Heathkit ID 4850 Manual

Page 1

HEATHKIT®
MANUAL.

HEATH COMPANY - BENTON HARBOR, MICHIGAN

Page 18

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Heathkit

Section 3

( ) swaoz.
( ) swam.
( ) swaog.

Section 4

SWGIB.
SW615.
SW614.
SW613.
SWGIZ.
SW611.

[ ) Carefully remove and discard the pin from
either end of the four 20-pin plugs to make
19-pin plugs as shown in the illustration
below.

REMOVE END
PIN AND DISCARD

PRESS SHORT END
OF ALL REMAINING
PINS EVEN WITH

PLUG BODY

PREPARED 19-PIN PLUG

[ ) Use a pair of pliers to press the short end of
the pins on the four 19-pin plugs down into
the plug body until the end of the pins are
even with the bottom of the body as shown
above.

Section 1

[ ] Carefully insert the pins of a 19-pin plug into
the circuit board holes on the component side
of the board at P601 and press the plug body
flat against the board as shown. Solder the
pins to the foil and be careful not to get any
solder on the upper portion of the pins.

COMPONENT SIDE
OF DISPLAY
CONTROL BOARD

( ] Similarly, install a 19-pin plug at P602 in Sec-
tion 2.

( ) Similarly, install a 19-pin plug at P603 in Sec-
tion 3.

[ ] Similarly, install a 19-pin plug at P604 in Sec-
tion 4.
CIRCUIT BOARD CHECKOUT

Carefully inspect the circuit board for the following
problems.

[ ) Unsoldered connections.

[ ) Poor solder connections.

( ) Solder bridges between foil patterns.

[ ) Protruding leads which could touch together.

This completes the circuit board assembly. Set it
aside until it is called for later.

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Page 23

[ ) Similarly insert the remaining ribbon cable
wires, in the order they appear on the cable,
into the socket holes 2 through 25. Be careful
not to cross any of the wires when you install
them.

( ] Position the polarizing pin with the tab as
shown and insert the pin into hole 5 [black
wire) of the ZS-hole socket.

( ) Position the free end of the 25-conductor rib-
bon cable at P501 with the outside yellow wire
at hole 1. Then insert the wires into the circuit
board holes at P501 in the order they appear
on the cable. Solder the wires to the foil after
you connect them and cut off the excess wire
lengths. Be careful not to cross any of the wires
when you connect them. '

[ 1 Carefully recheck the 3-wire and the 25-wire
cable wiring at both ends to make sure that
none of the wires are crossed.

( ) Remove the outside black wire from the re-
maining 25-conductor ribbon cable and re-
move 1/4" of insulation from the ends. Discard
the remaining 25-conductor ribbon cable but
save the remaining 8-wire ribbon cable.

[ ] Connect one end of the black wire to the indi-
cated hole next to capacitor C507. Solder the
wire to the foil and cut off the excess wire
length. NOTE: You will use this wire as the
ground (GND) connection for the Resistance
Checks."

CIRCUIT BOARD CHECKOUT

Carefully inspect the circuit board for the following
problems.

[ ] Unsoldered connections.

[ ) Poor solder connections.

( ) Solder bridges between foil patterns.

[ ] Protruding leads which could touch together.

Refer to Pictorial 2-2 and Detail 2-3A as you make
the following visual checks.

{ ] Transistor for the proper type and installation.
[ ] le for the proper type and installation.

[ ) Electrolytic capacitors for the correct position
of the positive [+) or negative (-] marked
ends.

RESISTANCE CHECKS
Refer to Pictorial 24 for the following steps.

You will need a VOM [volt ohmmeter). a VTVM
(vacuum tube voltmeter), or a DVM [digital voltme-
ter) for the following tests. You will use the voltme-
ter function for voltage tests later in this Manual.
The voltmeter should have at least a 10 MI) input
impedance.

When a specific part (such as U503) is called out
as a possible problem. check that part for such errors
as improper installation, soldering, or wrong part in-
stallation. Also check the circuitry associated with
that part for similar errors.

Connect the common meter lead to the block wire
next to C507 and the positive lead to the following
test points.

TEST POINT # RESISTANCE POSSIBLE CAUSE

RANGE OF PROBLEM

( )TP1 (U507. pin 4) Greater than U503
4 kn

( )TP2 (U507. pin 7) Greater than U504
10 k1!

( )TP3 (U501. pin 16) Greater than 5-volt toil shorted
50k!)

[ ) Disconnect the ohmmeter leads and set the
ohmmeter aside.

( ) Cut off and discard the black ground wire from
the circuit board.

This completes the circuit board assembly. Set it
aside until it is called for later on.

g

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KEY HEATH QTY. DESCRIPTION CIRCUIT
No. Part No. Comp. No,
#8 Hardware

D1 250-1436 1 8-32 X 3/8" phillips screw

D2 250-1476 1 8-32 x 11'2 phillips flat-head screw

D3 252-4 2 8-32 nut

D4 254-2 2 #8 lockwasher

Other Hardware

E1 253-198 1 Nylon shoulder spacer

E2 255-49 6 5/ 1 6" round spacer

E3 255-860 2 3/8 hex spacer

E4 255-757 2 Threaded hex spacer

E5 259-27 2 3/8" solder lug

figflNSISTORS - INTEGRATED CIRCUITS
5

NOTE: Transistors and integrated circuits may be marked for iden-
tillcation in any one of the following four ways:

1_ Pan number.

2. Type number, (This refers only to the numbers and
letters shown in BOLD print In the Parts list. Disre-
gard any other numbers or letters shown on the de-

vice.)
3. Part number and type number.
4_ Part number with a type number other than the one
shown.
F1 417-902 1 NPD5566 transistor 0311
F1 417-975 2 CA3127 tranSIstor 0105. 0205

CAUTION: Some of the following integrated circuits can be easily
damaged by static electricity. DO NOT remove any le that are
installed in conductive loam pads until you are instructed to do so
in a step.

F2 442-54 1 UA7805 IC U1
F1 442-640 4 CASOBO IC U103, U104.
U203. U204

W4
mm

F1 442-751 2 LM1408N-8 IC U301. U506
F1 442-759 8 LF4111C U101. U102,
U201. U202.
U302. U309.
U313. U507

KEY HEATH
No. Part No.

QTY. DESCRIPTION

Integrated Circuits (Contd)

F1
F1
F1
F1
F1
F1
F1
F1
F1
F1
F1
F1

F1

F1
F1
F1
F1
F1
F1
F1
F1
F1
F1

F1
F1
F1
F1
F1

442-768
442-769
442-771
442-782
443-636
443-679
443-683
443-730
443-794
443-795
443-81 1
443-863

443-877

443-885
443-896
443-942
443-948
443-951
443-952
443-953
443-967
443-992
443-1 020

443-1027
443-1039
443-1080
443-1367
444-344 - l

d-_.__._._._._t_._.

to

QM-.._._._._._._.

1
1
1
1
1

DAC1D21 IC
ADCOBZO IC
LM361 IC

LF357 IC
MC10116 IC
MC1 0131 IC
MC10102 IC
74LS74 IC
75188 or 1488 IC
75189 or 1489 IC
74LS125 IC
74LS374 IC

74LS138 IC

74L5245 IC
74502 IC
74LS123 IC
74LS112 IC
74L551 IC
8250 IC
3880/ZBOA IC
7406 IC

4051 IC

7407 IC

6116-P4 IC
74LS365A
74AL500 IC
74HCT00 IC
2764-3 IC

PINS - CONNECTORS

G1
52
G3
G4
G4

G4

432-1 20
432-1 033
438-55
432-1 1 42
432-866

432-753

2
9
1

Female pin

CIRCUIT
Comp. No.

U312
U415
U31 1
U105
U303
U305
U304
U401
U405
U404
U502
U417. U418.
U419. U421.
U422. U423.
U505. U503.
U509. U511.
U512. U513.
U514
U412. U413.
U501
U416
U106
U428
U402
U414
U407
U406
U305
U307. U308
U425. U426.
U427
U41 1
U409
U403
U424
U408

Gold male pin (includes one extra)

Polarizing pin

Small gold-plated spring connector

(includes one extra)

Small spring connector (includes two

extra)

Large spring connector (includes two

extra)

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( ) Disconnect the meter leads and set the meter
aside.

[ ) Refer to Detail 5-1A Part 1 and remove the
backing from the two 1X 4" strips of insulat-
ing paper. Press the paper onto the shield
flanges with the creases in the corners.

[ } Refer to Detail 5~1A Part 1 and remove the
backing from the 24/2 square insulating
paper and press the paper against the inside
of the shield as shown.

[ ) Remove the paper packing from the Danger
label and press it against the AC shield.

[ ) Mount the shield to the rear of the chassis with
two #6 X 1/4 phillips screws. Make sure that
you do not pinch any of the wiring between
the shield and the chassis. and that the shield
is between capacitors C407 and C408 as
shown.

This completes the Primary Wiring Checks." If all
of the checks were satisfactory, proceed to Voltage
Checks."

VOLTAGE CHECKS

Refer to Pictorial 5-1 for the following steps.

When you apply power to your Digital Memory Os-
cilloscope. if you experience any difficulties. turn
the power off and disconnect the line cord. Do not
proceed with any other tests until you correct the
problem.

WARNING: When the line cord is plugged into an
AC outlet. potentially hazardous voltage is present
in the area covered by the AC shield. Do not remove
this shield with the line cord connected to an AC
outlet; you could receive a severe electrical shock
if you should come in contact with the AC voltage.

[ ] Refer to Detail 5-13 and push the alignment
tool blade into the small end of the plastic nut
starter. Always use this tool to adjust the main
circuit board controls.

( ] Position the front panel assembly next to the
chassis assembly as shown. Connect 25-hole
socket $501 to main circuit board plug P401.
The plug is polarized to fit only one way.

( ) If it is not already there. set the POWER switch
to off.

[ ) Connect the Digital Memory Oscilloscopes
line cord to an AC outlet.

Refer to the following chart and perform the mea-
surements in the following manner:

1. Set the voltmeter range switch for each
step. if possible. to obtain a near full-
scale DC reading.

2. Connect the positive voltmeter lead to
the indicated test point [TP] location and
the negative (common) voltmeter lead to
the indicated power transformer screw.

3. If you do not get the proper response at
one of the test points. first check your
voltmeters accuracy. If its okay. then
refer to the Possible Cause of Problem"
column. You may also want to refer to
the In Case of Difficulty" section on
Page 65. Make sure you correct any prob-
lems before you go on to install the [Cs
in the next section.

NOTE: When a specific part is called out in a voltage
chart as the possible cause of a problem. such as
U101. it could mean that the part was not soldered
properly. or it was installed incorrectly. [backwards
bent pins, wrong part. etc.). or that the associated
circuit components are incorrectly installed or are
interchanged.

( ] Press the POWER switch to turn the unit on.