My friend asked him to help him with Allwave 23

[Scott Petersen]

Hi,

This is my first post. My friend just bought an Allwave 23, it arrived without receiving any Rf at all, just the Audio was working, I was going to recap it, but someone already restuffrd all of the paper caps in the unit already. I found the coil disk was not tightened all of the way, and then I was able to receive some stations on everything except the broadcast band, I dug a little deeper

and found the mica cap on that coil was shorted by a wire touching it, I moved the wire and was able to pick up the strongest station, buried in noise.

The receiver picks up something on all bands, but there is so much noise it is hard to listen to.

I wanted to align it, (the manual says to make sure the selectivity caps are aligned,and set screws are tight) but upon opening the square covers under the IF's,I saw that two of the small capacitors are opposite the other two, Is this correct, I cannot find a clear picture of the proper orientation.

Thanks,

Scott

[Norman S Braithwaite]

There are four square cans covering six variable selectivity trimmers.  They should be oriented as follows:  Meshed - Unmeshed, Unmeshed - Meshed, Meshed - Unmeshed.  The pot metal collars holding the rotors of these trimmers have a habit of expanding thus rendering the rotor loose or at least having a bad electronic connection.  The set screws should be loosened and retightened.  Three of the trimmers increase the frequency of the local tuned circuit and the other three decrease the frequency of the local tuned circuit thus broadening the IF bandpass.

Norman

[Scott Petersen]

Hi Norman,

They are correct then, a few of the set screws were loose though.

Thank You!

[Scott Petersen]

The receiver seems to be better, but I still have the same basic problem,The stations are buried in noise, and are hard to listen to.I can get huge volume, but the background noises cover everything(all bands)I can use the beat oscillator to pick the stations out, but they are nearly the same level as the noise and have interference. Do you have any idea what might be wrong?

[Kent King]

From the discussion so far, I gather the noise occurs on all bands, correct? If so, I'd look to the IF and AGC. My method is a bit unconventional, but I would disconnect the IF input coming out of the mixer. Is the set quiet? If so I'd inject the signal starting down at the 4th IF and work back...where does the noise appear. If it is noisy with no input at the 1st IF, start lifting the grid caps on each stage...try to isolate the noise to one of the stages. Scott sets are notoriously quiet with no signal, so locating the offending stage would be my objective. I'm sure others probably have better ideas :-)

Kent

[Scott Petersen]

The set is completely quiet without an antenna, and with a RF generator the 400hz tone is pure.How would I test the AGC?

I went through the alignment procedure from the manual, I read about adjusting the the IF diode, and RF diode, but the RF diode dosen't seem to do anything

[Norman S Braithwaite]

The RF diode should be tuned for the lowest output with a strong signal fed to the antenna.  It sure sounds like there is a problem with the IF amplifier.  The amplifier is designed with so much gain that a signal will make it through even if one IF section is bad.  I presume you aligned the IF with the selectivity-fidelity control in the full CCW (selective) position.  Did you observe a distinct peak for each IF adjustment plus the IF diode and detector (audio) diode?  If you did not observe a distinct peak at any location, look there first.

Norman

[Scott Petersen]

Yes, I aligned it per the instructions, I certainly saw a peak at each IF adjustment, and the diode, If I put my hand within an inch of the antenna terminal I pick up background noise, I can hear the local station within the noise.

[Scott Petersen]

It's like I have trouble separating the signal from the noise. I tried a modern radio, and the ratio of noise to signal is quite a bit better, I realize the radio is 70 years newer, but many of the Youtube videos show the set working a bit better.Maybe my location is a problem, as there is a bit of noise on the modern radio as well, but when centered the station is much clearer than on the Allwave.

[Scott Petersen]

When they say to attach the sig gen to the grid of the 6A7, that is the cap on the tube,correct? The basing of the tube shows several different grids, I am a little unsure if i used the correct one.

[Norman S Braithwaite]

Yes.  The top cap on a 6A7G tube is the control grid into which the incoming signal is fed.

Norman

[Scott Petersen]

Well... I brought it back to my friend, the 3 shortwave bands work extremely well, but the broadcast band sounds poor with quite a bit of rushing noise in the background, I am at a loss as what to do next. The terrible noise i had at my place is local, and that cleared up at my friends house.

[Norman S Braithwaite]

Check the primary winding on the antenna coil.  It may well be open.  The coil can be checked by measuring the DC resistance between the antenna post and ground (two posts only) or antenna and antenna (three posts).  The coil should measure around 45 ohms.

Norman 

Scott Petersen said:

Well... I brought it back to my friend, the 3 shortwave bands work extremely well, but the broadcast band sounds poor with quite a bit of rushing noise in the background, I am at a loss as what to do next. The terrible noise i had at my place is local, and that cleared up at my friends house.