[doctormap]

I finally finished replacing all the old paper capacitors, the electrolytic capacitors and the bakelite capacitors yesterday, put everyting back together and POWER ON!  Hey! It works!  Even my wife was surprised!

I have two questions about the function,
1.  The volume is very low.  Even when I pick up a strong station (AM) I have to turn the volume up all the way to hear it without putting my ear on the speaker.

2.  On the AM range, I get a lot of stations up to about 700, and nothing higher than that.

Any suggestions?  I can also pick up stations on the medium and short wave ranges, but they are also very faint.

[morzh]

Congratulations.

What is it that you have finished? (I understand it is a radio, and it is a Philco).

1. Without the model......a)you have not, probably, aligned it yet. b) it is possible you have some RF interstage transformers open, so even though you receive, you might not get the amplification intended.
Other reasons might exist.
2. Same thing. Alignment first.


Also: have you checked your tubes to make sure they are good tubes and not duds?

[doctormap]

Thanks for the reply.
1.  It is a 37-620 console (floor) model.
2.  I am totally lost when you talk about "alignment".
3.  I purchase 4 of the tubes new.  The other 2 seem to work, but how would I go about checking them.  They come on and glow at the top, beyond that, I have no way to "check" them.  I do own a digital multimeter, but I have never used it.

[morzh]

Is the volume universally low across the bands? Or is it OK on one band and bad on another?

Your lack of volume might be due to

1) Bad RF 6K7G tube.
2) Bad RF transformers (9, 10 or 11). This would cause a band-depended effect.
3) Same - bad Ant. transformers.
4) Bad antenna?
5) Some bad/weak tubes. The fact that tubes glow and you have reception does not by itself mean they are all good.


Which tubes are new and which are not?

Alignment: page 4 in the Rider's manual for 37-620 which is on the Nostalgia Air has the alignment procedure (Adjustment they call it there).

PS. if you are serious about the hobby you need proper equipment. The way you do it is relying on some dumb luck and this may or may not work. This time it somewhat worked.

[Raleigh]

Alignment is making the adjustments so that the tuned circuits in the radio are all tuned to the proper frequencies, and in the correct relation to one another. In your radio there are a good many adjustment screws that you should be able to see. Most, if not all, of these are adjustable capacitors, known variously as compensators, trimmers, or padders.

The alignment does a few things:

1) It makes sure the circuits tuned to the intermediate frequency (IF) are all tuned identically, so you get the maximum throughput. Your radio is designed for an IF of 470 kilo hertz (also called kilo cycles). If both your IF transformer circuits are not tuned identically, your volume will be low.

2) It makes sure the dial is adjusted so that the dial pointer is pointing to the right frequency all the way across the dial. If you are listening to a station at, say, 850, you want the dial to point to 850. If this is adjusted wrong, not only will the dial point to the wrong frequency, but you might lose stations at each end.

Usually, alignment is done by injecting known modulated frequencies into the radio with an instrument called a signal generator, and adjusting the compensators to those known frequencies. Often you have to re-do the adjustments several times.

Alignment of the AM band can be done to a fairly good approximation without a signal generator if it isn't too far out of adjustment when you start out. To do this, you use strong local stations that are close to the frequencies that you would use if you had a signal generator. There are some pitfalls to doing it this way. A signal generator makes it a good bit easier.

If you adjust the IF this way, you will almost certainly not be able to tune the IF to 470 KHz, but you can get the IF circuits tuned to the same frequency as each other. That is almost as good, as long as they aren't too far away from 470.

The same procedure can be used with police and short wave bands, but it is a lot harder to find broadcasts close to the frequencies you need, and to be sure what the actual frequencies of the broadcasts are.

Because your radio is a fairly complicated one with many compensators, I'd advise using a signal generator and getting some help and advice the first time through. At least do some reading so you understand what you are trying to accomplish. After you do a couple of radios it is usually pretty easy, but I know my first few times through were kind of intimidating.

Most of the time your schematics will have alignment instructions along with pictures that show where the adjustments are.

[AI2V]

Since you don't have any test equipment for alignment, this should help some to get you going.

Turn your dial to a known station (if you get 710 in your area, set the dial there. Hopefully you will hear your selected station. Looking from the rear of the chassis, there are two tall aluminum cans on the left side; on the top of each can are two screw adjustments (these are the "IF" adjustments). Using a small screwdriver with electrical tape wrapped just above the tip, turn the screws for maximum reception. There is high voltage (not deadly) on two of these screws and that is what the tape is for; you don't want to short the screws to the can nor do you want to touch the screwdriver shaft.

This isn't the proper way to do a quick alignment but it should make a big difference in your reception. Not hearing anything above 800 is usually associated with the 6A8 tube circuitry or the tube itself.

Look for an antique radio club in your area; that's where you will find someone who can hold your hand and get you started the right way.

[Raleigh]

When you adjust the IF compensators on top of the aluminum cans, be sure to adjust them in the order suggested by the schematic. Usually you adjust the 2nd IF compensators first, then the 1st IF compensators. Once you finish all four, you'll probably need to do it again at least once. Be sure to do them in the same order.

Your radio has adjustments for both the primary and secondary compensators. The order is: 37a, 37, 31a, 31.

You didn't say if you had a schematic. There is a free schematic in pdf format here:

http://www.nostalgiaair.org/Resources/212/M0013212.htm

The reproduction quality is not very good. You can buy a better quality reproduction of the original Philco service data for a reasonable price from Chuck Schwark at his web site:

http://www.philcorepairbench.com/schematics.htm It's worth the price to buy it from Chuck.

On the free schematic, top of page 3, there is a diagram showing where each of the compensators is.

[doctormap]

First, thank you so much for your kind replies.  I do appreciate your wililingness to help me.  Some answers to questions:
1.  I was under the impression, from reading the posts in the forum, that anyone who was willing to spend time and some money could get a radio in fairly good condition up and running again by replacing the paper caps and needed tubes.  That you don't have to be an electonics expert and have a lot of expensive testing equipment on hand.  (I'm not, and I don't)
2.  I replaced (they were missing) the two 6K7 tubes and the 6A8 and 6Q7.  The tubes I did not replace were the 5Y4 and the 6F6.
3.  I was ablet to tune in a station at 560 AM all day yesterday with a really good strong signal, and the dial appears to be correct on the tuning.  It was so loud I had to turn the volume down about halfway.
4.  Yes I have a good schematic, which has been very helpful when I was working on replacing all the capacitors.
5.  Yes I have the page that has the factory instructions for the alignment procedure.

Questions:
1.  Since I was able to pull in a good strong AM station, does that mean that the tubes are OK?
2.  I know this sounds like a stupid question, but why do I need to go through this "alignment" thing?  Shouldn't that have all been done at the factory?

I will take your advice seriously, and do my best to go through your recommended alignment procedure and we will see what we can get.

[morzh]

Questions:
1.  Since I was able to pull in a good strong AM station, does that mean that the tubes are OK?
2.  I know this sounds like a stupid question, but why do I need to go through this "alignment" thing?  Shouldn't that have all been done at the factory?

I will take your advice seriously, and do my best to go through your recommended alignment procedure and we will see what we can get.

1. Likely but not always the case.
2. OK. Let me rephrase it: why do car tune-ups, wasn't this all tuned at the factory? The answer is, after 80 years, or in fact after any repair there is a good chance that due to some moving and touching, changing tubes etc, and due to sheer aging the parameters will drift. Capacitors age and tubes have variance to their inter-electrode capacitance which will cause misalignment.
Which is why the radios get aligned from time to time.
Unaligned radio will still work, but will not perform as well as a properly aligned one.
If you want the radio strictly as a conversation starter piece, which you can, to create a "wow!" moment, plug in, turn on and pull in a station, then unaligned one is just fine. Most times though, as a conversation starter, it does not even have to work, it may just sit there. Like an old skillet or a weaving machine.

[Warren]

As for "anyone" can fix a radio by replaceing paper caps and tubes, that would depend on what is wrong with the radio... could have bad coil, transformer etc. There is no gaurantee and obviously the more you know the better.
Tubes could be marginal, depends on performance, etc. You say you get "a" station, do you get stations all through the dial?
The alignment is like tuning your car it may run but it will work better if you keep it tuned. Yes, the factory did an alignment but over the years components change values which can throw the alignment off.

[Radioroslyn]

Hi DM and welcome to the Phorum!
To answer your question #2  1937 was a very long to ago and some thing may have changed in all that time. Just by moving some of the wires under the chassis you can detune the set. Replacement of the cap can do the same. So a little  tune up can usually help the performance.

The equipment you'll need isn't very expensive. You have the volt meter (if it is a digital one would recommend an analog model) . A signal generator and I'll add a signal tracer. With these you can do a good job of troubleshooting. You can insert a signal (with the signal generator)l and follow it(with the tracer) thought the set till it stops, most of the time thats where the problem excise.

Would recommend something like a Heathkit SG-7 or 8 for the signal generator they go for about $20 or so. Try to get one with the cables. The Heathkit T-3 is a good unit (tracer) for about the same price. The T-3 if it's all there it should come with a probe it's important to get it. You may need to wait for the right one comes around price wise. With these few items and some good practice you'll be able to troubleshoot like a pro.

Lots of good sage advise here on the Phorum!

Terry

[LASJayhawk]

You do have an antenna hooked up to it?