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 Post subject: Does anyone have a Chelsea Model 107 or Photos of One?
PostPosted: Sep Tue 07, 2021 9:28 pm 
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I have a Chelsea Model 107 and it's obviously missing a terminal strip. I pulled it out of it's chassis to figure out what all it needed as there were some obvious issues. I need to replace the one rheostat, but what is strange is there was no obvious place to hook up power or an antenna. After going through all the wiring I finally figured out what was happening. There is a junction contact that you would usually see on the bottom of a terminal board attached to a piece of buss wire, but it was laying loose in the case. I discovered it attaches to the lower pin on the phone jack on the left side looking at the inside of the front panel. It goes straight up to where there are two nuts and screws above the rheostats that apparently serve no function. Well, they do. They would normally screw into a bracket that holds a terminal strip! I'm basing this on photos I've seen of the Model 104 and the model 102 I have in my possession. Unfortunately I don't know anyone that owns a 107 that I can compare it to.


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 Post subject: Re: Does anyone have a Chelsea Model 107 or Photos of One?
PostPosted: Sep Wed 08, 2021 6:17 am 
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Based on the mess I have, I was able to figure out how it was wired and drew up a schematic. I'm unsure of some of the wiring here as I had to guess where the terminal strip hook ups might have been. One wire I don't understand is one going from the filament on V2 above the resistor to the top of VC2. I have no Idea what that connection is all about unless that's the plate voltage for the RF tuning circuit. BTW, S2 is a ganged switch. Also, the bottom of the primary on T1 going to ground is a bit odd. This is part of the detector circuit and I've not seen a primary tied to ground like that in the detector circuit, usually it would be attached to B+ to supply voltage to the plate of the Detector.


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 Post subject: Re: Does anyone have a Chelsea Model 107 or Photos of One?
PostPosted: Sep Fri 10, 2021 10:49 pm 
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So, what's confusing is that both transformer connections on the primary of T1 are buss wire connections and look original to the radio. I did make one minor mistake on the schematic in that the C1 cap actually attaches to the bottom of the tickler coil, not the top as shown in my first schematic draft, but the same issues still exist. I do believe there should be another B+ wire. My hunch on that has to do with holes drilled into the back of the cabinet. The number of holes in Chelsea radios tend to follow the number of cinch terminals on the terminal strips. There are 9 holes, so I believe, there must be another B+ going somewhere. I had an epiphany. The buss wire going from the bottom of the T1 Primary is hitting the top of the ground buss which runs along the top of the panel. That connection looks like it's been either repaired or wasn't there to begin with. What if that buss bar isn't supposed to connect to that ground buss, but to the terminal strip B+ 45V? The only other thing tied to that piece of buss wire is the bottom of the multi-tapped L3 which I show as ground, but now change that to B+ 45V. Now I have B+ on the plate of V1 through the multi-tapped coil, B+ on the plate of V2 through T1 primary and L2, and the speaker now can have B+90V. The only issue left is the filament voltage going to the top of VC2, which I've been suspicious of from the start. So I'll eliminate that and I believe I will have a working radio! I think the previous owner may have hooked up the buss wire to the top since it went up to that area. Who knows what happened to the original terminal strip. Then maybe while trying to get something to work they shorted the filament voltage to the plate of V1 and got static. It's hard to say what the thought process was. But I think this might be a functional diagram. Many thanks to Jim Nichols of the 1920's Radios Facebook Forum for steering me in the right direction!


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 Post subject: Re: Does anyone have a Chelsea Model 107 or Photos of One?
PostPosted: Sep Sat 11, 2021 1:44 am 
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I think there is a problem with "A" distribution and the input to the detector. Note that the grid is biased with B+ the detector tube would go into full conduction.

One of the problem areas is the plate circuit of the RF tube as common to the input to the detector. Routing the grid leak to A+ takes the B+ of the detector grid and lets the grid cap block the DC from the tuned plate circuit. Ninety volts on the detector is far too much, maximum is 45 often 22-1/2, if a gas detector 18...

I suggest a complete re-draw into a more conventional schematic layout with the power input on the lower right and the common sources coming from horizontal lines. In this rendition by somewhat mimicking the diagrammatic, signal flow and voltage distribution is confusing.

Confine the ground symbol, to only the power strip as this is "A-"

I will look around for a similar circuit which uses single circuit coils for stages, I know A-K 55 does but he is not changing frequency ranges, using directly heated tubes or a 90 volt detector.

Chas

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 Post subject: Re: Does anyone have a Chelsea Model 107 or Photos of One?
PostPosted: Sep Sat 11, 2021 2:34 pm 
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Will:
Sorry, This isn't much help if any.
I ended up with most of Alan Douglas catalog collection and his photos but all I came up with is these pages from a Boston firm. I'm still looking and will do more when Kutztown is done. I have never seen most of these. I'm surprised the 104 isn't shown - it looks a lot like the 109. There are a few 104's that are around.
It may be helpful to examine the interior of a 122. It may be a follow-up of sorts of the 107. Do you have the terminal strip or, if not what it is supposed to look like? Are you sure it had one?
Merrill


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 Post subject: Re: Does anyone have a Chelsea Model 107 or Photos of One?
PostPosted: Sep Sat 11, 2021 5:41 pm 
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Location: Keystone Heights, FL, USA 32656
Here is what I see for the filament circuit.
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 Post subject: Re: Does anyone have a Chelsea Model 107 or Photos of One?
PostPosted: Sep Sat 11, 2021 10:36 pm 
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Ok, so I redrew the schematics in a more Chelsea-esq format. I did it because I do have an accurate Chelsea Super 5 schematic that I've personally verified on several sets. I drew it as it's wired with the exception of tying the buss bar that is hitting the top ground bar to B+. It shows a lot of similarities to the Chelsea Super 5 in how power is distributed.


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Chelsea 107.jpg
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Super 5 Schematic Diagram.jpg
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 Post subject: Re: Does anyone have a Chelsea Model 107 or Photos of One?
PostPosted: Sep Sat 11, 2021 11:05 pm 
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The new schematic does not show separate windings for the 2nd RF transformer. If B+ is appearing because it is not a separate winding for a secondary on the grid leak, the detector will fail.

Not that I care if the diagrammatic of the coils is correct or not but if the coil is all one winding with taps there will be a problem.

First look appears the stage jack is incorrect and that the tuned circuit return for the detector is "supposed" to go to the A+.

None the less if this is to be used to wire a set and it works, Kudos!

Chas

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 Post subject: Re: Does anyone have a Chelsea Model 107 or Photos of One?
PostPosted: Sep Sat 11, 2021 11:50 pm 
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Technopol wrote:
Ok, so I redrew the schematics in a more Chelsea-esq format. I did it because I do have an accurate Chelsea Super 5 schematic that I've personally verified on several sets. I drew it as it's wired with the exception of tying the buss bar that is hitting the top ground bar to B+. It shows a lot of similarities to the Chelsea Super 5 in how power is distributed.

I am confused. You said you drew it as-wired but in the photo nothing is connected to the amplifier rheostat (R1?).

In your schematic R1 is an adjustable short circuit between A+ and A-; not controlling anything. I am saying the filament circuit can’t work as-drawn.

Don’t know what you mean by “…buss bar that is hitting the top ground bar…”.

Minor pick, primary transformer windings are normally marked B and P.

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 Post subject: Re: Does anyone have a Chelsea Model 107 or Photos of One?
PostPosted: Sep Sun 12, 2021 2:18 am 
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jrehkopf wrote:
Technopol wrote:
Ok, so I redrew the schematics in a more Chelsea-esq format. I did it because I do have an accurate Chelsea Super 5 schematic that I've personally verified on several sets. I drew it as it's wired with the exception of tying the buss bar that is hitting the top ground bar to B+. It shows a lot of similarities to the Chelsea Super 5 in how power is distributed.

I am confused. You said you drew it as-wired but in the photo nothing is connected to the amplifier rheostat (R1?).

In your schematic R1 is an adjustable short circuit between A+ and A-; not controlling anything. I am saying the filament circuit can’t work as-drawn.

Don’t know what you mean by “…buss bar that is hitting the top ground bar…”.

Minor pick, primary transformer windings are normally marked B and P.


I'll do up an illustration on how the components are actually wired. That top bar in the picture is obviously A- or Ground. That buss bar that intersects it doesn't look like an original connection. The buss bar laying in front of the picture ties to the bottom of the Telephone jack and runs straight up to thin air. It fits perfectly with the broken solder connection on it, so I can see where it lines up. The brass strip tied to it is exactly like brass strips used to tie two cinch terminals together, which is done a lot on Chelsea Radios between A+ and B-, as well as B+ and Speaker. The bolts above the rheostats are attached to nothing. Based on other Chelsea radios, those would be used for brackets tied to a bakelite terminal strip. That would explain the brass strip with the holes in it. The buss bar from the bottom of T1 that's soldered to the A- or ground bar at the top center, if unsoldered would attach nicely to that missing terminal strip. Tying the bottom of T1 to ground makes absolutely no sense, it most likely needs to be tied to B+. So that's how I drew it. The rheostat connection was removed by me as I had pulled it to try and find another, which I couldn't but this one was rigged up for that knob with cellophane tape, so I put it back in the panel for now. So I knew it went there, I just didn't reattach the wire yet as I'm still going to replace it. I know what you mean on the filament circuit. The Rheostat R1 that is in there is fried. I think the reason they attached it the way it was drawn is due to the location of the terminals on the replacement rheostat. I will make sure both wipers are tied to A- once I find the correct rheostat. The primary winding on the Chelsea Transformer Model 50 is marked P and F, the Secondary is G and F. I have no idea why, but they have always been like that.


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Last edited by Technopol on Sep Sun 12, 2021 4:30 am, edited 2 times in total.
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 Post subject: Re: Does anyone have a Chelsea Model 107 or Photos of One?
PostPosted: Sep Sun 12, 2021 4:11 am 
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I'm thinking that the Chelsea odd transformer markings may be a mold error that was never corrected.

Since the radio is not fully wired a diagrammatic would serve but if the radio does not work the diagrammatic will be difficult to troubleshoot, but not impossible.

It is relatively easy to detect "design" errors in a schematic, with exception to component interference or stray coupling. Many radio build it yourself articles cam with both types of drawings for the inexperienced builder. All of the "101" type circuit books were schematics. It was up to the builder to decide how to position the devices.

Since device positioning is already determined in the 107. There is not much left to decide.

GL Chas

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 Post subject: Re: Does anyone have a Chelsea Model 107 or Photos of One?
PostPosted: Sep Sun 12, 2021 4:32 am 
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Here is a diagram showing EXACTLY how it's currently wired, errors and all. Note there are some missing wires as far as A-/GND and the B+ if there is a second one, which would make sense.


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 Post subject: Re: Does anyone have a Chelsea Model 107 or Photos of One?
PostPosted: Sep Sun 12, 2021 4:39 am 
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Chas wrote:
I'm thinking that the Chelsea odd transformer markings may be a mold error that was never corrected.



I might agree if the actual blueprint wasn't marked the same way. I have an actual 1925 blueprint of the Chelsea 5. The Chelsea 5 diagram above is a reproduction of it. Believe me, these radios frustrate the crap out of me sometimes, because the engineers did little things I believe to differentiate their radios from others. Truth is, I believe they would be sued by other manufacturers if they did that today because I think their radios are too close to others in design. I almost wish I could go back in time, visit the factory and ask "what on earth were you thinking!"


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 Post subject: Re: Does anyone have a Chelsea Model 107 or Photos of One?
PostPosted: Sep Sun 12, 2021 7:23 am 
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I always thought Chelsea's were oddly designed.

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 Post subject: Re: Does anyone have a Chelsea Model 107 or Photos of One?
PostPosted: Sep Sun 12, 2021 5:06 pm 
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Technopol wrote:
Here is a diagram showing EXACTLY how it's currently wired, errors and all. Note there are some missing wires as far as A-/GND and the B+ if there is a second one, which would make sense.

This is a great drawing and it matches what I was thinking about the filament hook-up. I agree, that buss wire should go to +45, not A-.

Carry on.

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 Post subject: Re: Does anyone have a Chelsea Model 107 or Photos of One?
PostPosted: Sep Mon 27, 2021 10:58 pm 
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Here arte some photos of my 104. They don't show much but it looks as though it might be tough removing the chaisis.


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 Post subject: Re: Does anyone have a Chelsea Model 107 or Photos of One?
PostPosted: Sep Tue 28, 2021 2:12 am 
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Merrill Bancroft wrote:
Here arte some photos of my 104. They don't show much but it looks as though it might be tough removing the chaisis.


Thanks Merrill, this gives me some insight on how to do up the Terminal strip in the 107. I need 9 terminals as that's how many holes are in the back of the cabinet. I'm sure the original strip, which is obviously missing, staggered the terminals like that. This helps me with the order as well.


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