Anyway- I recently acquired a nice GE T-200 AM-FM. It originally had an intermitent FM problem which was addressed in this forum. At that time someone, (sorry I forgot who-but thanks), sent me a schematic for a C510A & T-170A, which seems to be electrically similar. That problem turned out to be an intermitent 19EZ8. I replaced it and now it works great, except...
I have this set next to my bed and it plays the local classical station all night, which helps me sleep. I never paid attention to the dial, or changed the station, until the other day. Imagine my surprize when I found 107.7 where 88.1 should be. That got my attention. (Ok, the dementia pills seem to be doing a great job.) Now I can see that the whole dial is off-90.5 is around 95, etc.
Now- the "So what?" part of my mind can live with this, but the obsessive part would like to get it fixed. I have a decent signal generator, but not one designed for FM. I have a good scope, signal tracer, etc. but servicing FM front end problems are not my strong point. So I guess my question to the forum is whether I should leave well enough alone, or spend a little time and energy fixing it?
Any ideas?
Thanks
Terry
:Anyway- I recently acquired a nice GE T-200 AM-FM. It originally had an intermitent FM problem which was addressed in this forum. At that time someone, (sorry I forgot who-but thanks), sent me a schematic for a C510A & T-170A, which seems to be electrically similar. That problem turned out to be an intermitent 19EZ8. I replaced it and now it works great, except...
:I have this set next to my bed and it plays the local classical station all night, which helps me sleep. I never paid attention to the dial, or changed the station, until the other day. Imagine my surprize when I found 107.7 where 88.1 should be. That got my attention. (Ok, the dementia pills seem to be doing a great job.) Now I can see that the whole dial is off-90.5 is around 95, etc.
:Now- the "So what?" part of my mind can live with this, but the obsessive part would like to get it fixed. I have a decent signal generator, but not one designed for FM. I have a good scope, signal tracer, etc. but servicing FM front end problems are not my strong point. So I guess my question to the forum is whether I should leave well enough alone, or spend a little time and energy fixing it?
:Any ideas?
:Thanks
:Terry
:
You describe what should be a simple alignment problem. So simple it may be just a slip of the pointer. Is AM off also?
Of course you know where your favorite radio station is. You may just want to leave it. However, my opinion of radio restoration is that these are works of art and the artist's intent was that the radio be just right. It is the goal I look for. My goal is less important than yours. If yours is to have a vintage radio to listen to your favorite station. Good news, you have it!
Best Regards,
Bill Grimm
: You describe what should be a simple alignment problem. So simple it may be just a slip of the pointer. Is AM off also?
: Of course you know where your favorite radio station is. You may just want to leave it. However, my opinion of radio restoration is that these are works of art and the artist's intent was that the radio be just right. It is the goal I look for. My goal is less important than yours. If yours is to have a vintage radio to listen to your favorite station. Good news, you have it!
:
:Best Regards,
:
:Bill Grimm
:
The AM and FM dials are vertical and together. The number 88 is at the bottom of the dial and 108 at the top. Except that the station at frequency 107.7 is at the BOTTOM of the dial, then 88 appears part way up, and so on. The dial, of course, is not very precise, it's only about 8" long. The only two stations I listen to are the classical station and my own FM transmitter. I'm sure the oscillator has gone out of alignment, and I guess I was hoping someone had a "Quick fix". I had the set apart today, but decided to just live with it for the time being. If anyone does have a way to get the thing set up, I'll get back into it. The reason I posted it is because I felt fixing it would make an interesting thread. And yeah, I think things should work as they were meant to. We'll see what happens.
Terry
Naturally, with the same shift upwards on the other stations across the band. Then you tune in ye olde 90.5 station be it WUOL (or WTHL ?) . . . woooooops . . . my high level ESP is not fully kicking in yet . . .and take note of it making its show, way up at the "95" dial pointer positioning. |
HI Terry, The AM and FM dials are vertical and together. The number 88 is at the bottom of the dial and 108 at the top. Except that the station at frequency 107.7 is at the BOTTOM of the dial, then 88 appears part way up, and so on. The dial, of course, is not very precise, it's only about 8" long. The only two stations I listen to are the classical station and my own FM transmitter. I'm sure the oscillator has gone out of alignment, and I guess I was hoping someone had a "Quick fix". I had the set apart today, but decided to just live with it for the time being. If anyone does have a way to get the thing set up, I'll get back into it. The reason I posted it is because I felt fixing it would make an interesting thread. And yeah, I think things should work as they were meant to. We'll see what happens.
You describe what should be a simple alignment problem. So simple it may be just a slip of the pointer. Is AM off also?
:
: : :  : : : : : :Sir Terry. . . . . . : : : : :I remember pulling that schema and also marking up a thumbnail, of the top of the chassis since you had ALSO queried the TOTALLY "missing" . . .( W'hut you talkin' 'bout, Willis ?) . . . osc trimmer screw for its Eff Emm band. : : :Referenced via the hand reference #2. : : :HOW-SOME-EVER you came back with a 19 EASY EIGHT as being your problem,fixed it, so that post was aborted. : : :Now . . . a dusting off the initial thumbnail drawing . . . . : : :What they had done on your set was eliminate that trimmer and laboriously . . on the design bench . . ran normal temperature cycles on the chassis and osc freq monitorings. That ended up with the final precise selection of the temp compensating capacitor of C10 as is shown on the FM osc thumbnail schema at the bottom of referencing. :That then left the sole FM oscillator adjustments as being on the L4 inductor . . .osc coil . [ AQUA ] marked up winding . . . not it's adjunct minor, small plate winding link over on the right side of the schema. : : :The AM portion has its trimmer adjustments screws as the [GREEN] circled adjustments, while the FM portion has its [ RED ] circled ANT trimmer adjustment. : : :With the tuning error which you are experiencing, if I DIDN'T "Ross Cread" the dial scale reading versus the actual frequency of the station, which seemed to be what you implied, as that being of a 90.5 station showing up at 95 on your dial scale. : :Naturally, with the same shift upwards on the other stations across the band. : : :Look at my hand reference #1 and you see the L4 oscillator coil placed down to the side of the main tuning condenser. : : :Since the unit does not have a slug to vary its inductive value, you will be dependent upon slightly compressing the coil winding to increase its inductance value or spreading the turns . . . known in the RF trade as knifing . .the turns apart a bit, thus being able to decrease its inductive value. : : :Now on the FM band , with the use of a 10.7 I.F. frequency, it is plausible to shift oscillator frequency 10.7 in relation to a high 88.8 or 108 mhz to make that high frequency station be coming as an image on the lower frequency.( Accounting for your squirrely high freq station coming in at the low end of the FM band also.) : : :(On the AM band, you would be hard pressed to detune enough to get a 455 image, when initially ONLY working with a mere 520-1740 Mhz spread for the WHOLE AM band.) : : : :On the upper portion of the FM band where . . . . .90.5 is around 95 . . . that has the dial pointer at 95, but the local oscillator needs to be lowered in frequency to shift that stations reception down to that 90.5 dial positioning. : : : :Now . . .How to do-it-to-it: : : :Initially, do a Cindy . . .Oh Cindy . . don't let me . . .ya da - ya da . . suggested check, to see if the dial cord stringing is equidistant on its pointer positioning at the ends . . . I think it will be . . as well as noting that the AM calibration is ALSO probably being correct, as it stands, since they ARE using a COMMON pointer . . . Pic ref supplied. : : : :Then you tune in ye olde 90.5 station be it WUOL (or WTHL ?) . . . woooooops . . . my high level ESP is not fully kicking in yet . . .and take note of it making its show, way up at the "95" dial pointer positioning. : : :What you want to do now is fully ascertain the corrective action needed, this will be done by moving the FM dial pointer to the lower side of the reception of that 90.5 station until it starts to sound a bit noisy and "off station". : : :Next, you take a “pocket screwdriver size” of screwdriver blade / iron nail/ hex wrench, etc and start to move it vewy-vewy slowly into the edge of the central open core of L4 osc coil. If you are then skewing the osc tuning such that the 90.5 station comes into tune again, and sounds good, at least, until you plunge in on deeper, you have found specifically WHAT inductive corrective action is needed. : : :That being . . . that you need a higher inductive value for L4, which is what you were accomplishing when you just shifted the dial tuning DOWNSCALE with the iron slightly entering the inductor. : : :More inductance of L4 should shift that now 90.5 station on down to its proper position, on the dial scale. : : :Its now just a matter of COMPRESSING the L4 coil turns . .en masse . . .a bit closer together, while taking repeated freq checks to see if you have gradually “walked” the frequency down enough to make 90.5 end up at 90.5 on the dial scale. : : :It might require intermediate touch ups of the [RED] circle marked up FM RF trimmer capacitor, but probably NOT, since that adjustment is usually ending up being peaked for max sensitivity at the HIGH end of the FM band. : : :Then check out ‘ole WRFL down at ~ 88.1 and at the extreme other end of the spectrum . . . do you hear and find WKCA coming in at its ~ 107.7 slot ? : : : :Standing by for feedback or further queries . . . :Thanks EDD - as always your advice is incredible. I've been tied up today but I'm printing out the info and this looks like a fun Sunday afternoon project. : : : :  : |
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:HI Terry,
: You describe what should be a simple alignment problem. So simple it may be just a slip of the pointer. Is AM off also?
: Of course you know where your favorite radio station is. You may just want to leave it. However, my opinion of radio restoration is that these are works of art and the artist's intent was that the radio be just right. It is the goal I look for. My goal is less important than yours. If yours is to have a vintage radio to listen to your favorite station. Good news, you have it!
:
:Best Regards,
:
:Bill Grimm
:
:
:
:
:
:The AM and FM dials are vertical and together. The number 88 is at the bottom of the dial and 108 at the top. Except that the station at frequency 107.7 is at the BOTTOM of the dial, then 88 appears part way up, and so on. The dial, of course, is not very precise, it's only about 8" long. The only two stations I listen to are the classical station and my own FM transmitter. I'm sure the oscillator has gone out of alignment, and I guess I was hoping someone had a "Quick fix". I had the set apart today, but decided to just live with it for the time being. If anyone does have a way to get the thing set up, I'll get back into it. The reason I posted it is because I felt fixing it would make an interesting thread. And yeah, I think things should work as they were meant to. We'll see what happens.
:Terry
:
:
:
: : : : : : : : :Sir Terry. . . . . . : : : : :I remember pulling that schema and also marking up a thumbnail, of the top of the chassis since you had ALSO queried the TOTALLY "missing" . . .( W'hut you talkin' 'bout, Willis ?) . . . osc trimmer screw for its Eff Emm band. : : :Referenced via the hand reference #2. : : :HOW-SOME-EVER you came back with a 19 EASY EIGHT as being your problem,fixed it, so that post was aborted. : : :Now . . . a dusting off the initial thumbnail drawing . . . . : : :What they had done on your set was eliminate that trimmer and laboriously . . on the design bench . . ran normal temperature cycles on the chassis and osc freq monitorings. That ended up with the final precise selection of the temp compensating capacitor of C10 as is shown on the FM osc thumbnail schema at the bottom of referencing. :That then left the sole FM oscillator adjustments as being on the L4 inductor . . .osc coil . [ AQUA ] marked up winding . . . not it's adjunct minor, small plate winding link over on the right side of the schema. : : :The AM portion has its trimmer adjustments screws as the [GREEN] circled adjustments, while the FM portion has its [ RED ] circled ANT trimmer adjustment. : : :With the tuning error which you are experiencing, if I DIDN'T "Ross Cread" the dial scale reading versus the actual frequency of the station, which seemed to be what you implied, as that being of a 90.5 station showing up at 95 on your dial scale. : :Naturally, with the same shift upwards on the other stations across the band. : : :Look at my hand reference #1 and you see the L4 oscillator coil placed down to the side of the main tuning condenser. : : :Since the unit does not have a slug to vary its inductive value, you will be dependent upon slightly compressing the coil winding to increase its inductance value or spreading the turns . . . known in the RF trade as knifing . .the turns apart a bit, thus being able to decrease its inductive value. : : :Now on the FM band , with the use of a 10.7 I.F. frequency, it is plausible to shift oscillator frequency 10.7 in relation to a high 88.8 or 108 mhz to make that high frequency station be coming as an image on the lower frequency.( Accounting for your squirrely high freq station coming in at the low end of the FM band also.) : : :(On the AM band, you would be hard pressed to detune enough to get a 455 image, when initially ONLY working with a mere 520-1740 Mhz spread for the WHOLE AM band.) : : : :On the upper portion of the FM band where . . . . .90.5 is around 95 . . . that has the dial pointer at 95, but the local oscillator needs to be lowered in frequency to shift that stations reception down to that 90.5 dial positioning. : : : :Now . . .How to do-it-to-it: : : :Initially, do a Cindy . . .Oh Cindy . . don't let me . . .ya da - ya da . . suggested check, to see if the dial cord stringing is equidistant on its pointer positioning at the ends . . . I think it will be . . as well as noting that the AM calibration is ALSO probably being correct, as it stands, since they ARE using a COMMON pointer . . . Pic ref supplied. : : : :Then you tune in ye olde 90.5 station be it WUOL (or WTHL ?) . . . woooooops . . . my high level ESP is not fully kicking in yet . . .and take note of it making its show, way up at the "95" dial pointer positioning. : : :What you want to do now is fully ascertain the corrective action needed, this will be done by moving the FM dial pointer to the lower side of the reception of that 90.5 station until it starts to sound a bit noisy and "off station". : : :Next, you take a “pocket screwdriver size” of screwdriver blade / iron nail/ hex wrench, etc and start to move it vewy-vewy slowly into the edge of the central open core of L4 osc coil. If you are then skewing the osc tuning such that the 90.5 station comes into tune again, and sounds good, at least, until you plunge in on deeper, you have found specifically WHAT inductive corrective action is needed. : : :That being . . . that you need a higher inductive value for L4, which is what you were accomplishing when you just shifted the dial tuning DOWNSCALE with the iron slightly entering the inductor. : : :More inductance of L4 should shift that now 90.5 station on down to its proper position, on the dial scale. : : :Its now just a matter of COMPRESSING the L4 coil turns . .en masse . . .a bit closer together, while taking repeated freq checks to see if you have gradually “walked” the frequency down enough to make 90.5 end up at 90.5 on the dial scale. : : :It might require intermediate touch ups of the [RED] circle marked up FM RF trimmer capacitor, but probably NOT, since that adjustment is usually ending up being peaked for max sensitivity at the HIGH end of the FM band. : : :Then check out ‘ole WRFL down at ~ 88.1 and at the extreme other end of the spectrum . . . do you hear and find WKCA coming in at its ~ 107.7 slot ? : : : :Standing by for feedback or further queries . . . :By the way EDD- HOW DO YO DO THAT VOO DOO YO DO? I mean-some of your graphics are amazing- Thanks- t. : : : : : : : : :  : : : : : :73's de Edd : : : : |
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:HI Terry,
: You describe what should be a simple alignment problem. So simple it may be just a slip of the pointer. Is AM off also?
: Of course you know where your favorite radio station is. You may just want to leave it. However, my opinion of radio restoration is that these are works of art and the artist's intent was that the radio be just right. It is the goal I look for. My goal is less important than yours. If yours is to have a vintage radio to listen to your favorite station. Good news, you have it!
:
:Best Regards,
:
:Bill Grimm
:
:
:
:
:
:The AM and FM dials are vertical and together. The number 88 is at the bottom of the dial and 108 at the top. Except that the station at frequency 107.7 is at the BOTTOM of the dial, then 88 appears part way up, and so on. The dial, of course, is not very precise, it's only about 8" long. The only two stations I listen to are the classical station and my own FM transmitter. I'm sure the oscillator has gone out of alignment, and I guess I was hoping someone had a "Quick fix". I had the set apart today, but decided to just live with it for the time being. If anyone does have a way to get the thing set up, I'll get back into it. The reason I posted it is because I felt fixing it would make an interesting thread. And yeah, I think things should work as they were meant to. We'll see what happens.
:Terry
:
: