I rescued a ~100 year old radio a while back (SWMBO likes to decorate with antiques and this gives me a place to hide some kit). It is tuned with a massive "arm" that rotates a variable capacitor. The exposed end of the actuator is visible in photo 10/11 at <https://www.proxibid.com/Art-Antiques-Collectibles/Collectibles/Victor-Micro-Synchronus-Radio-R-35/lotInformation/62516544> [Not the same model but I've been hard-pressed to find the model I have!] The interior can be seen at photo 8/11 at that same URL (the flat disk in the center with arm running off towards the "back" of the photo (front of the cabinet). I'd like not to alter the existing electronics/mechanisms -- but won't be using them (I just want the cabinet as a veneer for my kit). But, I WOULD like to be able to either use the arm as an indicator (unlikely as it needs a bit of effort to drive it) or a control (far more likely). Not sure of exact purpose as that will depend on how much resolution I can get from it. It seems the safest/easiest way of interfacing to it would be mechanically; i.e., leave all of the electronics "as is" and just "watch" the motion of the arm or disc. Ideally, it is ferrous and I can just adhere something to it magnetically. But, it begs the question: why such a large mechanism?
Antique radio
Started by ●June 18, 2023
Reply by ●June 18, 20232023-06-18
On Sunday, 18 June 2023 at 13:35:23 UTC-7, Don Y wrote:> I rescued a ~100 year old radio a while back (SWMBO likes to decorate > with antiques and this gives me a place to hide some kit). > > It is tuned with a massive "arm" that rotates a variable capacitor. > > The exposed end of the actuator is visible in photo 10/11 at > <https://www.proxibid.com/Art-Antiques-Collectibles/Collectibles/Victor-Micro-Synchronus-Radio-R-35/lotInformation/62516544> > > [Not the same model but I've been hard-pressed to find the model I have!] > > The interior can be seen at photo 8/11 at that same URL (the flat disk > in the center with arm running off towards the "back" of the photo > (front of the cabinet). > > I'd like not to alter the existing electronics/mechanisms -- but won't > be using them (I just want the cabinet as a veneer for my kit). > > But, I WOULD like to be able to either use the arm as an indicator > (unlikely as it needs a bit of effort to drive it) or a control > (far more likely). Not sure of exact purpose as that will depend on > how much resolution I can get from it. > > It seems the safest/easiest way of interfacing to it would be mechanically; > i.e., leave all of the electronics "as is" and just "watch" the motion > of the arm or disc. Ideally, it is ferrous and I can just adhere > something to it magnetically. > > But, it begs the question: why such a large mechanism?From the schematic (www.radiomuseum.org/r/rca_r_35_victor.html) it is a TRF with 5 separate tuning capacitors. The large disk looks like it drives all 5 simultaneously. In a TRF receiver with multiple stages it is necessary to minimize coupling between stages or they will oscillate as they all work at the same frequency. One way to assist that is to keep them apart physically. A normal multigang turning capacitor might not have permitted that. kw
Reply by ●June 18, 20232023-06-18
On Sunday, June 18, 2023 at 4:35:23 PM UTC-4, Don Y wrote:> I rescued a ~100 year old radio a while back (SWMBO likes to decorate > with antiques and this gives me a place to hide some kit). > > It is tuned with a massive "arm" that rotates a variable capacitor. > > The exposed end of the actuator is visible in photo 10/11 at > <https://www.proxibid.com/Art-Antiques-Collectibles/Collectibles/Victor-Micro-Synchronus-Radio-R-35/lotInformation/62516544> > > [Not the same model but I've been hard-pressed to find the model I have!] > > The interior can be seen at photo 8/11 at that same URL (the flat disk > in the center with arm running off towards the "back" of the photo > (front of the cabinet). > > I'd like not to alter the existing electronics/mechanisms -- but won't > be using them (I just want the cabinet as a veneer for my kit). > > But, I WOULD like to be able to either use the arm as an indicator > (unlikely as it needs a bit of effort to drive it) or a control > (far more likely). Not sure of exact purpose as that will depend on > how much resolution I can get from it. > > It seems the safest/easiest way of interfacing to it would be mechanically; > i.e., leave all of the electronics "as is" and just "watch" the motion > of the arm or disc. Ideally, it is ferrous and I can just adhere > something to it magnetically. > > But, it begs the question: why such a large mechanism?To use this sideways tuning control, I would use is as a three position switch. Leave in the middle for hold frequency, left for lower frequency and right for higher frequency. It might be a bit touchy to adjust if it is as hard to move as you describe. But a variable speed auto increment should make it reasonable. A couple of microswitches should be easy to mount to the chassis just behind the front panel. Of course, this will require a readout of your choice, to see what station you are tuning, unless you simply want to do that by ear. -- Rick C. - Get 1,000 miles of free Supercharging - Tesla referral code - https://ts.la/richard11209
Reply by ●June 19, 20232023-06-19
On 2023-06-18, Don Y <blockedofcourse@foo.invalid> wrote:> But, it begs the question: why such a large mechanism?It's the same size as the tuning scale. -- Jasen. 🇺🇦 Слава Україні
Reply by ●June 19, 20232023-06-19
On Sunday, 18 June 2023 at 21:35:23 UTC+1, Don Y wrote:> I rescued a ~100 year old radio a while back (SWMBO likes to decorate > with antiques and this gives me a place to hide some kit). > > It is tuned with a massive "arm" that rotates a variable capacitor. > > The exposed end of the actuator is visible in photo 10/11 at > <https://www.proxibid.com/Art-Antiques-Collectibles/Collectibles/Victor-Micro-Synchronus-Radio-R-35/lotInformation/62516544> > > [Not the same model but I've been hard-pressed to find the model I have!] > > The interior can be seen at photo 8/11 at that same URL (the flat disk > in the center with arm running off towards the "back" of the photo > (front of the cabinet). > > I'd like not to alter the existing electronics/mechanisms -- but won't > be using them (I just want the cabinet as a veneer for my kit). > > But, I WOULD like to be able to either use the arm as an indicator > (unlikely as it needs a bit of effort to drive it) or a control > (far more likely). Not sure of exact purpose as that will depend on > how much resolution I can get from it. > > It seems the safest/easiest way of interfacing to it would be mechanically; > i.e., leave all of the electronics "as is" and just "watch" the motion > of the arm or disc. Ideally, it is ferrous and I can just adhere > something to it magnetically. > > But, it begs the question: why such a large mechanism?It did the job, avoided gears, unreliable strings, & the user-hated need o adjust several tuning dials at once. It just didn't catch on. Early tech has lots of such ideas. The superhet made it obsolete - even reaction/regeneration made it unnecessary.
Reply by ●June 19, 20232023-06-19
On 6/18/2023 4:54 PM, ke...@kjwdesigns.com wrote:>> But, it begs the question: why such a large mechanism? > > From the schematic (www.radiomuseum.org/r/rca_r_35_victor.html) it is a TRF > with 5 separate tuning capacitors. The large disk looks like it drives all 5 > simultaneously.Yes, but wouldn't they all turn on the same "shaft"?> In a TRF receiver with multiple stages it is necessary to minimize coupling > between stages or they will oscillate as they all work at the same > frequency. One way to assist that is to keep them apart physically. A normal > multigang turning capacitor might not have permitted that.Ah! That makes sense. So, there's likely something non-intuitive (i.e., single shaft) hiding beneath the disk. And, that would explain all of the effort (mechanism) put there to constrain the motion of the disk. That piques my curiosity to open it up and have a look inside... but, not enough to risk "unforeseen challenges". (I'm content to live with the mystery to keep the device intact) Thanks!
Reply by ●June 19, 20232023-06-19
On Monday, June 19, 2023 at 3:57:48 AM UTC-4, Don Y wrote:> On 6/18/2023 4:54 PM, ke...@kjwdesigns.com wrote: > >> But, it begs the question: why such a large mechanism? > > > > From the schematic (www.radiomuseum.org/r/rca_r_35_victor.html) it is a TRF > > with 5 separate tuning capacitors. The large disk looks like it drives all 5 > > simultaneously. > Yes, but wouldn't they all turn on the same "shaft"? > > In a TRF receiver with multiple stages it is necessary to minimize coupling > > between stages or they will oscillate as they all work at the same > > frequency. One way to assist that is to keep them apart physically. A normal > > multigang turning capacitor might not have permitted that. > Ah! That makes sense. So, there's likely something non-intuitive > (i.e., single shaft) hiding beneath the disk. And, that would explain > all of the effort (mechanism) put there to constrain the motion of the > disk.See the five little wheels pressing against the large disk? They are connected to the five separate tuning capacitors. Not one shaft, five shafts. The trick is getting them all aligned, so they are synchronized. They probably have stops on each tuning capacitor and the dial is turned from one end to the other. The small wheels can slip against the large disk so that when the stops on the tuning dial are reached, the tuning capacitors are then in sync.> That piques my curiosity to open it up and have a look inside... > but, not enough to risk "unforeseen challenges". (I'm content to > live with the mystery to keep the device intact)It's just five separate tuning capacitors, all the same. You could pick up the position of the tuning disk by laying a disk on top of it, with a pattern of stripes around the outer edge. Two optical pickups could then give you the position of the tuning disk. Moving the tuning disk from one end to the other would calibrate it easily. -- Rick C. + Get 1,000 miles of free Supercharging + Tesla referral code - https://ts.la/richard11209
Reply by ●June 19, 20232023-06-19
On Tuesday, 20 June 2023 at 03:41:08 UTC+10, Ricky wrote:> On Monday, June 19, 2023 at 3:57:48 AM UTC-4, Don Y wrote: > > On 6/18/2023 4:54 PM, ke...@kjwdesigns.com wrote: > > >> But, it begs the question: why such a large mechanism? > > > > > > From the schematic (www.radiomuseum.org/r/rca_r_35_victor.html) it is a TRF > > > with 5 separate tuning capacitors. The large disk looks like it drives all 5 > > > simultaneously. > > Yes, but wouldn't they all turn on the same "shaft"? > > > In a TRF receiver with multiple stages it is necessary to minimize coupling > > > between stages or they will oscillate as they all work at the same > > > frequency. One way to assist that is to keep them apart physically. A normal > > > multigang turning capacitor might not have permitted that. > > Ah! That makes sense. So, there's likely something non-intuitive > > (i.e., single shaft) hiding beneath the disk. And, that would explain > > all of the effort (mechanism) put there to constrain the motion of the > > disk. > See the five little wheels pressing against the large disk? They are connected to the five separate tuning capacitors. Not one shaft, five shafts. The trick is getting them all aligned, so they are synchronized. They probably have stops on each tuning capacitor and the dial is turned from one end to the other. The small wheels can slip against the large disk so that when the stops on the tuning dial are reached, the tuning capacitors are then in sync. > > That piques my curiosity to open it up and have a look inside... > > but, not enough to risk "unforeseen challenges". (I'm content to > > live with the mystery to keep the device intact) > It's just five separate tuning capacitors, all the same. > > You could pick up the position of the tuning disk by laying a disk on top of it, with a pattern of stripes around the outer edge. Two optical pickups could then give you the position of the tuning disk. Moving the tuning disk from one end to the other would calibrate it easily. > > -- > > Rick C. > > + Get 1,000 miles of free Supercharging > + Tesla referral code - https://ts.la/richard11209Or choose the best of the "wheels" that are operating reliably mechanically, and substitute a rotary encoder? -- Cheers, Chris.
Reply by ●June 19, 20232023-06-19
On Monday, June 19, 2023 at 10:03:20 PM UTC-4, Chris wrote:> On Tuesday, 20 June 2023 at 03:41:08 UTC+10, Ricky wrote: > > On Monday, June 19, 2023 at 3:57:48 AM UTC-4, Don Y wrote: > > > On 6/18/2023 4:54 PM, ke...@kjwdesigns.com wrote: > > > >> But, it begs the question: why such a large mechanism? > > > > > > > > From the schematic (www.radiomuseum.org/r/rca_r_35_victor.html) it is a TRF > > > > with 5 separate tuning capacitors. The large disk looks like it drives all 5 > > > > simultaneously. > > > Yes, but wouldn't they all turn on the same "shaft"? > > > > In a TRF receiver with multiple stages it is necessary to minimize coupling > > > > between stages or they will oscillate as they all work at the same > > > > frequency. One way to assist that is to keep them apart physically. A normal > > > > multigang turning capacitor might not have permitted that. > > > Ah! That makes sense. So, there's likely something non-intuitive > > > (i.e., single shaft) hiding beneath the disk. And, that would explain > > > all of the effort (mechanism) put there to constrain the motion of the > > > disk. > > See the five little wheels pressing against the large disk? They are connected to the five separate tuning capacitors. Not one shaft, five shafts. The trick is getting them all aligned, so they are synchronized. They probably have stops on each tuning capacitor and the dial is turned from one end to the other. The small wheels can slip against the large disk so that when the stops on the tuning dial are reached, the tuning capacitors are then in sync. > > > That piques my curiosity to open it up and have a look inside... > > > but, not enough to risk "unforeseen challenges". (I'm content to > > > live with the mystery to keep the device intact) > > It's just five separate tuning capacitors, all the same. > > > > You could pick up the position of the tuning disk by laying a disk on top of it, with a pattern of stripes around the outer edge. Two optical pickups could then give you the position of the tuning disk. Moving the tuning disk from one end to the other would calibrate it easily. > > > > -- > > > > Rick C. > > > > + Get 1,000 miles of free Supercharging > > + Tesla referral code - https://ts.la/richard11209 > Or choose the best of the "wheels" that are operating reliably mechanically, and substitute a rotary encoder?If he doesn't want to disturb the guts, I would expect he would not want to remove any parts. A rotary encoder could be added the same way the tuning caps are installed, just on top, rather than underneath. Any mods would require holes drilled for a frame, unless he uses an RF remote with no attachments to the chassis at all. I guess using the speakers again would be a very minimal intrusion. -- Rick C. -- Get 1,000 miles of free Supercharging -- Tesla referral code - https://ts.la/richard11209
