Sinclair ZX Spectrum Service Manual
Spectrum For Everyone https://spectrumforeveryone.com/
50
9.8 ISSUE 6 BOARD - NONE ISSUED
9.9 ISSUE 6A BOARD
This board is similar to Issue 5 but can be fitted with either a Ferranti or a Saga main ULA. The circuit
diagram is shown here and the board layout is shown here.
9.10 FAULT FINDING – SERVICING ADDENDA
The following are additions to Section 4 of the servicing manual:
• Picture quality and possible RAM failures. Test at elevated temperature to show up faults.
• Interface 1 fault. Inspect the edge connector to check for damaged pins. Check the M1 signal from
the CPU; this signal is only used with Interface 1 and so a failure is not evident when the Spectrum
is used on its own.
• SAVE/LOAD failure. Inspect the jack sockets for deformation of contact springs.
9.11 WARRANTY SEAL
From August 1984, a new warranty seal label is fitted. The label is applied over the central screw hole at
the rear of the base and has a four-digit code. Breaking of this seal invalidates the warranty.
9.12 PARTS LISTS
As alternatives to ZTX 213 in TR5 position, transistors BC213, BX214 or FRB925 may be used.
As alternatives to ZTX 313 in TR1, TR2, TR3 and TR6 positions, transistors MPD 2369 or MPS 2713 (both in
TO-92 packages) can be used.
The parts lists follow. Some components on this table are not always fitted. Each is identified by reference
to the note number in the NB column. The notes are explained below.
9.12.1 Notes
1. With Issue 5 boards, if R80-R86 are seen to be fitted, the value of R17-R23 is 470R. If R80-R86 are
fitted, the values of R17-R23 are 330R.
2. With Issue 6 boards, this is not necessary with the SAGA version of IC1.
3. With Issue 6 boards, this is not necessary with the FERRANTI version of IC1.
4. With Issue 6 boards, this is only required on VHF models.
5. With Issue 6 boards, this is only required on the 48k model.
6. With all issues of Spectrum, if TR3 is type KSC839, resistor R24 should be 15k.
7. With all Issue Spectrums, if TR4 is to be replaced by type KTC2236A-Y, the pin connections differ
to all other replacement types (Pin 1 is emitter, Pin 2 is collector and Pin 3 is base, i.e. the base
and collectors are reversed).
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