[loosecannon]

hi all.

first post here.

i normally restore radios from the late 70's era, but a friend asked me to try my hand at his old philco.

definitely a different world than im used to.

i am at the moment replacing all the old components in the radio, and i have a couple of questions im hoping someone here can help me with.

1. there is a 325 ohm wirewound resistor that looks like a small roll of toilet paper.
can anyone tell me the wattage of this resistor and if i have to use a certain type?

2. the volume control is completely seized and im having a H**l of a time finding a replacement with the right specs, size, and that includes a switch.
its a 20K pot (im assuming its an audio taper) and the switch needs to handle 3a at 125 volts. the shaft is a D type, and its 25mm long.
can anyone point me to a vendor that might have one of these?

thanks, and im also open to any schematics or diagrams you guys might have.
(i have the six pages from nostalgiair)
LC

[ccomer1955]

Gary at "Playthings of the Past" has a Mallory replacement for that pot. The Mallory book shows it as Philco part 7439 and the Mallory replacement is Mallory part Y with Mallory switch 6 added. A note in the Mallory book says "left hand terminal must be grounded to chassis viewed from shaft end,terminals down."
If you ask him, Gary might even have the Philco part that won't need the added switch. Read Gary's homepage for ordering instructions and follow them if you decide to get in touch with him.

http://www.oldradioparts.com/potmanuf.txt

[morzh]

1. 325 Ohm resistor could use a 5W rated part.
Why? Is it open?

2. The radio is a regenerator, pay attention to this fact.
Page 5 of the Rider's copy on NA has "Philco 80 Whistles" paragraph, read it.

[Radioroslyn]

Hiya Loose & Welcome to the Phorum!!
You may want to search the Phorum on the subject of the model 80. You will most likely find answers to a lot of your questions there in. From a practical standpoint you should measure the parts you are thinking of replacing just to be sure that they need to be replaced. Just because they are 80 some yrs old doesn't necessarily mean there defective or trouble makers.

These are the troublemakers: #2 open primary,#9,#11,#8 open feedback winding,#19,#20,&#22. Check these resistors with an ohm meter and replace if they differ more than 10 percent of original value. As per normal replace all wax/paper condensers micas are usually are OK.

Wouldn't mess with the volume control or the bias resistor in the power supply unless they are known to be bad.
GL
Terry

http://www.nostalgiaair.org/PagesByModel...013843.pdf

[loosecannon]

thanks for all the replies so far.

ccomer1955, i looked at Gary's page, and these two philco pots stood out to me.
maybe someone here can tell me which, if either, would be the closest to the original:

1501-728 PHILC 33-5002 20K, MODELS 38, 81 .......... 1 5.00
1501-730 PHILC 33-5011 20K, W/SW, MODEL 53/57/58/59. 1 8.00


Morzh, i havent tested the pot yet, im trying to get all of/most of my ordering done before i go diving in so that i dont get half way through and then have to stop and wait for a part. (i do realize this is a pipe dream, but ive got to at least try)

thanks for the tip about the regen. ive seen quite a few posts that refer to the "delicacy" of the alignment of this section.

Radioroslyn,
i appreciate the tips. could you possibly give me a bit more detail with regards to checking the coils?
do i have to remove wires and components from them to get an accurate resistance reading?
when you say "feedback winding", do you mean the secondary?
im still learning about this stuff, so any details will really help.

thanks again to all!
this is getting fun!

oh, almost forgot. does anyone add fuses to the main AC cord, or use a three pronged cord with the ground to the chassis?
just curious.
LC

[ccomer1955]

Ron would have a better grasp on interchangeability of volume pots than me. Gary at Playthings will advise you, though. Just be sure your communications follow his rules listed on the "How to order" page when you write to him.

[Radioroslyn]

Ant coil, Unplug set turn vol all the way up. Measure resistance from ant post to chassis. If good should measure a few ohms. If higher rewind.
Terry

[loosecannon]

thanks again for the replies!

i have a question about a mod on the philco repair bench site.

its the "gimmick" mod where you wrap three turns of wire around the volume wiper wire and connect one end to the det-osc. tube.
this is probably a stupid question, but i just want to be double sure.

only one end of this wire is connected to anything right?
the schematic makes it look as though one end goes to the det-osc tube, and the other gets soldered to the volume control.
im pretty sure thats just a confusing drawing, but i want to be sure.

also, i seem to have a note here that says to change the 9K resistor (9) to a 13K. and now i cant find where i got that note from.
can someone confirm that this is indeed an upgrade for the model 80?

how much voltage does the hookup wire ill be using need to handle?

and lastly (for now LOL) the speaker in the one im working on seems to be pretty well intact, but boy does the paper look old! (it is i know LOL)
is there anything that can be done to strengthen it a bit? like something i could spray or brush on?

thanks again for all the help so far.
ill post pics when im finished.
LC

[Ron Ramirez]

http://www.philcorepairbench.com/tips/svctip43.htm

I came up with that mod. Model 81 and 84 have the "gimmick" but Model 80 did not, so I tried it in an 80 and found that the "gimmick" cap improves the performance of the 80.

You need two wires. One gets soldered to the wiper arm of the volume control. Another is soldered to the cathode of the 36 det-osc tube. Make each wire long enough so that they will overlap by an inch or so where they meet. Twist these wires together where they meet with the insulation left on each wire so they do not actually make contact with one another. This gives the effect of a small value capacitor.

The voltage involved is low. Any old hookup wire will do.

The same link above mentioned my other mod of changing the 9K resistor to 13K, 3 watts.

These mods really do help the performance of Model 80 sets.

As to the speaker cone, I have a friend who brushes mineral oil on all of his speaker cones. You don't pour the stuff on the cone; put it in something that fits the brush, and then carefully brush it on the cone.

[Ron Ramirez]

Another tip I came up with to improve performance of Model 80, as well as Models 81, 84, 37-84, 57, 58, 59:

http://www.philcorepairbench.com/tips/svctip44.htm

[loosecannon]

thank you Ron for your input.

i do have to say though that im more confused now than i was before about how the "gimmick" is wired in.

in the write-up on the "philco repair bench" site, you say to solder one end of an insulated wire to the cathode lead of the detector/oscillator tube.
then, this wire gets coiled tightly around the wire coming off of the center "wiper" lead of the volume control pot.

to me, this meant that one end of the wire is left unconnected to anything.

in your response to me in the forum, you state that you need two wires, one soldered to the cathode of the det/osc tube, and one soldered to the center lead of the volume pot. then, the free ends of these two wires are twisted together (insulation on of course).
your response did not mention wrapping either of the wires around the "wiper" wire.

so, while i understand the concept of trying to gain a little bit of capacitance between the two leads, it sounds like there are two different ways of doing it.

i do apologize if it sounds like im over-complicating a simple idea, but i do want to get it right the first time.

thanks in advance for any further explanation you can offer.

thanks also for the 13K resistor tip.

ill be doing a fair bit of this work tomorrow and the next day, so ill be able to post my progress after that.
boy i sure hope i dont have to rewind any coils!
LC

[morzh]

I tell you this: do not change anything yet, make the radio work first.
Then once it works, try the improvements.

Oherwise you will scare yourself.

[Ron Ramirez]

+1 what Mike (Morzh) said.

You should not work on vintage electronics unless you know what you are doing and have a grasp of the basic fundamentals. Some excellent tutorials for beginners may be found here:
http://www.antiqueradio.org/begin.htm

[loosecannon]

just wanted to put your minds at ease with the knowledge that i have been rebuilding/repairing/modding radios and other electronics for years.
ive rebuilt tube linear amplifiers, and tube guitar amps.

i do mostly solid state though.

its the age of this stuff that has me questioning things.
LC

PS-when i asked the question about what voltage the hookup wire needs to handle, i meant throughout the chassis, not just in the specific section i was speaking of at the time.
so, i guess a re-phrasing is in order: what is the highest voltage coming out of the secondary of the main power transformer in this chassis?

[morzh]

Well, the AC volage is about 700V, as it is a full wave centerpoint that cuts the output in half
The highest DC you see is 400V with excursion to 500V fr a few seconds.
This does not mean the wire has to withstand 700V.

But typical insulation will be a 600V type