HEATHKIT IN-37 Resistance Substitution Box Instruction Manual
- June 5, 2024
- HEATHKIT
Table of Contents
Assembly and Operation of the
RESISTANCE SUBSTITUTION BOX MODEL IN-37
**HEATH COMPANY BENTON
HARBOR, MICHIGAN 49022**
SPECIFICATIONS
Range……………..15 ohms to 10 megohms.
Accuracy ……………….*10% EIA values.
Power Rating …………..1 watt, all values.
Voltage Rating……………500 volts continuous.
Dimensions………………6″ long x 3″ wide x 3″ high.
Net Weight …………………1 lb.
The Heath Company reserves the right to discontinue instruments and to change
specifications at any time without incurring any obligation to incorporate new
features in instruments previously sold.
Refer to the “Kit Builders Guide” for complete information on unpacking, parts
identification, tools, wiring, soldering, and step-by-step assembly
procedures.
DESCRIPTION
The Model IN-37 Resistance Substitution Box was designed to provide a rapid
and flexible means of determining the resistance Naluec required in electronic
circuits.
The “shorting type” switches with make-before-break action permit smooth
selection of the resistance values without opening or shorting the circuit.
The HI-LO switch makes it possible to switch from one range switch to the
other for high or low-value resistances. Each resistance value that can be
selected is marked by value on the front panel. All values are EIA standards
so that resistors of the same values can be obtained.
PARTS LIST
Unpack the kit carefully and check each part against the Parts List. The numbers in parentheses in the Parts List correspond to the numbers of the parts drawings to aid in quick and positive parts identification.
| PART NO | PARTS Per kit | DESCRIPTION |
|---|---|---|
| RESISTORS | 1 | Watt |
| 1 – 12 – 1 | 1 | 15 Ω (brown-green-black) |
| 1-13-1 | 1 | 22 Ω (red-red-black) |
| 1-14-1 | 1 | 33 Ω (orange-orange-black) |
| 1-15-1 | 1 | 47Ω(yellow-violet-black) |
| 1-16-1 | 1 | 68 Ω (blue-gray-black) |
| 1-17-1 | 1 | 100 Ω (brown-black-brown) |
| 1-18-1 | 1 | 150 Ω (brown-green-brown) |
| 1-19-1 | 1 | 220 Ω (red-red-brown) |
| 1-20-1 | 1 | 33.0 Ω(orange-orange-brown) |
| 1-1-1 | 1 | 470 Ω (yellow-violet-brown) |
| 1-21-1 | 1 | 680 Ω(blue-gray-brown) |
| 1-2-1 | 1 | 1000 Ω (brown-black-red) |
| 1-22-1 | 1 | 1500Ω (brown-green-red) |
| 1-23-1 | 1 | 2200 Ω (red-red-red) |
| 1-3-1 | 1 | 3300 Ω(orange-orange-red) |
| 1-24-1 | 1 | 4700Ω(yellow-violet-red) |
To order a replacement part. use the Parts Order Form furnished with this kit. If a Parts Order Form is not available. refer to “Replacement Parts” inside the rear cover of the Ms Maui. For pricing information, re I- r to the separate “Heath Parts Price last.”
| PART NO. | PARTS Per Kit | DESCRIPTION |
|---|---|---|
| Resistors | 1Waat | cont”d. |
| 1-25-1 | 1 | 6800 Ω(blue-gray-red) |
| 1-9-1 | 1 | 10 K Ω (brown-black-orange) |
| 1-26-1 | 1 | 15 K Ω (brown-green-orange) |
| 1-5-1 | 1 | 22 K Ω(red-red-orange) |
| 1-27-1 | 1 | 33 K Ω(orange-orange-orange) |
| 1-7-1 | 1 | 47 K Ω (yellow-violet-orange) |
| 1-8-1 | 1 | 68 K Ω (blue-gray-orange) |
| 1-28-1 | 1 | 100 K Ω (brown-black-yellow) |
| 1-29-1 | 1 | 150 K Ω (brown-green-yellow) |
| 1-30-1 | 1 | 220 K Ω(red-red-yellow) |
| 1-31-1 | 1 | 330 K Ω (orange-orange-yellow) |
| 1-32-1 | 1 | 470 K Ω (yellow-violet-yellow) |
| 1-33-1 | 1 | 680 Ω(12 (blue-gray-yellow) |
| 1n34-1 | 1 | 1 megohm (brown-black-green) |
| 1-35-1 | 1 | 1.5 megohm (brown-green-green) |
| 1-36-1 | 1 | 2.2 megohm (red-red-green) |
| 1-37-1 | 1 | 3.3 megohm (orange-orange-green) |
| 1-38-1 | 1 | 4.7 megohm (yellow-violet-green) |
| 1-39-1 | 1 | 6.8 megohm (blue-gray-green) |
| 1-40-1 | 1 | 10 megohm (brown-black-blue) |
| PART NO | PARTS Per Kit | DESCRIPTION |
| --- | --- | --- |
HARDWARE
(1)250-213| 4| 4-40 x 5/16″ screw
(2)250-9| 2| 6-32 x 3/8″ screw
(3)252-3| 2| 6-32 nut
(4)252-7| 2| Control nut
(5)253-1| 2| Fiber flat washer
(6)253-2| 2| Fiber shoulder washer
(7)253-10| 2| Control flat washer
(8)254-4| 2| Control lock washer
(9)259-1| 2| Solder-lug
MISCELLANEOUS
60-4| 1| SPDT slide switch
63-451| 2| Rotary switch
:10)100-16-2| 2| Binding post cap
203-415-2| 1| Front panel
11)213-1| 1| Resistor mounting ring
408-11| 1| Case
12) 42 7- 3| 2| Binding post base
462-245| 2| Knob
:131455-50| 2| Knob bushing
44-59| 1| Hookup wire
091-34| 1| Blue and white identification label
597-260| 1| Parts Order Form
597-308| 1| Kit Builders Guide
| 1| Manual (See front cover for part number.)Solder
PARTS PICTORIAL
ASSEMBLY
The following instructions are presented in a logical step-by-step sequence to
enable you to complete your kit with the least possible confusion Be sure to
read each step all the way through before bev. innit,2 the specified
operation. Also, read several steps ahead of the actual step being performed.
This will familiarize you with the relationship of the subsequent operations.
When the step is completed, check it off in the space provided. This is
particularly important, as it may prevent errors or omissions, especially if
your work is interrupted.
In general, the illustrations in this manual correspond to the
NOTES
the actual configuration of the kit; .however, in some instances, the
illustrations may be slightly distorted to facilitate clearly showing all of
the parts.
When soldering, position the work, if possible, so that gravity will help to
keep the solder where you want it. The joint to be soldered should be heated
with the flat side of the soldering iron tip sufficiently to melt the solder.
Apply only enough solder to the heated terminal to thoroughly wet the
junction. Remove the solder and then the iron when a smooth soldered junction
appears. Do not move the leads until the solder is solidified.
ROSIN CORE SOLDER HAS BEEN SUPPLIED WITH THIS KIT. THIS TYPE OF SOLDER MUST BE
USED FOR ALL SOLDERING IN THIS KIT. ALL GUARANTEES ARE VOIDED AND WE WILL NOT
REPAIR OR SERVICE EQUIPMENT IN WHICH ACID CORE SOLDER OR PASTE FLUXES HAVE
BEEN USED. IF ADDITIONAL SOLDER IS NEEDED, BE SURE TO PURCHASE ROSIN CORE
(60:40 or 50:50 TIN-LEAD CONTENT) RADIO TYPE SOLDER.
Refer to Pictorial 1 for the following steps,
STEP-BY-STEP ASSEMBLY
Mount binding posts at A and B on the front panel, Use the fiber shoulder
washers, fiber flat washers, solder lugs, and 6-32 nuts as shown in Detail 1A.
Position the solder lugs as shown.
Install binding post caps on the binding posts at A and B.
Mount the SPDT slide switch (#60-4) at location C on the front panel. Use two
6-32 x 3/8″ screws.
Look into the edge of each of the two rotary switches and notice the position
of the rotor contact. If the rotor contact is not at lug 1, turn the switch
shaft with a pair of pliers until the rotor is at lug 1. See Detail 1B,
Mount the two rotary switches at D and E with control lock-washers, control
flat washers, and control nuts. Position lugs 1 and 19 of each switch as shown
in Pictorial 1.
Refer to Detail IC and notice that the knob bushing is tapered. Br sure. in
the next step. to place this bushing on the shaft %dill the small end faring
out. or the knob will not slide onto it. (Roll the bushing on a flat surface
if you are unsure about it: the hushing will gradually turn toward the small
end.)
In the following steps, you will install a knob un each of the two switch
shafts as shown in Detail IC. Perform these steps carefully. as a knob bushing
cannot lw removed from a knob once it is fully inserted.
- Push a knob bushing part way onto each of the two switch shafts.
- At the switch location nearest the binding posts, line up the pointer of a knob with the 15 K mark on the panel. Then press the knob slightly onto the bushing.
- At the other switch location, line up the pointer of a knob with the 15 mark on the panel. Then press the knob lightly onto the bushing.
- Turn the knob clockwise to each of the switch stop positions. Check to see that the pointer lines up with each panel marking.
NOTE: Perform the next three steps only if either pointer does not line up at each switch marking.
-
( ) Turn the knob pointer to a selected marking on the panel.
-
( ) Remove the knob from the bushing and turn it slightly to line up the pointer with the selected marking.
-
( ) Press the knob slightly onto the knob bushing. Then turn the knob to each switch position and recheck the pointer alignment. If more than a slight error is noticed at either end position, repeat these three steps.
( ) Carefully remove the knob bushing and knob together.
( ) Place the knob on a table or other hard surface, then press the knob bushing firmly into the knob. Use a towel of soft cloth on the work surface to avoid scratching the knob.
( ) Press the knob and bushing firmly onto the switch shaft,
( ) Repeat the above Knob Installation steps to install a knob on the other switch shaft.
(
) Cut three hookup wires, one 1-1/2″, one 3-3/4″, and one 3″. Remove 1/4″ of
insulation from the ends of these wires.
( ) Solder a 1-1/2″ wire from lug 19 of switch D to lug 3 of switch C.
( ) Solder a 3-3/4″ wire from lug 19 of switch E to lug 1 of switch C.
( ) Solder a 3″ wire from lug 2 of switch C to binding post base B.
Refer to Pictorial 2 for the following steps.
NOTE: The major portion of the wiring consists of connecting the
resistors between the rotary switches and the resistor mounting ring. This
wiring should be done as neatly as possible, and as instructed.
- Cut one lead of each resistor to 3/8″. The other lead of the resistor should not be cut.
- Form a hook in the cut lead of each resistor. Refer to Detail 2A.
- Arrange the resistors in order starting with the lowest value, 15 C2 (brown-green-black) and proceed to the highest value, 10 megohms (brown-black-blue). The resistors are listed in this sequence in the Parts List.
Connect the resistors to rotary switch E according to the following chart. Position each resistor so that the resistor lead hooks into the switch lug from the outside, then solder. Refer to Detail 2A. The resistor mounting ring will be installed after all the resistors are connected to the switches.
| CONNECT A | TO LUG |
|---|---|
| ( ) 15 KS/ (brown-green-orange) | 1 |
| ( ) 22 KS/ (red-red-orange) | 2 |
| ( ) 33 KCI (orange-orange-orange) | 3 |
| ( ) 47 K51 (yellow-violet-orange) | 4 |
| ) 68 KS2 (blue-gray-orange) | 5 |
| --- | --- |
| ) 100 Kg? (brown-black-yellow) | 6 |
| ) 150 KS-1 (brown-green-yellow) | 7 |
| ) 220 K.S2 (red-red-yellow) | 8 |
| ) 330 KS2 (orange-orange-yellow) | 9 |
| ) 470 KSZ (yellow-violet-yellow) | 10 |
| ) 680 1CS-Z (blue-gray-yellow) | 11 |
| ) 1 megohm (brown-black-green) | 12 |
| ) 1.5 megohm (brown-green-green) | 13 |
| ) 2.2 megohm (red-red-green) | 14 |
| ) 3.3 megohm (orange-orange-green) | 15 |
| ) 4.7 megohm (yellow-violet-green) | 16 |
| ) 6.8 megohm (blue-gray-green) | 17 |
| ) 10 megohm (brown-black-blue) | 18 |
Slip the resistor mounting ring over the resistor mounted on the rotary
switches. The resistors should be placed on the inside of each circle as shown
in Detail 2B. The mounting ring should be pushed close to the resistor bodies
and the leads bent around the mounting ring to make a good mechanical
connection, Cut off the excess resistor lead lengths. Now flow solder smoothly
over each joint.
( ) Solder a 2″ wire from binding post base A to the resistor mounting ring,
NOTE: The blue and white identification label shows the Model Number and
Production Series Number of your kit. Refer to these
numbers in any communications with the Heath Company; this assures you that
you will receive the most complete and up-to-date information in return,
( ) Carefully peel away the backing paper from the identification label, Then
press the label into position on the inside of the case,
) Refer to Pictorial 3 and mount the front panel in the case with the 4-40 x
5/18″ screws. Do not overtighten the screws or you may damage the case, This
completes the assembly,
APPLICATIONS
In radio or television service work, the Heathkit Resistance Substitution Box
will prove of great assistance in experimentally determining the desired value
of a charred or unmarked resistor through temporary substitution. It can also
be substituted for any resistor in a circuit so that the value of the resistor
may be changed during operation in order to determine the desired resistance
value that will provide maximum circuit performance. No attempt will be made
to detail all of the various applications; through continued usage, many
additional applications of the Resistance Substitution Box will suggest
themselves to the serviceman.
In laboratory or circuit development work, the Resistance Sub-
stitution Box will prove invaluable. The advantages of using several
Resistance Substitution Boxes are obvious, as any change in a circuit constant
usually requires a corresponding change in some other component. By having
Resistance Substitution Boxes connected in the plate, grid, cathode or screen
supply circuits, the entire experimental setup can be quickly changed.
Because the Heathkit Resistance Substitution Box kit uses standard EIA values,
it is possible to select from your working stock the exact resistor needed for
any application. The resistors used are all rated at I watt and this rating
should not be exceeded in use. The continuous operating voltage rating of 500
volts should be observed to prevent a flashover within the unit.
IN CASE OF DIFFICULTY
- Recheck the wiring. Trace each lead in colored pencil on the Pictorial as it is checked. It is frequently helpful to have friends check your work. Someone who is not familiar with the unit may notice something consistently overlooked by the constructor.
- It is interesting to note that about 90% of the kits that are returned for repair do not function properly due to poor connections and soldering. Therefore, many troubles can be eliminated by reheating all connections to make sure that they are soldered properly.
- Check the values of the component parts. Be sure that the proper part has been wired into the circuit, as shown in the pictorial diagrams and as called out in the wiring in-instructions.
- Check for bits of solder, wire ends or other foreign matter which may be lodged in the wiring.
- An ohmmeter can be used to check the resistance values as the switches are turned to each position. Make sure the knob pointers line up properly with the markings on the panel. Refer to the Kit Builders Guide for Service and Warranty information.
NOTE: In extreme ease where you are unable to resolve a difficult). refer to the “Customer Service” information inside the rear cover of the Manual. Your Warranty is located inside the front cover.
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