0Z4 vs 6X5 full wave rectifiers question

[Texasrocker]

Seems I remember *Ford Autos* IE:"Fomoco",.. (motorola) vintage 6v car radios used the 6X5 full-wave rectifiers? (w/filaments inside tube), and (Delco) GM (VS)..used the old "hard to find, especially, in the late 40s-50s found, NEVER locally in-stock (never in most cases in small towns),.. the 0Z4 tubes? The 0Z4 type rectifier tubes (full-wave rectifiers) with no filament were used in the 6v Delco chassis and several others? Seems as by design, the 0Z4 tubes depended entirely on perfect internal specs to operate correctly overall. Therefore, they would fail prematurely in many cases?
Since the 0Z4 tubes relied on proper gas inside the tube to work properly, Im thinking the 6X5 was a better choice for overall dependability in a 6v automotive radio chassis design?
After looking at the GE Tube manual, comparing both tubes basing diagrams, Im thinking about replacing the *special order* type 0Z4 with a easy to find 6X5 that uses the filament to excite the tube to work more dependably.
Switching out the tubes are very simple mechanically. Both type tubes use the same 8-pin type octal socket. As I can see by the tube manual, the only difference changing the tubes is by adding the filament voltage to use the 6X5, which would be done by grounding pin 2 to chassis, and jumping a added wire from pin #7 to another 6v filament pin on nearby tube to complete the circuit.
My question is, the added filament voltage ,*added*, to the orig circuit filament string is only .3 amps ( 1/3rd ampere), would??.. that drop filament-string voltage enough overall, to have a negative impact on the overall orig circuitry of the vintage 6v auto radio?
Seems to me that this conversion would work? I have many good spare 6X5's in stock , and dont stock the 0Z4's at all but they are cheap to purchase, except when adding minimum order requirements S&H etc! Then those cheap (orig bad designed) 0Z4 rectifier tubes get expensive when you need em!! Im thinking of trying the conversion, because seems to me, it would also add much more *reliability* to the overall vintage automotive type radios that used the orig 0Z4 rectifiers??
Your thoughts please!?? ol TxRockr

[Ron Ramirez]

My brief initial thoughts:

The 6X5 is, overall, a notoriously bad rectifier. Ask anyone who owns a Zenith or Philco that uses this tube...also ask them if they have had to replace a power transformer - many have had to due to failure of the 6X5.

You see, Randal, the 6X5 has this nasty habit of shorting internally, with no warning at all...the short circuit is sufficient to kill the power transformer.

I have heard of the 0Z4 to 6X5 conversion. Personally, I'm not sure I would do it...I would probably convert the rectifier to solid-state silicon instead. An 0Z4 metal shell could be disassembled, new silicon diodes installed inside, insulated well, then reassembled...no-one would be the wiser, and the radio would be much more reliable overall.

You would want to install current limiting resistors in series with the silicon diodes...then you would be all set.

One man's opinion...that's all...

[gary rabbitt]

Hi Randal,
0Z4's are readily available for around $1 to $3 on Ebay. Not really a scarce tube at all.

[Texasrocker]

Thanks for the replys guys!! I also have heard many storys from the past of the 0Z4's & 6X5s both were orig bad choices for vintage auto radios. Seems the suspension on those vintage vehicles were a rough-ride at best for passengers, and even worse for the radio tubes.
This orig 47 delco radio I am restoring is going to be used in a orig 47 chev truck that still has orig rough-ride suspension leaf springs.
I plan on using a new solid-state vibrator in the radio , and now after reading Rons info, I will use his suggestion of building a reliable rectifier in a orig 0Z4 metal tube case. If this radio was going into one of my vehicles, I would simply use a cheap 0Z4. However, since this restoration is going into a restored truck of one of my best customers, I want to restore it to be as dependable as possible for many yrs in the future. And, removing the radio from the vehicle and taking the metal case apart is something my customers hope to not have to do again for a long time, especially after they hit a *bump* in the road. These old radios take a beating sometimes indeed, depending on terrain. Since I have previously restored many,many vintage radios for this customer in the past, I want to do the best restoration possible, as they live over 400 miles away from my shop. They expect me to do their vintage radios restorations right the 1st time. Thanks again for your suggestions!!

[BILL]

I no longer use original 0Z4 or the 6X4 I biuld diode rectifier install it in the original tube can works great!

[BILL]

6X5 and build that's what happens when your in a hurry

[Doug Houston]

The 0Z4 always had a reputation for questionable reliability. I worked in a radio shop in the forties, when the '40-'42 cars were on the road. It was said that an 0Z4 would last for 2 weeks or 2 years, or anything in between. They were a good tube in that they had no filament drain on the battery. Their reputation was well earned.

On many of the GM sets I worked on, I wired the socket for a 6X5 filament, if the contacts were in the socket wafer. I did often install a 6X5, but I never had any trouble with them in car radios, as many have said would happen. I bhave four '41 Cadillacs, and a '41 Chevrolet. I've restored the radios in all of those cars, and I believe that all of them have 6X5s in them.

Now, the fact that I haven't had any trouble, doesn't mean that no one else will, either.

Zenith had the bad habit of bloating their tube count, by using two 6X5s in the rectifier circuit, instead of a single 5Y3 or 5Y4. Coupled with Zenith's under rated power transformers, a bad 6X5 would do its damage in a hurry. Then too, in a home radio, the high voltage on the rectifier plates is often higher than on an auto radio, so that has to be considered in thinking about tube life.

Reviewing my own experiences, I feel that the 6X5 may be getting a bad rap.

[Texasrocker]

Thank You for sharing your vast yrs of experience on this subject Doug!! I learn from so much from you veterans that actually worked in those radio repair shops of the day!! Your input is always vastly appreciated on these type subjects indeed!! I did replace the old 6v vibrator tube to solid-state type by purchasing since I didnt have necessary components on hand to sub, on the old orig 47-53 Chev/GMC indash radio. The OZ4 tubes all had the same reputation from that era indeed of being "flaky" at best. A USAF retired radio tech "my teacher" (78 yrs young) most definately agrees with us on this subject in regards to vintage 6v auto type radios. Zenith did like the hype of tube-count to sell their sets in a push-pull audio stage. I agree that perhaps the 6X5s rectifiers got a bad rap from failing the home-radio sets, but must have been a much more reliable tube in a 6v auto radio. So says every tech that serviced many, many of the same sets from those yrs! Switching a couple filament wires around, and seems the current draw all worked just fine, and more reliable to boot! Back in those days, seems all the radio shops had 6X5s in stock always, and not many stocked OZ4s , especially in smaller towns. Just bet their were many conversions done that have since proved success, as it seems to be a great mod that isnt discussed much these days.