Hello Could anyone tell me what the plate voltage should be on the 6J5? Then what would the voltage be before and after resister #7 51k ohms. The schematics I have do not show what it should be and I only have -1.25. Then passes through resister #34 1m ohms to #7 resistor 51k and end result is approximately .200 to .300 millivolts not sure if this is correct. Thank You paul
Hi Paul & Welcome.
I would suspect that your plate voltage on the 6J5 is going to be very low. If the 6J5 was used as an audio amp it would require much more voltage, but it isn't. It's used as a diode to convert the RF signal to audio and to develope AVC voltage to control the gain RF and IF stages.
The voltage should change as signal is applied to the antenna. The alignment and the condition of the tubes will also have an effect on it too.
Terry
(04-10-2015, 02:21 PM)Radioroslyn Wrote: [ -> ]Hi Paul & Welcome.
I would suspect that your plate voltage on the 6J5 is going to be very low. If the 6J5 was used as an audio amp it would require much more voltage, but it isn't. It's used as a diode to convert the RF signal to audio and to develope AVC voltage to control the gain RF and IF stages.
The voltage should change as signal is applied to the antenna. The alignment and the condition of the tubes will also have an effect on it too.
Terry
Hello Terry. Thank You I am not getting any stations at all and was looking at the tube voltages as a start and it wasn`t listed on the Riders schematic. I am going too recheck the wafer switches. But they seem ok all the other tube voltages are good. Checked all the coils and read through them but still can`t get a station Broadcast or short wave. paul
Hi Paul,
The 6J5 probably not my first thing I'd look it. Lets try some easy troubleshooting. Take a transistor radio and set the dial at 1500kc. Place it near the 6A8 tube or the band switch. Tune the Philco between 1000kc to 1200kc. If all is well you hear the local oscillator in the transistor set. Will sound like loud hum. Do you have a signal tracer or signal generator?? What have you done to the chassis so far??
Terry
Hello I got the radio working some what. I can pick up a few local stations and a lot of short wave. I found (through researching pages of posts written on these forums pertaining too the 37-650) that one of the band switch jumper wires was slightly grounded to the mounting post of the band switch. Had to pull out the antenna section too find and fix it. Put everything back together and it came too life. But now I believe I have another ground in the broadcast section ( which I already had pulled out too rebuild it had a short that was sparking) when I put my finger on the 6K7 RF tube the radio gets louder and picks up more stations. I am currently reading 2 meg ohms on the broadcast band coil secondary to chassis and it also is reading into the antenna stage secondary. I will desolder the coil wires and try too trace out where the ground is coming from. Thanks for the help and any suggestions. paul
Hello The 2 meg ohms I was reading on the coils was ok. It was coming from the two i meg resisters 34 and 35. Can`t find a ground in either the broadcast section or the antenna section. The local stations come in fine but distance stations only come in when I put my finger on the 6K7 cap. Any advise would be appreciated. Thanks paul
So what do you get for resistance across the red and black antenna terminals on the back of the chassis? With the band switch in the BC position.
Terry
Hello Terry. I have 1.4 ohms. From red to chassis 1 ohm and black to chassis 1 ohm which seems fine. I have to go to work will check back around 4pm est, would rather work on radio but duty calls. paul
I'm not interested the red or black to gnd. What is the resistance across the red and black(to each other).
Terry
I think he said 1.4 Ohms.
In any case if both have low to GND, it will be possibly twice that across.
Hello I have 1.4 between the Red and Black. The red and black to ground reads through the center tap,and I thought that may be of interest also. Thank You paul
Hello. Well how about this the secondary of the broadcast antenna coil terminals 4 and 5 are only reading 5.2 ohms instead of 6 ohms the schematic shows. Would this cause a power loss and loss of reception on distance stations. Thank You paul