Posts: 44
Threads: 9
Joined: Apr 2011
City: Pittsburgh, PA
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???
(This post was last modified: 04-08-2012, 03:55 PM by sjhs1962.)
Posts: 7,248
Threads: 266
Joined: Dec 2009
City: Roslyn Pa
(04-08-2012, 03:50 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
Posts: 44
Threads: 9
Joined: Apr 2011
City: Pittsburgh, PA
(04-08-2012, 09:43 PM)7estatdef Wrote: (04-08-2012, 03:50 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.
(This post was last modified: 04-09-2012, 10:20 AM by sjhs1962.)
Posts: 7,248
Threads: 266
Joined: Dec 2009
City: Roslyn Pa
(04-09-2012, 09:40 AM)sjhs1962 Wrote: (04-08-2012, 09:43 PM)7estatdef Wrote: (04-08-2012, 03:50 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
Posts: 44
Threads: 9
Joined: Apr 2011
City: Pittsburgh, PA
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???
Posts: 15,444
Threads: 539
Joined: Oct 2011
City: Jackson, NJ
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.
Posts: 7,248
Threads: 266
Joined: Dec 2009
City: Roslyn Pa
(04-16-2012, 04:32 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
Posts: 44
Threads: 9
Joined: Apr 2011
City: Pittsburgh, PA
(04-16-2012, 08:31 PM)7estatdef Wrote: (04-16-2012, 04:32 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???
Posts: 7,248
Threads: 266
Joined: Dec 2009
City: Roslyn Pa
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
Posts: 44
Threads: 9
Joined: Apr 2011
City: Pittsburgh, PA
(04-18-2012, 07:36 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!
Posts: 7,248
Threads: 266
Joined: Dec 2009
City: Roslyn Pa
(04-18-2012, 01:11 PM)sjhs1962 Wrote: (04-18-2012, 07:36 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
Posts: 2,128
Threads: 18
Joined: Oct 2008
City: Merrick, Long Island, NY
(04-16-2012, 08:31 PM)7estatdef Wrote: (04-16-2012, 04:32 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.
Posts: 7,248
Threads: 266
Joined: Dec 2009
City: Roslyn Pa
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
Posts: 44
Threads: 9
Joined: Apr 2011
City: Pittsburgh, PA
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.
Posts: 7,248
Threads: 266
Joined: Dec 2009
City: Roslyn Pa
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
(This post was last modified: 04-23-2012, 09:40 PM by Radioroslyn.)
Users browsing this thread: 1 Guest(s)
|
Recent Posts
|
Cannot Adjust an IF Transformer’s cores
|
Outstanding work indeed. I wish I could come up with solutions like this.slford310 — 11:16 PM |
Cannot Adjust an IF Transformer’s cores
|
The abilities of our 'Phorum Pholks" never ceases to amaze me! Fantastic fabrication, Joseph! I'm waiting now for...GarySP — 08:27 PM |
PT-6 antenna connections
|
Thanks. I never realized that was a notch noted in the schematic as described. I’ll recheck my wiring.bridkarl — 08:13 PM |
Cannot Adjust an IF Transformer’s cores
|
Thank you! I was quite new to the Phorum when I started this post, so I feel like it might be advantageous to publish a ...jrblasde — 08:07 PM |
PT-6 antenna connections
|
Notice in the schematic the notch at the bottom of the antenna coil is between pins 3 & 4.
Yes, pin 6 of the 7C6 is...RodB — 07:34 PM |
bridkarl
|
I have two PT-6 chassis. On both there is a blue wire that runs from the above chassis transformer to pin 6 of 7C6. So t...bridkarl — 07:23 PM |
Cannot Adjust an IF Transformer’s cores
|
Joseph, now you are an engineer!!RodB — 06:37 PM |
PT-6 antenna connections
|
Hi, reading your explanation I can see the confusion. If you take it one connection at a time it should result in a desi...RodB — 06:34 PM |
Cannot Adjust an IF Transformer’s cores
|
It works! I received the PCBs this morning in the mail, and put everything together. I reused the base from the original...jrblasde — 04:32 PM |
PT-6 antenna connections
|
I seem to have lost my way on this PT-6.
I see the antenna aerial transformer schematic - I’m reading pins 1 through ...bridkarl — 12:30 PM |
Who's Online
|
There are currently no members online. |
|
![>](https://philcoradio.com/phorum/images/bootbb/asb/right_arrow.png)
|