A1200 External DD, strange clicking noise and composite faults

12 August 2013, 23:22

Hi there, I've been a lurker on here for a while so though I'd register to ask a question as you guys and gals seem to know your stuff!

I have recently inherited 2 A1200s and both have faults. The first has a problem with the external drive port. It detects the drive but won't read from it (External drive works on the other A1200).

The other one has distorted composite output and a weird fault that when you right-click the mouse button an audible click can be heard on the TV / monitor even on the purple disk screen. The machine outputs ok on both RF and RGB so I'm a little bemused. Any ideas folks?

12 August 2013, 23:29

Sorry I should have mentioned, they are both CBM machines so its not a PC drive issue.

demolition · 12 August 2013, 23:52

On the first one, if the internal drive is working well, it could be a broken track on the motherboard, since the external drive shares most of the connections with the internal one. Maybe a screwdriver slipped at some point? Open it up, remove the drive and inspect the upper right corner for physical damages.

On the other 1200, it could have bad caps if you can hear the mouse clicks. Does the audio otherwise sound good in both channels? The RF signal comes from the composite signal, so there must be a composite signal coming from the IC which is somehow not reaching the connector properly. This could also be caused by leaking caps, corroding the MB and messing it up.

13 August 2013, 00:28

Cheers demolition. Yeah looks like bad caps on the 2nd one all the SMD 22uf 25v caps have leaked

board looks Ok I suppose. Ill order some tonight. The one behind the keyboard ZIF socket looks a pain though. Come to think of it the RF out on the one with the composite is temperamental so possibly the fault is connected. The audio is fine other than the RMB noise. I'll investigate the external floppy issue board tomorrow. Gutted I have 2 with faults and no working Amiga lol. Thanks for your help. Oh I forgot to ask, are all the 22uf caps for audio or both audio and video?

demolition · 13 August 2013, 09:33

If you are replacing caps, just replace all of them (the aluminium electrolytic ones) as they probably all need replacing. And clean off the electrolytic fluid before fitting the new ones so it won't continue corroding.
The two behind the keyboard connector can be removed by first removing the top part of the keyboard connector (it clips off). This will give you a bit more space. Then the caps can be removed by twisting them off. I actually do this with all caps as it is easier than trying to solder them off when the pads are all dull.
See this thread:
http://eab.abime.net/support-hardwar...c324-c334.html

Schematics of the Amiga can be found here:
http://www.amigawiki.org/doku.php?id...ice:schematics

13 August 2013, 23:01

Yeah i have ordered enough to do both of them. Just bought polorised radials. Should do the trick. Had a look at the other one today. The PCB has no damage around the port and I cleaned both the port and connector as well as the PCB with IPA......still no joy. If the caps fix the other one ill just leave this one as a donor machine I think.

demolition · 13 August 2013, 23:37

If you have a continuity tester (pref. with sound), you can look at the schematic and check the connections between the internal 34-pin connector and the 23 pin external one. The ones with the same names should be connected. This test will cover most of the pins and would reveal any broken connections.

15 August 2013, 16:24

Quick update....fixed the external floppy issue with some hot air along the SMD devices at the drive port now working perfectly.

Re-capped the other one. Composite output is now crystal clear but sound issue is worse? The audio is cracking and when it does crackle the menu bar flickers as if RMB is being pressed. Very strange.

demolition · 15 August 2013, 16:48

Sounds great regarding the first one.

Well, you did also have noise when you pressed RMB, so maybe there's a short between the two lines somewhere?

Edit: Do you get noise in both channels when you press RMB? Also, try to play sound in one side at a time to see if they both crackle and trigger RMB. Many players have a balance slider for it.

12 August 2013, 23:22	#1
rafkris Posts: n/a	A1200 External DD, strange clicking noise and composite faults Hi there, I've been a lurker on here for a while so though I'd register to ask a question as you guys and gals seem to know your stuff! I have recently inherited 2 A1200s and both have faults. The first has a problem with the external drive port. It detects the drive but won't read from it (External drive works on the other A1200). The other one has distorted composite output and a weird fault that when you right-click the mouse button an audible click can be heard on the TV / monitor even on the purple disk screen. The machine outputs ok on both RF and RGB so I'm a little bemused. Any ideas folks?

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12 August 2013, 23:29	#2
rafkris Posts: n/a	Sorry I should have mentioned, they are both CBM machines so its not a PC drive issue.

12 August 2013, 23:52	#3
demolition Unregistered User Join Date: Sep 2012 Location: Copenhagen / DK Age: 44 Posts: 4,190	On the first one, if the internal drive is working well, it could be a broken track on the motherboard, since the external drive shares most of the connections with the internal one. Maybe a screwdriver slipped at some point? Open it up, remove the drive and inspect the upper right corner for physical damages. On the other 1200, it could have bad caps if you can hear the mouse clicks. Does the audio otherwise sound good in both channels? The RF signal comes from the composite signal, so there must be a composite signal coming from the IC which is somehow not reaching the connector properly. This could also be caused by leaking caps, corroding the MB and messing it up.

13 August 2013, 00:28	#4
rafkris Posts: n/a	Cheers demolition. Yeah looks like bad caps on the 2nd one all the SMD 22uf 25v caps have leaked board looks Ok I suppose. Ill order some tonight. The one behind the keyboard ZIF socket looks a pain though. Come to think of it the RF out on the one with the composite is temperamental so possibly the fault is connected. The audio is fine other than the RMB noise. I'll investigate the external floppy issue board tomorrow. Gutted I have 2 with faults and no working Amiga lol. Thanks for your help. Oh I forgot to ask, are all the 22uf caps for audio or both audio and video?

13 August 2013, 09:33	#5
demolition Unregistered User Join Date: Sep 2012 Location: Copenhagen / DK Age: 44 Posts: 4,190	If you are replacing caps, just replace all of them (the aluminium electrolytic ones) as they probably all need replacing. And clean off the electrolytic fluid before fitting the new ones so it won't continue corroding. The two behind the keyboard connector can be removed by first removing the top part of the keyboard connector (it clips off). This will give you a bit more space. Then the caps can be removed by twisting them off. I actually do this with all caps as it is easier than trying to solder them off when the pads are all dull. See this thread: http://eab.abime.net/support-hardwar...c324-c334.html Schematics of the Amiga can be found here: http://www.amigawiki.org/doku.php?id...ice:schematics

13 August 2013, 23:01	#6
rafkris Posts: n/a	Yeah i have ordered enough to do both of them. Just bought polorised radials. Should do the trick. Had a look at the other one today. The PCB has no damage around the port and I cleaned both the port and connector as well as the PCB with IPA......still no joy. If the caps fix the other one ill just leave this one as a donor machine I think.

13 August 2013, 23:37	#7
demolition Unregistered User Join Date: Sep 2012 Location: Copenhagen / DK Age: 44 Posts: 4,190	If you have a continuity tester (pref. with sound), you can look at the schematic and check the connections between the internal 34-pin connector and the 23 pin external one. The ones with the same names should be connected. This test will cover most of the pins and would reveal any broken connections.

15 August 2013, 16:24	#8
rafkris Posts: n/a	Quick update....fixed the external floppy issue with some hot air along the SMD devices at the drive port now working perfectly. Re-capped the other one. Composite output is now crystal clear but sound issue is worse? The audio is cracking and when it does crackle the menu bar flickers as if RMB is being pressed. Very strange.

15 August 2013, 16:48	#9
demolition Unregistered User Join Date: Sep 2012 Location: Copenhagen / DK Age: 44 Posts: 4,190	Sounds great regarding the first one. Well, you did also have noise when you pressed RMB, so maybe there's a short between the two lines somewhere? Edit: Do you get noise in both channels when you press RMB? Also, try to play sound in one side at a time to see if they both crackle and trigger RMB. Many players have a balance slider for it.

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