Some info on many mpu 5 errors
Code Sup Description Message
00 00 Unknown Error UNKNOWN ALM
01 00 Non Payout of Other PAY OTHER ALM
01 40 Non Payout 5p Cash PAY 5P ALM
01 41 Non Payout 10p Cash PAY 10P ALM
01 42 Non Payout 20p Cash PAY 20P ALM
01 43 Non Payout 50p Cash PAY 50P ALM
01 44 Non Payout 100p CashPAY 100P ALM
01 4A Non Payout 20p TokenPAY 20T ALM
01 60 Opto Other Error (5p) OPT OTHER ALM
01 61 Opto 10p Error OPT 10P ALM
01 62 Opto 20P Error OPT 20P ALM
01 63 Opto 50p Error OPT 50P ALM
01 64 Opto 100p Error OPT 100P ALM
01 6A Opto 20 Token Error OPT 20T ALM
10 00 General Coin Mech. ErrorCOIN MECH ERR
11 00 £1 Coin Mech. Fault MECH 100P ERR
12 00 50p Coin Mech. Fault MECH 50P ERR
13 00 20p Coin Mech. Fault MECH 20P ERR
14 00 10p Coin Mech. Fault MECH 10P ERR
15 00 20p Token Coin Mech. FaultMECH 20T ERR
16 00 General Note Acceptor ErrorMECH NOTE ERR
16 01 Note Jammed Error NOTE JAM ERR
16 02 Note Tamper Error NOTE TMPR ERR
19 00 Strim Alarm STRIM ALM
20 00 General Reel Errors GEN REEL ERR
21 00 Reel 1 Fault REEL 1 ERR
22 00 Reel 2 Fault REEL 2 ERR
23 00 Reel 3 Fault REEL 3 ERR
24 00 Reel 4 Fault REEL 4 ERR
25 00 Reel 5 Fault REEL 5 ERR
26 00 Reel 6 Fault REEL 6 ERR
27 00 Reel 7 Fault REEL 7 ERR
28 00 Reel 8 Fault REEL 8 ERR
29 00 Reel 9 Fault REEL 9 ERR
2A 00 Reel 10 Fault REEL 10 ERR
30 00 General Lamp Failure GEN LAMP ERR
31 00 Multiplexor Alarm - Row MUX ROW ERR
32 00 Multiplexor Alarm - Column MUX COL ERR
40 00 General Operational Errors GEN OPER ERR
42 00 Memory Cleared MEM RESET ALM
43 00 Button Stuck STUCK BUT ERR
44 00 No % Key NO % KEY ERR
45 00 Options or % changed NEW OPTS ALM
48 00 On/Off Tamper Alarm ON/OFF ALM
49 00 No stakes/prizes key STAKE KEY ERR
50 00 General Electronic Problems GEN ELEC ERR
51 00 EPROM Failure EPROM ERR
52 00 PAL Error PAL ERR
53 00 Ram Check Fail RAM ERR
54 00 General Hardware Error H/W ERR
54 01 DSP Hardware Failure H/W DSP ERR
54 02 PIC Hardware Failure H/W PIC ERR
54 03 Multiplexor 1 Failure MUX1 FAIL ERR
54 04 Multiplexor 2 Failure MUX2 FAIL ERR
55 00 ESD / Sparking detected SPARKING ALM
56 00 Power supply fail PSU ERR
60 00 General Meter Fault GEN METER ERR
61 00 Meter 1 - (Cash In) Fault MET1 CIN ERR
62 00 Meter 2 - (Cash Out) Fault MET2 COUT ERR
63 00 Meter 3 - (Token In) Fault MET3 TIN ERR
64 00 Meter 4 - (Token Out) Fault MET4 TOUT ERR
65 00 Meter 5 - (Token Out) Fault MET5 REF ERR
66 00 Meter 6 - (Prizes Out) Fault MET6 PRIZ ERR
68 00 General LCD Meter Fault GEN LCD ERR
68 01 LCD Meter Read Write Error LCD R/W ERR
68 02 LCD Meter Fingerprint Fault LCD FP ERR
68 03 LCD Meter Firmware Checksum Failure LCD FWCHK ERR
68 04 LCD Meter EPROM Bus Failure LCD BUS ERR
68 05 LCD Meter Transmission Checksum Corrupt LCD CSUM ERR
70 00 General Comms Failure GEN COMMS ERR
70 01 Datapak NAK Received DP NAK RX ERR
70 02 Datapak Locked Up Error DP LOCKED ERR
70 03 Datapak Buffer Full Error DP BUF FL ERR
71 00 Waiting For Dataport DATAPORT ERR
72 00 Fault Comms Link COMMS LNK ERR
90 00 General Software Error S/W GEN ALM
90 01 Software Divide by 0 S/W DIV 0 ALM
90 02 Software Bus Error S/W BUS ALM
90 03 Software Address Error S/W ADD ALM
90 04 Software Illegal Instruction S/W INSTR ALM
90 05 Software Watchdog S/W WDOG ALM
91 00 Control Illegal Mode ILL MODE ERR
91 01 Control No Mode Matched MODE MACH ERR
91 02 Control Mode Changed MODE CHNG ALM
92 00 Access Cover ACC COVER ALM
92 01 Negative Credit NEG CRD ALM
92 03 PIC Security Error PIC SEC ERR
92 04 Invalid PIC Error PIC INVLD ERR
Could be the 19 error (coin mech) or the unknown error, which may be the anti tamper above. No idea really, but the list above is bound to be useful to someone sometime