[David]

Since the 2 caps are inside the metal box for the FM tuning forget what i suggested for now. Please due replace the Ecaps first and any dark tubes.

[TTech]

Sounds good David. My plan is to work my way through each stage while injecting audio/modulation/ rf to help sort out tubes that light up but may still be defective like the Power tube. Thinking the ecaps will last through a half hour of troubleshooting.Then I'll place an order for tubes, ecaps and a few wire wound resistors. The old ones still function and are barely in tolerance. Guessing they were also heat dissipating, the white outer shell is mostly gone exposing the wrapped wire inside. Wanting to save some in postage instead of ordering one piece at a time.

Thanks

Tim

[TTech]

Cleaned selector switch contacts and volume control. Ordered Ecaps and 5 tubes. Was able to get AM working enough to pull in one station clearly. But as tubes warmed up a lot of cracking and popping appeared  in audio. Sometimes all cleared up, no cracking or popping and AM has very nice audio.Then the cracking and popping set back in. So wait for parts and then see if it's cleared up and ready to align.

[TTech]

Replaced Ecaps and suspected tubes.  No more cracking and popping audio. Reception is considerably weaker, guessing from all the new replacement parts. So...alignment next, then see how things are. But now no FM. will just focus on AM for now.

[David]

If you replaced the 12AT7 try the old one and see what happens on FM. Good Luck David

[TTech]

Thanks for the suggestion David, tried it out, still AWOL FM. But, re soldered a few wiring points switched to AM, turned on the Talking House and listened for a good hour. Otis Redding, Bob Seger, and the Beatles were good company while I cleaned up the work area. Had to make room for the Sig Gen so an alignment can take place. Just waiting for a couple of wire wound resistors to arrive then hopefully good to go on alignment for AM.

Then back to the AWOL FM.

Thanks

[TTech]

Realized when trying quickly to get some life back in the FM, I simply pulled another 12AT7 tube from an FM receiver I'd not even looked at yet. When I reinstalled the 12AT7 to that FM radio no indication of any FM reception on that radio either. So... may have just traded one bad tube with another bad tube in a fit of lazy trouble shooting. Since there is a chance it was knocked off a table while plugged in and playing it may have saved me a lot of time just ordering all new tubes to start with.  Hello credit card my old friend.

[David]

Keeping several extra 12AT7 tubes on hand is a good thing your credit card will understand. Stay Safe David

[David]

Just thinking the 12AT7 heater pins 4&5 is what you would connect if feeding 12 volts. but your set is using 6 volt tubes except the rect tube. The 12AT7 heater is center tap to pin 9 to allow operation at 6 volts. You said something about dark tubes might be a easy fix check the connection to pins 4,5,9. Pins 4&5 should be tied together.

[TTech]

Very good David. I should have caught that knowing that all the other tube numbers start with a 6. I missed the 12AT7 sitting below the other seven six volt tubes on the schematic. Should have some time tomorrow to make needed checks you suggested. Being a newby at tube type radio repair my spare tube collection consists of what remains in the sockets in five radios I bought from a local family. As time passes I'm guessing the understanding credit card will be appreciated. Thanks again David.

Tim

[TTech]

Couldn't leave it alone. Tube pin outs check correct. Also good heater voltage between 9-4, 9-5.

[TTech]

Replaced (5 watt) wire wound resistors on the power out tube. Don't know why but since their replacement cracking and popping audio has disappeared. Listened to another good hour of clear and strong AM. Was considering aligning the AM but realized it had better sensitivity through the full frequency range of any AM radio I've worked on yet, so decided to leave alignment alone. Reinstalled the covers over the tuning cap and part of the FM circuitry. Once covers were installed listened and enjoyed AM stations I normally can't tune in. Next day received the new 12AT7 tube I suspected was the problem child of lost FM reception. Installed new tube, powered up the radio and was rewarded with reception of a few FM stations. More work needed, FM fairly weak, should be able to tune in over 50 FM stations but could manage only three. Was elated that FM was no longer AWOL. Guilty of patting myself on the back in congratulations for bringing a long dead radio back to life. Imagining in the near future of installing the chassis back in the cabinet, another successful project completed. Later the same day turned the radio on to enjoy listening to my AM and FM radio only to be rewarded with.... nothing. Only sound is static on both AM and FM. Returned the old 12AT7 just in case the new one at cooling developed a problem that opened the heater circuit. Still nothing. I know, more lazy fast trouble shooting, but I wanted my hard earned success back. Still nothing. Have left radio alone while licking my wounds and chastising myself for prematurely awarding myself the Best Retired Electronics Tech Award. While filling my days since the massive failure replacing the floor and hand rails on the backyard deck. I begrudgingly allow part of my brain to form a game plan to move forward slowly, again. Just like the old snakes and ladder game I played as a child. One more space and I win, only to have a bad roll of the dice, down the snake, and back at the beginning. Once my wounds are healed a bit, will humbly fire up the volt meter, check supply voltages. If all is well, time for the sig gen and injecting signals to see where they fail. Realized what a wonderful life I have when a cantankerous old radio is my biggest problem.

[TTech]

Other projects kept me away. Finally took some time today and checked things out. Plugged radio into the dim bulb tester and brought the voltage up to 120.5 vac household voltage level. Surprisingly  radio came up on A.M. tuned in several stations. Decided to take voltage readings while things were working again. They are as follows.  
                    Incoming power at radio on/ off switch,  radio on = 78.6 vac
                    Radio amperage = .36 amp
                    A.C.voltage across plates of 5Y3 rectifier = 366.9 vac. Should be 500 vac 
                    D.C. output of rectifier pin-8 = 200 vac  
                    5 vac output from transformer = 3.24 vac
                    6.3 vac output from transformer = 4.01 vac

Realized I had always run radio off of dim bulb tester and variac. Radio after recapping always ran at .36 amp, 75 watt bulb on dim bulb tester seemed just more than dimly lit. Decided I'd turn on the Talking House transmitter and listen to some music while I swept out the garage. Listened for about a half hour. Audio very clear, great tone, audio undistorted even at high volume. Decided to plug radio into wall outlet and see what things looked like without the dim bulb testers 75 watt bulb in series with radio. When I turned radio on noticed the two lamps came up bright and stayed that way. After 30 sec, radio still has no audio. Shut radio off and thought about things. Remembered I had plugged radio in wall outlet just one other time and that was the last time I turned it on and everything seemed to die. Plugged it back into dim bulb tester and all functions are back. Plugged it back into the wall and preformed most of the same tests as above. Radio back to no audio, seems dead. The results are as follows.

                    Incoming power at radio on/off switch, radio on. = 120.7 vac household  voltage
                    A.C. voltage across plates of 5Y3 rectifier = 556 vac
                    D.C. output of rectifier pin-8 = 366.9 vdc
                    5 vac output from transformer = 4.92 vac
                    6.3 vac output from transformer = 6.16 vac

The high voltage output from the new transformer was supposed to be 50 vac hotter than the original, and I never saw that. Being new with tube type radios and dim bulb testers guessing the filament in the 75 watt bulb was dissipating the hotter voltage and giving me low operating voltages?  Seems I'm just over driving everything when plugged into wall outlet. What would be your suggestions. Add a resistor to each high voltage wire from the transformer to the plates of the rectifier? Thought that would place less of a strain on the rectifier and place correct DC voltage on pin-8 of the rectifier. Any thoughts would be appreciated.

Thanks

Tim

[TTech]

Or a voltage divider circuit for each 279 vac leg? Calculated using a 2k and 17.5 k should get me close to 250 vac each leg.

[TTech]

Sorry, scratch that, a.c not d.c.