Sinclair MTV1 service manual V2.1 Page 35 of 39
FAUL
T FINDING
General notes
With increasing age the electrolytic capacitors all become suspect due to possible drying out. The
1µF caps are reportedly particularly prone to this. Failure of the -45V rail smoothing cap (4µ7) can
also cause strange-looking faults.
The original design used the four 1.24V Ni-Cd cells in series as a crude voltage stabiliser.
Wherever you see +5V mentioned in the circuit diagrams or descriptions, it really means ‘or
whatever the battery terminal voltage is’. With the Ni-Cd cells long dead, usually open circuit, the
‘+5V’ rail is likely to be more or less whatever voltage is coming out of the mains adapter. Using an
original Sinclair ‘6V’ adapter, it’s not unusual to see the ‘+5V’ rail sitting at well over +7V. Thankfully
the set seems to survive this, but it’s worth bearing in mind and perhaps running the set from a +5V
supply when fault-finding.
Total receiver failure
Try on an adaptor to prove condition of
batteries. If the batteries are completely flat, it
will take a few minutes charging to produce
results.
If results OK, check input socket for
good connection, charge batteries.
Battery fuse link O/C
Batteries faulty or O/C connection at
ends or connection via audio board
If still no results after dismantling from the
other boards (Tuner, Vision IF, Sound IF) it is
possible to run the main board and CRT up
separately via the power adapter socket on
the rear panel.
If power board does not run up, go to
power board faults table.
Check connection to Berg sockets. Go
to sound faults table.
picture or
sound
Check for raster. If no raster then suspect
power board. If raster present check Vision IF
board and Tuner board.
Check Berg connections. Go to Vision
IF fault table. Check Tuner board.
no line
Check Power board and Vision IF board
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General