next question - and thank you to all for sound advice -
Should I attempt to replace the caps/resistors and then send to have the radio cleaned/adjusted? Or does it make more sense to save my money and send it out. At $500 to start a professional rebuild it would be more painful to invest in doing the grunt work to find out I'm still at $50/tube...
I wouldn't let the lack of fancy equipment stop you from doing your own work if you're going to enjoy it. You can replace most components just by removing them one at a time and putting a new cap, resistor, or wire where the old one came out. Take pictures and/or make diagrams before you move anything. Sometimes you have to desolder and move multiple wires or components to get one loose, so you can forget where everything goes.
Anything that is messed up or hard to understand because of a funky old repair you can ask folks on the forum about, and they'll often bend over backwards to help you. Having a decent schematic helps a lot, not only because they show what is connected to what, but often they'll have the manufacturer's diagram that shows the location of most of the parts.
You have to have a soldering iron and a half-decent multimeter. The VOM I use most of the time will measure capacitance up 80 microfarads, and down to about 500 picofarads. I use the capacitance feature mostly to make sure that I haven't misread part value codes before I put them in.
I aligned my first few AM radios without a signal generator; I just used local radio stations close to the frequencies recommended and otherwise followed the instructions. For the IF alignment I first tuned in a station and then adjusted the IF cans by ear in the order suggested. The IF was certainly a little off, but the cans were all aligned to the same frequency. Everything sounded fine. I've done short wave and FM that way, but it's better to use the sig. gen.
A few radios later I got a signal generator and hooked it up to an old frequency counter I got surplus from my employer. I also got an analog VTVM. I'd rather do alignment with the signal generator and VTVM output meter, but I didn't let not having one stop me. Sometimes I wish I had a scope and a tube tester, but I rarely have call for one.
Somebody recommended cutting old components out, leaving the lead wire attached to the chassis, and then soldering the new component to the old lead wire. I do that sometimes if the radio isn't too unique and most of the wires are good. It saves time and is barely noticeable compared to desoldering everything. I'm a slow worker, so saving time is good.
(08-01-2015, 06:44 PM)Raleigh Wrote: I wouldn't let the lack of fancy equipment stop you from doing your own work if you're going to enjoy it. You can replace most components just by removing them one at a time and putting a new cap, resistor, or wire where the old one came out. Take pictures and/or make diagrams before you move anything. Sometimes you have to desolder and move multiple wires or components to get one loose, so you can forget where everything goes.
Anything that is messed up or hard to understand because of a funky old repair you can ask folks on the forum about, and they'll often bend over backwards to help you. Having a decent schematic helps a lot, not only because they show what is connected to what, but often they'll have the manufacturer's diagram that shows the location of most of the parts.
You have to have a soldering iron and a half-decent multimeter. The VOM I use most of the time will measure capacitance up 80 microfarads, and down to about 500 picofarads. I use the capacitance feature mostly to make sure that I haven't misread part value codes before I put them in.
I aligned my first few AM radios without a signal generator; I just used local radio stations close to the frequencies recommended and otherwise followed the instructions. For the IF alignment I first tuned in a station and then adjusted the IF cans by ear in the order suggested. The IF was certainly a little off, but the cans were all aligned to the same frequency. Everything sounded fine. I've done short wave and FM that way, but it's better to use the sig. gen.
A few radios later I got a signal generator and hooked it up to an old frequency counter I got surplus from my employer. I also got an analog VTVM. I'd rather do alignment with the signal generator and VTVM output meter, but I didn't let not having one stop me. Sometimes I wish I had a scope and a tube tester, but I rarely have call for one.
Somebody recommended cutting old components out, leaving the lead wire attached to the chassis, and then soldering the new component to the old lead wire. I do that sometimes if the radio isn't too unique and most of the wires are good. It saves time and is barely noticeable compared to desoldering everything. I'm a slow worker, so saving time is good.
Thanks John - I am ordering a wiring diagram - need to find the check book, haven't seen that in years LOL, and then will prepare a material list, order, and enjoy the challenge while my 3 daughters and bride watch the idiot box...crazy what junk is available on TV. I digress. Even if I get a couple channels there is an RCA input and a switch for the RCA input. I might just throw a CD Player or even a Bluetooth receiver on that bad boy. It would be a hoot to have to a 1940 radio playing Metallica or some crazy stuff that 15-17 year old daughters are listening to.
(08-01-2015, 06:44 PM)Raleigh Wrote: I wouldn't let the lack of fancy equipment stop you from doing your own work if you're going to enjoy it. You can replace most components just by removing them one at a time and putting a new cap, resistor, or wire where the old one came out. Take pictures and/or make diagrams before you move anything. Sometimes you have to desolder and move multiple wires or components to get one loose, so you can forget where everything goes.
Anything that is messed up or hard to understand because of a funky old repair you can ask folks on the forum about, and they'll often bend over backwards to help you. Having a decent schematic helps a lot, not only because they show what is connected to what, but often they'll have the manufacturer's diagram that shows the location of most of the parts.
You have to have a soldering iron and a half-decent multimeter. The VOM I use most of the time will measure capacitance up 80 microfarads, and down to about 500 picofarads. I use the capacitance feature mostly to make sure that I haven't misread part value codes before I put them in.
I aligned my first few AM radios without a signal generator; I just used local radio stations close to the frequencies recommended and otherwise followed the instructions. For the IF alignment I first tuned in a station and then adjusted the IF cans by ear in the order suggested. The IF was certainly a little off, but the cans were all aligned to the same frequency. Everything sounded fine. I've done short wave and FM that way, but it's better to use the sig. gen.
A few radios later I got a signal generator and hooked it up to an old frequency counter I got surplus from my employer. I also got an analog VTVM. I'd rather do alignment with the signal generator and VTVM output meter, but I didn't let not having one stop me. Sometimes I wish I had a scope and a tube tester, but I rarely have call for one.
Somebody recommended cutting old components out, leaving the lead wire attached to the chassis, and then soldering the new component to the old lead wire. I do that sometimes if the radio isn't too unique and most of the wires are good. It saves time and is barely noticeable compared to desoldering everything. I'm a slow worker, so saving time is good.
Thanks John - I am ordering a wiring diagram - need to find the check book, haven't seen that in years LOL, and then will prepare a material list, order, and enjoy the challenge while my 3 daughters and bride watch the idiot box...crazy what junk is available on TV. I digress. Even if I get a couple channels there is an RCA input and a switch for the RCA input. I might just throw a CD Player or even a Bluetooth receiver on that bad boy. It would be a hoot to have to a 1940 radio playing Metallica or some crazy stuff that 15-17 year old daughters are listening to.
Why do the original 2uF on the rectifier circuit seem so much physically larger than replacements??
Looking at blurry schematic off NA site looks like cap 77 is 25uf and cap 78 is 18uf I could be wrong about 77 ,guess it could be 2.5 but that dosen't sound right. If they are 18 & 25 you could use a 22uf 450v caps. If I'm wrong someone will correct this. Good luck
(08-06-2015, 04:44 PM)David Van Wickler Wrote: Right on the smaller uF values - I just had them in my hand and was wonder what is wrong with using such a high value and if would be detrimental
Next question. I cannot locate this mono input and switch. Was it added at a later date? It's not grounded either oddly enough and is not in the wiring diagram that I can see.
It was fairly common for people to add phono inputs to radios of this vintage. That way they could buy a turntable without an amplifier and speaker, and play records through the radio.
Usually the owner or a repair man would add the phono connection (an RCA jack like you have) between the 2nd detector diode section of the 1st audio tube and the amplifier section of the same tube so they could take advantage of the volume and tone controls. A switch was usually added to disconnect or ground out the radio signal so sound from the radio wouldn't bleed into the phono signal.
There were different ways to connect the phono input and disconnect switch. You might want to make a careful diagram of where these wires go so you can reconnect them when you finish the restoration, sine they won't be in the schematic. You can connect various modern music players like iPods and so forth to them if you want. Or you can remove the modification, since it wasn't original.
I have an excellent book that was a textbook for radio repair students. It's "Elements of Radio Servicing" by Marcus and Levy. You can download it from the alternate radio forum here. http://antiqueradios.com/archive.shtml It's in six pdf downloads that you can read on your computer or print out. Used copies are also available for $26.79 and up from Amazon's partner booksellers. In my copy, (1947), there is a section on how to wire-in phono inputs for radios that didn't come with them. Chapter 12, page 179.
next question - looking at the wiring diagrams (thank you Chuck!) and looking at the chassis - it appears that there is no ground at #79, at the ground side of the 27ohm portion of the BC resistor (does this stand for invented Before Christ?).
It's supposed to ground #77 25uf electrolytic.
Where did the ground wire go? I asked the chassis a couple times, then the darn BC resistor, but it's resisting to answer me...
Is it grounded through the mounting rivet or bolt that holds the resistor to the chassis? Cap #77 is probably grounded through its mounting on the chassis.
