Forums :: Resources :: Features :: Photo Gallery :: Vintage Radio Shows :: Archives :: Books
Support This Site: Contributors :: Advertise


It is currently Dec Sat 16, 2017 5:59 pm


All times are UTC [ DST ]





Post New Topic Post Reply  [ 15 posts ] 
Author Message
 Post subject: Schematic for Chelsea Radio Co. Model 122
PostPosted: Nov Thu 23, 2017 4:51 am 
Member

Joined: Sep Mon 28, 2009 1:53 am
Posts: 121
Location: Bloomington, IN
Picked up this little 3 tube, single tuning dial radio off Goodwill! Quick check of the components shows pretty much everything in working condition! On the back, I have indications for B+ 45 and B+ (Unknown), as well as A+, A- and B-. I intend to run the A+ at ~6V due to the condition of my tubes. Any ideas what that other B+ might be?

The cabinet will need to be refinished, and the front slanted face is cracked. I'm tempted to replace it with a clear Plexiglass face (properly labelled), with LED strips to light it up from the inside; your thoughts on that vs. keeping it as near to original as possible?

Uses 01A tubes, which is nice.

If you have any info or schematic, I would be grateful. Also, thoughts on clear & lighted vs. traditional. I'll try to post photos soon, but you can see a sample here: https://www.radiomuseum.org/r/chelsea_122_1.html.


Top
 Profile  
 
 Post subject: Re: Schematic for Chelsea Radio Co. Model 122
PostPosted: Nov Sun 26, 2017 4:34 am 
Member

Joined: Sep Mon 28, 2009 1:53 am
Posts: 121
Location: Bloomington, IN
Here's a look inside the radio:

Image

And here's the schematic (as near as I can figure):

Image

Turning the VOLUME knob physically rotates the loop coil closer to the antenna loop coil. TUNING is via the variable cap.

Any ideas what the B+ voltage might be?


Top
 Profile  
 
 Post subject: Re: Schematic for Chelsea Radio Co. Model 122
PostPosted: Dec Sat 02, 2017 4:29 am 
Member

Joined: Sep Mon 28, 2009 1:53 am
Posts: 121
Location: Bloomington, IN
Searched all over, even contacted several folks who sell radio schematics. No one has one for this radio! 8-(

So, I decided to take a risk and put 90VDC on B+. Got nothing. Filaments didn't light, which seemed strange. So, disconnected everything and took the chassis out of the cabinet to get a better look. Think I made a few errors in my original drawing, so have produced a new one:

Image

I also took photos of the chassis from several different angles. You can see the album here: https://imgur.com/a/Ei8ut.

In my first schematic, T2 showed the Primary at 28K5 ohms, but now it shows as open. IMHO, T1 and T2 are identical transformers, so I'm guessing a winding on T2 was getting ready to fail, and putting current through it did the job. I have a PT156 replacement (have used it on several A-Ks), so I'll put it in here and see what happens.

This radio is far different from operation that the A-Ks, Day-Fan and Equitable Claratone that I have. Seems really strange to me to have 45VDC on the tuning capacitor, which feeds to the FILAMENT voltage. Seems like that voltage could overwhelm A+, which I'm thinking should still be in the 5-6VDC range. The tube bases show a "+" sign on the wire to A+/B-, so bringing in a higher voltage on F- seems really odd.

Anyway, except for T2 being open, the other components appear functional. Adjusting the VOLUME rotates Coil 2 until it lies on top of Coil 1 at "full volume".

Any thoughts?


Top
 Profile  
 
 Post subject: Re: Schematic for Chelsea Radio Co. Model 122
PostPosted: Dec Sat 02, 2017 8:40 pm 
Member
User avatar

Joined: Aug Tue 19, 2014 8:08 pm
Posts: 471
Location: Dallas, TX USA
I believe this is a Model 122, as described on page 130 of the June 1925 issue of Radio World, available at http://www.americanradiohistory.com/hd2 ... e-0130.pdf

The Three Tube Chelsea

Clear volume on the loud speaker, with ability to bring in distant stations within
reasonable range, is the feature of the Three -Tube Chelsea, Model 122. This
set has been on the market for some time and has gained a reputation for its consistently
remarkable performance. One station is received at a time, proving it is also selective.
The Chelsea 3-Tube Set is of the triple circuit type, controlled by a single tuner.
No knowledge of radio is necessary to operate this simple receiver. The cabinet
is slightly sloping, as in the Chelsea Super Five. It is of attractive finish.
The price is now 40.00.

The October 6, 1923 issue of Radio World (http://americanradiohistory.com/Archive ... Oct-06.pdf) shows the following schematic on page 18:
Attachment:
Armstrong 3-circuit Radio World Oct 6 1923 p18.jpg
Armstrong 3-circuit Radio World Oct 6 1923 p18.jpg [ 65.95 KiB | Viewed 216 times ]


and describes the circuit on page 20:

THE ARMSTRONG THREE CIRCUIT REGENERATIVE. This circuit shown in Fig. 1, Page 18,
is popular with the average amateur who has been in the field for some time. Due to the fact that it
takes a little time to get used to its proper manipulation it has not been bruited around as the popular
circuit which it should be. Tuning is accomplished by means of the variocoupler in the antenna circuit
and the two variometers, which also control the regeneration. They should be of good construction
and able to cover all waves from 200 to 600. Any sturdily made variometers will serve for the grid
and plate circuits.
While the circuit is pictured for the 6 volt tubes, the 1 1/2 volt tubes may be used by the substitution
of dry cells for the 6 volt battery and by using the 6 volt tubes and the grid condensers and leaks made
for such. The amplifying transformers should be of good make, preferably a high ratio in the first
stage and one of lower ratio in the second, although the same ratio may be used in both stages. Selective
in a high degree and somewhat critical in tuning, but not bothered by interference when rightly tuned.

Hope this helps!

_________________
Please see my profile for alternate schematic sites.


Top
 Profile  
 
 Post subject: Re: Schematic for Chelsea Radio Co. Model 122
PostPosted: Dec Sat 02, 2017 9:01 pm 
Member

Joined: Sep Mon 28, 2009 1:53 am
Posts: 121
Location: Bloomington, IN
Thanks!! Was beginning to wonder if anyone had a schematic!

Seems strange the set I have has the B+ connection when it doesn't seem to appear in the old schematic. I guess putting 90V on it was a mistake! Pretty sure the 2nd transformer is bad, so will swap that out.

I'll compare schematics and will update.


Top
 Profile  
 
 Post subject: Re: Schematic for Chelsea Radio Co. Model 122
PostPosted: Dec Sun 03, 2017 3:35 am 
Member

Joined: Sep Mon 28, 2009 1:53 am
Posts: 121
Location: Bloomington, IN
Okay, an initial looks would seem to indicate that my "Coil 1" and "Coil 2" form a "pancake" or "spider-web" variometer, which is consistent with the antenna "vari-coupler" in Armstrong circuit. "Coil 3" appears to adjust the effective length of the Coil 1. There are no other variometers.

The Armstrong circuit shows 2 rheostats on the filaments; my set has the single, 4.3 Ohm rheostat. Also, the + and - signs for the either the A or B battery appear swapped in the Armstrong circuit. How else to have a "A+/B-" connector?

So, if I'm looking at my circuit correctly, there's 45V on the variable half of the TUNING capacitor. There's no question of that, and the wiring appears original. I still don't know the value of the B+ voltage on the primary of the first transformer. It seems to me that when the variable cap is fully open, the voltage on the primary is essentially B+. As the var. cap is adjusted, the 45V begins to act against B+, reducing the voltage through the primary. I'm just not grasping how this impacts the tuning. To me, it seems the varicoupler determines what frequency is picked up, and the var. cap adjusts the volume (which is backward from what is shown on the set).

My understanding is very limited at this point, but I think I grasp some of the functions of the various components. Just not seeing the larger picture. Obviously, when coils 1 and 2 are far apart, there's no coupling between the 2; that is, it acts like a variometer with the coils at 90 degrees. When coil 2 is turned so that it lies almost directly on top of coil 1, this would conform to a near-zero angle in a standard variometer, and coupling is the greatest between the coils.

How far off am I on the theory? Any ideas on what B+ should be?

BTW, while cleaning the cabinet a bit, I did find a small, paper slip inside the cabinet indicating that this is a regenerative receiver, and is licensed by the Armstrong patent holders. That would have helped me a few days ago!


Top
 Profile  
 
 Post subject: Re: Schematic for Chelsea Radio Co. Model 122
PostPosted: Dec Mon 04, 2017 5:49 pm 
Member

Joined: Sep Mon 28, 2009 1:53 am
Posts: 121
Location: Bloomington, IN
Also of note: The "B+45" that goes to the variable cap also connects directly to ground! Why would that be?


Top
 Profile  
 
 Post subject: Re: Schematic for Chelsea Radio Co. Model 122
PostPosted: Dec Mon 04, 2017 9:07 pm 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 11539
Location: S. Dartmouth MA 02748-1225 USA
B+ for the detector should be around 22-1/2, for the amp 67-1/2 volts if no "C" battery is used.
"A" supply is 6 to 6.6 volts at the radio, the rheostat lowers/controls the filament voltage and it's voltage drop provides some bias.

If the tubes can be tested for gas, choose a gassy one for the detector... A gassy tube is non-linear, it is this characteristic that is exploited in a regenerative grid leak detector, a gassy tube enhances this, as does a gas detector the 00a.

Tuned circuit or grid return for the detector should be to +"A".

The rotating coil is the regeneration, it should be in the detector plate circuit.

The coil adjacent to the variable condenser should be in parallel with the condenser, this is the principle tuned circuit and range is selected by the taps on same coil. This circuit should be connected to the grid via the grid condenser and a parallel grid leak around 2 to 10 meg. Grid leak can return directly to A+.

Grid leak resistance is not in stone, in fact intent is to adjust grid leak to the characteristics of the detector tube. Too little resistance and the detector will be insensitive, the radio cannot be smoothly brought into regeneration. If the leak resistance is to high, the detector tube will go in/out of a cut-off condition usually making a putt-putt sound.

The right most coil in the image is the antenna coupling coil, there may or not be a fixed resistor in parallel. This coil is un-tuned, antenna and ground are connected. The ground may be common to the A+, or not.

The filament rheostat may control just the detector and a fixed resistor used for the Amp. filament. Either can be called a volume control, as well as the regeneration, but moving coil in this set is best called amplification. Doesn't really matter, just so the user knows how/when to adjust whatever...

Expect all tuning/regeneration controls to interact. That is common when regeneration coil is adjacent to the antenna coupling coil.

indy_kid wrote:
The cabinet will need to be refinished, and the front slanted face is cracked. I'm tempted to replace it with a clear Plexiglas face (properly labeled), with LED strips to light it up from the inside; your thoughts on that vs. keeping it as near to original as possible?
Do not do any of that, this is a radio of limited manufacture. You want a light show buy some old parts and screw them to a board...

BTW The Armstrong circuit shown is a tuned grid/tuned plate regenerator it is the earliest form of Armstrong circuit. later designs are more repeatable in tuning, even this Chelsea will be hard to reset to the same station without using a logging card.

IMHO I think the circuit was hacked for what ever reason, likely very early in its life, then set aside because of the hack failure...

GL

Chas


Top
 Profile  
 
 Post subject: Re: Schematic for Chelsea Radio Co. Model 122
PostPosted: Dec Tue 05, 2017 1:16 am 
Member

Joined: Sep Mon 28, 2009 1:53 am
Posts: 121
Location: Bloomington, IN
If it was hacked, they did so using the same wire as the original. Everything looks original; no sloppy solder joints, no un-matched wires, etc.

The old Armstrong circuit image that was provided shows a variable 45V "B" battery (with "-" on both the "A" and "B" batteries connected - strange), so I may start with 45V and leave "B+45" empty. The odd thing is, there's a factory plate on the back with both "B+45" and "B+" connections. Really hard for me to figure out.

Still need to swap out the bad transformer first...


Top
 Profile  
 
 Post subject: Re: Schematic for Chelsea Radio Co. Model 122
PostPosted: Dec Tue 05, 2017 1:19 am 
Member

Joined: Sep Mon 28, 2009 1:53 am
Posts: 121
Location: Bloomington, IN
Chas wrote:
IMHO I think the circuit was hacked for what ever reason, likely very early in its life, then set aside because of the hack failure...

Chas


These were EXPENSIVE radios back in the day! The Chelsea retailed for $40 (about $750-800 in today's dollars), so I can't imagine someone spending the money, hacking it, then not paying someone to fix the damage.

Then again, it was one of the cheaper sets on the market, so you might be right.


Top
 Profile  
 
 Post subject: Re: Schematic for Chelsea Radio Co. Model 122
PostPosted: Dec Thu 07, 2017 12:50 am 
Member

Joined: Sep Mon 28, 2009 1:53 am
Posts: 121
Location: Bloomington, IN
Chas wrote:
B+ for the detector should be around 22-1/2, for the amp 67-1/2 volts if no "C" battery is used.
"A" supply is 6 to 6.6 volts at the radio, the rheostat lowers/controls the filament voltage and it's voltage drop provides some bias.

If the tubes can be tested for gas, choose a gassy one for the detector... A gassy tube is non-linear, it is this characteristic that is exploited in a regenerative grid leak detector, a gassy tube enhances this, as does a gas detector the 00a.

Tuned circuit or grid return for the detector should be to +"A".

The rotating coil is the regeneration, it should be in the detector plate circuit.

The coil adjacent to the variable condenser should be in parallel with the condenser, this is the principle tuned circuit and range is selected by the taps on same coil. This circuit should be connected to the grid via the grid condenser and a parallel grid leak around 2 to 10 meg. Grid leak can return directly to A+.

Grid leak resistance is not in stone, in fact intent is to adjust grid leak to the characteristics of the detector tube. Too little resistance and the detector will be insensitive, the radio cannot be smoothly brought into regeneration. If the leak resistance is to high, the detector tube will go in/out of a cut-off condition usually making a putt-putt sound.

The right most coil in the image is the antenna coupling coil, there may or not be a fixed resistor in parallel. This coil is un-tuned, antenna and ground are connected. The ground may be common to the A+, or not.

The filament rheostat may control just the detector and a fixed resistor used for the Amp. filament. Either can be called a volume control, as well as the regeneration, but moving coil in this set is best called amplification. Doesn't really matter, just so the user knows how/when to adjust whatever...

Expect all tuning/regeneration controls to interact. That is common when regeneration coil is adjacent to the antenna coupling coil.

Chas



So, from what I able to understand from your description above, and comparing it to what I had, the schematic should appear something like this (values shown are for existing parts; number by the transformers are winding resistances):

Image

I think you were correct in that the set had been hacked. Whomever did it had pretty much everything tied into the earth ground, which made no sense (and which would cause the set to fail to work). I suspect the user was confusing the notion of an earth ground with that of a chassis ground, which I added to the circuit for clarity.

I've deleted both variometers from the 1923 schematic, as my set has none (nothing that looks like a traditional variometer, with a variable coil inside of a fixed coil) . It has a single vari-coupler (Coils 1 and 2), and the variable condenser.

Having "B+45" makes sense when compared to the other TRF sets I have. Most run 90V directly to the speaker output. "B+", therefore, makes sense at 22.5V.

So, anyone kindly have a look and let me know if I'm close or not. I'm a bit concerned with the location of the 0.27uF cap between Coil 1 and a primary of T1; unless the voltage varies with the interaction between Coil 1 and Coil 2 (the vari-coupler), that cap will appear as an open circuit, and no voltage will reach the plate of DET.


Top
 Profile  
 
 Post subject: Re: Schematic for Chelsea Radio Co. Model 122
PostPosted: Dec Thu 07, 2017 1:16 am 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 11539
Location: S. Dartmouth MA 02748-1225 USA
The .27mf bypass cap cannot be in series with the 1st AF transformer, there will be no plate current for the detector. It also too large a value for a RF bypass at the "P" connection of the 1st AF transformer. Move the .27mf from the plate side to the "B+" side and connect the other side of the .27mf to the "B-" In that location it will suitably bypass the Detector "B+".

BTW the plate or rotating coil is coupled magnetically, to the tuner coil, has to be or there would be no regeneration.

Swap labels "TEL" and "LS" and use them as such. High impedance headphones will work in both locations.

DO use 6 to 6.6 volts for the "A" voltage. The single filament rheostat for the three tubes will be fine.

If there are any other left over components not shown in the schematic please post...

Once the cap is corrected, the set should work, do expect that the tuning controls will interact.

Leave off the B+ and burn the tubes at 6.6 volts rheostat dialed out for an hour or two. This is a 1st level of rejuvenation and will awaken the tubes. If the tubes are depleted then more aggressive rejuvenation is required.

GL

Chas


Top
 Profile  
 
 Post subject: Re: Schematic for Chelsea Radio Co. Model 122
PostPosted: Dec Thu 07, 2017 6:54 pm 
Member

Joined: Sep Mon 28, 2009 1:53 am
Posts: 121
Location: Bloomington, IN
Chas wrote:
The .27mf bypass cap cannot be in series with the 1st AF transformer, there will be no plate current for the detector.


That's what I figured. Ran into this problem with that Equitable Claratone I brought to the groups several weeks back. Someone with no knowledge had rewired that in all the wrong ways.

Chas wrote:
BTW the plate or rotating coil is coupled magnetically, to the tuner coil, has to be or there would be no regeneration.


This has me a bit confused. Coil 2 is the VOLUME control, and is the only coil that moves. It rotates from a 90-degree position to lying flat just above Coil 1. Which coil are you calling the TUNING coil? Coil 2 or Coil 3? Coil 3 is connected to Coil 1 via 4 wires, for the 4 levels of sensitivity. I'd like to get the schematic totally correct so that ARF can archive it for when the next Chelsea owner comes asking.

Chas wrote:
If there are any other left over components not shown in the schematic please post...


No other components. Everything in the original set is shown in the revised schematic.

Chas wrote:
Leave off the B+ and burn the tubes at 6.6 volts rheostat dialed out for an hour or two. This is a 1st level of rejuvenation and will awaken the tubes. If the tubes are depleted then more aggressive rejuvenation is required.

Chas


Will do.

PS: I was thinking about your notion that the set had been hacked. As I noted, the wiring/solder joints appears original (and much wiring will need to be replaced, as its rubberized covering is cracked and flaking off). The transformers and variable cap are labelled as "Chelsea". I'm beginning to wonder if this might have been a kit vs. an assembled & tested Chelsea product. Explains how the components are Chelsea and how the wiring was so wrong.

The kit builder got it much of it wrong, and simply gave up on it. I can see a kit going vs. $15-20 in 1924 vs. $40+ for an assembled radio. The fact that the cabinet has a factory plate on the back with a connection post labelled "A+/B-" makes me think this is a generic plate (given the 1923 schematic above, which shows an "A-/B-") connection), and Chelsea may have offered several kits of varying complexity (such as hand-building the two variometers shown in the 1923 schematic). Hard to say without more documentation about Chelsea Radio Co.


Top
 Profile  
 
 Post subject: Re: Schematic for Chelsea Radio Co. Model 122
PostPosted: Dec Thu 07, 2017 9:17 pm 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 11539
Location: S. Dartmouth MA 02748-1225 USA
I recall we work together on the Claratone :D

Many radio manufacturers "simplified" controls by renaming them. The regeneration can be called "volume" and it will do exactly that, however, the regeneration in some designs will pull the tuning frequency so the filament control is used for the volume, it too will pull regeneration...

As I said earlier, some early radio designs, the controls will interact.

For AM reception the radio is never set to regenerate. The heterodyne tone caused by regeneration is not only annoying, not as loud and sets the radio into oscillation that can blanket the neighborhood at the tuned frequency. Optimum is setting is just below oscillation. Another "problem" with "critical" regeneration setting is manipulating the tuning will change the regeneration, either greater or lesser sensitivity. The four taps on the tuning coil would control sensitivity to some degree but also shift the tuning rage. That fact alone makes locating stations repeatably difficult unless a tuning chart is used. Hand capacity adds to the "fun"...

So, it does not matter what one calls the controls so long as it is understood how to use them effectively.

As for the Chelsea being a kit. Dunno if they made kits, an advertisement for a kit would confirm that.

The rubber wire will be hard to duplicate. Possibly some 20 ga. 300 volt black strand from Alpha may look close, go to 600 volt if the 300 volt insulation plastic isn't as thick as the rubber. Pull the wire through acetone to remove the label while sticky, pull through some talc in a cotton ball, that should make it look authentic. Talc is often used on rubber to keep it from sticking together.

So far your batting 1000 finding obscure battery sets with no published schematic...

Candidates for Merrill Bancroft's "Rare 1920's Battery Sets": viewtopic.php?f=1&t=328478&start=20

Chas


Top
 Profile  
 
 Post subject: Re: Schematic for Chelsea Radio Co. Model 122
PostPosted: Dec Fri 08, 2017 2:11 am 
Member

Joined: Sep Mon 28, 2009 1:53 am
Posts: 121
Location: Bloomington, IN
Chas wrote:
So far your batting 1000 finding obscure battery sets with no published schematic...

Candidates for Merrill Bancroft's "Rare 1920's Battery Sets": http://antiqueradios.com/forums/viewtop ... 8&start=20

Chas


I may have another. An early Freshman Masterpiece (no C voltage), and instead of a serial number, the nameplate shows "Kit 3678". "Kit" is printed; the number is stamped.

Went looking for voltages for this one, since everything seems good, but no mention of a kit!


BTW: here's the updated schematic for the Chelsea:

Image

I'll likely get the new faceplate made before I put it back together. May be a few weeks before I have the results of the changes.


Top
 Profile  
 
Post New Topic Post Reply  [ 15 posts ]  Moderators: Marcc, Norm Leal

All times are UTC [ DST ]


Who is online

Users browsing this forum: Crist Rigotti, Hondo, jhbowman, John Bartley, Lee Petrie, Tdlunsfo and 17 guests



Search for:
Jump to:  


















Privacy Policy :: Powered by phpBB