Occasional no signal from a1200

Nostromo · 08 September 2017, 09:49

I have noticed that once in a while, when I switch on my A1200 with Indivision MK1, I get a no signal error on my benq 702a monitor but I can hear my a1200 floppy drive clicking away. If I switch the monitor back off and on I still get no picture, but if I switch the a1200 back off and on, it works fine. Ideas?

Nostromo · 08 September 2017, 09:56

Update: if I do a soft reset after no signal, then it works fine

Update 2: I have tightened the VGA cable to the Indivision MK1 connector and *so far* the no signal issue did not happen again, makes no sense to be honest.

fordav1 · 09 September 2017, 02:36

1. Set a VGA-compatible screen mode like Productivity then save it. Remove the MK1 and see if you get an output at first power on from the normal Amiga video connector (assuming you have a DB23-HD15 adapter). If you have a monitor capable of receiving a 15kHz signal use one of the common Amiga video modes. If it works without the MK1 then you may have a suspect connection to the A1200 board where it plugs in on top of Lisa chip. Check the socket and re-seat the MK1.

2. On the A1200 the reset signal is a software-based one and comes from Gayle. That is why a Ctrl-A-A takes a couple of seconds to actuate. Check around the surface-mount capacitors near the power connector and in the middle of the board to the left of the DRAM. If it looks grey-ish or green-ish or crusty then you have the beginnings of leaky capacitors and if left alone will continue to eat away at the motherboard and eventually you'll have a dead A1200.

08 September 2017, 09:49	#1
Nostromo Registered User Join Date: Dec 2008 Location: The World! Posts: 454	Occasional no signal from a1200 I have noticed that once in a while, when I switch on my A1200 with Indivision MK1, I get a no signal error on my benq 702a monitor but I can hear my a1200 floppy drive clicking away. If I switch the monitor back off and on I still get no picture, but if I switch the a1200 back off and on, it works fine. Ideas?

08 September 2017, 09:56	#2
Nostromo Registered User Join Date: Dec 2008 Location: The World! Posts: 454	Update: if I do a soft reset after no signal, then it works fine Update 2: I have tightened the VGA cable to the Indivision MK1 connector and so far the no signal issue did not happen again, makes no sense to be honest. Last edited by Nostromo; 08 September 2017 at 10:41.

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09 September 2017, 02:36	#3
fordav1 Registered User Join Date: Jan 2017 Location: Australia Posts: 84	1. Set a VGA-compatible screen mode like Productivity then save it. Remove the MK1 and see if you get an output at first power on from the normal Amiga video connector (assuming you have a DB23-HD15 adapter). If you have a monitor capable of receiving a 15kHz signal use one of the common Amiga video modes. If it works without the MK1 then you may have a suspect connection to the A1200 board where it plugs in on top of Lisa chip. Check the socket and re-seat the MK1. 2. On the A1200 the reset signal is a software-based one and comes from Gayle. That is why a Ctrl-A-A takes a couple of seconds to actuate. Check around the surface-mount capacitors near the power connector and in the middle of the board to the left of the DRAM. If it looks grey-ish or green-ish or crusty then you have the beginnings of leaky capacitors and if left alone will continue to eat away at the motherboard and eventually you'll have a dead A1200.

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