Tandy 5000 MC Capacitor Replacement Guide

The 5000 MC system unit, with the power supply assembly at left and the CPU and memory boards standing above the main logic board.

No schematic or complete parts list for the Tandy 5000 MC has been found online, so no full list of its electrolytic capacitors has been published. The only capacitor values available are in Radio Shack's faxback parts lists for the machine, which list replacement parts by Radio Shack part number and give reference designators for only some of them. The configuration memory is held by two Dallas modules with internal lithium cells, which are not capacitors; see the Tandy 5000 MC General Maintenance guide. For the signs of a failing capacitor see Capacitor Failure Symptoms.

Power supply capacitors in Radio Shack's parts list

The lists for 250-6000 and 250-6002 include a group of parts that belong to a mains input and the primary side of a power supply: bridge rectifier CR101 (8 A, 800 V), surge absorbers NTC101 and NT102, line filter FL101, fuse F101 and fusible link PS101. The lists do not name the board. The capacitors with designators in that group are:

Capacitors listed with the supply parts

Ref	Value	Rating	Type as listed
C101, C102	680 µF	200 V	"ALP"
C104	2.2 µF	250 V	Polyester, radial
CX101	1 µF	250 V	Mylar or polyester (two parts listed)
CX102	0.33 µF	250 V	Mylar
CY101, CY102	0.0022 µF	400 V AC	Ceramic
C103	3300 pF	400 V	Ceramic or polyester disc (two parts listed)
C106, C109, C110, C111	0.01 µF	1000 V	Ceramic
C107, C108	1000 pF	1000 V	Ceramic
C119	0.1 µF	250 V	Mylar

C101 and C102 are the only electrolytics in the group. Fit replacements of 680 µF and at least 200 V, of the same diameter and lead spacing. Some of the same designators (C107, C111, C119) also appear in the lists against small surface-mount parts, so the lists mix parts from more than one board; check each position on the board before ordering. The CX and CY parts are mains filter capacitors; replace them only with X- and Y-rated parts of the same class.

The list for the 40 MB model, 250-6001, carries only the small ceramic capacitors, not this group.

Main logic, CPU and memory boards

The other capacitors in the lists are small ceramic and surface-mount parts from 22 pF to 1 µF, none of them listed as an electrolytic. The lists are not complete for the boards, so look at the boards themselves before ordering parts:

1. Photograph each board before starting.
2. Record every electrolytic and tantalum capacitor: designator, capacitance, voltage, temperature rating, size and polarity.
3. Replace like for like, with the same or a higher voltage rating.

Replacement procedure

1. Unplug the machine and open the case (see the Tandy 5000 MC General Maintenance guide).
2. Remove the power supply assembly; Tandy's exploded view shows it at the left of the chassis.
3. Discharge and measure C101 and C102 before working on the supply board.
4. After refitting, check +5 V, +12 V, −5 V and −12 V at main board connector J7 (pins listed in the Tandy 5000 MC Troubleshooting Guide).

Tools and parts

• Temperature-controlled soldering iron, desoldering pump or braid
• Two 680 µF 200 V (or higher) 105 °C electrolytics for C101 and C102
• X2 and Y-rated filter capacitors if CX101, CX102, CY101 or CY102 are cracked or burnt
• See Recommended Tools

Related pages

• Tandy 5000 MC
• Tandy 5000 MC General Maintenance
• Tandy 5000 MC Troubleshooting Guide