I would like to pick the collective brain for a few more pointers on restoring my United Motors model 985400. This radio was installed in a 1935 Chevrolet Master Sedan and is powered by a 6 volt battery system.
I have several questions after digging into the radio, so here goes:
First, after replacing many of the paper caps, but not yet the electrolytics, I checked the power lead input resistance (and directly on the heater rails) and found 0.6 ohms. I don’t think this could is quite right, or the radio would draw close to 10 amps, after digging around I found a few spec sheets on some of the tubes. It looks like this era radio probably used all 0.3 amp heaters or since this a 6 volt system the heaters should be about 21 ohms. With all the heaters in parallel there should be at least 21ohms/6tubes or 3.5 ohms total resistance on the heater power rail. So I pulled each tube and checked the resistance of the heaters, below are the measurements:
6D6 (rf amp) 3.8 ohms
6A7 (osc.) 3.5 ohms
6D6 (IF amp) 25.7 ohms
76 (1st AF) 3.6 ohms
41 (output) 2.5 ohms
41 (output) 2.6 ohms
Looking at these values my guess is all the tubes, except possibly the 6D6 IF amp, are bad. My theory is that someone maybe tried to jump start the car using a 12 volt battery while the radio was on. (?) Can someone let me know if in fact these measurements look like tube replacement is needed ? Also if anyone knows of a person with a tube tester in the northern Virginia area (Fairfax, Alexandia, Reston) who could help me I would appreciate it.
Next few questions are related to caps: (BTW I read several websites and the FAQ and could find no discussion on metal jacketed caps, except discussion of electrolytics.)
There is a 1” x 1” square x 2” long metal box, quad capacitor that has 2 x .05 and 2 x .1 stamped on the side and 4 terminals protruding from a plastic end cap. The .05 caps appear to tie S terminals of several tubes to ground. The cap is mounted under the chassis. My question is what type of cap is this and can it be replaced with orange drops ?
There are 3 metal cylinder caps located inside a metal shield enclosure under the chassis. The enclosure is located under the Delco oscillator and step up transformer. The caps appear to be part of a L-C filter network for the input power, one side of the filter is for the 6 volt rail the other for the input to the oscillator. The caps are tied to ground and are 0.5, 0.15 and 0.02 each. What type are they and can orange drops do the job ?
There is small metal cylinder 0.5”D x 1.5” long cap, I think it is 0.02, and it is in series with the antenna input. What type is it and what do I replace it with ?
Last question, what is an acceptable antenna to rig up to test this radio on the bench ? The antenna attached to the underside running boards of the car is in poor condition so I will need to replace it, any ideas ?
Thanks for your time. Steve Schreppler
The tubes will be ok. I would be more concerned with 6D6. You may want to resolder the two large pins. When the filaments are cold resistance will be very low. Once you apply power filaments will heat and tubes should be ok.
Use a short length of wire for antenna, 4 or 5 feet will be ok. The radio should have an antenna adjustment to match the wire.
Orange drop caps will replace the caps in your radio. Car radios have, what seems to be, a lot of extra caps to filter ign noise. Be sure electrolytic caps are replaced.
Norm
: Gents,
: I would like to pick the collective brain for a few more pointers on restoring my United Motors model 985400. This radio was installed in a 1935 Chevrolet Master Sedan and is powered by a 6 volt battery system.
: I have several questions after digging into the radio, so here goes:
: First, after replacing many of the paper caps, but not yet the electrolytics, I checked the power lead input resistance (and directly on the heater rails) and found 0.6 ohms. I don’t think this could is quite right, or the radio would draw close to 10 amps, after digging around I found a few spec sheets on some of the tubes. It looks like this era radio probably used all 0.3 amp heaters or since this a 6 volt system the heaters should be about 21 ohms. With all the heaters in parallel there should be at least 21ohms/6tubes or 3.5 ohms total resistance on the heater power rail. So I pulled each tube and checked the resistance of the heaters, below are the measurements:
: 6D6 (rf amp) 3.8 ohms
: 6A7 (osc.) 3.5 ohms
: 6D6 (IF amp) 25.7 ohms
: 76 (1st AF) 3.6 ohms
: 41 (output) 2.5 ohms
: 41 (output) 2.6 ohms
: Looking at these values my guess is all the tubes, except possibly the 6D6 IF amp, are bad. My theory is that someone maybe tried to jump start the car using a 12 volt battery while the radio was on. (?) Can someone let me know if in fact these measurements look like tube replacement is needed ? Also if anyone knows of a person with a tube tester in the northern Virginia area (Fairfax, Alexandia, Reston) who could help me I would appreciate it.
: Next few questions are related to caps: (BTW I read several websites and the FAQ and could find no discussion on metal jacketed caps, except discussion of electrolytics.)
: There is a 1” x 1” square x 2” long metal box, quad capacitor that has 2 x .05 and 2 x .1 stamped on the side and 4 terminals protruding from a plastic end cap. The .05 caps appear to tie S terminals of several tubes to ground. The cap is mounted under the chassis. My question is what type of cap is this and can it be replaced with orange drops ?
: There are 3 metal cylinder caps located inside a metal shield enclosure under the chassis. The enclosure is located under the Delco oscillator and step up transformer. The caps appear to be part of a L-C filter network for the input power, one side of the filter is for the 6 volt rail the other for the input to the oscillator. The caps are tied to ground and are 0.5, 0.15 and 0.02 each. What type are they and can orange drops do the job ?
: There is small metal cylinder 0.5”D x 1.5” long cap, I think it is 0.02, and it is in series with the antenna input. What type is it and what do I replace it with ?
: Last question, what is an acceptable antenna to rig up to test this radio on the bench ? The antenna attached to the underside running boards of the car is in poor condition so I will need to replace it, any ideas ?
: Thanks for your time. Steve Schreppler
Are you saying the 6D6 with the 25.7 ohm measurement
should have the socket wires resoldiered ? I think
the wires are ok, remember I checked the tube by
removing it from the socket.
So if 3-4 ohms is a typical cold heater resistance then
the radio will draw 10 amps when first powered up ? That means I need at least a 10 amp bench supply to power it up. What would you expect the warmed up
resistance to be ?
In any event is nice to know that I may only have one
bad tube.
Thanks for your help Norm.
Regards, Steve Schreppler
: The tubes will be ok. I would be more concerned with 6D6. You may want to resolder the two large pins. When the filaments are cold resistance will be very low. Once you apply power filaments will heat and tubes should be ok.
: Use a short length of wire for antenna, 4 or 5 feet will be ok. The radio should have an antenna adjustment to match the wire.
: Orange drop caps will replace the caps in your radio. Car radios have, what seems to be, a lot of extra caps to filter ign noise. Be sure electrolytic caps are replaced.
: Norm
: : Gents,
: : I would like to pick the collective brain for a few more pointers on restoring my United Motors model 985400. This radio was installed in a 1935 Chevrolet Master Sedan and is powered by a 6 volt battery system.
: : I have several questions after digging into the radio, so here goes:
: : First, after replacing many of the paper caps, but not yet the electrolytics, I checked the power lead input resistance (and directly on the heater rails) and found 0.6 ohms. I don’t think this could is quite right, or the radio would draw close to 10 amps, after digging around I found a few spec sheets on some of the tubes. It looks like this era radio probably used all 0.3 amp heaters or since this a 6 volt system the heaters should be about 21 ohms. With all the heaters in parallel there should be at least 21ohms/6tubes or 3.5 ohms total resistance on the heater power rail. So I pulled each tube and checked the resistance of the heaters, below are the measurements:
: : 6D6 (rf amp) 3.8 ohms
: : 6A7 (osc.) 3.5 ohms
: : 6D6 (IF amp) 25.7 ohms
: : 76 (1st AF) 3.6 ohms
: : 41 (output) 2.5 ohms
: : 41 (output) 2.6 ohms
: : Looking at these values my guess is all the tubes, except possibly the 6D6 IF amp, are bad. My theory is that someone maybe tried to jump start the car using a 12 volt battery while the radio was on. (?) Can someone let me know if in fact these measurements look like tube replacement is needed ? Also if anyone knows of a person with a tube tester in the northern Virginia area (Fairfax, Alexandia, Reston) who could help me I would appreciate it.
: : Next few questions are related to caps: (BTW I read several websites and the FAQ and could find no discussion on metal jacketed caps, except discussion of electrolytics.)
: : There is a 1” x 1” square x 2” long metal box, quad capacitor that has 2 x .05 and 2 x .1 stamped on the side and 4 terminals protruding from a plastic end cap. The .05 caps appear to tie S terminals of several tubes to ground. The cap is mounted under the chassis. My question is what type of cap is this and can it be replaced with orange drops ?
: : There are 3 metal cylinder caps located inside a metal shield enclosure under the chassis. The enclosure is located under the Delco oscillator and step up transformer. The caps appear to be part of a L-C filter network for the input power, one side of the filter is for the 6 volt rail the other for the input to the oscillator. The caps are tied to ground and are 0.5, 0.15 and 0.02 each. What type are they and can orange drops do the job ?
: : There is small metal cylinder 0.5”D x 1.5” long cap, I think it is 0.02, and it is in series with the antenna input. What type is it and what do I replace it with ?
: : Last question, what is an acceptable antenna to rig up to test this radio on the bench ? The antenna attached to the underside running boards of the car is in poor condition so I will need to replace it, any ideas ?
: : Thanks for your time. Steve Schreppler
The 6D6 might have poor solder connections on the pins of the tube itself. This is fairly common..
Resistance of the filaments will increase as they heats. The radio will surge when first turned on but current will decrease as tubes heat. That happens within a second.
For a test, measure the resistance of a 100 watt light bulb. We know a 100 watt light will draw nearly 1 amp when it's lit. Resistance will be a little over 100 ohms. I just measured one for information and found cold resistance to be 12 ohms. You might find it a little different. I just wanted to give a comparison where other reading can run the same test.
Norm
: Norm,
: Are you saying the 6D6 with the 25.7 ohm measurement
: should have the socket wires resoldiered ? I think
: the wires are ok, remember I checked the tube by
: removing it from the socket.
: So if 3-4 ohms is a typical cold heater resistance then
: the radio will draw 10 amps when first powered up ? That means I need at least a 10 amp bench supply to power it up. What would you expect the warmed up
: resistance to be ?
: In any event is nice to know that I may only have one
: bad tube.
: Thanks for your help Norm.
: Regards, Steve Schreppler
:
: : The tubes will be ok. I would be more concerned with 6D6. You may want to resolder the two large pins. When the filaments are cold resistance will be very low. Once you apply power filaments will heat and tubes should be ok.
: : Use a short length of wire for antenna, 4 or 5 feet will be ok. The radio should have an antenna adjustment to match the wire.
: : Orange drop caps will replace the caps in your radio. Car radios have, what seems to be, a lot of extra caps to filter ign noise. Be sure electrolytic caps are replaced.
: : Norm
: : : Gents,
: : : I would like to pick the collective brain for a few more pointers on restoring my United Motors model 985400. This radio was installed in a 1935 Chevrolet Master Sedan and is powered by a 6 volt battery system.
: : : I have several questions after digging into the radio, so here goes:
: : : First, after replacing many of the paper caps, but not yet the electrolytics, I checked the power lead input resistance (and directly on the heater rails) and found 0.6 ohms. I don’t think this could is quite right, or the radio would draw close to 10 amps, after digging around I found a few spec sheets on some of the tubes. It looks like this era radio probably used all 0.3 amp heaters or since this a 6 volt system the heaters should be about 21 ohms. With all the heaters in parallel there should be at least 21ohms/6tubes or 3.5 ohms total resistance on the heater power rail. So I pulled each tube and checked the resistance of the heaters, below are the measurements:
: : : 6D6 (rf amp) 3.8 ohms
: : : 6A7 (osc.) 3.5 ohms
: : : 6D6 (IF amp) 25.7 ohms
: : : 76 (1st AF) 3.6 ohms
: : : 41 (output) 2.5 ohms
: : : 41 (output) 2.6 ohms
: : : Looking at these values my guess is all the tubes, except possibly the 6D6 IF amp, are bad. My theory is that someone maybe tried to jump start the car using a 12 volt battery while the radio was on. (?) Can someone let me know if in fact these measurements look like tube replacement is needed ? Also if anyone knows of a person with a tube tester in the northern Virginia area (Fairfax, Alexandia, Reston) who could help me I would appreciate it.
: : : Next few questions are related to caps: (BTW I read several websites and the FAQ and could find no discussion on metal jacketed caps, except discussion of electrolytics.)
: : : There is a 1” x 1” square x 2” long metal box, quad capacitor that has 2 x .05 and 2 x .1 stamped on the side and 4 terminals protruding from a plastic end cap. The .05 caps appear to tie S terminals of several tubes to ground. The cap is mounted under the chassis. My question is what type of cap is this and can it be replaced with orange drops ?
: : : There are 3 metal cylinder caps located inside a metal shield enclosure under the chassis. The enclosure is located under the Delco oscillator and step up transformer. The caps appear to be part of a L-C filter network for the input power, one side of the filter is for the 6 volt rail the other for the input to the oscillator. The caps are tied to ground and are 0.5, 0.15 and 0.02 each. What type are they and can orange drops do the job ?
: : : There is small metal cylinder 0.5”D x 1.5” long cap, I think it is 0.02, and it is in series with the antenna input. What type is it and what do I replace it with ?
: : : Last question, what is an acceptable antenna to rig up to test this radio on the bench ? The antenna attached to the underside running boards of the car is in poor condition so I will need to replace it, any ideas ?
: : : Thanks for your time. Steve Schreppler
Can you explain how resoldier the pins ? Do I simply
heat the pins with an iron or is the bakelite base of the tube removeable so that one can get directly to
the soldier area of the pin ?
Steve
: The 6D6 might have poor solder connections on the pins of the tube itself. This is fairly common..
: Resistance of the filaments will increase as they heats. The radio will surge when first turned on but current will decrease as tubes heat. That happens within a second.
: For a test, measure the resistance of a 100 watt light bulb. We know a 100 watt light will draw nearly 1 amp when it's lit. Resistance will be a little over 100 ohms. I just measured one for information and found cold resistance to be 12 ohms. You might find it a little different. I just wanted to give a comparison where other reading can run the same test.
: Norm
Just heat the pins with a soldering iron and apply a little more solder. In some cases the wire is oxidized then I remove as much solder as possible, scrape the wire end and resolder.
Norm
: Norm,
: Can you explain how resoldier the pins ? Do I simply
: heat the pins with an iron or is the bakelite base of the tube removeable so that one can get directly to
: the soldier area of the pin ?
: Steve
: : The 6D6 might have poor solder connections on the pins of the tube itself. This is fairly common..
: : Resistance of the filaments will increase as they heats. The radio will surge when first turned on but current will decrease as tubes heat. That happens within a second.
: : For a test, measure the resistance of a 100 watt light bulb. We know a 100 watt light will draw nearly 1 amp when it's lit. Resistance will be a little over 100 ohms. I just measured one for information and found cold resistance to be 12 ohms. You might find it a little different. I just wanted to give a comparison where other reading can run the same test.
: : Norm
I now have 4.3 ohms on the heater after
heating the pins, Thanks Norm.
: Just heat the pins with a soldering iron and apply a little more solder. In some cases the wire is oxidized then I remove as much solder as possible, scrape the wire end and resolder.
: Norm
: : Norm,
: : Can you explain how resoldier the pins ? Do I simply
: : heat the pins with an iron or is the bakelite base of the tube removeable so that one can get directly to
: : the soldier area of the pin ?
: : Steve
: : : The 6D6 might have poor solder connections on the pins of the tube itself. This is fairly common..
: : : Resistance of the filaments will increase as they heats. The radio will surge when first turned on but current will decrease as tubes heat. That happens within a second.
: : : For a test, measure the resistance of a 100 watt light bulb. We know a 100 watt light will draw nearly 1 amp when it's lit. Resistance will be a little over 100 ohms. I just measured one for information and found cold resistance to be 12 ohms. You might find it a little different. I just wanted to give a comparison where other reading can run the same test.
: : : Norm