Working on my Philco Model 60 (run 7) again. After cleaning and recapping I had a motorboating issue that was solved by slightly adjusting the 2nd IF sec and 2nd IF pri trimmers. Doing so stopped the motorboating but reduced the receivers sensitivity to weak stations.
So, I decided to get setup to do a complete alignment. Bought a Heathkit Model IG-102 signal generator, went through the calibration process for it (seems good) and started through the instructions to align.
The first step, remove control grid from 6A7, set signal generator to 460kc hooked to 6A7, dial at 55kc, adjust trimmer 4 (2nd IF Sec) to max out put.
What should I hear out of the speaker? All I get is static/motorboating that I CAN adjust to max, but does not seem right.
When tuning the HF and Antenna trimmers on the tuning condenser I hear the 1400kc signal From the sig generator hooked to the ant post) and tune to that. That part seems to be working fine.
Having zero idea what to expect when setting the IF trimmers, I'm just stumbling in the dark...
Am I on the right path?
>What should I hear out of the speaker?
Depends. If the have the modulation turned off you won't hear much at all. With it on you should hear a 400cy tone.
I would leave the grid cap on the 6A7 and connect the generator to it. Keep the generator's output turned down so you can just hear the tone. As you adjust the IF trimmers for the loudest tone in the spkr.
What are you using for your service info?? Please post link to it as the Rider's is for an early model.
http://www.nostalgiaair.org/pagesbymodel...013793.pdf
(10-28-2016, 07:34 PM)Radioroslyn Wrote: [ -> ]>What should I hear out of the speaker?
Depends. If the have the modulation turned off you won't hear much at all. With it on you should hear a 400cy tone.
I would leave the grid cap on the 6A7 and connect the generator to it. Keep the generator's output turned down so you can just hear the tone. As you adjust the IF trimmers for the loudest tone in the spkr.
What are you using for your service info?? Please post link to it as the Rider's is for an early model.
http://www.nostalgiaair.org/pagesbymodel...013793.pdf
400cy tone, that is what I expected but not happening. With the frequency generator set to int. mod./AF Out I can use my (modern) AM radio to listen to the generated frequency and hear the 400cy tone and zero beat it almost precisely on the set frequency.
The grid cap on my 6A7 was slightly loose. I ordered a nos 6A7 and will retry when it arrives. Will also try it with the grid clip connected.
I believe this is the correct procedure for the run 7 Model 60 -
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attachment=11439]
Well you should be hearing a 400cy tone. Try connecting the sg to the grid cap of the 78 tube and adj #4 for max signal at 460kc/400cy tone heard from the spkr. You didn't switch the 77 and 75 around?? It will fit but won't work.
(10-31-2016, 03:24 PM)Radioroslyn Wrote: [ -> ]Well you should be hearing a 400cy tone. Try connecting the sg to the grid cap of the 78 tube and adj #4 for max signal at 460kc/400cy tone heard from the spkr. You didn't switch the 77 and 75 around?? It will fit but won't work.
I'll have some time latter this week to try again. Something is certainly odd. I just re-checked and 78 and 75 are in the correct spots.
Just for grins you may want to double check your sg at 460kc on the off chance that that band isn't working. You can do this by listening for it on a working broadcast set @ 920kc (460 X2) to hear it's second harmonic.
(10-31-2016, 05:30 PM)Radioroslyn Wrote: [ -> ]Just for grins you may want to double check your sg at 460kc on the off chance that that band isn't working. You can do this by listening for it on a working broadcast set @ 920kc (460 X2) to hear it's second harmonic.
On the Philco 60 I can hear the 460kc tone at 920kc. Signal generator hooked to the control grid of 6A7, 6A7 grid clip attached, ground clip clipped to shield.
At no frequency lower than 920kc do I hear the generated tone.
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attachment=11447]
Ok Let's try the grid cap of the 77 IF amp tube. Can you hear the 400cy tone when connected there? If you can measure the voltage on pin 2 and 4 of the 6A7. If you can't measure pins 3 and 2. All of these pins should have some HV on them. If not you may have a bad (open) IF transformer.
Just as an aside, the cap on the 6A7 isn't the control grid it's the 4th grid which is the rf input grid. The actual control grid is grid 1 which is on pin5. In a pentagrid converter the cathode, G1 and G2 (acts like the plate and has HV on it) is wired as a triode oscillator, that's the bottom half. The top half is setup as a pentode amplifier ( this is where the input signal is applied to G4)
http://www.r-type.org/pdfs/6a7.pdf
(11-02-2016, 02:07 PM)Radioroslyn Wrote: [ -> ]Ok Let's try the grid cap of the 77 IF amp tube. Can you hear the 400cy tone when connected there? If you can measure the voltage on pin 2 and 4 of the 6A7. If you can't measure pins 3 and 2. All of these pins should have some HV on them. If not you may have a bad (open) IF transformer.
Frequency generator connected to grid cap of my IF amp tube (it's a 78) - Yes, I hear the 400cy tone (tuned to 550kc) and can peak it with trimmer 4. Voltage at 6A7 pins 2 and 4 is 110 vdc. Voltage at 6A7 pins 2 and 3 is 186 vdc
(11-02-2016, 02:07 PM)RadioroslynJust as an aside, the cap on the 6A7 isn\t the control grid it's the 4th grid which is the rf input grid. The actual control grid is grid 1 which is on pin5. In a pentagrid converter the cathode, G1 and G2 (acts like the plate and has HV on it) is wired as a triode oscillator, that's the bottom half. The top half is setup as a pentode amplifier ( this is where the input signal is applied to G4) Wrote: [ -> ]http://www.r-type.org/pdfs/6a7.pdf
So is the correct procedure to connect the freq gen to pin5?
(11-02-2016, 03:00 PM)Solamar Wrote: [ -> ] (11-02-2016, 02:07 PM)RadioroslynJust as an aside, the cap on the 6A7 isn\t the control grid it Wrote: [ -> ]http://www.r-type.org/pdfs/6a7.pdf
So is the correct procedure to connect the freq gen to pin5?
Think I got it. Running through the whole procedure now...
Hah I've got a radio now!!
Was getting two strong channels, now at least 15 (with a bit of static).
Did starting with the IF amp tube get me close enough to hear the tone through the 6A7? Or is it that I'm using pin 5, the actual control grid of 6A7?
Peeking the 1st IF primary and 1st IF sec was a bit touchy just beyond peak I lose the tone and start picking up harmonic distortion/feedback.
Terry, I sure do appreciate all the help you've given me!
(11-02-2016, 03:00 PM)Solamar Wrote: [ -> ] (11-02-2016, 02:07 PM)RadioroslynJust as an aside, the cap on the 6A7 isn\t the control grid it Wrote: [ -> ]http://www.r-type.org/pdfs/6a7.pdf
So is the correct procedure to connect the freq gen to pin5?
No. If you connect the sg to pin5 it will stop the oscillator from working.
Connect to the grid cap on the 6A7.
At this point you'll want to connect the sg to the grid cap on the 6A7 then adj the IF trimmers for max with the sg turned down low so you can just hear it. After you get the IF trimmers on the back lip of the chassis peaked up connect the sg to the ant post and adj trimmer5 for minimum signal.This completes the IF alignment. Glad to help out!