The Old Ferroresonant MAGNATEK Converters...
These dinosaurs were 30X as common as competitive converters and were a flawed design from the word go... OEM chose the BW Magnatek units because they were the least expensive of the lot. I came a MAG...
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Performance wise, electrolytic capacitors will, over time, degrade. With the Magnetek units for every unit that grew old and lost voltage I found many many more that gained voltage. Fifty to one would not be an exaggeration. Folks here with more radio experience than I can tell you the mechanism in which electrolytic capacitors fail with more or less capacitance.
The 735-2, 750-2. and 775-2 were spec'd for 14.0 volts. But it wasn't this model of charger that caused all the misery. It was the relay switched-source converter with bleed resistor that was a miserable failure.
The 75 ferroresonant chargers were aimed at the high-end market: Vogue and Blue-Bird motorhomes for instance. The relay, bleeder resistor, was a favorite of mass-marketed Fleetwood, Terry, and other manufacturers.
Gjac, your 50-amp charger aged in the safe direction. Actually Magnatek used wildly different quality capacitors in their different models. The 7 series caps were not bad, but it was the legion of cheap relay and bleeder resistor converters that did all the damage and persuaded all but technicians that claimed charging specification of 13.8 volts, boiled batteries dry.
Later on Magnatek introduced their 952 series switched charger that was not ferroresonant based. I played briefly with one, and I remember it had a voltage set point below 14.0 volts. I do not know the history or the outcome of this charger. This was around the time that Todd introduced their 75 amp switched charger. BTW the relay bleeder models were enclosed by a fuse and breaker panel the latter chargers were the size of a loaf of bread and did not even have an on-off switch. I used 800 volt rated milspec caps when I played with the 7 series chargers. Lockheed surplus auctions were a gold mine.
Magnatek must have manufactured a dozen different chargers based on ferroresonant control. Again, it's the converter model - AC breakers, fuses, relay and bleed resistor that caused most of the uproar. The cost of a capacitor swap out made repair costly and most owners did not opt for it.
But to repeat this is how "13.8 volts" got a bad rap.
The 735-2, 750-2. and 775-2 were spec'd for 14.0 volts. But it wasn't this model of charger that caused all the misery. It was the relay switched-source converter with bleed resistor that was a miserable failure.
The 75 ferroresonant chargers were aimed at the high-end market: Vogue and Blue-Bird motorhomes for instance. The relay, bleeder resistor, was a favorite of mass-marketed Fleetwood, Terry, and other manufacturers.
Gjac, your 50-amp charger aged in the safe direction. Actually Magnatek used wildly different quality capacitors in their different models. The 7 series caps were not bad, but it was the legion of cheap relay and bleeder resistor converters that did all the damage and persuaded all but technicians that claimed charging specification of 13.8 volts, boiled batteries dry.
Later on Magnatek introduced their 952 series switched charger that was not ferroresonant based. I played briefly with one, and I remember it had a voltage set point below 14.0 volts. I do not know the history or the outcome of this charger. This was around the time that Todd introduced their 75 amp switched charger. BTW the relay bleeder models were enclosed by a fuse and breaker panel the latter chargers were the size of a loaf of bread and did not even have an on-off switch. I used 800 volt rated milspec caps when I played with the 7 series chargers. Lockheed surplus auctions were a gold mine.
Magnatek must have manufactured a dozen different chargers based on ferroresonant control. Again, it's the converter model - AC breakers, fuses, relay and bleed resistor that caused most of the uproar. The cost of a capacitor swap out made repair costly and most owners did not opt for it.
But to repeat this is how "13.8 volts" got a bad rap.
