In case you have a CORONET from 1950 to 1954 with a R1 thru R3 chassis, this should give you some help.
This week I decided to try and finalize repairs to my R-3 (1951 Coronet) with a wonky tuner on AM. Previously the plates on the Variable capacitor(V.C.) have dropped out and i put them back on with "SUPER GLUE" and pressed them in by hand. Invariably one or more of the plate sets on the AM band would drop out and I'd lose AM AGAIN.
I also had gotten some 50uf/50uf 500v JJ dual caps to replace the individual caps I had originally installed when I first got it. It worked fine, but looked like shit, and I wasn't happy with how it looked. So out went the Panasonics with all the terminal strips and in went the JJ's with clamps.
Pics at end. No sense in Before pics as it hasn't changed from 2 years ago so I used those. Last 3 are today.
The tuning shaft on the V.C. has grooves in it to install the plates. Lining up the FM Plates is a Grade A PITA, with the AM being less so, but it still has to be right. I found that the FM Plates were all tight but the AM plates were either loose or altogether separated. 2 previous installs (mine) had resulted in a film of superglue on the shaft that needed to be removed. A very small surgical pick and some time, took care of it. Then a dry mockup. The plates would hold from the open position all the way closed, but would fall off when trying to tune back to open. Which is what was happening before.
The middle group of plates was causing all the problem of losing tuning about 1/2way down the dial from the top. A couple of the plates were slightly bent so they would make contact with the stationary plates causing loss of signal. These were carefully rebent so flat against a piece of glass. So I cut a bunch of strips of paper about 3/8" wide x 2-1/2" long. Also the "Super Glue" has poor lateral strength. It would detach from and allow the plates to become loose or drop off when dialed down to the lower end of the dial. So an adhesive with good adhesion properties and lateral strength was needed. A thin layer of Shoe GOO forced into the grooves of the shaft seemed to be appropriate( We'll see longterm). It has very good adhesion, and lateral strength is very good when left alone to set up. Once the GOO was placed on the shaft each group of plates was pressed in and adjusted against the upper end stop. Then it was left to set up for 10 minutes. At the end of 10 minutes it was holding but malleable so I very carefully closed the V.C. (ran it down to the lower end.of the dial so the plates were meshed. I noticed some rubbing but knew where it was from. Here's where the paper strips come in. Placed strips on either side of each moveable plate evenly, so that the plates were equidistant from the stationary plates. (NOTE: The AM plates are approx 1/8" apart so it takes 3-4 layers of paper each side). Once that was done I walked away for 36 hours. The unit was not touched,moved, turned during this time.
After 36 hours I removed the paper, and visually checked the plates during rotation of the dial knob. No touching of any plates, and they all appear to be parallel. So i powered it up. Very poor AM Reception. Hooked up the Sig gen and went thru an alignment procedure on it. Quite simple on this one. I did find the RF trimmer tab on the bottom of the unit had become flattened out so it was making intermittent contact. Just picking up one corner of chassis would cause intermittent's on the AM with a lot of static. Adjusted it so it made a variable contact as the screw was adjusted in /out. Got it set to where it's supposed to be. Now we're cookng with gas. With just the AM flat coil antenna it was picking up stations strongly across the band. They are real close to dial reading, so i didn't mess with the AM Alignment any further.
After that the installation of the JJ CAPS was a breeze. Pull one set of caps and install the JJ. FISHER used METAL plates for the CAN CAPS to attach to, similar to the phenolic ones used for isolated cans'. These are riveted to the chassis. These were removed so the JJ's terminals would not short to the chassis. The holes left by the plate rivets were used for attaching the clamps. The CAN of the JJ's are not connected to Negative or positive. So there is a NEGATIVE TERMINAL on the CAN. After connecting the Positives, I ran a short negative to the closest NEGATIVE GROUND (usually a terminal on a strip). I did break a resistor near the discriminator/detector 4.7uf cap. Had to series two resistors to get the value. After everything finished, powered it up on the variac and DBT. No Smoke and after 1:05 up came music from the AM BAND. Switched to FM and had very good reception on a 6 ft piece of wire.
Still have to put it back in the cabinet but it's running very well. I may change out the 3 pin speaker output connection for an RCA jack, with a switch for 8 ohm and 16ohm. I'll have to think hard on it as it's an external mod. The 3 pin is breaking (chipping) down and eventually will require replacement/rehab.
Pics;
Loose tab under screw causing intermittent.
LEFT And CENTER AM BAND PLATES were problem.
Underside BEFORE (This is from 2 years ago).
Underside Today.
Topside Today With new JJ's Tung-Sol 6V6GT ReIssues. VERY NICE Sounding.
V.C. before cover on.
This week I decided to try and finalize repairs to my R-3 (1951 Coronet) with a wonky tuner on AM. Previously the plates on the Variable capacitor(V.C.) have dropped out and i put them back on with "SUPER GLUE" and pressed them in by hand. Invariably one or more of the plate sets on the AM band would drop out and I'd lose AM AGAIN.
I also had gotten some 50uf/50uf 500v JJ dual caps to replace the individual caps I had originally installed when I first got it. It worked fine, but looked like shit, and I wasn't happy with how it looked. So out went the Panasonics with all the terminal strips and in went the JJ's with clamps.
Pics at end. No sense in Before pics as it hasn't changed from 2 years ago so I used those. Last 3 are today.
The tuning shaft on the V.C. has grooves in it to install the plates. Lining up the FM Plates is a Grade A PITA, with the AM being less so, but it still has to be right. I found that the FM Plates were all tight but the AM plates were either loose or altogether separated. 2 previous installs (mine) had resulted in a film of superglue on the shaft that needed to be removed. A very small surgical pick and some time, took care of it. Then a dry mockup. The plates would hold from the open position all the way closed, but would fall off when trying to tune back to open. Which is what was happening before.
The middle group of plates was causing all the problem of losing tuning about 1/2way down the dial from the top. A couple of the plates were slightly bent so they would make contact with the stationary plates causing loss of signal. These were carefully rebent so flat against a piece of glass. So I cut a bunch of strips of paper about 3/8" wide x 2-1/2" long. Also the "Super Glue" has poor lateral strength. It would detach from and allow the plates to become loose or drop off when dialed down to the lower end of the dial. So an adhesive with good adhesion properties and lateral strength was needed. A thin layer of Shoe GOO forced into the grooves of the shaft seemed to be appropriate( We'll see longterm). It has very good adhesion, and lateral strength is very good when left alone to set up. Once the GOO was placed on the shaft each group of plates was pressed in and adjusted against the upper end stop. Then it was left to set up for 10 minutes. At the end of 10 minutes it was holding but malleable so I very carefully closed the V.C. (ran it down to the lower end.of the dial so the plates were meshed. I noticed some rubbing but knew where it was from. Here's where the paper strips come in. Placed strips on either side of each moveable plate evenly, so that the plates were equidistant from the stationary plates. (NOTE: The AM plates are approx 1/8" apart so it takes 3-4 layers of paper each side). Once that was done I walked away for 36 hours. The unit was not touched,moved, turned during this time.
After 36 hours I removed the paper, and visually checked the plates during rotation of the dial knob. No touching of any plates, and they all appear to be parallel. So i powered it up. Very poor AM Reception. Hooked up the Sig gen and went thru an alignment procedure on it. Quite simple on this one. I did find the RF trimmer tab on the bottom of the unit had become flattened out so it was making intermittent contact. Just picking up one corner of chassis would cause intermittent's on the AM with a lot of static. Adjusted it so it made a variable contact as the screw was adjusted in /out. Got it set to where it's supposed to be. Now we're cookng with gas. With just the AM flat coil antenna it was picking up stations strongly across the band. They are real close to dial reading, so i didn't mess with the AM Alignment any further.
After that the installation of the JJ CAPS was a breeze. Pull one set of caps and install the JJ. FISHER used METAL plates for the CAN CAPS to attach to, similar to the phenolic ones used for isolated cans'. These are riveted to the chassis. These were removed so the JJ's terminals would not short to the chassis. The holes left by the plate rivets were used for attaching the clamps. The CAN of the JJ's are not connected to Negative or positive. So there is a NEGATIVE TERMINAL on the CAN. After connecting the Positives, I ran a short negative to the closest NEGATIVE GROUND (usually a terminal on a strip). I did break a resistor near the discriminator/detector 4.7uf cap. Had to series two resistors to get the value. After everything finished, powered it up on the variac and DBT. No Smoke and after 1:05 up came music from the AM BAND. Switched to FM and had very good reception on a 6 ft piece of wire.
Still have to put it back in the cabinet but it's running very well. I may change out the 3 pin speaker output connection for an RCA jack, with a switch for 8 ohm and 16ohm. I'll have to think hard on it as it's an external mod. The 3 pin is breaking (chipping) down and eventually will require replacement/rehab.
Pics;
Loose tab under screw causing intermittent.
LEFT And CENTER AM BAND PLATES were problem.
Underside BEFORE (This is from 2 years ago).
Underside Today.
Topside Today With new JJ's Tung-Sol 6V6GT ReIssues. VERY NICE Sounding.
V.C. before cover on.
