I'm restoring a Philco 48-1283 and having a few issues. I have the schematic ( of the 48-1262) and mods to the 1283,but there are some inconsistencies especially in the actual wiring of the 35L6GT tube. However, I basically just recapped and replaced the resistors. The unit worked before; checked only as a test, so I know the tubes and wiring must have been ok. Now, in radio mode all I get is a hum UNTIL I turn off the power, then for a short few seconds I can clearly hear an AM station. Test points A and C all read high at ~265v, but I've checked the resistors and caps as specified in the diagnoistics. Any help would be appreciated.
jtkmsms, reverse the wires on the on/off switch! PL
These type issues on correct-wiring of the 35L6 audio tubes socket-pins connections can be ascertained by the RCA tube manual for exact specs. Perhaps your sets wiring has been modified previously, by a hacker?
The RCA tube manual will tell the truth on correct pin-out connections of the 35L6 . Best luck in getting your vintage Philco working properly! A RCA tube manual is your best friend in regards to these type issues, and abit of "close" visual underchassis inspection. Keep one handy on your workbench, takes the mystery out of tube-socket vs schematic questions!
Thanks, on the way to getting a tube manual. regerding swithching the wires on the on/off switch I assume you mean the black/white high voltage line?? Does this reflect an incorrect wiring on the tubes?
http://www.pmillett.com/index.html
Try the above link. You can download all the tube manuals you will ever need for free, plus a whole lot more. These files are big, so don't try it on dial-up. Now all you have to do is get a PC on or near your workbench to bring up the information you need. But if it's only one or two tubes, just print the page and bring it to your bench. Or I suppose you could download the files at work, stay late one evening, and print 'em. If you do it during the day, they'll all know who it was that tied up the printer for a half hour, used all the paper, toner, and had 300 pages left to go when the D**n thing finally jammed. Been there, done that.
Of course I also have tattered and much used tube manuals at hand. I have neither a clock or a computer on my workbench, and also don't have a bluetooth hanging on my ear, because that's the way I like it, but to each his own.
jtkmmsms,hi. That crack about switching the wires on the on and off switch was a poor attempt at levity. I was implying that since the radio apparently played when you turned it off and not when you turned it on, that reversing the switch would correct the problem.
I appologize for any inconvience I may have caused. PL
that's ok, working with these older designs I've learned to take it with a grain of salt ( and a few high voltage shocks!). Eventually, it will work out.I suspect between incorrect schematics and some post-production Mod's, I will have to go back to basics to get it right. Let me pre-dial 911 before I try again
jtkmsms, thank you. Have you taken all the voltage checks on the unit. Your symtoms are curious and I can not think of an obvious cause. The power switch on your set is in the chassis side. You may want to be sure that when you plug the set in the blade on plug that goes to chassis goes to the gnd/low/long slot on receptacle (make sure receptacle is wired correctly). That could be the source of the jolts. Many restorers strongly suggest that you use an isolation transformer to plug the set into so it has no reference to house ground. The schematic and info on basic trouble shooting of that radio are available at Nostalgia Air under Resources, Philco Radio & TV, 48-1282. It shows changes for 1283. The changes in the 35L6 section 2 are the removal of C200, C205 changes value to .03mf (from .05mf), shield on phone cable goes directly to B- (not chassis in your unit). Check polarity C101 & C102, make sure neither can (if not in same can) grounded to chassis and + of C102 to - C101. B- on this unit is ungrounded side of R102 (120,000 ohm) and travels throughout set. I am interested to know what C304-305 are. Schematic shows cap with small coil next to it with no part #. I think they may be what I have heard called "gimmick" coils, used to filter out interferance from a marine band that is no longer used. If you go through the above and report back finding maybe others can help. PL
jtkmsms, just another word regarding the isolation transformers. When you use one you are protected from jolts between the chassis and house ground. You are free, however, to jolt yourself between the chassis and any high voltage AC and DC in the set. There is 214VDC and 120 VAC avaolable to do it and they can be lethal. The isolation transformer is sort of like my friend's cure for corns. It does not get rid of them but moves them to the bottom of your feet so only you can step on them. So much for laying off the levity! PL
So here's what I've got, does this sound like one of the tubes has gone south although all heaters still glow. Voltage are not correct in the following measure points.
50x6 pin 7 at r100- 130v not 214
+ side of c103B (10MF)- 60 v not 167
between r100-r101- 245v not 181
35l6gt pin 4- 60v not 167
7c6 pin 2- 50v not 80
7b7pin 2 ( blue wire from Z301) 215 v not 165
other 7b7 pin 2 - 55v nor 75
14af7 pin 6- 61v not 115
thanks for any advice. PS, the jolt was due to a minor slip when I was measuring voltages at the test points and I flipped the radio back over while still on,, live and learn what plugs are for.
jtkmsms, there is some problem with your wiring and I havent' had a chance to go over it. The highest voltage should be at the cathode, pin 7, before resistor R100. Your readings show your getting higher voltage between R100 & R101 than at cathode? No can do. Voltage before resistor can't be lower than after, right! Go back and recheck your readings and are you measuring from B- (resistor R102, side that's not grounded? PL
jtkmsms, hi. The pictorial from Nostalgia shows the R101 resistor connected between a 3 terminal strip and pin 5 of the 50X6. This, in and of itself, is going to cause confusion. R101 is the last of a string that move away from (downstream) the 50X6 yet for connection perposes it seems circles back! Going downstream from the 50X6 there should be a wire from pin 7 to one side of the "candohm" (jargon for canned ohms = wire wound resistor wrapped in insulating/fish paper and crimped in a metal strip) on the rear wall of chassis and on same side of candom the + lead from C101. There should be nothing else connected to either. Downstream (other side) of candohm should have + lead C103A, red lead from T200, wire to one one side of R101 and two resistors R303 & R404. Here lies the first problem as I can only guess from looking at pictorial where all the connections are made. I'm inclined to believe they go to the top/rear most terminal of the terminal strip nearest to 50X6. Some could go to the candohm itself as it has a large terminal. Another guess here, since pin 5 terminal not large most likely wire from there to bottom/front terminal of the terminal strip nearest 50X6. See if the wiring conforms to near or close to the above. That connection to pin 5 is misleading since there is a terminal strip nearby I cant understand why the went to pin 5 rathar than straight between top/rear terminal and lower/front terminal of that strip. Also pin 4 is not connected in tube and some tube charts show pin 5 as being connected to shield? Let me know how your doing. PL
thanks for the information, I have found the source of my problems. The schematic shows r101 and r 303 as 8200r yet the parts list show these as 82,000 and 82,000 which I ordered and used. I replaced these with the orginals ( ie 8200R) and there it is , it works!!. I still have a slight buz and the test points read slightly high, but this may be due to the old resistors: I await replacements. Also, I plan on constructing a new AM antenna to be installed within the cabinet. Thanks for the information. My next project is a reconstruction of a Model 46-1201 "Bing Crosby" AM-Phonograph. Wish me luck.
I am looking for information regarding a replacement cartridge for my 48-1283 which has a D-10 Record changer chassis. The label has fallen off of the orginal cartridge and no model number is shown. The orginal is missing the needle and small screw at the end of the cartridge. Any advice as to a replacement and/or a source to purchase one? Thanks.