A1200 RGB No output without Indivision plugged in!

[voyager_1701e]

Hi All,
Ive spent many hours on this one....hoping someone may have an idea whats going on!

Like the topic says...I have an A1200. Standard, it has no composite and no RGB output. If I connect an Indi Mk2 with the DVI connected to a monitor the Indi gives perfect pic, and the RGB works, though the composite doesn't. With the Indi connected, but the DVI cable unplugged from the monitor, no RGB. So something the monitor feeds back to Lisa via the Indi is fixing 50% of the problem!

Someone before me has been messing extensively with this board. Plenty of dodgy soldering...including on almost all the custom chips. In fact, one of the pins on Lisa was bridged by a pad ripped off by the soldering effort! First time for everything, I had to desolder Lisa and put her back on....regretfully it didn't fix the situation. All the caps have been changed. Both Lisa and the video DAC have correct voltages reaching the correct pins. A quick continuity check between Lisa's pins and wherever they go indicate nothing amiss. So I'm stumped!

Anyone with any thoughts?

thanks
Ash

[FOL]

Originally Posted by voyager_1701e

Hi All,
Ive spent many hours on this one....hoping someone may have an idea whats going on!

Like the topic says...I have an A1200. Standard, it has no composite and no RGB output. If I connect an Indi Mk2 with the DVI connected to a monitor the Indi gives perfect pic, and the RGB works, though the composite doesn't. With the Indi connected, but the DVI cable unplugged from the monitor, no RGB. So something the monitor feeds back to Lisa via the Indi is fixing 50% of the problem!

Someone before me has been messing extensively with this board. Plenty of dodgy soldering...including on almost all the custom chips. In fact, one of the pins on Lisa was bridged by a pad ripped off by the soldering effort! First time for everything, I had to desolder Lisa and put her back on....regretfully it didn't fix the situation. All the caps have been changed. Both Lisa and the video DAC have correct voltages reaching the correct pins. A quick continuity check between Lisa's pins and wherever they go indicate nothing amiss. So I'm stumped!

Anyone with any thoughts?

thanks
Ash

You have answered your own question. It will be a solder issue with lisa.
Maybe when you push indi on, it pushes a pin / pins and makes contact.

I would rework LISA first see what happens, there shouldn't be any shorted pins.

[voyager_1701e]

I would have thought what you suggested with the pressure thing, however if I unplug the monitor cable from the Indi (but leave the Indi connected to Alice) no RGB. With the monitor cable again connected to the Indi, the RGB works. Neither operation would change the pressure applied to Alice. Without the Indi over Alice, I did apply pressure to Alice and saw no signs of life from the RGB. I just can't see it being a pressure on Alice/Alice's pads issue.

You are right, as far as I can see from the schematics, there should be not shorted pins! The short was corrected when I removed Alice and re soldered it. I've measured continuity between all adjacent pins, and nothing seems bridged.

The difference seems to be an electrical load or supply to Alice via Indy when it is only connected to the monitor....something not present with Alice or Alice+Indi alone. Considering the above details, it seems the only logical conclusion.

Any other thoughts?

[FOL]

Originally Posted by voyager_1701e

I would have thought what you suggested with the pressure thing, however if I unplug the monitor cable from the Indi (but leave the Indi connected to Alice) no RGB. With the monitor cable again connected to the Indi, the RGB works. Neither operation would change the pressure applied to Alice. Without the Indi over Alice, I did apply pressure to Alice and saw no signs of life from the RGB. I just can't see it being a pressure on Alice/Alice's pads issue.

You are right, as far as I can see from the schematics, there should be not shorted pins! The short was corrected when I removed Alice and re soldered it. I've measured continuity between all adjacent pins, and nothing seems bridged.

The difference seems to be an electrical load or supply to Alice via Indy when it is only connected to the monitor....something not present with Alice or Alice+Indi alone. Considering the above details, it seems the only logical conclusion.

Any other thoughts?

First thought, why are you messing with ALICE for, . Surely you mean LISA?

Maybe there is a damaged trace under LISA, you did say the board had been butchered. Missing ground? that is resolved when monitor is plugged in.

[voyager_1701e]

Yes right you are, I mean Lisa! Imagine I managed to connect the Indi to Alice! LOL

Anyway, I have solved the problem, and FOL you were so so close to the problem! It was so simple I feel s-s-s-stupid!

I plugged my A4k on the same Kipper RGB>Composite adapter I always use to the same TV. No pic! WTF??? So I powered up my GBS8220, its not plugged into the Amiga RGB port of course, as the RGB>Comp adapter is using the RGB port already...I plugged in the VGA cable to the GBS (not remembering the GBS has no input!)...suddenly a pic on the comp! Weird! Unplug VGA....pic disappears. For some reason, I plugged the audio RCA jack back into the Amiga, suddenly pic on comp has returned. It hits me....I have a ground issue on the video lead. Swapping the audio RCA plug to the comp video and no other audio/GBS connected...I have a pic! So stupidly simple...chasing my butt thinking the A1200 is at fault, and its a broken video lead on the ground wire! Grrrrrrrrrrrrrrrrrrrrrrrrr!

And just to add coincidence to stumbling over the stupidly simple answer.....for the technically minded, you might be wondering why with the GBS plugged into the TV via its VGA input would the Amiga composite work? Really simple answer again! The GBS was being powered from the Amiga power supplies 5v rail.....and using the Amiga's ground! Hence connecting the Amiga's ground to that of the TV not via the composite cable, but via the GBS and the VGA connector!

And along the same lines.......why did connecting the Indi to the DVI on the very same TV allow the Amiga composite to work? Basically the same answer.....it connected the Amiga ground to the TV!

So Im off to find some more stupid to smack myself with

Thanks for your efforts in replying FOL!

[FOL]

Originally Posted by voyager_1701e

Yes right you are, I mean Lisa! Imagine I managed to connect the Indi to Alice! LOL

Anyway, I have solved the problem, and FOL you were so so close to the problem! It was so simple I feel s-s-s-stupid!

I plugged my A4k on the same Kipper RGB>Composite adapter I always use to the same TV. No pic! WTF??? So I powered up my GBS8220, its not plugged into the Amiga RGB port of course, as the RGB>Comp adapter is using the RGB port already...I plugged in the VGA cable to the GBS (not remembering the GBS has no input!)...suddenly a pic on the comp! Weird! Unplug VGA....pic disappears. For some reason, I plugged the audio RCA jack back into the Amiga, suddenly pic on comp has returned. It hits me....I have a ground issue on the video lead. Swapping the audio RCA plug to the comp video and no other audio/GBS connected...I have a pic! So stupidly simple...chasing my butt thinking the A1200 is at fault, and its a broken video lead on the ground wire! Grrrrrrrrrrrrrrrrrrrrrrrrr!

And just to add coincidence to stumbling over the stupidly simple answer.....for the technically minded, you might be wondering why with the GBS plugged into the TV via its VGA input would the Amiga composite work? Really simple answer again! The GBS was being powered from the Amiga power supplies 5v rail.....and using the Amiga's ground! Hence connecting the Amiga's ground to that of the TV not via the composite cable, but via the GBS and the VGA connector!

And along the same lines.......why did connecting the Indi to the DVI on the very same TV allow the Amiga composite to work? Basically the same answer.....it connected the Amiga ground to the TV!

So Im off to find some more stupid to smack myself with

Thanks for your efforts in replying FOL!

Glad it was something simple.