07-12-2011, 10:11 AM
On the RCA Victor 18T I currently have had on the bench for weeks, I get no station reception at all. I do get audio, and interference buzz from overhead fluorescent lights, and plenty of loud buzz and clicks when touching the center post of the volume control and other places throughout, so I know I have audio. I've replaced all caps, resistors, checked tubes 2-3 times, checked all coils 2-3 or more times.
http://www.nostalgiaair.org/PagesByModel...014801.pdf
When I first tried the radio after replacing caps and resistors, I faintly received one local strong station. Volume started fading, however, and I thought it needed a good alignment. Several days later, I turned it on and this time, no station at all. Have tried troubleshooting several times. I can send a 455kc signal through and the IF transformers seems to adjust well when looking at them with a scope, but when you turn the screws on the IF transformers, no increase in volume occurs, and the volume of the sig. gen. signal is faint, even with the sig. gen. turned all the way up.
The voltages on tubes (except heater volts-they are all fine) are low when measured with my DMM. They are as follows:
both 6K6: 224 volts DC (should be 240) on SG of both 6K6's
222 volts DC (should be 235) on plates of both 6K6's
18 volts DC (should be 19) on Ksups of both 6K6's
6SF5: 89 VDC on plate (should be 60)
.8 on cathode (should be .9)
2nd det. 6SQ7: plate 80 VDC (should be 64)
6SK7 IF: plate 228 VDC (should be 240)
screen grid 85 VDC (should be 88)
cathode 1.5 VDC (should be 1.1)
6SA7: plate 228 VDC (should be 240)
screen grid 85.5 (should be 88)
6SK7 RF : plate 227 VDC (should be 240)
screen grid 87 VDC (should be 88)
cathode .7 VDC (should be .6)
In Rider's 12-85 for RCA changes, it mentions a coil that was added, a low frequency oscillator push button coil, that I believe my set has. It is potted in black tar. If I attach one leg of the coil to where it was soldered when I first started working on the set, the above voltages go WAYYYY down. I get the above voltages with this coil out of the circuit. In either case, with this coil in the circuit, or out of the circuit completely, I still get no stations.
I'm thinking I have a bad new capacitor somewhere. I did change crumbling rubber wiring, but I was very careful replacing the new wires, however not all rubber wires were replaced. If anyone has any thoughts where I should look next, I'd appreciate them. THANK YOU!
http://www.nostalgiaair.org/PagesByModel...014801.pdf
When I first tried the radio after replacing caps and resistors, I faintly received one local strong station. Volume started fading, however, and I thought it needed a good alignment. Several days later, I turned it on and this time, no station at all. Have tried troubleshooting several times. I can send a 455kc signal through and the IF transformers seems to adjust well when looking at them with a scope, but when you turn the screws on the IF transformers, no increase in volume occurs, and the volume of the sig. gen. signal is faint, even with the sig. gen. turned all the way up.
The voltages on tubes (except heater volts-they are all fine) are low when measured with my DMM. They are as follows:
both 6K6: 224 volts DC (should be 240) on SG of both 6K6's
222 volts DC (should be 235) on plates of both 6K6's
18 volts DC (should be 19) on Ksups of both 6K6's
6SF5: 89 VDC on plate (should be 60)
.8 on cathode (should be .9)
2nd det. 6SQ7: plate 80 VDC (should be 64)
6SK7 IF: plate 228 VDC (should be 240)
screen grid 85 VDC (should be 88)
cathode 1.5 VDC (should be 1.1)
6SA7: plate 228 VDC (should be 240)
screen grid 85.5 (should be 88)
6SK7 RF : plate 227 VDC (should be 240)
screen grid 87 VDC (should be 88)
cathode .7 VDC (should be .6)
In Rider's 12-85 for RCA changes, it mentions a coil that was added, a low frequency oscillator push button coil, that I believe my set has. It is potted in black tar. If I attach one leg of the coil to where it was soldered when I first started working on the set, the above voltages go WAYYYY down. I get the above voltages with this coil out of the circuit. In either case, with this coil in the circuit, or out of the circuit completely, I still get no stations.
I'm thinking I have a bad new capacitor somewhere. I did change crumbling rubber wiring, but I was very careful replacing the new wires, however not all rubber wires were replaced. If anyone has any thoughts where I should look next, I'd appreciate them. THANK YOU!
