So I have a Philco 80 I picked up and just like every other Philco from this era it has two open coils. The primary for the antenna and the one off the Cathode of the Oscillator 36 tube.
I was curious of anyone knew the number of winds, the direction and gauge enameled magnetic wire to use in re winding these coils?
It looks to me like
-Antenna primary is 17 or 18 turns of 36-38 gauge wire clockwise.
-Osc cathode coil, 17 turns, clockwise of 38 or lighter gauge.
Anyone have any info on this to verify.
Also I noticed on the 80 schematic it has the cap#5 (710uf) and resistor #6 (10k ohm) going from the cathode of 36 to ground in series with the coil. Mine seems to have #5 and #6 in parallel with that coil...? It looks as though #5 and #6 are going to the first terminal of the coil.
Also mine is a very late version of the 80 with round coil cans etc. was there a circuit change in this area possibly?
Hi Todd and welcome,
The ant coil winding isn't very critical. Within reasonable limits you won't notice a difference.
The osc coil is more critical, direction and #of turns is. Wrong direction (out of phase) won't oscillate. Not enough turns and it won't oscillate at the low end of the band.
38Ga I believe is the original size but 36 or34 is fine.
The cathode resistor was changed a bit over the run to add a little more gain to the mixer and makes the osc a little more reliable.
That reminds me I got an 81 to look at.
Terry
ps Don't forget to change all of the paper caps and check the resistors you'll find most are out of tolerance.
pss I think one of the coil pins is connected the bracket so it's gnd connection for the resistor and cap.
(This post was last modified: 09-25-2015, 07:09 AM by Radioroslyn.)
Thanks for the welcomes, been on here often searching for info but guess I never joined (thought I had) until now.
Anyhow...so I have previously re wound the osc coil in my 1936 ish Philco 60. There was a LOT of info on that one in here and online but not much if anything on this little 80. I bought and used some 38gauge for the 60 as Ron recommended on this site. It worked well.
So last night I used that enameled 38gauge to do the open antenna coil. Did it just like original, same winding direction, turns and plastic insulator cut outs ect. My only concern is my DC resistance measured 3.5 ohms and the schematic called for 2.66. Should this make any difference?
Does anyone know the physics of winding coils? For instance would a coil with 17 turns of 38g wire have more or less resistance then a coil with 17 turns of 36g wire? I was just curious if one could experiment and get the correct DC resistance.
Also forgot to bring this up. on the osc coil that is open the cap and resistor on the cathode go to ground and are in series after the coil. in my set it looks like these two parts and parallel with the open osc coil. Was this a circuit change for later sets??
> My only concern is my DC resistance measured 3.5 ohms and the schematic called for 2.66. Should this make any difference?
Short answer is no. DC resistance isn't that important, it's the inductance that is.
>For instance would a coil with 17 turns of 38g wire have more or less resistance then a coil with 17 turns of 36g wire?
More, 38g is smaller than 36g and can handle less current. There are charts that will tell the resistance per ' of copper wire, as the ga goes higher the resistance goes up too.
>Also forgot to bring this up. on the osc coil that is open the cap and resistor on the cathode go to ground and are in series after the coil. in my set it looks like these two parts and parallel with the open osc coil. Was this a circuit change for later sets??
I think the cap and resistor are ground through the coil bracket
Sleep well tonight don't worry about resistance of inductors.
Terry
(This post was last modified: 09-25-2015, 04:50 PM by Radioroslyn.)
I re wound my osc tonight and it is drying right now. Hope to try it later tonight.
I did figure out the cap-resistor situation. It was NOT in parallel with the coil but in series like the schematic. The only thing is on mine the cap and resistor are in series BEFORE the coil now instead of after it. The two parts in earlier runs had the two after the coil and this newer run they mounted those two on the coil itself. The first coil pin it is on is blank (what confused me) and the 36 attaches there. The opposite end of the cap-resistor ends on the beginning of the osc coil. That then comes out at the ground pin. This was very difficult to see until I actually took removed all the bas osc coil and insulator and could see where the wires-pins were all attached to.
I tell you what....I sure don't like winding coils. Had enough of that for a while.
Wound the osc coil tonight and installed her. She is working pretty darn good. She sounds great up at the top end of the dial 1400 area but weak-er down low 700-800. Will do an alignment and see if that cleans it up at all. Would that have anything to do with the re-wound coils? I used 38g but seems the osc used a bit thinner like 40g.
Hi Todd,
What I would do is listen in another radio for the local osc signal. Easily done by using a little "shirt pocket" xsistor set. Would tune the Philco to 1000 kc. Listen for the osc around 1460kc on the xsistor set. Place it near the 36 mixer tube. The osc is operating at 460kc above the incoming signal. With the Philco dial at 700kc osc should be at 1160kc (700kc+460kc= 1160).
This holds true for pretty much all superhet sets (frequency on dial + the IF frequency= local oscillator frequency) Some sets the LO runs below the incoming frequency (frequency - the IF frequency= local oscillator frequency). This would be the exception rather than the rule.
So if you find that you LO is conking out towards the low end of the dial you'll need to add a few more turns to coil you just rewound ( tickler or feedback winding). You don't need to remove what you already wound just solder a length of 38g wire to what you have and add 3 more turns to it. That should put you in good shape.
I would suspect that the 710mmfd condenser is OK. For a four tube set they are good performers, but alignment of the IF is critical for good sensitivity. By adjusting the sensitivity trimmer on the rear apron of the chassis just below the point of oscillation will give you the best sensitivity, selectivity, and audio frequency response. The model 84's are a little better as they use a 8" spkr rather than your 6"er.
Oh and one other thing about the 80 and sets of it's ilk it works a lot better with a good earth ground to the chassis. You'll find that without a good ground the volume control won't be very effective. The VC is connected to the antenna and varies the amount of signal going into the set. Without a good gnd the VC doesn't have a good way the lower the amount of RF signal coming into the set.
Whenever I attach pics they always are out of order. Philco 81 w/xsistor set and xsistor set to listen for LO.
Are they still making Willys jeeps over there???
GL
Terry
(This post was last modified: 09-27-2015, 10:10 AM by Radioroslyn.)
Yes, I have an good antenna and ground to copper water pipes I use with my other radios in the workshop. I did adjust the sensitivity control and that is working great but as mentioned 1370 is ROCKING loud and 800 is about 60% of that and both usually are equal strength. If I can get the entire band to sound normal compared to what 1370 usually sounds like this will be a great little radio.
Now obviously not sure what the LO was so set it at 450 which is where it seemed to be set with my signal gen but that probably does not mean much. As well, I did not have a proper alignment tool and use a metal 1/4 drive which swamped out the first two adjustments. So...I need to get the right LO and realign with a insulated too which I am making today and see what happens.
BTW Jeep plant is still here, my father was a Material Handling Engineer for Jeep. Started at AMC in Kenosha in `68 and then transferred to Jeep in `82 when AMC went under, he retired just a couple years back. I have many friends and family that still work for Jeep. Right now Jeep is owned by Fiat who are total A-holes and constantly threaten moving production someplace else unless The City of Toledo (us) gives them free land, tax breaks and a list of other demands despite a state of the art plant that is less then 20 years old. It never ends and constant threat and annoyance. Toledo is Jeep and vice verse but the rotating list of foreign owners never give D**n about anything like that. Toledo is doing great but would probably turn into Detroit of Jeep left.
BTW thanks for the help!
T
(This post was last modified: 09-27-2015, 10:31 AM by bastardbus.)
I have been a `50s-early `60s tube hi-fi and record player guy. I came across friend doing an estate and the elderly woman had three radios she bought new. One was a Philco 60 (she says was actually her parents and bought new around `36-`37) and then a `50s bakelite RCA and `60s RCA. All three were absolutely mint one owner units. I thought it neat to have at least one cathedral style radio with my collection so bought em all for $50. I electronically restore the 60 as that is all it needed and REALLY like it.
Jump forward to a hamfest this past weekend and I hadn't really bought a thing. Then I see this little 80 sitting on a table and was like WOW! That is so little and cool! The fact it was so small-cheap and simple really grabbed me. The sad part is someone else was making a deal on it and bought her for $30 (asking price $40). I offered the $40 but no go it was sold.
I knew the fellow that purchased it was also seller and this would probably be up for sale at the next meet so I went up to his spot and asked if he would sell it. Of course he would...LOL I offered $40 and he kinda moaned and said no. Then as I was about to walk away I figured what is $10.. and offered him $50 and he took it. I was happy I at least scored something cool at the swap meet and I think in the end it was well worth the $50.
She is a REALLY nice all original unit in great shape. Electronically untouched which I really like. The cabinet is excellent as well and everything there. Only issue is the speaker cloth is a getting thin in spots but I purchased some repop cloth just in case I decide to swap it out.
Will post some pics in a bit...
T
(This post was last modified: 09-27-2015, 03:02 PM by bastardbus.)
