Philco 37-84--no sound - Printable Version
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Philco 37-84--no sound - sjhs1962 - 04-08-2012
I can't get a AF signal through the radio...even from the audio output stage. The output tube is a 6 K 6 and maybe is bad...no tester. I have recapped the bakelite in this stage but I have two more bakelites to do. E-caps done and resistors look good. Coils have be checked and 2 meg resistor put on the IF coil. Any thoughts?
The sensitivity control is crumbling...I think it is a dielectric cover on the adjustment screw, correct???
RE: Philco 37-84--no sound - Radioroslyn - 04-08-2012
(04-08-2012, 04:50 PM)sjhs1962 Wrote: I can't get a AF signal through the radio...even from the audio output stage. The output tube is a 6 K 6 and maybe is bad...no tester. I have recapped the bakelite in this stage but I have two more bakelites to do. E-caps done and resistors look good. Coils have be checked and 2 meg resistor put on the IF coil. Any thoughts?
The sensitivity control is crumbling...I think it is a dielectric cover on the adjustment screw, correct???
Time to start to check the voltages around the 6K6. Check pins 3,4,5,& 8. 3and 4 should have 275vdc or so. 5 should be at -15vdc or so. 8 should be at 0.
Terry
RE: Philco 37-84--no sound - sjhs1962 - 04-09-2012
(04-08-2012, 10:43 PM)7estatdef Wrote:(04-08-2012, 04:50 PM)sjhs1962 Wrote: I can't get a AF signal through the radio...even from the audio output stage. The output tube is a 6 K 6 and maybe is bad...no tester. I have recapped the bakelite in this stage but I have two more bakelites to do. E-caps done and resistors look good. Coils have be checked and 2 meg resistor put on the IF coil. Any thoughts?
The sensitivity control is crumbling...I think it is a dielectric cover on the adjustment screw, correct???
Time to start to check the voltages around the 6K6. Check pins 3,4,5,& 8. 3and 4 should have 275vdc or so. 5 should be at -15vdc or so. 8 should be at 0.
Terry
Terry: Pins 3 is 202 vdc and pin 4, 182 vdc, pin 5 is -.1vdc and pin 8 is 0. Does this seem to indicate bad 6K6? Thanks.
RE: Philco 37-84--no sound - Radioroslyn - 04-09-2012
(04-09-2012, 10:40 AM)sjhs1962 Wrote:(04-08-2012, 10:43 PM)7estatdef Wrote:(04-08-2012, 04:50 PM)sjhs1962 Wrote: I can't get a AF signal through the radio...even from the audio output stage. The output tube is a 6 K 6 and maybe is bad...no tester. I have recapped the bakelite in this stage but I have two more bakelites to do. E-caps done and resistors look good. Coils have be checked and 2 meg resistor put on the IF coil. Any thoughts?
The sensitivity control is crumbling...I think it is a dielectric cover on the adjustment screw, correct???
Time to start to check the voltages around the 6K6. Check pins 3,4,5,& 8. 3and 4 should have 275vdc or so. 5 should be at -15vdc or so. 8 should be at 0.
Terry
Terry: Pins 3 is 202 vdc and pin 4, 182 vdc, pin 5 is -.1vdc and pin 8 is 0. Does this seem to indicate bad 6K6? Thanks.
Ya got no grid bias, shorted cap on pin 5 or the center tap of the high voltage winding of the power transformer is grounded.
Terry
RE: Philco 37-84--no sound - sjhs1962 - 04-16-2012
Riders shows a plate voltage of 40 Vdc on the plate of 2nd detector 1st audio. Is this correct? My radio is showing a 230 Vdc???
RE: Philco 37-84--no sound - morzh - 04-16-2012
The detector voltages were always a mystery for me. They are all shown to be 25 - 40V and they are usually way, way higher.
Not sure what they meant by it.
RE: Philco 37-84--no sound - Radioroslyn - 04-16-2012
(04-16-2012, 05:32 PM)sjhs1962 Wrote: Riders shows a plate voltage of 40 Vdc on the plate of 2nd detector 1st audio. Is this correct? My radio is showing a 230 Vdc???I've got a better question. How come you have 230v when you should have 40v??? Is the cathode open? Filament good? Tube doesn't seem to be conducting.
Terry
RE: Philco 37-84--no sound - sjhs1962 - 04-17-2012
(04-16-2012, 09:31 PM)7estatdef Wrote:(04-16-2012, 05:32 PM)sjhs1962 Wrote: Riders shows a plate voltage of 40 Vdc on the plate of 2nd detector 1st audio. Is this correct? My radio is showing a 230 Vdc???I've got a better question. How come you have 230v when you should have 40v??? Is the cathode open? Filament good? Tube doesn't seem to be conducting.
Terry
Terry and all others: changed tube and now have good voltages all around. Bakelites are done; AF and RF signals are good. Resistors are good. Oscillator rewound and working. I have tried adjusting trimmers. Now I am getting a crackling static. No reception. I have a long wire antenna...60 feet....I wonder if it is too much???
RE: Philco 37-84--no sound - Radioroslyn - 04-18-2012
So what happens when you inject a 470kc signal into the cap of the mixer tube? Do the IF adjustments have a nice peak?
Terry
RE: Philco 37-84--no sound - sjhs1962 - 04-18-2012
(04-18-2012, 08:36 AM)7estatdef Wrote: So what happens when you inject a 470kc signal into the cap of the mixer tube? Do the IF adjustments have a nice peak?
Terry
Not really good at alignment until I get a station coming thru...and finally one came thru and I was able to adjust the trimmers and voila it came alive across the dial. I get a little static between stations but station come in strong! Volume control doesn't work real well...but actually good enough ...It must short out except at the very loudest with miniscule adjustment that is....good enough. I guess I could try to open it up and clean the control. Thanks to all for help and support!
RE: Philco 37-84--no sound - Radioroslyn - 04-18-2012
(04-18-2012, 02:11 PM)sjhs1962 Wrote:(04-18-2012, 08:36 AM)7estatdef Wrote: So what happens when you inject a 470kc signal into the cap of the mixer tube? Do the IF adjustments have a nice peak?
Terry
Not really good at alignment until I get a station coming thru...and finally one came thru and I was able to adjust the trimmers and voila it came alive across the dial. I get a little static between stations but station come in strong! Volume control doesn't work real well...but actually good enough ...It must short out except at the very loudest with miniscule adjustment that is....good enough. I guess I could try to open it up and clean the control. Thanks to all for help and support!
A couple of things... You won't be able the best of performance until till the IF is peaked up on frequency (470kc). Can't fudge it by peaking all the trimmers for max signal on the BC band!!! No no no!
Volume control won't work properly without a good ground connected to the chassis. The set needs a good earth ground to work against the antenna through the volume control.
Terry
RE: Philco 37-84--no sound - codefox1 - 04-18-2012
(04-16-2012, 09:31 PM)7estatdef Wrote:(04-16-2012, 05:32 PM)sjhs1962 Wrote: Riders shows a plate voltage of 40 Vdc on the plate of 2nd detector 1st audio. Is this correct? My radio is showing a 230 Vdc???I've got a better question. How come you have 230v when you should have 40v??? Is the cathode open? Filament good? Tube doesn't seem to be conducting.
Terry
Most old radios were tested with voltmeters that had 1000 or 2000 ohms/volt sensitivity. Look at the circuit. Modern digital meters and VTVM's have virtually no load at all on the circuit being measured.
RE: Philco 37-84--no sound - Radioroslyn - 04-19-2012
Regen detectors don't necessarily require a lot of plate voltage to operate. Some work quite well with 12-20vdc on the plate. I suspect that the 40v is part of the design of the circuit rather than loading from the volt meter.
Terry
RE: Philco 37-84--no sound - sjhs1962 - 04-21-2012
Volume control only works at very end with only miniscule adjustment. Volume is just barely adequate for listening and only for real close proximity. I have good external ground and long wire antenna and good in the house ground. Any thoughts? The vol control measure .625 meg to 12 ohms. Thanks.
RE: Philco 37-84--no sound - Radioroslyn - 04-22-2012
Half a meg is way too high. Volume is the wrong value. What you need is something around 10 to 30 k. This should work fine.
Terry
ps Did you get your -15v back on pin5 of the 6K6 which should be a 6F6