Magnetek / Parallax 6300 converter DC power noisy?

**ShrimpBurrito** · 01-05-2011, 11:44 PM

I seem to recall reading complaints here that the older style Magnetek / Parallax 6300 converter had a noisy DC output, and that was the reason for early LED failures, radio problems, and probably tire blowouts.

I have such a converter. With the TM plugged into AC power, I measured VAC across the DC output of the converter with the fridge operating on DC (a ~9-10A load), and only measured 30-50 mV. That doesn't seem noisy at all. Am I missing something?

Dave

scrubjaysnest · 01-06-2011, 04:48 AM

For that converter probably not bad, turn off the refeer and see what you have.
You are also measuring a rms value which will be low if the converter output is more of a square wave instead of a sinewave. Noise in the form of a square wave is harder on electronics, but won't bother the refeer or something like a motor.

**Bill** · 01-06-2011, 11:29 AM

Dave -

The problem isn't so much that it is noisy. The real problem is that the voltage is completely unregulated. After passing through a voltage-reducing transformer, shore power is simply full-wave rectified and sent out to all the 12VDC appliances. That means that if the shore power voltage is high, then the voltage to the appliances is high. And if there is a transient on the shore power line (very common in campgrounds as air conditioners turn on and off), then that transient is passed through to the appliances. The high voltage - especially with the transients riding on it - is what kill LEDs. (Note that high-quality LED modules for the RV market have a built-in regulator to take care of this.) The lack of filtering/smoothing after the full-wave rectifier is what makes a buzzing sound in radios, though it is not harmful.

By the way, your meter is not really capable of making an accurate measurement on any of this. The reason is that the meter's measurement process involves a number of simplifications, all of which are based on the assumption that the voltage to be measured is either pure DC, or pure sine-wave AC at 60 cycles per second. Neither of these assumptions is even close to true at the output of the converter. A "true-RMS" meter would read accurately, but they are very expensive.

I have the Magnetek 6300 manual. I could send you the schematic if you have any interest.

Bill

**ShrimpBurrito** · 01-06-2011, 12:32 PM

Interesting. Thanks for the explanation, Bill. I appreciate the offer for the schematic, but I don't think I'm going to do anything about it because I'm not suffering any ill effects....at least yet. I just put the LED boards in a few weeks ago, but since we rarely camp with hookups, and the LED boards can supposedly run on 10-30 VDC, I am hoping we won't have an issue anyway.

Dave

**mjlaupp** · 01-06-2011, 02:53 PM

From a string about LED replacement lights:

"
Quote: Betty Ann
We replaced 6 of our interior bulbs with LED clusters. Liked the lighting effect, low bug attracting characteristics and low battery draw but we are not happy with the viability of the LEDs we got from www.superbrightleds.com . Of the 6 bulbs (1156) we bought which came with 19 LEDs per bulb --- 3 have only 7 LEDs still burning, one has only 4 LEDs, one has one LED and the last has zero. Will check with the company and see what's up with their bulbs. Since they only had a few hours use, I hardly consider this satisfactory. Endquote

My answer:
It sounds as if there is a problem with the power supplied to the bulbs. I checked my 12v power supply and found that the power supplied to the roof circuits is unfiltered. When the TM is operating off of shore power, the 12v circuits are running from the converter and not from the battery. Since there is no filter or battery to act as a filter the 12v supplied is actually 12.97vdc with a 6.69vac ripple on top of it. This means that the voltage supplied is peaking out at somewhere near 23 volts (I don't have a 'scope so I had to estimate from DVM readings). This is far above the 14vdc limit recommended by the LED suppliers. When you are operating from the battery there is no problem.

BTW, the filtered 12vdc measures 13.69vdc on my meter.

If the LED bulbs you used do not have voltage and current protection, then they will have a very short life. The answer may be to add a filter to the roof circuits. In my TM it would have to support the vent fan as well as the lights. You could also add a regulator to each of the lights as needed. See http://www.theledlight.com/ for examples.
"

Dave,

The leftmost 6 circuits on the 6300 DC fuse panel are not filtered. The Dc power for them comes directly from the converter. The do not get filtering from the battery nor are they regulated. The lower the current draw on these circuits, the more noise and AC ripple will be present.

The rightmost 3 circuits on the 6300 DC fuse panel are filtered by the battery. They provide power for the radio, TV power outlet, TV antenna amplifier and the propane monitor.

If you measured the AC ripple at one of the filtered positions, I would expect to see the results you posted. My measurements from above were made at an empty roof light socket with only one light on and shore power connected.

I was chasing radio 60 cycle hum and TV 60 cycle noise at the time. My radio would hum between tracks on the CD player and dead air on the radio. But only when I was connected to shore power. The TV would operate OK when on AC power. Was OK on DC power when the shore line was disconnected and noisy with the shore line connected.

I attribute the noise on the filtered circuits to the fact that the filtered and unfiltered wires are run parallel to each other in the same wiring bundle. And that it is very hard to filter 60 cycle AC using just a battery.

All of the noise problems were corrected with a converter replacement. The replacement converters have built-in active component filters as well as using the battery as a filter.

p.s. Evidently a converter replacement does not prevent tire failure. I was getting the TM ready to go into the dealer's for some TLC and found the left rear tire flat but only on the bottom. It held air when I filled it, but all 5 tires will be replaced now. (More in the Tires forum)

Wavery · 01-06-2011, 03:32 PM

Quote:

Originally Posted by mjlaupp

F
Quote: Betty Ann
We replaced 6 of our interior bulbs with LED clusters. Liked the lighting effect, low bug attracting characteristics and low battery draw but we are not happy with the viability of the LEDs we got from www.superbrightleds.com . Of the 6 bulbs (1156) we bought which came with 19 LEDs per bulb --- 3 have only 7 LEDs still burning, one has only 4 LEDs, one has one LED and the last has zero. Will check with the company and see what's up with their bulbs. Since they only had a few hours use, I hardly consider this satisfactory. Endquote

I had basically the same experience with LEDs as Betty Ann had with the smae supplier. I don't use a "Converter". I had a Progressive Dynamics 9245 converter wired in as a battery charger. I only ran those LEDs off of straight battery current. I seldom camp with hook-ups and when I do, the converter merely keeps the battery charged. My house current ran off of battery only.

scrubjaysnest · 01-06-2011, 05:06 PM

The one we used for 6 months in the pop-up is still going strong. It was purchased from a RV dealer in Helena MT. Run mostly on battery. Its in the TM now and I have another double fixture and two singles in route from a RV dealer on ebay. I'll check the converter next week when we get home from our gulf fishing trip.

**ShrimpBurrito** · 01-08-2011, 09:47 PM

Mike - Thanks for the followup. I measured the voltage at a light socket after reading your post, and found the exact same thing as you -- a ~6.6-6.7 VAC ripple. I did not know only some of the circuits are unfiltered, so that's good to know, although I hopefully will be ok as my LEDs are rated up to 30 volts.

Bill - On second thought, I'd like to take a look at the schematic. Would you mind sending or posting it when you get a chance? No rush.....

Thanks,
Dave

scrubjaysnest · 01-10-2011, 04:34 PM

Checked mine and the WFCO 8955 has a very clean output, a a few mV riding the DC. Also have the new led installed. Much brighter then the 1156 bulbs.

**ShrimpBurrito** · 01-15-2011, 04:17 PM

Thanks to the schematic and manual Bill sent me of the converter, I pulled out the converter expecting to change the power source of the light circuits from the converter to the battery. Unfortunately, the fuses are on a circuit board and the converter output is connected to those unfiltered circuits via traces on the board, so there is no way to remove the converter output from those circuits without changing the board.

So I decided to simply move each of the light circuits onto separate filtered circuits. The only thing on one of these filtered circuits was marked "test panel", which I believe is the monitoring panel that monitors the tank levels and battery. The only thing on the other filtered circuit I used was marked "TV", which I believe is the cigarette outlet by the fridge, along with the preamp.

With the LEDs, the current requirements on the light circuits will be much lower, but I don't see a problem with this even if the incandescent bulbs were still installed.

Alternatively, I could bypass the fuse panel and simply install an inline fuse for each of those circuits, but I am thinking what I did will work fine.

Does anyone see a problem with this solution?

Thanks,
Dave