Sparton Equasonne Radios

Sparton Equasonne Vacuum Tubes

Tubes used in the various Equasonne models are no longer manufactured.  You must either obtain ‘used’ tubes that have been pulled out of some other less fortunate radio, or New Old Stock (NOS) tubes (tubes which have never been used, but rather have been sitting around, probably in their original boxes, for 80+ years waiting to be used).

Although you might get lucky and come across some old vacuum tubes at a flea market, auction, thrift store or something of that nature, it might take some time to come across appropriate tubes for the Equasonne this way.

Tubes can be obtained from several on-line stores, which often test and guarantee the tubes they sell for some period of time at least. 

Not all Equasonne models use the same tubes, and some allow for a choice of tubes to be used.  To utterly complicate things, many, but not all, of the tubes used in Equasonne sets were unusual "Sparton" type tubes. These were used in Equasonnes, and a couple of other Sparton radios, but I am unaware of any radio sets made by other companies that used them. It would appear that Sparton was playing some sort of game with the design of these tubes. They are electrically very similar to other more conventional tubes of the era, and mainly differ in heater voltage. A 485 tube, for example, is essentially a 27 tube with a 2.5V filament rather than a 3 volt filament. I am imagining that this discouraged users from using non-Sparton tubes as replacements, as they would likely have a shorter lifespan since they would be running over-voltage. 

Sparton made its own vacuum tubes, but for a time they were made by a spin-off company called Cardon. The name of the company was derived from a combination of the names Carter and Donald, the grandsons of William Sparks. For this reason Sparton tubes are often prefixed with the letter C, as in C-485. Interestingly, all Cardon branded Sparton tubes have the C- prefix on the number, but Sparton branded tubes occasionally do not. Not sure what was up with that... Anyways, ignore the C- prefix in the tube number when searching for replacements. A 485 and a C-485 are the same tube.

These unusual Sparton tubes also have their own numbering system, which is incompatible with the system used by other companies, which causes some confusion.  For example, an old globe style type 80 rectifier tube is often found labelled as 280, the 2 is a manufacturer code, and can generally be ignored. When shopping for a replacement, you need an 80. In the case of several Sparton tubes, this is not the case.  The tubes have three digits, but they all count. Several models use a power output tube numbered as 183, or sometimes 483. These are both the same tube, and the first digit cannot be ignored, the tube is not an 83. It is not unusual for radio restorers to be left wondering why their radio uses 83 rectifier tubes as audio amplifiers! (an 83 is a rectifier tube).

Some Sparton tube data is presented in the table below.  Also, Service Bulletin 7B, located in the Service Bulletin section of this website details the exact tube types that go in each Equasonne model.  By far, the two most common Equasonne models are the 931 and the 301. The 931 uses an 80 rectifier, six 484 (or 485) tubes. [do not mix and match, use all of one type or the other], and a pair of 182-B or 183 (same as 483) power output tubes. The 301 uses a pair of 81 rectifier tubes,  six 484 (or 485) tubes. [do not mix and match, use all of one type or the other], and a pair of 585 or 586 tubes. 

It would appear that Sparton abandoned its use of weird Sparton specific vacuum tubes in the early 1930s, and carried on producing radios that used conventional types of vacuum tubes after that. Existing stocks of odd Sparton tubes seem to have been used up by designing them into a couple of early non-Equasonne sets produced in about 1931, the Sparton junior for example uses a pair of 183 tubes.  It is a wonder that Sparton tubes can even be found today. Likely it would be much harder to find them than it actually is, if it were not for the fact that Sparton and quite a few other tube manufacturers (Philco, Sylvania etc) continued to make these unusual tubes for replacement purposes for quite a number of years after Equasonnes were no longer made.  More modern ST versions of these tubes are actually quite common.

Some on-line Sources for tubes:


Antique Electronic Supply, Tempe, Arizona

Tubes Tubes Tubes, Orono Maine

Play things of The Past, Cleveland, Ohio

I will add more as I find them.  Since most of the tubes used in Sparton Equasonne radios are in short supply, store inventories change rapidly, so you might have to hunt around a bit.  Tubes are often available on eBay. 

Sparton tube data

 

Tube

 Type

Base

Use

"A" supply

Filament voltage

Filament current amps

Detector plate voltage

Detector Plate current mA

Amplifier plate voltage

Grid voltage

Amplifier plate current mA

Plate impedance Ohms

Mutual conductance micromhos

Amp

factor

C-112-A

standard 4 prong

Power amplifier

Storage 6 volt transformer 5 volts

5.0

0.25

-

-

135
157.5
180

-9.0
-10.5
-13.5

7.0
9.5
7.8

5000
4700
4700

1600
1700
1700

8.0

C-181

Side pin 4 prong

Power amplifier

Transformer 3 volts

3.0

1.3

-

-

200

-40

16

2850

1050

3.0

C-182

Standard 4 prong

Power amplifier

Transformer 5 volts

5.0

0.9

-

-

200

-45

18

2000

1500

3.0

C-182-A

Standard 4 prong

Direct Current Power amplifier

Transformer 5 volts

5.0

0.8

-

-

200

-45

18

2000

1500

3.0

C-182-B

Standard 4 prong

Power amplifier

Transformer 5 volts

5.0

1.25

-

-

200

-29

18

3330

1500

5.0

C-183

Standard 4 prong

Power amplifier

Transformer 5 volts

5.0

1.25

-

-

200

-45

20

2000

1500

3.0

C-210

Standard 4 prong

Power amplifier

Transformer 7.5 volts

7.5

1.25

-

-

350

-27

20

5500

1450

8.0

C-231

Standard 4 prong

Power amplifier

6 dry cells series Parallel

2.0

0.150

-

-

135

-22.5

8.0

4000

575

3.5

C-245

Standard 4 prong

Power amplifier

Transformer 2.5 volts

2.5

1.5

-

-

180
250

-33
-50

26
32

1460
2250

2400
1450

3.5

C-586

Standard 4 prong

Power amplifier

Transformer 7.5 volts

7.5

1.25

-

-

250
350
450

-45
-63
-84

28
45
55

2150
2000
1950

1575
1700
1750

3.4

C-201-A

Standard 4 prong

Detector Amplifier

Storage 6 volts

5.0

0.25

45

1.5

90
135

-4.5
-9.0

2.5
3.0

11000
10000

725
800

8.0

C-230

Standard 4 prong

Detector Amplifier

6 Dry cells series parallel

2.0

0.060

45

1.5

90

-4.5

2.0

12500

700

8.8

C-401

Side Pin 4 prong

Detector Amplifier

3 volts

3.0

1.3

45

2

90
120

-3
-4

5.0
6.0

9500
7000

1000
1200

9.5
8.7

C-427

Standard 5 prong

Detector Amplifier

2.5 volts

2.5

1.75

180

0.8

90

-3

5.0

10800
9300

1150

12.5

C-484

Standard 5 prong

Detector Amplifier

3 volts

3.0

1.3

135

0.8

90
120

-3
-4

5.0
6.0

10800
9300

1150
1350

12.5

C-484-A

Standard 5 prong

Direct Current Detector Amplifier

3 volts DC

3.0

1.6

100

0.5

90
120

-3
-4

5.0
6.0

9300

1150
1350

12.5

C-226

Standard 4 prong

Amplifier

1.5 volts

1.5

1.05

-

-

180

-13.5

6.0

7000

1170

8.2

C-686

Standard 5 prong

Amplifier

Storage 6 volts

3.0

0.25

-

-

90

-3.0

3.0

28000

450

12.5

C-224

Standard 5 prong

Screen Grid Amplifier

Storage 6 volts Transformer 2.5 volts

2.5

1.75

Screen Grid voltage plus 90

-

180

-3.0

4.0

400000

1000

400

C-232

Standard 4 prong

Screen Grid Amplifier

6 dry cells Series Parallel

2.0

0.060

Screen Grid Voltage plus 67.5

-

135

-3.0

1.5

800000

550

440

C-280

Standard 4 prong

Full Wave Rectifier

5.0 volts

5.0

2.0

Max. AC Voltage per plate 350 volts RMS
Max Rectified Current 125 mA

C-281

Standard 4 prong

Half Wave Rectifier

7.5 volts

7.5

1.25

Max. AC Voltage per plate 700 volts RMS
Max Rectified Current 85 mA

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Click here to download a MicroSoft Word version of this table