Heathkit 337 C Owners Manual

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HEATEKIT DEMODULA'IOR PROBE #337-C
The #331-C Madam: Probe greatly extends the usefulness 0! any oscilloscope. ltprovidls
:1 meme of showing modulation envelopes oi RF or IF csnriers as iound in radio and television
moivorsi Thus the oscilloscope can be used as a signal tracer, a min analyzer and an align-
ment indicator. Many other uses will become evident as the user becomes more familiar with
the characteristics oi the probe and oscilloscope combination.

A well shielded probe with the detecting elements contained in the housing is necessary for sat-
isiactory indications at high RF frequencies. The Heathsit #337-0 Demodulator Probe meets
these requirements. input leads are extremely short in order to eliminate extraneous signal
pickup which can give ialse readings. The metal probe housing is grounded to prevent hand
capacity effects irom causing deflection of the trace. Etched circuit wiring cuts down circuit
capacity, improving high irequency performance.

The input capacitor is rated at 500 volts DC and the probe shouldmt be applied moircuits where
DC voltages higher than this are ioumi. AC or RF voltages in excess of 80 volts EMS should
not be measured as damage to the crystal diode may result. However, the probe can be con-
nected to high voltage points in a unit, such as the plate of a tube, as long as the DC voltage
present does not exceed the 500 volt DC limit.

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PROBE CONSTRUCTION

NOTE: ALL GUARANTEES ARE VOIDED AND WE WILL NOT REPAIR OR SERVICE
INSTRUMENTS IN WHICH ACID CORE SOLDD? 0R PASTE FLUXES HAVE BEEN
08-. WHEN IN DOUBT ABOUT SOLD, IT IS RECOMMENDED THAT A NEW
ROLL PLAINLY MARKED "ROSDI CORE RADIO SOLDER" BE PURCHASED.

The pictorial clearly shows assembly detail oi the probe and etched circuit board. Begin con-
struction by mounting the components on the circuit board in the numbered sequence shown on
the pictorial. All parts will mount on the unmarked side of the board, with their leads coming
out on the etched side. Generally, it is best to mount all components before soldering, bending
the leads over slightly to lock the parts in place. After all parts are secured, the board should
be turned over and each lead soldered at the point where it comes through with a 25 or 50 watt
soldering iron. After soldering, all leads should be clipped oft.

For best soldering results, a 25 to 50 watt iron is recommended. The up should be clean and
well tinned in order to obtain a quick, clean solder joint. Hold the tip of the iron at the iunction
of the component lead and the etched board conductor, and apply goodquality rosin core solder
at the same point until a good connection is obtained between the two parts. When all parts are
clean, the connection can be made very quickly, preventing heat damage to resistors and con-
densers. In order to protect crystal diodes, a clamp, needle nosed pliers or some outer type
of heat barrier should be clamped on the diode lead between the diode and connection, on the
opposite side of the board from the connection.

Place the length of flat braid and the shielded cable through the black probe end. Remove 1" of
black outer insulation. Push the braid back until a bulge develops near the end of the outer in-
sulation. Bend the end over, poke a hole in the shield braid and pull center conductor through
as shown. Bend the flat braid and shield braid back together over the {lat portion of the probe
end and solder together. Make sure that the two braids areas flateas possible or it will be dif-
ficult to install the probe body.

Fit the insulator strip tight against the probe end and solder the shield lead coming from the
circuit board to the two braids near the center conductor. Cut the center conductor to a length
suliicient to reach the hole marked "lead." Strip away 1/8" of insulation and solder the center
conductor at this point. Cut off all excess wire at this end.

Prepare the probe body by inserting the large sleeve. Slip the entire assembly over the circuit
board and rear probe end and secure with two self-tapping screws. Install the phone tip in the
red probe end and remove the collar. Insert this end into the probe body, making sure that the
lead from the circuit board tip appears through the hole at the side of the tip. Secure with the
remaining sell-tapping screws, Wrap the wire around the tip in the space provided and reinstall
the collar. Solder an alligator clip to the end of the flat braid.

At the opposite end 01 the cable, strip away 3" of black outer insulation. Prepare as before.
Solder one spade lug to the shield braid and the other to the end of the center conductor. This
completes the assembly of the Demodulator Probe.

USE OF THE PROBE
standard RF signal tracing techniques can be observed using the oscilloscope and Demodulator
Probe. RF and IF signals can be traced from the second detector of the unit in question back
to the mixer and antenna circuits. The probe can be applied to the grid and plate of each stage
without the necessity of using isolation capacitors, etc. It must be remembered that the sen-
sitivity of the probe is limited by the characteristics of the oscilloscope and it will be difficult to
obtain adequate indications in low level circuits. However, strong signals will usually be evident
from the grid of the first IF stage to the second detector. indications in the first stages may
require the use of a signal generator to provide adequate signal level. Television sweep align-
ment procedures are made easier by use of the probe, for it is possible to check waveiorms at
different points in the 11 circuits as well as the overall bandpass characteristics in tuners and
boosters.
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SPEC IFICATIONS

All prices are subject to
changewithoutnotice. The
Heath Company reserves
the right to discontinue 1n-
struments and to change
specifications at any time
without incurring any oh-
ligation to incorporatenew
teatures ln instruments
previously sold.

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WARRANTY

The Heath Company limits its warranty of parts supplied with any kit (except tubes, meters and
rectifiers, where the original manufacturer's guarantee only applies) to a period at three (3)
months from the date of purchase. Replacement will be made only when said part is returned
postpaid, with prior permission and in the judgment of the Heath Company was defective at the
time oi sale. This warranty does not extend to any Heathkits which have been subjected to mis-
use, neglect, accident and improper installation or applications. Material supplied with a kit
shall not he considered as defective, even though not in exact accordance with specifications, if
it substantially iuiiills performance requirements. This warranty is not transferable and ap-
plies only to the original purchaser. This warranty is in lieu of all other warranties and the
Heath Company neither assumes nor authorizes any other person to assume for them any other
liability in connection with the sale oi Heathklts.

Phe assemblefis urged to foiiow the instructions exactly as provided, The Heath Company as-
sumes no responsibility or liability for any damages or injuries sustained in the assembly of
the device or in the operation of the completed instrument

HEATH COMPANY
Benton Harbor, Michigan

PART PARTS DESCRIPTION
No, Per Kit

1-20 I 10 Kn resistor

1-23 1 27 Kn resistor

21-11 1 150 out condenser

21-14 l .001 Md condenser

56-2 1 Crystal diode

70-4 1 Acetate insulator sleeve
85-3 1 Etched circuit board
250-1 4 Sen-tapping screw

259-7 2 spade lug

260-1 1 Alligator clip

340-2 1 length Bare wire

343-2 1 length Shielded test lead
345-1 1 length Flat braid

390-13 1 label

Ass-M2 1 Red probe tip end (tapped)
459-M3 1 Black probe tip end (not tapped)
476-M8 1 Aluminum probe body
477-3 1 Solderless phone tip
595-97 1 instruction sheet

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