Amiga 500+ display problems - ghosting and vertical bands

09 February 2018, 15:01

Hi everyone,

Recently bought an A500+ from eBay and it's got an issue with the display output, both through the RF modulator and Composite.

There's a significant amount of distortion and ghosting, as well some vertical bands

I know battery leakage is a problem with this model and I'm going to open it up and check for corrosion and continuity as best as I can. It does appear to be functioning well apart from this display issue.

Are there any specific areas I should focus on after opening it up?

Kipper2k had a similar (but less severe) problem with his A600 here:
http://eab.abime.net/showthread.php?t=47782

It was suggested that a recap might be a good idea and then checking U12. Does anyone have any experience of a similar issue with the A500+? Can anyone help with some useful pointers?

Many thanks

Amiga1992 · 09 February 2018, 15:56

The A500+ doesn't have capacitors like an A600, so you can't compare.
It could be the video decoder, but dunno. Try it with RGB and see what happens.

Daedalus · 09 February 2018, 16:13

True, it's unlikely to be because of capacitors leaking and causing damage. But if the capacitors have dried out and aren't doing their jobs any more, you could be seeing electrical noise that could manifest itself like that. It could also be a poor ground connection somewhere, either the cable or on the PCB, so it's worth checking the ground continuity in the area. RF is particularly prone to ghosting - do you have any other cables to try? What does composite directly from the machine look like? It will be greyscale but might be free of the ghosting.

pandy71 · 09 February 2018, 17:27

It may be bad cable... looks like impedance mismatched.

robinsonb5 · 09 February 2018, 17:31

Quote:

Originally Posted by Daedalus

What does composite directly from the machine look like? It will be greyscale but might be free of the ghosting.

Yes, definitely check that.

My guess would be this is a cracked solder joint or dried out capacitor in the A520 modulator somewhere, rather than in the Amiga itself.

09 February 2018, 19:03

Thanks to everyone who has replied.

I did check with the composite output and the image is very similar, ghosting and vertical bands, although obviously the display is in mono. I think that rules out a modulator or cable problem unless I'm missing something.

@Daedalus - when you mentioned to check ground continuity in the area, I'm assuming you mean in the RF area of the board. Is it possible that the grounding issue could also happen around the Denise and CIA?

Amiga1992 · 09 February 2018, 20:09

It could also be a PSU problem, I would check that too. It could well be the ground on it has a problem.

alexh · 10 February 2018, 02:04

It's going to be a battery leak and corrosion on the legs of the video chip

10 February 2018, 03:00

Tried an alternate PSU and same issue. The battery corrosion hypothesis sounds like it could be very plausible, I'm going to have time to have a root around the mobo tomorrow so I guess I'll find out then.

10 February 2018, 17:41

Yeah, looks like the battery has leaked causing corrosion to a number of caps and resistors, as well as the first couple of pins on U12

The item was listed as working so going to return it I think. The leak isn't as bad as some i've seen but there are probably at least 8 components that I'd need to replace and my desoldering skills are not the greatest

Thanks to everyone for the help

09 February 2018, 15:01	#1
hb129 Posts: n/a	Amiga 500+ display problems - ghosting and vertical bands Hi everyone, Recently bought an A500+ from eBay and it's got an issue with the display output, both through the RF modulator and Composite. There's a significant amount of distortion and ghosting, as well some vertical bands I know battery leakage is a problem with this model and I'm going to open it up and check for corrosion and continuity as best as I can. It does appear to be functioning well apart from this display issue. Are there any specific areas I should focus on after opening it up? Kipper2k had a similar (but less severe) problem with his A600 here: http://eab.abime.net/showthread.php?t=47782 It was suggested that a recap might be a good idea and then checking U12. Does anyone have any experience of a similar issue with the A500+? Can anyone help with some useful pointers? Many thanks Attached Thumbnails

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Bands that used the Amiga to make Music	Nova	Nostalgia & memories	70	05 June 2023 13:39
Vertical display sharing of screens, possible?	volvo_0ne	Coders. AMOS	7	29 June 2016 16:11
Indivision AGA MkII vertical lines, banding and ghosting!	trixster	support.Hardware	25	02 August 2014 12:58
Amiga 500 display problem	gemstone	support.Other	3	20 August 2013 13:29
Amiga 500/1200 and LCD display	wlcina	support.Hardware	18	24 September 2004 22:37

09 February 2018, 15:56	#2
Amiga1992 Registered User Join Date: May 2001 Location: ? Posts: 19,645	The A500+ doesn't have capacitors like an A600, so you can't compare. It could be the video decoder, but dunno. Try it with RGB and see what happens.

09 February 2018, 16:13	#3
Daedalus Registered User Join Date: Jun 2009 Location: Dublin, then Glasgow Posts: 6,334	True, it's unlikely to be because of capacitors leaking and causing damage. But if the capacitors have dried out and aren't doing their jobs any more, you could be seeing electrical noise that could manifest itself like that. It could also be a poor ground connection somewhere, either the cable or on the PCB, so it's worth checking the ground continuity in the area. RF is particularly prone to ghosting - do you have any other cables to try? What does composite directly from the machine look like? It will be greyscale but might be free of the ghosting.

09 February 2018, 17:27	#4
pandy71 Registered User Join Date: Jun 2010 Location: PL? Posts: 2,741	It may be bad cable... looks like impedance mismatched.

09 February 2018, 19:03	#6
hb129 Posts: n/a	Thanks to everyone who has replied. I did check with the composite output and the image is very similar, ghosting and vertical bands, although obviously the display is in mono. I think that rules out a modulator or cable problem unless I'm missing something. @Daedalus - when you mentioned to check ground continuity in the area, I'm assuming you mean in the RF area of the board. Is it possible that the grounding issue could also happen around the Denise and CIA?

09 February 2018, 20:09	#7
Amiga1992 Registered User Join Date: May 2001 Location: ? Posts: 19,645	It could also be a PSU problem, I would check that too. It could well be the ground on it has a problem.

10 February 2018, 02:04	#8
alexh Thalion Webshrine Join Date: Jan 2004 Location: Oxford Posts: 14,333	It's going to be a battery leak and corrosion on the legs of the video chip

10 February 2018, 03:00	#9
hb129 Posts: n/a	Tried an alternate PSU and same issue. The battery corrosion hypothesis sounds like it could be very plausible, I'm going to have time to have a root around the mobo tomorrow so I guess I'll find out then.

10 February 2018, 17:41	#10
hb129 Posts: n/a	Yeah, looks like the battery has leaked causing corrosion to a number of caps and resistors, as well as the first couple of pins on U12 The item was listed as working so going to return it I think. The leak isn't as bad as some i've seen but there are probably at least 8 components that I'd need to replace and my desoldering skills are not the greatest Thanks to everyone for the help

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)