A1200 RGB Port Woes :(
 

Hi all,

Does the A1200 have a fuse on the RGB port like the A2000 does (I encountered problems before due to it being blown on my A2000)?

I knocked out the RGB connector with the machine running...hoping it's just a fuse! :crying

My lounge room A1200 is displaying nothing from the RGB port, RCA output works fine though (if you can call the usual fuzziness "fine").

Anyway, if there is a fuse on the A1200 RGB port traces, can someone please point it out to me? :bowdown

PZ.

@Fingerz

Hi m8y, I will hit the specs later for you, BUT the good news is if the compos[h]ite RCA is good then the RGB is still good, as this is the source for the CXA1145 Y/C and Composite encoder, it should be easly repairable =D

That is good news indeed, from a great guy!

Yeah Z-man, please let me know.

In addition, the "blank" screen flickers a little at the bottom, but only once all HDD start-up activity has finished...so this must be the 1200 trying to display.

PZ.

Quick question....

from the RGB port on the back of the miggy, are you using a standard RGB SCART cable or another type of adapter (like Ultra Reliables SVideo adapter?)

Yeah, I'm using Nathan's S-Video adaptor.

In case it was the adaptor that was at fault I tried another one (I own a couple), but neither of them work.

Thanks for all this!

PZ.

by the sounds of it i think the +5v line is blown....

using a multimeter (in continuity mode) you should be able to trace it back to the fuse.

at each point you rach a cap or resistor, check contnuity (in regards of caps) and check ohms (in regards to resistors)

good luck my friend

Cool, many thanks again :)

As a side note, I just tried out an A520 & it works for composite from the RGB port...wierd...

PZ.

now that is weird, tthe A520 would use a LOT more power, mind you I am unsure if it uses +12 as opposed to +5.....

strange..... very strange indeed...

I take it you have tried the composite out on Nathans Svideo Cards.

Well here is were it gets even stranger...

Tried out my 1081 & DCTV on it & they both work!

Seems both my AmigaManiac adaptors must have died at once...but I don't understand why. Maybe I killed the first one by disconnecting while powered up, but the other doesn't work either.

Yeah, I tried the composites on the adaptors, but they don't work either.

Bizarre stuff!

PZ.

Update:

I just tested the S-Video adaptors on my A2000 (which I'm using with 1081 display to type this right now).

They both failed to work, but as with the A1200, every other method out outputting video works :(

So, the problem must the the adaptors, not Amigas.

I really like Nathan's product & I know I killed at least one by shorting it...just a stupid conincidence I suppose that the other would fail on the same day.

Anyway, it would seem the A1200 is fine, so this thread is no longer required.

Thanks heaps for the assistance too Z-man :)

PZ.

@Fingerz

my friend, before you run off, lets just check that +5 on the video port

Have you multimeter standing by and take a reading from the A1200 and A2000...

I will hit up the specs tonight, but If i am right I think the tantulumn cap would be the thing to go if anything does....

It might be a good idea to check source voltages too, test the Ad724 chip +5 / Y, C and Comp outs

No worries Z, I just checked pin 23 & got +5.06V, so that's fine.

As for the Ad724 chip, please excuse my ignorance, but which legs should I be testing for the signals mentioned above?

Thanks again :)

PZ.

@Fingerz

you can use this schematic my friend

http://www.guildserver.co.uk/data_im...-schematic.jpg

see if you get any readings from the output signals

I am curious about the Hsync and Vsync

Man, now I'm quite confused.

According the the schematic above, Hsync & Vsync output signals come from 74LS08N.

Only problem is that I don't know where it is/which device you want me to test.

My AmigaManiac adaptors have the AD724 chip, but I cannot find 74LS08N anywhere...the adaptor has ONLY AD724 & I can't see 74LS08N inside the A1200.

I'll need further clarification sorry :(

PZ.

The TTL 7408 (and variants) are for the (in)famous silver gender changer.

Thanks Rogerio, at least I know I'm not going insane! :laughing

PZ.

@Fingers

LOL

I truely am sorry m8, I have completely confused you, the Above is a primative schematic of the Narmi SVideo, ignore the 74LS08N its not part of Nathans build, infact it was the wrong IC to use anyway.

Check the sources going to and comming from the adapter, (i.e. the RGB values *before the cap) and the Composite, Luma and Chroma from the device, (*before and after the caps)

sorry about confusing you.

Thanks Z-Money, but you'll have to be more specific...what am I looking for value-wise?

As mentioned before, all Amigas display through every OTHER device I own that connects to the RGB port....so I've asked Nathan to sell me some new chips...surely I killed something in the adaptors...I'm pretty much convinced that there is nothing wrong with the Amigas...

Sorry to be asking for details all the time, but I don't know sh*t...as you know...hehehe :(

PZ

@Fingerz

I tell you what my friend, hold off from doing anything, and wait untill nathan can sort you out =D

dont worry about not knowing owt.... with my memory its a persistent thing for me lol!

Silly question, when you knocked out the Svideo adapter, did you damage the svideo cable or connector. the chances of both adapters dying at the same time is really slim unless when you knocked out the first one you created a short inside the amiga which effectively wiped out the other adapter when you plugged that in.

Swap/check the cable and TV by using a different device plugged into the TV, check the pins on the cable.

I probably shouldnt do so but i hot swap my adapter all the time when checking other inputs etc and never had a problem.

It is possible either the composite OR horizontal/vert sync lines have been damaged. Some devices use the composite sync and others the combined hor/vert sync so that could be why other devices output video