I thought I remembered seeing on one of Bret's radio repair DVD's (I loaned them out & didn't get them back yet to double check this) that you could do a basic alignment by using a strong radio station on each end of the dial ?

I'm not gonna be a radio tech when I grow up, I might only do a handful in my lifetime for my personal collection.

I'm just curious if I saw the DVD correctly, I promise I wasn't drinking when I saw it. Just curious if this is a realistic option for someone who might only do 1 or 2 radios in their lifetime ?

Thanks in advance for your thoughts on this question.
Dan

You can do MOST of the alignment using the method above........

The issue is getting the IF frequency correct---I won't say that it's impossible without a signal generator, but it would certainly be difficult.

If you assume that the IF is "close enough", and and only adjust the oscillator and antenna trimmers, then your method will work.

There's a dark and dirty little secret to radio alignments, and that is, you can be off a couple of kHz on the IF's, and as long as you set the oscillator to track, the radio will work fine. In fact, back in the day this was done on purpose when necessary to eliminate image responses before all the AM stations in the US and Canada were lined up in 10-kHz channels.

The way to proceed is to make sure the dial pointer is mechanically correct (i.e. stops in the right place on both ends of the band), then tune in a low to medium strength signal around 600 kHz. If necessary, adjust the oscillator trimmer so the station comes in "on the button." Then tweak the IFs for maximum volume. Finally, tune in a weak station around 1400 kHz and adjust the antenna trimmer for maximum volume. That should get the radio lined up well enough for regular service.

Mind that this is a "ballpark" procedure that should be used only to peak up a radio that is already working reasonably well. If you find yourself turning the trimmers or IF slugs more than a half-turn either way, you're going too far. It means that there is a possibility of a component defect, or somebody seriously misaligned the set in the past. Either way, a signal generator and output indicator should be used to find out what is going on. It also goes without saying that this kind of alignment procedure is only suitable for simple AM radios; more sophisticated receivers must not be "tweaked" haphazardly.

In a word - yes. In my early days, I could not afford such luxuries but I could usually repair old radios adequately. I'm talking about a kid back in the 50s, 60s. I have a pdf of an article from 1959 describing the process and there have been a couple of write ups by some of the old timers on here. It certainly is not the best way, and may not satisfy an OCD purist like most of us, but it will get your radio playing well enough to satisfy the general public. Send me a PM with an e-mail address and I'll send you whatever I have in my files about methodology.

Thanks for confirming the little secret I will also keep it a secret

I am sending you a PM TexMac ! Thanks !

Dan

A variation on that trick is to intentionally alter the IF frequency to improve the dial tracking. The IF circuits themselves don't care much of they are tuned to 400 or 500, as long at they are tuned. Altering the IF has a far greater effect on the low end of the dial than the high end. Alter the IF to adjust the low end of the dial, and the oscillator to alter the high end.

Brett

Agreed, without a dependable frequency counter, most old time signal generators are not that accurate.
But if you leave one of these old beast on for a half hour or so, hook up the counter to the output and adjust to frequency you need, proceed. Beware of harmonics. I had a set on my bench that was supposed to have 455 KHZ IF and was so far off I had to blast a signal through. Someone hacked the set.

That being said, if the radio is working it is certainly possible to use a weak station at either extreme of the dial to touch things up after refurbushment of capacitors and resistors. Adjustments rarely require more than one turn in either direction to accomplish this. Unless it has been hacked.

Usual warning, please use an isolation transformer. And also a good old fashioned analog VTVM is very much preferred to measure output. A digital meter will drive you to stop drinking.

Dan,
FWIW...I would be careful to let the radio warm up good before doing your seat of the pants alignment. I have seen a radio play good when cold and get progressively worse with this type of estimated frequency adjustment. Any one else seen this?
Eric

Good advice here guys ! Thank You !
I'm just sitting back and absorbing it all in, TexMac sent me a lot of reading material on this, Thanks !
Dan

If using the "dark and dirty little secret" approach to aligning a radio, which of the IF's (first or second) is tweaked first when one gets to that step? Also, in which order does one do the primary and secondary of a given IF?

Thank you for your help.

Joseph

If you are getting any reception at all, you work it just like everything else in a radio. Assuming you have the proper power going where it should, start nearest the speaker and work backwards to the antenna. That would mean secondary of the last IF first. If you are getting nothing at all to start with, as when a tweaker has tweaked them all as tight as they can go, all bets are off and you have to start injecting a signal right at that last IF (just like trouble shooting to find a bad stage). Not every case can be done by these rough and dirty methods.

Wouldn't the oscillator trimmer have little or no effect on the tracking at the low end? One method that I've used (assuming the IF's are in the ballpark) is to 1) tune to a weak station around 600 kHz and tweak the IF's for maximum volume, 2) mechanically adjust the pointer so that the station is at the correct position on the dial (it may not be possible to due this exactly and get the correct tracking -- compromises might have to be made, depending on the results of the next step), 3) adjust the oscillator trimmer so that a station around 1400 comes in at the correct position on the dial, and 4) adjust the antenna trimmer for maximum performance.

Here's an interesting thread on the topic:

viewtopic.php?t=34300

Bob

Funny, I always think of that as working forwards to the antenna.



My thinking exactly - assuming that the oscillator coil doesn't have an adjustable core or padder.

My understanding has always been to adjust the oscillator trimmer at 1600+ Kc, to set the upper end, and the antenna trimmer at 1400, to peak the gain.

For sets W/O an adjustable oscillator coil, very slightly bending the last variable plate will affect the lower frequency range.

You're right on that. It would be better to adjust the oscillator coil at a station around 1600 instead of 1400 (though as a practical matter it probably doesn't make much difference). I usually just look for a convenient station somewhere at the upper end of the dial.

Bob

Cute, but without a lot of formal training, I've always had to work by instinct. I just imagine myself as a single electromagnetic signal floating around with millions of others out there in the ether and visualize bumping into an antenna and being shaped and molded as I move through each stage of a radio to magically become sound coming from the speaker.

To elaborate a bit on what I was saying ... yes, in a normal alignment, you want to set the oscillator trimmer somewhere near the top of the dial. That's where it has the most effect. However, in a "quickie" alignment, the idea is to center up the oscillator and primary of the first IF together, with the radio tuned into a station. The oscillator trimmer still has enough effect at 600 kHz to do this--if needed--and there's less chance of throwing the radio out of alignment if you set the oscillator to the IF transformer rather than the other way around. Then you peak up the secondary of the first IF, and primary and secondary of the second IF. Finally, as a last step, set the antenna trimmer on a weak station near the top of the dial.

It is to be noted that a few radios do have series trimmers for the oscillator circuit, or adjustable slugs in the coil--in addition to the regular parallel trimmer. In those cases, the series trimmers or slugs are customarily set at or around 600 kHz.