ColecoVision fuzzy / static sound problem.

[Oldschoolgamer1]

Hi I’ve read about this problem on several threads from several different forums including this one I think. However I seem to have a different motherboard version (in the attached pictures) I think from anything I’ve seen before regarding this problem. Apparently it’s ‘Coleco ColecoVision US Rev D’ and is partly why I’ve created a new post regarding the fuzzy / static sound problem I’ve been having.

 

This ‘Coleco ColecoVision US Rev D’ again seems to have a different motherboard design and in particular the RF box. I’ve read about the two pots for video and audio but again all of the designs I’ve seen are for different versions to mine. I’ve attached a picture of the RF box and discovered that the pot towards the top right is for video so I think that the other one is the one for audio which is at the centre bottom and inside sunken down in the silver cube type component with some writing on it. I tried adjusting this but had no joy regarding the audio. It was harder to access than the video pot. I also tried some different RF leads.

 

Is all of this correct? If so I was wondering if there is anything else I can do to get the audio fixed? Again I’ve heard about an AV mod, an RGB mod, a VGA mod and also a mod involving the sound chip. I am also aware of recapping particularly with video / audio problems. However I don’t have these skills, experience and equipment / components to do anything like this and an attempt by myself could make the problem worse, a lot worse or to the point where the machine is basically dead. I live in the Uk Doncaster area if there is anyone that does any kind of work like this who could maybe repair my machine and audio?

 

Anything would be greatly and genuinely very much appreciated.

 

 

 

 

[Falonn]

This is definitely a PAL system.  Most of the tutorials and guides out there are for the various NTSC revisions.  They're completely different designs, so an NTSC Rev.D won't look anything like a PAL Rev.D.  While the components are fundamentally the same, they're all in different places and they've all got different labels.

 

(I don't have any answers for you, sorry!  But hopefully this sheds some light on why it's been hard to find answers so far.  It would be cool if the community was eventually able to bring the information available for all three versions---PAL, NTSC, and SECAM---to parity.)

 

I hope someone else can help you!

[ChildOfCv]

Yeah, that is definitely NOT a US version.  It even has a delay line for PAL on the main board.  So if you're trying to use that on a NTSC television, you're definitely going to have issues.

[Oldschoolgamer1]

Ah ok thank you very much for all of your info. I think my CRT TV is PAL that I've been using.

[ChildOfCv]

Hmm.  The datasheet for the modulator says it's supposed to output to channel E36.  But so far I can't find a more detailed doc that includes adjustment instructions.

 

Well anyway, the sound carrier is likely still that metal-encased transformer.  I'm guessing that the channel tuner is the one inside of that sub-box.  It needs to run at around 480MHz, so it's likely specially shielded.  The other two may have something to do with PAL phasing.

 

 

[Oldschoolgamer1]

Yeah I couldn't find a lot regarding my motherboard design.

 

I guessed that's where the audio would be via elimination and what I'd seen on another motherboard design so I had a good go at trying to adjust it but no joy with that it seemed. Just hope I haven't caused more harm. The video was the one above it and to the right.

 

I'm not sure if there's anyone in the Uk that could fix it if some kind of mod needs to be performed?

 

Thanks for your help and info, it's very much appreciated.

[ChildOfCv]

5 hours ago, Oldschoolgamer1 said:

Yeah I couldn't find a lot regarding my motherboard design.

 

I guessed that's where the audio would be via elimination and what I'd seen on another motherboard design so I had a good go at trying to adjust it but no joy with that it seemed. Just hope I haven't caused more harm. The video was the one above it and to the right.

 

I'm not sure if there's anyone in the Uk that could fix it if some kind of mod needs to be performed?

 

Thanks for your help and info, it's very much appreciated.

So the adjustment did nothing at all?  That's odd.  It should at least change the signal.

 

One possibility is to look for another Astec UM-1286 modulator.  They appear on eBay every once in a while.  They were once common in European TV-output devices.

 

The Astec UM-1662 looks (from pictures) to be a nearly identical replacement that might be worth trying too.

[Oldschoolgamer1]

Hi again nah the audio one (if it is) in the silver cube type component didn't do a lot of difference from what I could hear when trying to turn and adjust the pot. There may have possibly been some changes but no more obvious ones like the sound coming through as it should I think. However the video one above it and to the right did change when turning and adjusting this pot. It got worse when adjusting it so I just turned it back to what I thought was the best picture. 

 

I've seen some of the Astecs on eBay. I saw the Astec UM-1662 but not the Astec UM-1286 which is the one I have. I saw some other models as well. I looked at the solder connections of my Astec UM-1286 and there seemed to be maybe four main legs and also maybe four or so wire connections. I'm not sure if any other Astec models would be compatible with my machine and even if they were technically specification wise I'm not sure if they differ in size so their legs and the wire connections may not be lined up for the right position on the board so maybe physically incompatible?

 

My main motherboard I've noticed is labelled as '91162 Rev D' and the smaller board where the RF modulator is I think is labelled as 91194 Rev B.

 

Anyway thanks again for all your cool info. 

[ChildOfCv]

Yeah going counterclockwise from the RF output back around to the lowest leg in the picture, the connections are:

 

+5 (through a resistor).  On NTSC versions, this is the channel 3/4 switcher

Sound input

+5 power supply

Composite video

 

Ground is through the case.

 

The 1662 appears to be the same thing, but with the RF out on a different side of the box.

 

Still another option might be to wait for Falonn/Mr Big's improved RGB output board, which would give you SCART or upconverter capability.

[Falonn]

Just for reference, here's the other side of that RF board.  Apparently the system I just picked up for PAL testing for the new RGB output board ("TMS-RGB") is exactly the same as Oldschoolgamer1's: 91162 Rev.D motherboard and 91194 Rev.B RF board with a UM-1286.

 

 

So I suppose the good news is that you can be reasonably confident it'll work with yours.

 

18 minutes ago, ChildOfCv said:

Still another option might be to wait for Falonn/Mr Big's improved RGB output board...

Who is Mr Big? ?

[ChildOfCv]

3 minutes ago, Falonn said:

Who is Mr Big? ?

Sorry, wrong franchise

 

But if he can sing "To Be With You", I'll still be impressed.

[Oldschoolgamer1]

The RGB sounds interesting. I guess that'd give possibly a better picture and easier to use on a TV and possibly especially an LCD with a HDMI lead to scart socket converter. How much would the RGB board cost? Also I have very little if any soldering experience although even considering that the Astec didn't look too bad a soldering job especially as these things go. It seemed about maybe 8 what looked like reasonably straight forward connections. I think the Astec comes with the four wires that come from it and into the board. I was just wondering if the RGB board would be difficult to install and solder considering my very much lack of experience here? 

 

Anyway thank you both once again for all of the really cool info, advice and of course your time. It's been very kind of you. 

[Falonn]

Assembling a board is a little trickier, but assuming you can buy one pre-assembled, the installation isn't much more than placing the mod PCB over the graphics chip's pins on the bottom of motherboard, then adding solder to five standard DIP through-holes.  Beyond that, you'd just need to run the output pads to any style jack of your choice (8- or 9-pin mini DIN, or directly to SCART, I suppose, if you don't mind cutting that large of a hole in the case). 

 

... on second thought, that little removable panel at the back of the PAL version of the case looks just right for a SCART connector.  I bet that same case was used for both the PAL and SECAM version of the console.

[Oldschoolgamer1]

It sounds harder as well as requiring more know-how which I haven't got a lot of here. I guess placing the mod PCB over the graphics chip's pins on the bottom of motherboard would involve some soldering I think? 

 

I could try the Astec UM-1662 at least as a starting point and see from there if it's successful. It seems easier in terms of know-how as well as soldering possibly? than the RGB so could be an alright place to start. What do you think?

Edited June 11, 2020 by Oldschoolgamer1
mistake

[ChildOfCv]

 

On 6/8/2020 at 12:33 AM, Falonn said:

Just for reference, here's the other side of that RF board.  Apparently the system I just picked up for PAL testing for the new RGB output board ("TMS-RGB") is exactly the same as Oldschoolgamer1's: 91162 Rev.D motherboard and 91194 Rev.B RF board with a UM-1286.

 

BTW, I'd be happy to reverse engineer that box if I could get my hands on it

 

For OSG's case, there are a couple of possibilities:  1) The ferrite core in the audio modulator is crushed into a fine powder and no longer useful.  2) The audio modulation circuit is dead (possibly a transistor).

[Falonn]

On 6/11/2020 at 10:21 AM, Oldschoolgamer1 said:

I guess placing the mod PCB over the graphics chip's pins on the bottom of motherboard would involve some soldering I think?

Yep, just adding a little extra solder to five or so pins.  It's not so bad if you've already got an iron.

 

On 6/13/2020 at 6:56 PM, ChildOfCv said:

BTW, I'd be happy to reverse engineer that box if I could get my hands on it

When I'd mentioned why I was interested in it to the seller, he said (via PM) that it would be cool if his system was able to help the community in some way.  I think it would be cool if it could keep doing the same!  A set of PAL schematics at the level of your NTSC set would be like, 100x more valuable to the community than my quick double-check that an RGB mod works.

 

PM me whichever address you'd like a PAL Colecovision to materialize when I'm finished testing these v2 TMS-RGB boards in a few days and I'll send it along on the next leg of its journey.

 

Really, this is a weight off my shoulders: I didn't have any idea what to do with this thing---besides storing it indefinitely---once the testing was finished.  Having it be useful to someone else would be great.

[Oldschoolgamer1]

Thank you both again for your help, again it really is very much appreciated.

 

I think I may try the Astec UM-1662. It's not that I mind waiting for the possible RGB stuff it just seems the Astec UM-1662 is possibly more straight forward in terms of know-how and also possibly soldering neither of which I have much experience of.  

 

I could try the Astec UM-1662 and when I've hopefully done it I could post here the results. Either way the RGB stuff could possibly be something for the future. 

 

Again does this all sound ok?

[Falonn]

Sounds good to me.  I don't know about the compatibility of the UM-1662, but at least it will give me a chance to finish the installation instructions for the RGB mod.

[Oldschoolgamer1]

Hi again it could be something to at least try at first. ChildOfCv said the Astec UM-1662 appears to be the same thing as the Astec UM-1286 (the one I have), but with the RF out on a different side of the box which it seems to be by appearance. I guess if it is incompatible it would only possibly complicate the process of trying to identify any possible faults but maybe that's electronics and maybe especially old 40 year old electronics. I could try to research it a little and see if I find out anything. Again if I do I could post it here.

Thank you once again and I'll hopefully keep you guys posted. I guess for the RGB mod take your time - better to get it pretty much right than rushing too much and possibly causing problems as a result.

[ChildOfCv]

5 hours ago, Oldschoolgamer1 said:

Thank you both again for your help, again it really is very much appreciated.

 

I think I may try the Astec UM-1662. It's not that I mind waiting for the possible RGB stuff it just seems the Astec UM-1662 is possibly more straight forward in terms of know-how and also possibly soldering neither of which I have much experience of.  

 

I could try the Astec UM-1662 and when I've hopefully done it I could post here the results. Either way the RGB stuff could possibly be something for the future. 

 

Again does this all sound ok?

Yeah that sounds okay.  You should watch a few YT videos on soldering if you want to maximize your potential out of the gate.

[Oldschoolgamer1]

Ok. I found and ordered an Astec UM-1286. I realise the Astec UM-1662 may have worked but I don't know for sure and it could have perhaps complicated any fault finding stuff had it not worked and may have created more uncertainties. I did try to find out if there were any differences between the Astec UM-1662 and the Astec UM-1286 but I seemed to be unsuccessful although I did have what looked to be a possibly reasonable lead but may have been effected by the virus situation. I could perhaps try again with a few emails if you or anyone else were interested? 

 

I would have gone for the Astec UM-1662 if I couldn't get an Astec UM-1286 or if there were any other reasons or advantages in doing so. I guess like-for-like is probably the best policy generally speaking I hope.

 

I think 'out of the gate' means from the beginning / starting out? Is that similar to 'right off the bat' which I think is used more in the USA.     

[ChildOfCv]

"Right off the bat" is probably a baseball term (also how COVID entered the world)

"Out of the gate" is probably a horse racing term.

 

But yeah they basically mean the same.

[Oldschoolgamer1]

Ah I see.

I get the COVID joke now after reading it again after a couple of days - I'm sorry about that and a bit slow of me there but I can be like that despite having some sense of humour sometimes. Maybe my more serious side at times doesn't help with that. Although I heard COVID did indeed possibly originate from bats but then may have migrated to chickens which then were eaten although I could easily believe that bats were eaten 'right off the bat'. If not maybe 'right off the bat to the chicken'.

Got me thinking I wonder how HIV started and where it originated? I guess not on a John Holmes set RIP. I suspect it was only kind of named possibly by the scientific community in the early 80s but may have been a lot older and before then. I think how it originated if known or accepted may have been under considerably more disgusting circumstances however.

Sorry about the at least partly crap post.