F18A VGA installation and 5V mod

[marauder666]

A friend has dropped off 4 Colecovisions for me to mod, 2 are PAL, 2 NTSC, and a F18A VGA board.

In the UK, so powering the NTSC ones is a bit of an issue, having to use stepdown transformers, and the Coleco PSU isnt ideal for plugging into them due to size, so thats another issue to contend with.

 

Decided to use the nicer cosmetic condition NTSC one, all are tested and working with previous composite mods, the PAL ones look really good, which was surprising.

 

As the whole thing is having to come apart, I recapped it, and changed the reset capacitor for a 10uf, to allow more time for the F18A to boot up before the Coleco does.

The video chip came out really clean with no damage to pads or traces.

Soldered a turn pin socket in, and then realised the F18A board has short pins, this is the point I decided to mod it for a 5V PSU.  I removed the 100nf caps on the VRAM which would be in the way, and the inductors supplying 12V and -5V to the VRAM, and cut a single trace supplying them with 5V.  No power going to them at all.

 

F18A fits perfectly now, so its time to give it a test.  But before that I'd removed the modulator, and taken out the vertical connector that connects it to the main board, this is so I can repurpose the RF jack as audio out, and the switch to turn scanlines on and off on the F18A.  Unfortunately, the wire to the switch had to be soldered to the F18A jumper pins, I couldn't find any connectors which fit tightly enough.  A bit annoying, but its unlikely the F18A is ever going to be removed.  A bit of dremmeling and a hole for the VGA is cut in the back.

 

Testing worked perfectly into a crappy old CTX monitor, looks really nice.  I like the scanlines, so they are staying on while the console is in my possession.

 

Removed the existing composite output 3.5mm socket, enlarged it slightly and put a 2.1mm DC jack in its place.  Wires soldered to the back of the existing DC socket.  Also added a crude crowbar diode across the power rails on the back of the main board in case wrong polarity 5V PSU is used. It'll save the console in the event of wrong polarity, although the PSU might not like it.  Better than nothing.

 

I plugged into a Samsung LCD TV using a VGA-HDMI adapter, but the TV got a mode not supported error which is a bit annoying, but it works perfectly into the same TV using the VGA connection.

 

Pleased with how it's gone, hardest part is getting the console apart in the first place, that front panel is annoying.

 

 

[Ruggers Customs]

Well done!

[Ikrananka]

4 hours ago, marauder666 said:

In the UK, so powering the NTSC ones is a bit of an issue, having to use stepdown transformers, and the Coleco PSU isnt ideal for plugging into them due to size, so thats another issue to contend with.

You can use UK ColecoVision power supplies with US/Canadian ColecoVision's and vice versa - the supplies all output the same voltages on the same pins.

[marauder666]

5 hours ago, Ikrananka said:

You can use UK ColecoVision power supplies with US/Canadian ColecoVision's and vice versa - the supplies all output the same voltages on the same pins.

I know, but the owner only has 2 psus, one pal one ntsc,  and 4 consoles. Consoles were tested with uk psu.

 

[Ikrananka]

2 minutes ago, marauder666 said:

I know, but the owner only has 2 psus, one pal one ntsc,  and 4 consoles. Consoles were tested with uk psu.

 

It was just the fact that you mentioned using a stepdown transformer with the US power supply.  I guess I misinterpreted what you were saying and that you were, I assume, using the transformer to test that the supply was working.

[SiLic0ne t0aD]

For future reference, you don't have to take the front panel off to get the two halves of the case apart.

It might seem a little harder at first, but trust me, it's no big deal after you do it a couple times.

The front facia sticker/decal usually gets ruined when trying to remove it from the front panel too, so I'd avoid doing it that way at all costs, next time around.

[marauder666]

I didnt take the panel off, managed to get top off with it intact, it was very tight though.  Went back on easier.

[NIAD]

Here's a "How to" on disassembling the CV. Also, did you do the C88 Sound Fix or perhaps it was previously done seeing as the system were all Composite modded?

 

 

A Guide to Disassembling the ColecoVision - Rev. #01 (2010) (SlowCoder).pdf C88 TECHNICAL SERVICE BULLETIN.pdf

[marauder666]

That fix looks like its only for the Adam.

I took the audio from the input pin into the rf modulator.

 

[+-^CrossBow^-]

16 minutes ago, marauder666 said:

That fix looks like its only for the Adam.

I took the audio from the input pin into the rf modulator.

 

Audio needs to come from C88 is you plan to use the SGM or get one in the future. Even then, the audio from the SGM is still several DB lower than the audio from the CV itself. To help with this, I ended up having to remove C88 completely and then routed separate wires from each of the vias that C88 was in to the audio jacks.

 

[NIAD]

On 3/18/2022 at 1:41 PM, marauder666 said:

That fix looks like its only for the Adam.

I took the audio from the input pin into the rf modulator.

 

The majority of the OLD composite video with audio mods that were made (Eve Electronics, Ben Heck, etc.) for the ColecoVision tapped sound output from the wrong location and this would cause the volume output from device connected to the Expansion Interface like the EM#1 Atari Adapter and Opcode SGM to be very low... one had to raise the volume of the TV almost to the max. I included info on this seeing as you said the CVs you had were already composite modded, but should have also explained further.

 

The Stand-Alone ADAM Memory Console suffers from the same issue and the CV board has to be properly modded for correct sound output from devices connected to the Expansion Interface.

 

It's probably safe to say that the very first ColecoVision Game System Composite Video with Audio Mod by Eve Electronics in 1985/86 was based off of how Coleco improperly tapped into sound on the ADAM version of ColecoVision PCB.

 

Edited March 19, 2022 by NIAD

[GDT2019]

Just a quick note to Andy and Jon for the fantastic work they have done on my Colecos.  The boys do a top job, and the fantastic pictoral records they create of their mod work, now adorn my loft / games room, giving a real sense of history to each console.  Cheers chaps.  You have the patient of saints!

Edited March 27, 2022 by GDT2019