Tube rectifier equivalent question

[c.coyle]

Getting back to my original post, I'm not opposed to spending a few bucks on this boat anchor. This is a fun project, I consider it beer money.

Good thing I actually looked inside, because were apparently two versions of the Hallicrafters 8R40, one with the 5Y3GT tube ("Run 2"), and the other - mine - apparently less common, with selenium rectifiers ("Run 1"). The power supply designs and electrolytic values are completely different. My P.S. has been worked on before. Someone removed the seleniums and put in silicon diodes and some modern electrolytics. EDIT: I guess I should check voltages.

The widely available schematic for the 8R40 is for Run 2, which was what I'd been working off. I have located the schematic for Run 1, SAMS 181-7.

 

[mhardy6647]

These circuits are equivalent, right? Both full wave rectifiers? I could spend $10 on a drop-in solid state replacement, but I have the diodes lying around.

It's an old Hallicrafters receiver. I'm crazy for putting a nickel into it, since there's nothing left worth listening to on SW, but it was free and it looks cool.

View attachment 1181999 View attachment 1182000

Getting back to my original post, I'm not opposed to spending a few bucks on this boat anchor. This is a fun project, I consider it beer money.

Good thing I actually looked inside, because were apparently two versions of the Hallicrafters 8R40, one with the 5Y3GT tube ("Run 2"), and the other - mine - apparently less common, with selenium rectifiers ("Run 1"). The power supply designs and electrolytic values are completely different. My P.S. has been worked on before. Someone removed the seleniums and put in silicon diodes and some modern electrolytics. EDIT: I guess I should check voltages.

The widely available schematic for the 8R40 is for Run 2, which was what I'd been working off. I have located the schematic for Run 1, SAMS 181-7.

So -- wait -- I am confused. The radio has (or "originally had") selenium rectifiers for the HV supply, and an empty socket for a vacuum tube rectifier?

If the former, it should be straightforward to rehab the P/S with (new) silicon rectifier diodes -- some reduction of the P/S output voltages may still be required. Are the rectifier diodes in it now suspect?

PS cute little radio.

 

[c.coyle]

. . . So -- wait -- I am confused. The radio has (or "originally had") selenium rectifiers for the HV supply, and an empty socket for a vacuum tube rectifier? . . .

No. One version is tube, the other selenium. From just looking at the "Run 2" schematic, I incorrectly assumed I was going to find a tube rectifier and a 3-in-1 can capacitor inside. When I actually opened it up, I found a double wax/paper electro where I expected the tube, and an empty hole where I expected the 3-in-1 can cap.

The attached photo is from the web, but explains the difference between the 2 versions.

In other words, I assumed I had a "Run 2" but actually have a "Run 1." That's why you don't order parts off someone else's parts list without looking to see what's actually there.

 

[gadget73]

You have a copy of the schematic you need then? If not, I've got an early Sams collection that probably has it.


and this is why I also verify parts before ordering. Running production changes can really derail you.

 

[c.coyle]

You have a copy of the schematic you need then? If not, I've got an early Sams collection that probably has it.


and this is why I also verify parts before ordering. Running production changes can really derail you.

As they have me, more than once I'm embarrassed to say. And yes, I have the Run 1 SAMS schematic. Thank you very much.