[georgetownjohn]

Can someone tell me what saftey caps to use on my 37-660?

[morzh]

Any 0.01uF Y1/Y2 rated capacitors (usually disk ceramic) will do.

https://www.mouser.com/c/passive-compone...yle=Radial

[georgetownjohn]

morzh, thanks as always, John

[georgetownjohn]

I want to install a fuse and fuse holder on the chassis on the 37-660 I am working on. The schematic lists the wattage as 130 at 115volts. My household voltage runs at a constant 122 so I used that in my calulation.
I come up with 1.065amp. What will be the best choice in a fuse? Will 1 amp still be ok and should it be fast or slow acting,? Thanks, John

[morzh]

OK, well...some...education.

Your radio is not a constant power device. That is not a DCDC converter with a load, where you increase the voltage and the current drops proportionally.

It is a linear load, more or less, so your power rises as the square of your voltage.
That is it will be 146W.
And your current will be 146:122 = 1.2A.

Now, if this your operating current, considering the radios pull some inrush on the power-up, I would use 200% slow-blow fuse.
That is 2A to 2.5A slow blow would be my choice.

[georgetownjohn]

Here I am agian asking dor help on this 37-660.  While wotking on the set and having it upside down, I broke a tube as you can see from the attched photo.  From the pieces it looks like it was a 6J5 but when I look at the service data that I also attached, that tube on the far right looking from the top of the chassis looks like it should be one of the 6f6 tubes.  From the service data picture which is reversed, it looks to me like the 6J5 should be on the far left.  Please help.

[georgetownjohn]

Sorry Forum members, in my last post, I included the srvice notes for the 37-640 by mistake.  Here attached is the correct one for the3 7-660 I am working on.

[morzh]

Without looking, 6j5 is a triode and 6f6 is a beam tetrode. Look at your sch and see what is in there. Also good exercise for you. (A hint: 6F6 is the output tube)

[georgetownjohn]

MORZH, help me out here. The radio worked and my question is would it have worked if the 6J5 was installed next to the power transformer instad of 6F6? The service note shows that the 6J5 is located below the 6K7 rf tube. Once again the the radio was originally working with a 6F6 below the 6K7 RF tube and not the 6J5. What is corerect? Is it possible the orginal owner rerwired the sockets? Thanks as alway, John

[Arran]

The broken tube looks like a 6J5 to me, or possibly some other stand alone triode tube in a "G" style envelope, 6F5 and 6K5 being two others. A 6F6 is a power pentode, though you can swap one with a 6V6 which is a beam power tube, basically a #42 with an octal base. It's possible that the tube sockets were rewired, but why? Usually the only reason to do this would be because whomever had the set could not obtain the original tube, rewiring sockets is a lot of work to do for no reason. The service info you linked shows a chassis that is the mirror image of the one in the photograph, it has the power supply sub chassis on the left, and the IF sub chassis on the right, the one in the photo is the opposite. Anyhow the two power output tubes should have the plates connected to the output transformer primary through the speaker cable, the 6J5 will not be connected to the speaker cable at all.
Regards
Arran

[georgetownjohn]

Thanks for the reply Arran.  I am beginning to think that the wrong or different tubes were installed even though the set was working.  I really started to get confused when I just looked in the inside of the cabinet and took the photo of the tube layout(see attched).  I think I should install the tubes based on that tube layout label?  Do you and anyone else agree?  Thanks, John

[morzh]

Yes the broken tube is 6J5. It's triode, drives the pushpull.
However, it seems it is installed in a 6F6 place.
Just trace the wires. Both 6F6 plates will go to the output transformer prim ends.

And...there is no justifyable reason for anyone to rewire these.

[georgetownjohn]

MORZH, thanks for the repy. I will start tracing the wires afte I get a fresh start this weekend and little clearer head if that's possible. Thanks to you and Arran for the help.

[radiorich]

Hello John,
Morzh and Arron are such smart cookies, and I’m glad he got the tube number sorted out. Good luck with your radio.
Sincerely Richard

[MrFixr55]

With one of the 6F6s and the 6J5 accidentally switched, the radio may work but would not work well. The heater (Pins 2 and 7), cathode (Pin 8), control grid (Pin 5) and plate (Pin 3) connections for a 6J5 and 6F6 are the same. If a 6F6 were in the phase invertor position, the tube would amplify (poorly)and correctly invert phase for one of the 2 output tubes like a phase inverter should. Th 6J5 in a 6F6 position would amplify poorly.

The best way to verify correct location s to verify the diagram per the official Philco service document. Per this document, the 6J5 Phase Invertor is the furthest tube on the rear of the middle chassis from the transformer. The 2 6F6s will have pin 8 of each 6F6 socket at chassis ground and pin 3 of each 6F6 socket to the output transformer. The 6J5 socket will have two 0.03 uF caps (capacitors), one at pin 3, the other at pin 8. The other end of each of these caps will connect to pin 5 of each 6F6 socket. From this information, you should be able locate the correct sockets for the correct tubes.

The 6F6 is a fairly common tube. The 6J5 a little less so, but these should be available from many sources for a reasonable price. Performance will definitely improve with the correct tubes in the correct sockets. A pair of 6V6s can be substituted for the 6F6s without wiring changes, but output transformer impedances and bias may be different, somewhat affecting performance. Best ti use the 2 6F6s and the 6J5, all in the correct sockets.

Please note that the 5X4 rectifier is not common, and not directly replaceable by such rectifiers as a 5U4 as the wiring is very different. Per an RCA document "Tube Substitution Document for Emergency Servicing of Civilian Receivers" published during WWII, a 5U4 can replace a 5X4, but the socket must be rewired. The RCA Receiving Tube Manual, Version RC14 published 1940 states that the maximum operating characteristics for a 5X4 are the same as a 5U4. However, filament connections are pins 7 and 8 for the 5X4 but pins 8 and 2 for the 5U4. Plate connections are pins 3 and 5 for the 5X4 but are pins 4 and 6 for the 5U4. It is possible to connect pins 8 and 2, pins 3 and 4 and pins 5 and 6 to allow plug and play use of either tube. However, I think that would reduce the clearance between plate pins and with approximately 700V between plates, this may allow for arc-over.