Hi guys, I bought this 71 cathedral at the Lansing show a few weeks ago. It is my first cathedral, but not my first Philco, I have several others that are also ready for restoration. I am going to move back and forth from this set and a Philco 38-93. A complete re stuffing and as close to original as possible restoration will be made on both.
This 71, I have already looked over the set, you can see the original cans have been disconnected with a "newer, hack job" electrolytic can suspended in the wiring. After looking over everything else and noticing the electrolytic, I did a slow power-up on the variac to test the transformer, which was a success, it's good. I cleaned up the tubes, cross checked all seven and tested each. The 42 st in the set is weak, but will do what is needed until I can track down a replacement. The set looks to be all orginal, but I am no expert on the 71.
I did eventually power up to 115 volts, which is what this set is rated to run at. The pilot lamp and all tubes lit up, no strange signals, smells, or noises were noticed. As the set warmed up, I was not able to pick up any stations, tone control has a click sound when changed, so I know it works, the volume control also works, and sound from those two pot's are heard over the speaker, as well as a general static like sound. After examining the mica sheets on the trimmer caps, not so good. The third mica sheet (Farthest to right in the 3 gang picture), sitting closest to the 42 tube looks to be cracked and lifted up ward. the first mica sheet (Farthest to left) also is flaking quite a bit. Looks like I will have to replace them, I have no experience with this section of a tube radio, other than a simple alignment done on another set before. I will have to tackle this problem before I can move on to anything else, with no reception, there is no point in re stuffing until I could pick up some type of station.
Any help from you Philco guys, or anyone with experience with this matter, please help. Does anybody know what MF value these are? Could they be replaced? Ron if you have any experience with this I would also appreciate your help. Thank you all.
Jon
(This post was last modified: 07-30-2012, 09:57 PM by Philco281989.)
Just to look at them I'd say there ok. The true test is will they align properly when you go to tune up the set. The mica is just used as a spacer/insulator. If the mica is badly broken the trimmer will short thus rendering that stage inoperative. They are fairly small like 10-20pf and they do come apart with a solder iron.
Terry
Jon, I'm with Terry, I think your mica will be just fine. But if you want to replace them for looks, you can get mica sheets at McMaster-Carr http://www.mcmaster.com/#catalog/118/3621/=in8yak Item number 8802K16
You might have an open coil. That was the problem with mine. The primary of the oscillator coil was open and I had to rewind it. These sets and the 60 series sets were known for open coils. Ohm them all out. I bet you find one open.
Thank you all so far for the replies, I was concerned about the mica sheets. Steve and Terry thank you for your help, Steve, that website looks like it will be very helpful if I do have to change the mica sheets. Keith, I did check the coils for continuity, but will check them again for an Ohm reading. I have a schematic and information in my philco service notes and in Riders III. Could you tell me where I can find the Ohm readings, still kind of new with a schematic. Thanks so far guys, and help on Ohm values would be great. I will take this troubleshooting one step at a time.
The mica sheets are oh so fragile, and if go gunked up, should be cleaned up very well. Tak 'em out and blast out with Deoxit 5. Before that , tighten down each segment all the way and count turns and fractions very accurately. Then blast it out with deoxit 5 and treat the mica strips with utmost care. Let dry the parts overnight and put together the next day. Tighten down and back off to recorced turns. You should be approximately where you were in the beginning. Then re-align. Works most.
If the set is working I would suspect that the coils are ok. The typical ones that go open are the primary of the antenna (will cause poor sensitivity) and the oscillator feedback winding (set won't receive any signals).
When you are measuring the resistance of a coil you are looking for something of a low resistance something like a few ohms to maybe 50 ohms.
Terry
I have looked a bit more into the coils today, I am getting a variety of different ohm readings after testing each connection on the coils. The only problem is that I don't know the values of each pin coming off the coil. I have a schematic, but no values for the coils. I know you guys stated that a low number is good, but on the coil that connects to the R.F. stage 44 tube is reading 1.47M ohm on several pins and 11.1 Ohm on one pin, perhaps I am testing it wrong. Could anybody tell me the proper way to test these pins coming off the 5 coils. And if anybody has values to follow from that would be great.
As a beginner first starting out, early '30s radios are going to be a lot of guess work for you (voltage & resistance wise) because of the "limited" info on *All* schematics. You're goin' have to get use to it if these are the years you prefer.8)
As you get more restorations under your belt like a lot of forum members here have, you become accustom to what certain resistances (ohms) should be from most coils (oscillating transformers). Bob Anderson had to make some of these assumptions when fixin' his Brunswick 5KR.
Philco IS Very Good in the late 30s & early 40s at labeling their schematics better. Better Than Most at the time. Coil terminal #s & ohm values between each pair of terminal windings. Anything with more than 4 terminals you practically have to pull the whole coil out of the radio to see what terminals are paired with each other to get a good ohm reading.
At this point you can visually inspect the coils & hopefully IF there is a break it is right by the terminal to where it Was soldered. Acid flux over the years ate away at this small diameter enameled wire.
The leads (wire) going to these small value ohm coils should at least be unsolderd to get a Good ohm reading, that a Noob would be comfortable with. Just like resistors, if over in value change them., under in value, need to disconnect one side to get their true value.
Now there are goin' be some that will tell you that you don't have to disconnect the coils to get That True Reading that you can be confident about, & that maybe true if you're a veteran at these, but they forget what it was like when they were a noob, And....
If YA All don't believe me,
Just take a looksey at Bob's last video on his 15DX. He disconnected one side of the shadow meter so he could get an accurate reading. John(badrestorer) also done that on the shouldered tombstone he re-did.
I've been switching 3 of them around, on these 3 650Bs this last week. One Was Open All 3 were wired in differently. All produced under code 121.
Gotta Love Philcos
Lloyd
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Ooohhh Noooo, What’s the Matter NOW?? It WAS Working GREAT before I “FIXED IT”!!
(This post was last modified: 08-05-2012, 01:13 AM by CrumblingWires.)
like a lot of forum members here have, you become accustom to what certain resistances (ohms) should be from most coils (oscillating transformers). Bob Anderson had to make some of these assumptions when fixin' his Brunswick 5KR.
All 3 were wired in differently. All produced under code 121.
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