* ULTIMATE * ZX Spectrum Diagnostic Card + LED Board

* PLEASE CHECK ALL PHOTOS *

This is hands-down the best (ultimate) diagnostic card combo for the zx spectrums.

You get:

. 1x ROM BoX;

. 1x LED Box;

. 1x USB Digital indicator;

External ROMbox for ZX Spectrum (16/48k, 128 and +2,+3,...) with capacity for 32 different ROMs that can be selected manually or selected from the Spectrum itself (OUT 31,ROM#). Based on Dylan 'Winston' Smith's diagnostic board, Alioth Diagboard, to which all the subsequent modifications have been incorporated and is compatible with Brendan Alford's ZX Diagnostics ROM (slot 0 carries ZX Diagnostics v0.38).

It has RESET and NMI buttons and switches to specify the Spectrum model (Sinclair ZX or TK), enable or disable the use of /M1 and to turn the ROMbox on or off (if it is off the ZX Spectrum starts normally). The ZX Spectrum also has a DIP switch block, the first of which is used to switch between automatic (ZX) or manual (SET) ROM selection mode, in the latter mode the user selects the ROM using the last 5 DIP switches. The selected ROM ID is obtained by adding the numbers under the DIP switches in the ON position. For example, if all the switches are turned OFF, the ROM selection mode is manual and slot/ROM 0 would be selected; if instead DIP switches #3 (+8) and DIP #6 (+1) were turned ON, slot/ROM 9 would be selected (9=+8+1).

It has a top bus connector where another diagnostic board with LEDs and female USB-A connectors can be plugged in, which also works independently (i.e. can be connected as is directly to the ZX Spectrum). This additional board monitors 42 different signals (data bus, address bus, control signals,...) and 6 voltages, a total of 48 LEDs. It also incorporates USB-A female connectors to connect USB voltmeters (or voltmeters/ammeters) to read the voltages on their typical 7-segment displays.

The LED Box is used to monitor the voltages and signals of the ZX Spectrum (16/48k, 128 and +2,+3,...) and is compatible and can be connected behind the ROM BOX.

The status of the different groups can be checked by means of 6 LED matrices,

Group 1 Voltages (red indicators)
ZX Spectrum 16/48k: +5V, -5V, +9V, +12V, 12VAC, /CLK and /RESET
ZX Spectrum +2/+2A/+3/...: +5V, +12V, -12V, /CLK and /RESET

Group 2 Data bus (yellow indicators)

Groups 3 and 4 Address bus (green indicators)

Groups 5 and 6 Processor and ROM control lines (blue indicators)

It has its own oscillator that provides an internal clock to update, approximately 70 times per second, the state of the LEDs of blocks 2 to 6.

The SW1 (CLOCK) switch is used to select between this internal oscillator (INT) or to use an external clock signal provided by the ZX Spectrum, such as that generated by the ZX ROM. Diagnostics that only affects group 2 (data bus).

On the female USB-A connectors above and on the right side of the board, USB voltmeters can be connected to read the voltage values on their 7-segment displays. The MINUS LED represents the negative sign that serves to highlight that the voltage on the USB connector J4 is negative even if the external voltmeter shows it positive.