I need alignment instructions for my Philco 71. Have been told they are the same for the 70 as well.
I posted this in my 71 thread but to replies so figured id try this.. 8)
Well I went and followed the directions and aligned the 71. But now the sensitivity is gone only pulls in a couple stations. My sig gen is pretty accurate and everything worked out but now its all messed up.
It said to put an output meter on the cathode and plate of the 42 output tube. I used a VTVM on the 42 but there wasnt much deflection on the needle I ended up just doing it by ear.
I set the Sig Gen to 260kc and injected the signal into the grid of the 36 Osc tube. I peaked the IF's then moved on to HF tweaking. I set the dial to 1400, and the Sig gen to 1400 and injected the signal into antenna connector on the radio then peaked the HF lug on the tuning cap (rear lug). Did the same for the Low Freq. at 600. I didnt understand what I was supposed to do witht the Antenna and OCS lugs on the tuning cap (front and middle lugs).
Anyone wanna try to help me out. Ill tinker with it tomorrow.
FYI I did have it playing well before I tore it apart to clean the chassis so I know it will work.
The only thing that seems a bit odd is putting the signal generator output into the grid of the osc. Try the grid cap of the mixer tube for the IF. Double check that the trimmer that you where adjusting IS connected to the circuit that you are adjusting. Sometimes on these old sets the trimmer may not be located near the coil its tuning.
Terry
Yeah I figured I screwed something up. It's my first go at aligning a set.
I didn notice that when making adjustments to the HF (Rear) lug on the tuning cap it would squeal and was really sensitive. I dont have a non conducting tuning tool so I used a nut driver. I ended up tweeking it a little and removing the driver until it sounded the loudest.
What do you guys use to make adjustments?
Take a bic pen pull out the innards. Jam the end over the nut. You can use a heat gun to soften plastic. Let cool.
Terry
Good idea. I'll do that tonight while the Sig gen and VTVM are warming up.
Using a metal 1/4" nutdriver not a good idea as sometimes the IF trimmers have HV on them. Can be fun if you like getting knocked on your butt, not my idea of fun though.
Terry
well went through the procedure again and it still only pulls in about 3 or 4 stations both on the high and low side of the dial.
Made a tool out of a pen body to turn the 1/4 nuts on the caps.
I re aligned the IF section I injected the 260 tone into the grid cap of the 36 tube (detector/ocs). I tried injecting in the grid cap of the 1st IF tube (39/44) but nothing responded when tweaking the caps so went back to the 36 tube.
Then injected a 1400 tone into the antenna clip and tuned to 1400 on the dial and peaked the HF lug on the tuning cap, and then injected a 600 tone and moved the dial to 600 and peaked the low freq. cap.
I hooked up an antenna and tuned around the dial and its the same deal as last night, I did peak the RF and Detector lugs on the tuning cap for loudest volume on the stations I can pull in.
When tuning to say 1230 what little sound i get is garbled and the moving the tuning dial slightly makes it squeal.
When I took it apart to clean it I did pull the tuning cap apart including pulling the stators out of the assembly to remove the rust. I didnt this before reading that its pretty much a no no since its a pain to get them set right again. When I put them back in I checked each plate in the tuning cap for shorts and there are non.
Sucks I have many hours in this radio..
The
Sorry just looked at the diagram, I was thinking that it has a separate mixer and osc tubes. I'm pretty sure the 70 does but the 71 doesn't. So injecting the signal in to the grid of the mixer is fine.
I'm a little surpized that you can't pass a signal from the grid of the IF amp tube and adjust the trimmer. Should have the generator turned down fairly low to prevent overload. Check the resistance of the windings on the IF transformers. Also check plate and screen voltages on the IF amp tube should be around 200v or so.
Terry
Maybe im going about this wrong. I have the sig gen's gain turned all the way up. Could that be causing anything funny to happen with the AVC circuit?
Also a couple other things i noticed is when the radio is first turned on for the radio will motor boat and pop for a few seconds then it goes away. Also if I remove the grid cap of the 36 Osc tube it motor boats. Think I did a number on this alignment lol
I did inject a signal from another radio through a head phone cable into the grid cap of the 1st audio tube it the sound comes in very clean so seems the front end is ok.
Yup, that's your problem.
You should have the volume control on your radio turned all the way up, and then inject the weakest signal possible from your signal generator to avoid not only overloading the radio, but also to prevent AVC action from having an undesired effect on your alignment. This holds true for IF and RF alignment.