[FredM]

Restoring a 41-295.  Every schematic I've seen has an 80 rectifier tube and the electrolytics in the pi filter are 18uF and 25uF.  However, the specimen I have has a 5Z3 rectifier tube and the filter electrolytics are 30uF and 12uF, which appear to be the original caps.  Is this a legitimate variation, or should I go back to the 80 tube to help preserve the transformer?  And any recommendations on which set of electrolytic filter caps to use?

[Brad Winder]

If the 5Z3 and filters look original, I'd say stay with those components and values.The discrepancy may be the result of a production line change. The other possibility is difference between console and table versions of the chassis.

[vinzer]

I would the 80 less strain on power transformer

[GarySP]

The 80 and 5Z3 are both full-wave rectifiers, and interchangable. The difference is the current draw and output. The 5Z3 is the 80 on steroids, but at a price. The 80 draws 2.0 amps to the heater, and the 5Z3 draws 3.0 amps. Considering that the transformer is already dealing with the higher line voltages today from when built do you really want to push the issue by using a 5Z3? If the schematics say 80, I, like Vinser above, would use the 80. Take care and BE HEALTHY! Gary

[Radioroslyn]

Don't tell anybody the filament on the 5Z3 (like the 5U4) is 3a not 5a. But you can get 250ma of dc current output vs 125ma of the 80 (5Y3). I would go w/the 80 tube also.

[GarySP]

My bad, Terry. Meant to type 3a ... fat finger and foggy mind typed 5a! (since corrected) Take care and BE HEALTHY! Gary

[MrFixr55]

My $0.02 worth:
+1 on what others said.  I do worry about the extra 3A oops, 1A (Thx Gary SP) filament current on the 5Z3.  5Z3 is the 4 pin version of a 5U4.
Go back to the 80 and limit the input filter cap to 20uF.  This set does have some power, having the Push Pull 42s (They do have drivers after the cathodyne phase inverter).  The Philco manual for this set describes the Audio section as a "degenerative Push-Pull Output stave with drivers.  Rated power is 5 Watts.  Tis should be within the capabilities of the Type 80 Rectifier.
This set merges old and newer style tubes (Loctals are newer than the octals that are not in this radio).  Maybe someone mad the changes to the power supply to give the radio more 'punch'?

If you go with the 80, try to find the newer style that looks like a 4 pin 5Y3.  That is the latest version.  Seems to me that the last 80s that RCA sold looked like 5Y3s only having the 4D base.  Specs for the 80 and 5Y3 are the same but the newer versions are more rugged.

[Chas]

Let me say this about that....

Change the load on any radio/tv power transformer and four things will happen...
1- Increase the current on any filament winding the transformer will heat more, B+ will go down and primary current will go up. Other supplied voltages will go down. Magnetic field around the transformer will increase.
2- Decrease the current on any winding: All voltages will rise on all windings, the primary current will decrease. Magnetic field will decrease.

That said, the transformer is a finite supply of energy. Can't get something for nothing.

Chassis and power transformer mechanical hum can be an overall design issue but overload can be a factor.

Magnetic field can influence nearby chokes and audio transformer when that would not normally be an issue.

Strive to keep modifications within limits of design as much as possible. A plug in solution is, well too easy...

Type 80's are not rare, just be sure both diode elements are relatively equal in emission as a weak side will yield an un resolvable background hum from this out of balance condition.

YMMV

Chas

[RodB]

Chas, you forgot about the smoke.

[Chas]

Always leave some doubt

[FredM]

Thank you everybody. Living in constant fear of power transformers heating up and short-circuiting, I went with an 80 and the radio is back to life after decades. Using a bucking transformer setup I power all my vintage tube radios at 109VAC, also to save heat in the transformer. As a third measure, I always replace incandescent bulbs with LEDs, in this case of the bayonet bulb variety, from Pinball Life.

Thanks again. A friend's family heirloom and he will be very happy.

[rfeenstra]

FYI: I rebuilt this model a few years ago. It has an 80 and performs well. Fairly good sounding radio. With the loop antenna, I can listen to my favorite AM station inside my steel pole barn. Every other AM radio has virtually no reception and a lot of noise.

[FredM]

Thanks rfeenstra. It's up and running with the 80. Very well for a few days but now the speaker has torn. The bass response of this radio was too much for it. Tried repairing it with epoxy and that worked for a while, but I think now I need to replace it.

[Chas]

My experience has shown that a speaker that is not in it's baffle can have a great deal of resonance that can damage a brittle cone.

If the damage is extensive, re-coning is an option. Something that can be done by restorers with patience, procedure and correct materials...

[FredM]

"Resonance" is probably what happened. Blew out of its spider with some really good bass response. Tried epoxying it, and it worked well for about a half an hour but then it happened again. Going to replace it. Any tips for finding a 14" 4-ohm speaker that'll fit the existing screws, which are 13-5/8" in diameter?