrenchBern]

Sorry for the small picture. The 100k picture is small and the 33 k is big. Can't figure that one out. Fixing the Univolt is no problem if I can find the schematic for the voltage regulator board and a parts list. The only voltage that could be lethal is the 120 volts ac.
If anyone happens to be in the western SC, I'll be glad to check your system for free. So there you go Marshall. When I go camping I am usually bored and go around fixing electrical problems. So far 4 trips, 4 request, and four fixes.
I am trying to post that pic again. Here goes.

[sander17]

Originally Posted by Swanny

Hello everyone. I'm now experiencing the joy of 12vdc operation .

Anyway, I charged my deep cycle battery a couple of weeks ago and put it in the AS. After working in the trailer for a few days and running lights, radio and fans, I noticed that when I turned on the 'final' interior light, the radio would turn off. Once I turned the extra light off, the radio would kick back on.

So here's an AS with a humming converter (the original by the looks of it) and I'm not sure which item is the problem. Per your great advice, I've already checked the fuses on the panel and they all seem to be okay.

Any direction you can provide would be awesome. Thanks again.

Mitch

Mitch,
First the easy tests: With the lights on at nite, turn the converter on and off. Since it puts out more than 12 volts, the lights should get brighter when it is on. This is easiest to see at nite. If there is no change, then pick up a cheap digital voltmeter and check the voltages at the fuses with the converter on and off. Check the voltage at the converter itself with it on and off. If the converter is putting out more than 13 volts, try cleaning all the connections. Loosen the big wire clamps and retighten. Make sure the grippers are tight on the fuses.

Disconnect the battery and see if the converter will run the lights by itself. The radio will have a lot of noise, but it will test if the converter is putting out current.
When the capacitors went in my converter, it still made a quiet hum, but no where near as loud as when it was working properly.
Good Luck!

[Swanny]

Thanks Dave---I'll give this a try over the weekend. When I took the battery to the auto parts store, they told me that they can't use the battery tester on deep cycle batteries. The machine will short out the plates.

They did suggest that I charge the battery overnight, let it sit for a few hours and than test it for voltage. This lets us see if the battery is holding its charge. Does this sound right to you guys?

Mitch

[sander17]

Originally Posted by Swanny

Thanks Dave---I'll give this a try over the weekend. When I took the battery to the auto parts store, they told me that they can't use the battery tester on deep cycle batteries. The machine will short out the plates.

They did suggest that I charge the battery overnight, let it sit for a few hours and than test it for voltage. This lets us see if the battery is holding its charge. Does this sound right to you guys?

Mitch

With the overnite charge test, be sure to use a good digital voltmeter. The voltage difference between a charged and discharged battery with no load is pretty small. If you look on the web, you should be able to find a table of voltage vs. percent charged for deep cycle or automotive lead-acid batteries.

I would still do the simple tests on the univolt to confirm that it can power the systems without the battery in the circuit. Remember that a typical univolt only puts out 55 amps or so. You might check the wattage of the lamps and other 12v circuit items like the water pump and any fans. Light bulbs can add up.

[Lumatic]

Originally Posted by sander17

Disconnect the battery and see if the converter will run the lights by itself. The radio will have a lot of noise, but it will test if the converter is putting out current.

What does it mean if the converter will NOT run the lights or radio by itself?

Marshall

[sander17]

Originally Posted by Marshall

What does it mean if the converter will NOT run the lights or radio by itself?

Marshall

Basically it means you have a problem. It is time to start tracing the DC voltage. Start at the converter output. If you do not have voltage there, disconnect both leads and measure again. If you now have voltage, there is a short in the wiring. If the converter has 115VAC input power but no DC output, then you know the culprit. Either replace it or fix it. There are several threads about fixing the old ferroresonant univolts. The newer switching power supply converters are very complicated circuits and unless it has a blown internal fuse, you are probably better off replacing them.

If you have DC at the converter, but not at the devices, look for bad fuses that may look ok but are open, or pinched wires that have been cut by a sharp edge, loose connections, connector corrosion, or mice damage.

Hopefully your diagnosis will not involve belly pan removal...........

[raebaker06]

I am reasonably converse with electronics, and I too have a Univolt converter.
What it is is a large 6 volt transformer. with a voltage doubling circuit to give you 12Vpulsing dc. Your battery is the filter circuit.
Voltage doubling is facilitated with an AC capacitor in circuit. If your unit gives low voltage or does not work you could have .....Bad rectifiers (diodes) fuses.....or the capacitor has failed. It is a very simple circuit and should last and last. IT IS NOT A SMART CHARGER. Which could be expensive and cause much problems.
Have someone remove the unit and check for bad diodes, and a bad cpacitor(note I did not call it a condenser) If the capacitor is faulty it can be purchased at a Motor repair shop. (used for motor starting capacitors). 5 MFDs will work. Simply wire it in and hook it back up.
The capacitor should cost you less than $10.00.
The diodes can be checked with a simple Voltmeter in The OHMS SCALE.in the low scale. RX1.
Putting the leads across the diode you should be a reading in one direction...Reverse the leads and you should not get a reading (if the diode is good.) If it reads in both direction the diode is shorted and if no reading it is open circuit. simply replace the diodes that are bad and VOILA you are an Electronics expert. Remeber simple is better.
If you need further information please E-Mail me. Before Oct 20th
rbaker@nas.net

[Hippo]

I thought I had a bad univolt. I pluged the trailer into camp power on a 30amp plug. The battery had to be charged because the univolt did not work. I finally found the 30amp plug in did not work. I pluged into 110volt plug with an adapter plug and it works now. I felt so stupid.

[FrenchBern]

Rae, What model is your Univolt? Do you have a schematic for it?

[albert]

Where do I post or search to find a circuit board for the front control center? I have a 70 Ambassador and I think the board is toast. I want to replace it.
the part # is Airstream 05110

Sorry to inturrupt, and thanks for your time.

[raebaker06]

Originally Posted by FrenchBern

Rae, What model is your Univolt? Do you have a schematic for it?

I do not have a schematic, and please don't ask me to with much pain get the unit out.

I can and will draw a simple voltage circuit for you which should suffice for your needs..
There is very little in the circuit. Give me you E-Mail addr. and I will draw and mail it to you

rae

rbaker@nas.net

[Inland RV Center, In]

Albert.

Try a salvage yard.

Andy