EH Scott Radio Enthusiasts

The Fine Things are Always Hand Made

Hi All:

 I have been so busy the last while I have not had a chance untill tonight to start on my All Wave 23's. I have started on the 5 knob that I picked up in Montana and upon my inspection it has had only one cap changed in all its years. The underside of the chassis is super clean and the chrome is fair condition with some pitting and scratches and a couple dents. The dial scale is broken, will have to try to find another.

I have changed 12 caps so far and all but one had changed in value a lot and had high leakage. The resistor count so far is 10 and all but two have been at least 20% high and some as high as 100%. I have completed one IF transformer so far replacing both caps and three resitors and both rubber coated leads that go though the chassis as they were hard as a rock. They were both intact but dont want to risk them failing after all this work.

Other than the fact there are a lot of capcitors and resistors this chassis is nice and open and fairly easy to work on. I look forward to completing it and taking for its first test run.

Greg

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Greg:

How's the rebuild going? When I did mine, I changed all the caps. I did check some of the resistors and most were in good condition.I did change one. As for the caps, what values did you find in the chassis and what values are you replacing them with?

The schematic I have lists all of the bypass as .1uf. I found a lot of .05uf in the chassis. Except where the schematic calls for .05, I replaced all with .1's. There is a copy of the dial scale in the photo section. It is different from the one in my radio, in that it has the data for the 'hi fidelity' stations. It might be possible to take a pix of the original and print it out on a clear plastic sheet, then cut it to size. 

Check the wire from the center antenna coil to the grid of the RF tube. This was cracked and had a short to ground where it came out of the shield base. I was able to cut it back, solder on a new lead, put sleeving over the joint and feed it back to the terminal strip. I did this while the radio was in the cabinet and after I had it playing of course.

The dial tracking is off at the ends of the dial, but close in the middle part. All bands are off about the same amount.

I haven't done any type of alignment yet. 

Thom

Hi Thom:

 I am almost done, still have one little problem to figure out but here is my story to this point.

I was happy with how straight forward and easy I found this radio to work on. Everything is laid out really well and in general there is lots of room to work with, As I had very high expectations as to the performance of this radio I was a little picky about component values so I changed all of the paper caps,32, and two silver mica or bakelite caps as some call them. I tested every resistor and any that were over 20% out of tolerance,30, I  replaced with resistors that checked better than 5%. Repairs that I found were in the first IF a 1K resistor had been changed out to a 33K and the .1uf cap in the first IF have been changed. All of the grid lead wires had been changed and some of the rubber covered wires had been changed. I checked all of the tubes and replaced 6. I did find there was about a 50/50 mix of caps, .1uf and .05uf.

This is where the headache/fun begain. I powered the set up and it worked just barely. With my outside antenna connected I could just barely get the local stations, how disappointing after all this work. I then discovered that with or without the antenna connected there was no change in reception. So I began checking coils and switches to see what was going on. All checked good but still nothing! I had to put it aside for a few days to work on some other stuff and clear my head. I had asked Norman B for some suggestions and when I came back to it I started with just a look around and finished changing out rubber covered wire. While I was changing the wire on the BC antenna coil I noticed the little shorting contact on the bottom of the coil switch had been bent over and was shorting the antenna signal to ground. Looks like it was done on purpose by the last guy that worked on it. I corrected that and completed the wiring. I powered it up and it worked much better but no where near what I was expecting and it tuned really broadly and was very noisey.

I spent a couple days beating my self up trying to figure out why it worked so poorly. As per Norman I checked the sensitivty and selectivity pots and found the selectivity pot open, fixed that and it improved a little but not much.

Then I thought all of the problems I had found so far other than the pot were caused by the last guy that worked on it so I thought I should compare it to the 7 knob set I have. Started on the top side and found the lead wire from the bottom of the antenna switch to the first RF tube was connected to the wrong side of the coupling cap. I moved the wire to where it should be and the set came alive.

I did an IF alignment on it and I cant believe how good this radio works. I was listening to a station from Califonia and it sounded like a local station, just amazing!

I am not out of the woods yet, it is still noisey and I suspect its the voltage divider resistor because it gets quieter as that resistor gets hot and I have run into this problem with other sets as well.

I ordered a new dial scale from Radio Daze and I need to find a 100 watt 10k adjustable resistor and I think that will do it. It has been a real test of my abilities but worth every moment so far.

 

Greg

Greg: 

Nice to know that another Scott is back among the living. I have been pulling in radio China and radio Cuba with a 50 foot wire laid out on the  floor. I am going to put up an outside antenna soon. We have several dimmers in the house and they create a lot of noise.  I have been reading thru the alignment instructions in the service manual, but some things don't make sense to me. I have been doing this type of work for years, but the bandwidth control seems to work backwards from what the directions say, or I don't understand its operation. Far left is max bandwidth and far right is narrow bandwidth. Do you peak the IF with the control set to max bandwidth? The BFO doesn't work, but that isn't too important to me. Every thing else does work. Haven't tried using the phono input yet. 

Thom

Thom:

 The way I peaked the IF was connect my Fluke meter to the 10K resistor that goes to the volume control, inject the IF frequency through a .022uf cap to the grid connection of the 6A7 tube and with no antenna attached start peaking for max voltage reading. Seemed to work good for me and oh yah the sensistivity and selectivity controls all the way clockwise.

 

Greg

Greg:

I was wrong when I described the operation of the selectivity control on my radio. Full left, is the narrow bandwidth position and full right is the wide bandwidth position.  It detunes wide enough that the signal almost disappears and the tuning meter will drop off. About a 1/4 turn clockwise is as far as it needs to go for decent sound. 

The volume control has never been much beyond a 1/4 turn for good volume.

Does your set have the 'air tuned' variable capacitors for the IF? This one does and it looks like they are original to the radio. I used a little bit of de-oxit on them when I had the IF covers off. 

Thom

Thom:

 I thought you may have been mistaken when you discribed the operation of your controls. I think mine still needs some tune up on the selectivity control as it has to be all the way up for just ok sound quality. When I turn it down just a quarter the signal is gone so something still needs attention.

Yes mine does have the air tuned variable capacitors and I would say they are orginal to the radio as well. I cleaned them with a brush as they had a little bit of a white powder on them.

It does have tons of volume that is for sure! About 1/4 turn on the volume is more than enough me.

I will keep plugging away at it till I get everything figured out. I wish I could find one close by in good working condition so I could have a reference to go by.

Greg

Greg:

If you can only receive a signal with the selectivity-fidelity control full clockwise and you loose the signal when this control is rotated 1/4 turn counter clockwise, the IF is badly in need of realignment.  First, remove the covers over the IF selectivity trimmers (four square covers under the chassis along the back) and compare to the other chassis that you have with the control in the full clockwise and in the full counter clockwise positions.  If there is a difference in the position of the trimmers (full meshed vs full unmeshed), stop and report.  I will then identify the correct positions of these trimmers.  If they are substantially the same, then it is unlikely that they have been tampered with and the set may be realigned.  If you have not already done so, loosen and retighten the set screws holding the trimmer rotors to the common shaft to assure good electrical connection.  Replace the square shield cans.

With the IF alignment so far off, the process that I employ to get the receiver on track before finer adjustments is as follows.  1) With the selectivity-fidelity control at some clockwise position, tune to a station that comes in loud and clear.  Turn the selectivity control counter clockwise till the signal is weak but audible.  Adjust all trimmers for best reception of the station.  It should come in loud and clear again (if not, report).  Rotate the selectivity-fidelity control further counter clockwise and repeat the trimmer adjustments.  Continue until the selectivity-fidelity control is fully counter clockwise and again adjust trimmers.  The set will then be ready for a fine alignment per Scott instructions using a signal genarator and meter.  If an IF frequency is marked on the inside of the back apron using a black grease pencil, you may want to chase the IF back to the specified frequency.  Otherwise, Scott tuned the IF to 465 khz.  If peak aligning, always finish the IF alignment with the selectivity-fidelity control in the full counter clockwise position.  If sweep aligning, always peak align first.

Norman

OK Norman, It would I have done this wrong and will try you method, I will try it tonight and post back.

Greg

Greg:

I have a couple of questions for you about the 5 knob Allwave 23. The dial calibration on mine is way off. I have stations coming in above the scale markings on the first short wave band.(top end of the broadcast band). I have tried to reset the dial scale with the indicator bar, but this just makes it worse. I would like to verify the location of the indicator bar on your set. Mine is about 3/8 inch below the top edge of the trim cover. At some point, I will pull the chassis and check the original position of the set screws on the tuning shaft. This would be the defining adjustment starting point. It is also possible that at some point the IF could have been reset to 455 KHZ, but that would put the dial off by 10 KHZ and mine is off by about 20 KHZ. I am able to pull in a lot of East coast stations and some of the Southern US stations with a 50 foot wire draped around our dining room. 

Also with the dial scale set to the line under the Khz Mhz marks, the bottom mounting of the dial scale shows up with the dial all the way at the High end of travel. 

Thanks,

Thom
Greg Bilodeau said:

OK Norman, It would I have done this wrong and will try you method, I will try it tonight and post back.

Greg

Hi Thom:

 I am in the process of moving to another city and dont have access to my radios at the moment and it will be a couple months before I get my shop setup again and get everything unpacked. I will try to remember to look when I get settled into our new place.

 

Greg

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