Repairing an a1200 with green display

elmasta · 05 March 2010, 00:07

Hello all,

I bought an A1200 with a video problem. I knew of the video problem beforehand but the price was ok and I thought it could be easily repairable. Also, I always wanted an a1200

. However the problem seemed a little more complicated than I thought initially. I researched into the problem and concluded its was the DAC.

What I did was to check the input signals R0-R7, G0-G7, B0-B7 and the output from the dac IOR,IOG,IOB with different colour screens. The result was always the same, IOR and IOB stayed low no matter what color screen. Conclusion, the DAC is dead.

So am I starting to think on getting a DAC and replacing it myself, but being and old component it looks difficult to find one.

My questions are, ¿has anybody here replaced the dac? ¿where did you get it? ¿how much should I expect its cost to be?

thanks

Zetr0 · 05 March 2010, 03:12

@elmasta

I changed one on mine

I used a hot-air rework station -

removed the DAC from a dead A1200 motherboard
removed the dead DAC from the working motherboard
Soldered up the DAC with some nice Silver Bearing solder 0.015 and a soldering irion

About 20 minutes work.

Cosmos · 05 March 2010, 03:57

>removed the DAC from a dead A1200 motherboard
>removed the dead DAC from the working motherboard

Zetr0 · 05 March 2010, 04:11

*hehe*

reads a little crazy indeed!!

but thats the sum of it.

you could also then say

Soldered good DAC from dead motherboard onto the good motherboard with the dead DAC removed.

.... phewww... dont have a drink before that sentence!!!

lost_loven · 05 March 2010, 05:01

just had 4 beers.. had to read that twice!

lost

Zetr0 · 05 March 2010, 13:29

I removed both DAC's from two A1200 motherboards, one of which was dead.

On the working motheroard I then replaced the DAC with the working one...

(alcohol friendly version)

elmasta · 05 March 2010, 22:42

haha! It's was clear to me, no alcohol here

. yet...

Thing is, I don't have another a1200 mb. Does anyone know of any respectable company that sells them?

About the soldering part, I was planning to remove it by cutting the pins with a knife

following the techniques posted in eab's soldering hints post and this page i found on the net. I plan on being very careful

By the time being I'll investigate on getting the IC.

rkauer · 06 March 2010, 04:03

The CXA1145 can be a pain in the back to locate.

I don't know if its successors (CXA1645 is the latest one) are a drop-in replacement (read the datasheets from both parts!).

BTW: welcome to EAB, it is nice to see another fellow south-american here.

elmasta · 06 March 2010, 04:40

Quote:

Originally Posted by rkauer

The CXA1145 can be a pain in the back to locate.

Actually, it's the DAC which is VP101.

Quote:

Originally Posted by rkauer

BTW: welcome to EAB, it is nice to see another fellow south-american here.

Obrigado!

--

This is how it looks on composite out. It's the pallete from digipaint 3.

Fabie · 06 March 2010, 21:16

elmasta,

yo can purchase a RGB to SVHS /composite adapter for your amiga here
http://www.amigamaniac.com/
the adapter comes with own DAC and will not use anymore the sony CXA1145 chip

elmasta · 06 March 2010, 22:05

Quote:

Originally Posted by Fabie

elmasta,

yo can purchase a RGB to SVHS /composite adapter for your amiga here
http://www.amigamaniac.com/
the adapter comes with own DAC and will not use anymore the sony CXA1145 chip

Thanks for the info, but the CXA1145 is not the DAC. It's a video encoder. It takes the RGB analog signal generated from the VP101 DAC and generates a PAL/NTSC signal.

In my case, the VP101 is at fault, AFAIK the CXA1145 is fine.

Zetr0 · 06 March 2010, 22:09

@elmasta

there is an irony, I have an A1200 mobo here that blasts only red out LOL!!! blue and greed are deceased....

alas I dont have a spare either VP101 DAC either.

Fabie · 06 March 2010, 23:57

Quote:

Originally Posted by elmasta

Thanks for the info, but the CXA1145 is not the DAC. It's a video encoder. It takes the RGB analog signal generated from the VP101 DAC and generates a PAL/NTSC signal.

In my case, the VP101 is at fault, AFAIK the CXA1145 is fine.

if you think that the damage is in VP101 chip the only solution is to get a scandoubler....it will take the video directly from the Amiga Chips
Depends of the model of the scandoubler but for example flicker magic by DCE take video from lisa or alice....
Will work...I guarante...I had an A1200 with damage in blue.....red and green worked ok
Purchased flicker Magic scandoubler and everything was fine

Anemos · 07 March 2010, 01:05

Found one A1200 MB for replace, is cheaper than scadoubler and from all..

Zetr0 · 07 March 2010, 02:01

for those of you that are interested -

You can still get the "VP101 3BA" DAC that you find installed on the Rev 2B A1200

heres some info on the unit including a spec sheet and here is a order-request form thats from DigiKey .

I have no doubt that they would require a Minimum Order Quantity or now these days its a Minimum Order Cost, but theres no harm in asking for handfull of samples.

please make sure that you check the finer points, like the compatbility of this component to others in other revisions of A1200's

I have PM'd this infos to elmasta

Fabie · 07 March 2010, 02:27

Quote:

Originally Posted by Anemos

Found one A1200 MB for replace, is cheaper than scadoubler and from all..

fot the money of a scandoubler you get a full A1200 with VGA output...
otherwise you get a new A1200 mobo for idem price but not VGA
so...which is the best choice?

SCANDOUBLER

elmasta · 07 March 2010, 15:35

more info for those interested:

I've been researching how to sustitute the chip, what I found is that there were two types of DACs used by Commodore. The VP101 and the ADV101. I guess depending on the motherboard revision (mine is 1D).

Both, VP101 and ADV101 are obsolete, but you can still get them, as Zethr0 said before. I don't know at what price yet.

Also I found that Analog Devices, the maker of ADV101 has a replacement part called ADV7120 which is pin compatible with ADV101, thus also compatible with VP101. Datasheets looks copy and pasted, so I guess it's compatible

Hope this info helps.

As for the scandoubler, I'm sure its a fine piece of hardware. But there's a limit to what I want to spend in this.

coze · 07 March 2010, 15:48

have you checked for any leaked caps ? It might be that IOR and IOB are shorted somewhere on the board with GND so changing the DAC might be unncessary ... I think it's more likely than DAC dying on you for no reason.

elmasta · 07 March 2010, 17:54

Quote:

Originally Posted by coze

have you checked for any leaked caps ? It might be that IOR and IOB are shorted somewhere on the board with GND so changing the DAC might be unncessary ... I think it's more likely than DAC dying on you for no reason.

Thanks. Yes I checked that, and IOR, IOG and IOB measure 50ohm to ground, so no short there.

I didn't mention earlier, but the DAC gets hot almost inmediately. That was one of the reasons I suspected it was broken.

05 March 2010, 00:07	#1
elmasta Registered User Join Date: Sep 2007 Location: Uruguay Age: 41 Posts: 38	Repairing an a1200 with green display Hello all, I bought an A1200 with a video problem. I knew of the video problem beforehand but the price was ok and I thought it could be easily repairable. Also, I always wanted an a1200 . However the problem seemed a little more complicated than I thought initially. I researched into the problem and concluded its was the DAC. What I did was to check the input signals R0-R7, G0-G7, B0-B7 and the output from the dac IOR,IOG,IOB with different colour screens. The result was always the same, IOR and IOB stayed low no matter what color screen. Conclusion, the DAC is dead. So am I starting to think on getting a DAC and replacing it myself, but being and old component it looks difficult to find one. My questions are, ¿has anybody here replaced the dac? ¿where did you get it? ¿how much should I expect its cost to be? thanks

05 March 2010, 22:42	#7
elmasta Registered User Join Date: Sep 2007 Location: Uruguay Age: 41 Posts: 38	haha! It's was clear to me, no alcohol here . yet... Thing is, I don't have another a1200 mb. Does anyone know of any respectable company that sells them? About the soldering part, I was planning to remove it by cutting the pins with a knife following the techniques posted in eab's soldering hints post and this page i found on the net. I plan on being very careful By the time being I'll investigate on getting the IC. Last edited by elmasta; 05 March 2010 at 23:11.

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05 March 2010, 03:12	#2
Zetr0 Ya' like it Retr0? Join Date: Jul 2005 Location: United Kingdom Age: 49 Posts: 9,768	@elmasta I changed one on mine I used a hot-air rework station - removed the DAC from a dead A1200 motherboard removed the dead DAC from the working motherboard Soldered up the DAC with some nice Silver Bearing solder 0.015 and a soldering irion About 20 minutes work.

05 March 2010, 03:57	#3
Cosmos Banned Join Date: Jan 2007 Location: France Posts: 655	>removed the DAC from a dead A1200 motherboard >removed the dead DAC from the working motherboard

05 March 2010, 04:11	#4
Zetr0 Ya' like it Retr0? Join Date: Jul 2005 Location: United Kingdom Age: 49 Posts: 9,768	hehe reads a little crazy indeed!! but thats the sum of it. you could also then say Soldered good DAC from dead motherboard onto the good motherboard with the dead DAC removed. .... phewww... dont have a drink before that sentence!!!

05 March 2010, 05:01	#5
lost_loven Registered User Join Date: May 2007 Location: winnipeg Posts: 358	just had 4 beers.. had to read that twice! lost

05 March 2010, 13:29	#6
Zetr0 Ya' like it Retr0? Join Date: Jul 2005 Location: United Kingdom Age: 49 Posts: 9,768	I removed both DAC's from two A1200 motherboards, one of which was dead. On the working motheroard I then replaced the DAC with the working one... *(alcohol friendly version)*

06 March 2010, 04:03	#8
rkauer I hate potatos and shirts Join Date: Oct 2007 Location: Sao Leopoldo / Brazil Age: 58 Posts: 3,482	The CXA1145 can be a pain in the back to locate. I don't know if its successors (CXA1645 is the latest one) are a drop-in replacement (read the datasheets from both parts!). BTW: welcome to EAB, it is nice to see another fellow south-american here.

06 March 2010, 21:16	#10
Fabie Banned Join Date: Apr 2009 Location: France Posts: 478	elmasta, yo can purchase a RGB to SVHS /composite adapter for your amiga here http://www.amigamaniac.com/ the adapter comes with own DAC and will not use anymore the sony CXA1145 chip

06 March 2010, 22:09	#12
Zetr0 Ya' like it Retr0? Join Date: Jul 2005 Location: United Kingdom Age: 49 Posts: 9,768	@elmasta there is an irony, I have an A1200 mobo here that blasts only red out LOL!!! blue and greed are deceased.... alas I dont have a spare either VP101 DAC either.

07 March 2010, 01:05	#14
Anemos 70X7 Join Date: Apr 2008 Location: Ἑλλάς Posts: 1,078	Found one A1200 MB for replace, is cheaper than scadoubler and from all..

07 March 2010, 02:01	#15
Zetr0 Ya' like it Retr0? Join Date: Jul 2005 Location: United Kingdom Age: 49 Posts: 9,768	for those of you that are interested - You can still get the "VP101 3BA" DAC that you find installed on the Rev 2B A1200 heres some info on the unit including a spec sheet and here is a order-request form thats from DigiKey . I have no doubt that they would require a Minimum Order Quantity or now these days its a Minimum Order Cost, but theres no harm in asking for handfull of samples. please make sure that you check the finer points, like the compatbility of this component to others in other revisions of A1200's I have PM'd this infos to elmasta

07 March 2010, 15:35	#17
elmasta Registered User Join Date: Sep 2007 Location: Uruguay Age: 41 Posts: 38	more info for those interested: I've been researching how to sustitute the chip, what I found is that there were two types of DACs used by Commodore. The VP101 and the ADV101. I guess depending on the motherboard revision (mine is 1D). Both, VP101 and ADV101 are obsolete, but you can still get them, as Zethr0 said before. I don't know at what price yet. Also I found that Analog Devices, the maker of ADV101 has a replacement part called ADV7120 which is pin compatible with ADV101, thus also compatible with VP101. Datasheets looks copy and pasted, so I guess it's compatible Hope this info helps. As for the scandoubler, I'm sure its a fine piece of hardware. But there's a limit to what I want to spend in this.

07 March 2010, 15:48	#18
coze hastala vista winny vista Join Date: Feb 2006 Location: mt fuji Age: 46 Posts: 1,335	have you checked for any leaked caps ? It might be that IOR and IOB are shorted somewhere on the board with GND so changing the DAC might be unncessary ... I think it's more likely than DAC dying on you for no reason.

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