The PHILCO Phorum
1936? model 84 resistor - Printable Version

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RE: 1936? model 84 resistor - brownie45 - 01-28-2013

Hi! Fired the 84 up to check it out for voltages, & got mixed results.
The plate on the det./osc is 270---should be 240.
Plate on 2nd det. is 68---should be 70--close enough.
Grid 2 on det./osc is 127---service literature doesn't give voltage.
Grid2 on 2nd det. is 51---again no voltage given.
These voltages are from power supply neg.
Voltage from grid 3 to cathode is 23 volts on osc.
Variac is 115 volts in. The 42 output is apparently working--touching grid cap on 2nd detector gives loud 60 cycle
from speaker. Can't test the 77 on my B&K727, but I suspect a bad tube on the osc. Don't get any response
when touching the grid cap on the 77 det./ osc. Any ideas are welcome. Thanks. Jim

RE: 1936? model 84 resistor - Radioroslyn - 01-28-2013

Have you rewound the ant and the osc coil yet??? On most of those sets (80,84,and 37-84) the primary on the ant coil is open and the tickler winding on the osc coil is open. Both can be rewound with 32-38ga magnet wire. Seems like both are about 20 turns.Also check all of the resistors there's a couple of 1meg jobs that are usually bad. Most of the time your better off just replace all of the 1/2watt ones. It will save you time troubleshooting. The IF alignment is fairly critical on these sets for good performance. If you've got a generator go ahead and peak them up if not don't mess with them. Fix those and the darn thing will play like crazy!!
Terry

RE: 1936? model 84 resistor - brownie45 - 01-29-2013

Should have given more info in the above post. Using a DVM for readings.
I haven't replaced the R6--6K resistor biggybacked with C7---1400PF mica.
Don't have the mica. In-circuit resistance on the R6 C7 was 8200 ohms.
3rd item---I am going to have to jack the 77 osc tube out of its socket
& check for corrosion/ jungle rot on the pins/ socket connectors. As tight as
the tube is, I'm just about betting on breaking either the socket or tube
base. Grid 2 mentioned above is screen grid--sorry for the omission.
So, Terry---you're saying the antenna coil is rated a high failure area?
Have to Ohm it out.
Anyone have a good source for high value micas like C7 [1400PF]?
I'll check Dave at Just Radios & see what He's got. Thanks. Jim

RE: 1936? model 84 resistor - Ron Ramirez - 01-29-2013

Brownie45

brownie45 Wrote:I haven't replaced the R6--6K resistor biggybacked with C7---1400PF mica.

Replace it.

brownie45 Wrote:Don't have the mica.

Get it. Believe me, your radio will thank you.

If Just Radios doesn't have them, try Vacuum Tubes Inc. in Florida, or Radio Daze.

Now, here's a tip for removing that stubborn tube. Turn the chassis upside down and, using a small hammer and a small Phillips screwdriver, lightly tap each pin of the tube, alternating between left and right, until it comes out. Remember, tap lightly. Don't force it, don't use a sledgehammer, and don't act like you're the Incredible Hulk. You don't want to damage the socket.

RE: 1936? model 84 resistor - brownie45 - 01-29-2013

Success! Got the 77 osc. out without damage. Penetrating oil & time
did the trick. No corrosion or rust on socket or pins.
Does anyone know if AES still has old tubes [77's]? L
ooked on
their website, & all that is listed are new tubes.
Thanks, Ron. I've got a 6200 ohm 1 watt for R6. Close enough?
Have to order the cap.

RE: 1936? model 84 resistor - klondike98 - 01-29-2013

Brownie,
Try http://www.findatube.com/ or http://electrontubestore.com/index.php?main_page=product_info&cPath=68_78&products_id=1187 .

RE: 1936? model 84 resistor - Ron Ramirez - 01-29-2013

brownie45 Wrote:I've got a 6200 ohm 1 watt for R6. Close enough?

Close enough for gubmint work. Icon_smile

RE: 1936? model 84 resistor - brownie45 - 01-29-2013

Thanks for the tip on findatube, Bob. They have 77's listed. Jim

RE: 1936? model 84 resistor - Radioroslyn - 01-29-2013

Hi Jim
Here's some extra reading for you to study up on your superhet with a regenerative detector.
http://philcoradio.com/phorum/showthread.php?tid=2164&highlight=Model+84
http://philcoradio.com/phorum/showthread.php?tid=2639&highlight=Model+84http://philcoradio.com/phorum/showthread.php?tid=3090&highlight=Model+84
The models 80 and 84 and 37-84 are very similar all have the same basic circuit design.
GL
Terry

RE: 1936? model 84 resistor - brownie45 - 01-29-2013

Much obliged, Terry. This is the first regen set I've attempted to
restore. I need all the tutoring I can get. The people on here are
most helpful with their knowledge.
Maybe you can bring me up to speed on the Philco model numbering
system. From the posts I've read, the first 2 digits of the model
number are the year of manufacture? I had no idea what my model
number was until I looked at pics in the gallery. My set has a sticker
on the left rear of chassis with Philco patent numbers. There is a
stamped number on right center G83118--probably a serial #.
Nothing else to ID it.
Anyway, thanks. Jim

RE: 1936? model 84 resistor - Radioroslyn - 01-29-2013

Well any of the Philcos made after 1936 up into the '50s will have the year of production in the model # like 37-84. Before 1937 there's no rhyme or reason for the # system.
Terry

RE: 1936? model 84 resistor - brownie45 - 02-01-2013

Well, Terry---you really know your 84's. Finally got time to check the
osc. coil windings. Tickler was open. Re-wound it with #36, & she
works. Just have a 10 foot antenna in the basement on it, & it brings
in several stations on the upper half of the band. Lower half has nothing
on it. 910 KC. is as low as it will receive. I'm satisfied.
Thanks to all who have contributed. You are a great bunch of guys.
Jim

RE: 1936? model 84 resistor - brownie45 - 02-01-2013

Should have added---thanks for putting up with me. Jim

RE: 1936? model 84 resistor - Radioroslyn - 02-01-2013

Glad to help out. Have worked on a bunch of them of the years. Sounds like you may need to reverse the wires on the new tickler winding or not enough turns. I'd flip the wires real quick to see in it makes an improvement. Set will work better with a good ground (without it the volume may not work very well) and ant.
GL
Terry

RE: 1936? model 84 resistor - brownie45 - 02-02-2013

Had a good water pipe gnd. on it--tried it with gnd off while
running, & just a little less vol. & little more hash. Odd
you should mention the vol. control not working real well
because the schemo shows the "lower" end of the control
grounded, & my set isn't. Is control internally grounded?
Should I gnd. the lug on the control? Thanks. Jim