7800 Restoration

[juansolo]

As I’d started littering up posts in my other thread about video upgrades with this, @marauder666 suggested I started a new one covering the restoration of a 7800 for anyone interested… So here it is:

Being in the UK brings a few issues when it comes to the 7800, the PAL machine is a wee bit compromised in comparison to the NTSC one (see the other thread!), and getting hold of NTSC 7800’s here is a bit of an issue. What Cleggy (marauder6666) and I tend to do is buy spares/repair 7800’s in the sorriest states from eBay and restore them. Basically if I can bag an Atari for around £20 delivered, I’ll grab it and if all else fails, it a parts machine. Though we’ve only ever had to do that with one (a 2600jr). Still no idea what’s wrong with it as all the chips were fine. Indeed the TIA from it has ended up in Cleggy’s VCS as it was getting the star field bug in Cosmic Ark.

I digress, I’ve been trying to get my hands on an NTSC 7800 for about a year and they’re just super rare here or super expensive. So a couple of weeks back I decided to take a chance on a spares/repair machine from the US on eBay. However, unlike our usual frugal basket cases, this one worked out a little pricier. After shipping and import duty it was £134.54 (about $190 or there abouts). Seems a lot for a crappy untested machine but this was actually the cheapest up on eBay by some margin that had international shipping!

 

pics from the eBay advert, I don't wear pink nail polish, can't speak for Cleggy though...

It had a lot of what I look for in Atari auctions. It didn’t look utterly destroyed, it didn’t actually look bad (we’ve had a lot, lot worse!). There’s corrosion under the plastic, so there's no hidden pristine band (it's nice when that happens), but that also points to that there’s probably more to come… But most importantly it’s untested, our kind of machine as it stops the price going silly.

It’s just landed here after going on seemingly a US tour before leaving the country then being delivered domestically by our most feared UK courier in terms of parcel sympathy… So I was a little worried to say the least. Anyhow, it’s arrived with Mr Clegg and he’s already started proceedings (I’ll be over in a couple of days to assault it with the soldering iron).

[juansolo]

It landed this morning, and Cleggy got to work. Didn’t look too bad…

 

Best thing is it tested fine (it’s in B&W because it’s a PAL panel that’s not multi-standard).

 

A little bit of shipping damage. But nicely it hadn’t smashed it off, otherwise our only course of action would be finding the bits and epoxying them back in there.

 

Being intact allowed Cleggy to do some plastic welding on the inside This works far better than it has any right to.

 

[juansolo]

This is pretty much par for the course for a UK machine that's been stored in a loft or garage, we expect corrosion on PAL machines. I can only assume this one's lived a lot of it's life in one of the more humid states. Still, I've seen worse. My spare machine is called Rusty, because there was more rust on the shield than metal. The rust had leeched into the PCB, destroyed the switches and the ports. That donor 2600jr came in handy once again there, a tenner well spent that machine! I'll bin the shield as it's going to be my own machine and will likely be apart a lot for experimenting. Eventually it'll get an internal Atarivox which the shield negates anyhow. Were it to be a machine I'd sell, Cleggy would (because he CBA and I certainly can't) wire brush it, prime and paint it (apart from the bits that need to be bare) which can look rather nice.

 

 

Plenty of long dead things under the hood and this is destined for the sink to be washed given the mank inside.

 

 

What this did however bring to light is the mystery of the multiple labels. It's got two SN stickers and on top of those it's got a Made in China (printed in Hong Kong! Made in Taiwan under that) sticker. Quite why this might be the case is quite perplexing. Theorise away!

 

 

Finally, here it is naked. It doesn't look bad at all. The modulator is as expected given the shield, but that has to go anyhow as it's in the UK now and we don't speak NTSC, so we'll be teaching it PAL (using 'S' instead of 'Z', and the re-introduction of 'U', that sort of thing). Also on the cards is the usual, we'll swap out the bespoke power plug for ye-olde 2.1mm DC jack, it'll get re-capped (all 3 of them...), and the regulator will be swapped out for a higher rated item. The buttons are notorious for being rubbish, so they get swapped. Other than that, it'll get a clean up where needed.

 

Then it'll be on to the video mod, haven't completely decided what I'm doing there yet. I may yet do the Asteroids ROM mod, again I'm undecided on that. But we'll take it one step at a time.

Edited June 7, 2021 by juansolo

[+-^CrossBow^-]

Made in late '87 and essentially uses the newer revision board with the extra timing circuit silkscreened but bypassed completely. 120ns Sony RAM with the standard resistor off the WE line as well. I think I've only seen that resistor installed on the 120 and 100ns variants. I'm still trying to figure out why they added the masking tape in the upper right corner of the RF shield section? I've seen this more than and once and usually remove it. My guess is they might have had issues with the shielding sticking out a bit too far and possibly shorting against the + leg off the power port and perhaps scrapes in the soldermask on the + input voltage rail being a possible issue as well? I remove it when I find it.

 

And as you are adding in a barrel jack to replace out the current power jack, remove that ferrite bead just before the main filter cap and replace with a standard 400x series rectifier diode for some polarity protection in case someone decides to plug a Nintendo PSU into that thing or something.

 

I can only hazard a guess on the multiple labels, but this is my guess:

 

The case shell likely came from another 7800 that was returned to Atari and that unit was a slighter older revision board set hence the A1 on the label underneath. Then, this A3 revision board is done and fabbed and needs a shell to put into and Atari grabbed this one as it was in good shape, slapped a new serial label on it with the correct revision A3 and kicked it out the door. This is just further proof that Atari was cutting as many corners as they could on the console production side of things. No different that my late bought '87 era 7800 that actually contained an early '84 made board in it. Has the expansion port of course, but was sold in a case shell without the expansion port opening. That 7800 was bought new from Kay-Bee toys and was not listed as refurbished or anything. So my guess is it was originally a defective main board that sat on a shelf along and eventually was repaired and shipped out as new.

 

 

 

[marauder666]

I think the masking tape, is to protect against shorts, as the ground the shield sits on is very close to the power rail.

The other side of the board,  only one bodge.

Much nicer solder than a few of the PAL ones with had recently.

 

[+Muddyfunster]

A @juansolo & @marauder666 hardware thread. I knew it was going to be full of circuit board pr0n. !

 

 

[+-^CrossBow^-]

1 hour ago, marauder666 said:

I think the masking tape, is to protect against shorts, as the ground the shield sits on is very close to the power rail.

The other side of the board,  only one bodge.

Much nicer solder than a few of the PAL ones with had recently.

 

That bodge is a deglitch cap that was added and is present on the later redone schematics from 2003.  Basically just attaches a small cap off A15 (Pin 25) on the 6502 to ground. It isn't present on all 7800s but a fair number of the older units have these including most of the 1984 made era units as well. 

[juansolo]

Dawned on me I was talking (well writing) bollocks in that up there... But I can't edit the post to hide the evidence so here's the correction:

 

- The reason the image was black and white on the panel was a PAL only analogue tuner. That TV I think can handle NTSC via composite.

- We're not converting it from NTSC to PAL, no idea what I was thinking there, we're going to be outputting NTSC via S-Video ultimately. Though I did the opposite with my PAL SNES one-chip that is now an NTSC one chip. You have to change the crystal and region on that (pretty easy). It also helps if you remove the region lockout, which I haven't bothered doing as that machine only runs a flash cart anyhow. So it's a rather bizarre UK locked NTSC SNES now.

 

Nothing to see here, move along...

[juansolo]

I finally got around to Mr Clegg's today and got cracking with the 7800. He'd already cleaned it up rather nicely, re-capped it and swapped the regulator. He'd also pulled the cart guide off to clean it and the cart slot itself. Finally he de-rusted some of the screws by soaking them in vinegar. I finished the job by swapping out the buttons, then removing the regulator, channel switch, and a load of bits that are no longer required. On top of this, I gave it a bit of a clean around the bottom edge which was a bit manky, and re-flowed the solder for all the mechanical bits that see some abuse (cart slot & joystick ports). Finally I swapped out the bespoke power jack for a 2.1mm DC jack, dropping in a diode as @-^CrossBow^- recommended. I wouldn't normally bother with my own machines, but I thought I should probably get into the habit of doing it as it's good practice. Last thing was removing the glue from the colour trimmers as they'll be wrong, they always are.

 

all destined of the bin. We keep the pulled power jack and channel switch (not in the photo) as spares

 

For the cap-swap deniers, yep this machine was working prior to pulling them and the two 220u ones were fine. But the 2200u one was already measuring north of 3000u, showing that it was on it's way out.

 

...yes that's a cheapo cap measurer, it does the job we need it for.

 

Now it's ready for dropping some sort of video out onto it so we can test it properly before deciding what to do next.

 

shiny

 

If you open and zoom in on the above picture you can see why they put the masking tape on the top right of the before pic. The power rail is right next to the ground the shield sits on. A bit of rubbing and it could wear through the silk screen causing a short via the shield. Bit of poor layout work when it comes to that trace! That said, it's a massively better laid out PCB than the PAL 7800... I think they were drunk when they tackled that.

Edited June 9, 2021 by juansolo

[juansolo]

For testing we grafted in an old AJM that had been removed from Cleggy's machine when we changed to relay switching. It had already had the clock pulled from it and re-used on his new one, so we just tidied that up a little and chopped the board down a little. It's here bodged in with an s-video jack and phono jack (for audio).

 

 

The following are all pics taken of it plugged into a 14" PVM via S-Video. This CRT does have a dark patch on it on the left anyhow (you can see it on the grey and yellow), otherwise it's super difficult not to catch it scanning as it seems to be running at near as damnit the same speed as the camera CCD. I took a lot of photos just to get these! Just bear in mind it looks way, way better in the flesh and the colours might be a little out due to it's CCD not being a human eyeball.

 

2600 NTSC colour bars

 

7800 NTSC colour palette

 

I was pretty shocked just how good this actually turned out with just a little tweaking of the pots. The picture is surprisingly good. There's a little shadowing visible on some colours on the right hand side on the 7800, but it's not bad. Likewise there are very mild jailbars on the 2600 side, but you have to shove your face very close to the screen to even see them. From a normal playing distance it looks bloody good. Way better than I expected. It also doesn't do the colour rolling thing that the PAL systems do that you can't get rid of.

 

Indeed the picture quality of the NTSC machine is leagues ahead of the PAL machine. To the point I'm sure a UAV on it's own is more than enough to score a brilliant picture out of one. For those who haven't experienced it, I cannot emphasise enough just how bad the PAL 7800 is as standard.

 

the black line through the sun is the camera catching the scanning and is invisible to the human eye

 

likewise the fat shadowy bar in the middle 2/3 of this capture

 

Being unused to the NTSC colour palette set up the colours with the test card and assumed they were correct. Again they look way better in person and certainly seem to be in the right sort of area.

 

 an example of the shadowing you get on certain colours. We've seen this before, and I'm not greatly bothered by it

 

So, what's next...?

 

The problem we now have (thank Brexit) is that a UAV was £35 here, now it'll have further costs. When you're looking at potentially £45-50 for one ($67 or there abouts) it becomes a pricey bit of kit. I suspect it will give a better picture, certainly with our chroma switching added, but it isn't going to be masssively better than this, and certainly not the cost of an RGB mod for a 2600 good. Had it been bad with our old mod I'd have bitten the bullet and more testing would have occurred. However now, I think the pair of us see that as a bit of a waste of money given just how good it is right now. So the plan as of today is to fit the s-video and phono sockets to it on Saturday. I prefer the phono for the audio as it's the wiring I'll be using and it also means the machine will be way easier to pull from the case with only 2 additional screws for the S-Video jack to remove. It'll probably stay like that for the time being. It'll certainly get an Atarivox inside when our next order goes in with AA (I have a list, just waiting for the next batch to be completed/announced). Otherwise the next update is likely to be it completed.

 

I'm a very happy chappy today with how things have turned out.

Edited June 9, 2021 by juansolo

[juansolo]

UAV costs are worse than I thought as I thought I really should get one for the sake of science. Getting them direct from TBA seems to be the only option (https://www.ebay.co.uk/itm/283503178836?hash=item42021b3454:g:UXQAAOSwnvdcygRN), which comes to $69 inc postage. Add to that duty and handling and that can add 20% + £8-12 on top of that total. So a worst case scenario of around £70 or a buck short of $100. Yeah, science is gonna lose out on this one sadly

 

The other thing I was considering was the Asteroids ROM swap, then Cleggy mentioned that someone on here was contemplating an uber ROM with maybe one of Bob's games on it (I think it'd actually be pretty cool if it was his version of Asteroids). I think I'll hold on for that, but that's a no-brainer as far as I'm concerned if that comes to pass.

[juansolo]

Hmmm, ok it's cheaper direct. Just been through on their site getting a basic UAV without the manual + shipping, all up it works out at £29.50 + Duty/Handling, giving a possible maximum of £48 ($68, not totally horrific). However Cleggy has PM'd me and has mentioned the now £134 limit we have meaning small companies have to be VAT registered with UK customs to process anything less than that (possibly the most backwards thing our government has done in some time), I suppose I'll have to find out if getting one direct is still ok. A way around this is to use eBay of course, which gets me back to square one...

 

If anyone in the UK has a spare UAV kicking around they'd be prepared to sell to me please PM me. That said, I know at some point I'll just bite the bullet and buy one.

Edited June 10, 2021 by juansolo

[+-^CrossBow^-]

Yes the 7800 only requires the basic UAV board as everything has to be wired to it directly anyway. The only thing you gain with the Kit versions is the green terminal block. But most people are likely to solder the output wires straight to the UAV anyway, or like I do, use something else to connect to the outputs using connectors or something.

 

And yes TBA is the only place to get UAVs directly as the schematics and rights to their production and sale was handed over to TBA from Bryan about 2 years back now I guess?

 

[+mksmith]

On 6/10/2021 at 1:57 AM, juansolo said:

I finally got around to Mr Clegg's today and got cracking with the 7800. He'd already cleaned it up rather nicely, re-capped it and swapped the regulator. He'd also pulled the cart guide off to clean it and the cart slot itself. Finally he de-rusted some of the screws by soaking them in vinegar. I finished the job by swapping out the buttons, then removing the regulator, channel switch, and a load of bits that are no longer required. On top of this, I gave it a bit of a clean around the bottom edge which was a bit manky, and re-flowed the solder for all the mechanical bits that see some abuse (cart slot & joystick ports). Finally I swapped out the bespoke power jack for a 2.1mm DC jack, dropping in a diode as @-^CrossBow^- recommended. I wouldn't normally bother with my own machines, but I thought I should probably get into the habit of doing it as it's good practice. Last thing was removing the glue from the colour trimmers as they'll be wrong, they always are.

 

all destined of the bin. We keep the pulled power jack and channel switch (not in the photo) as spares

 

For the cap-swap deniers, yep this machine was working prior to pulling them and the two 220u ones were fine. But the 2200u one was already measuring north of 3000u, showing that it was on it's way out.

 

...yes that's a cheapo cap measurer, it does the job we need it for.

 

Now it's ready for dropping some sort of video out onto it so we can test it properly before deciding what to do next.

 

shiny

 

If you open and zoom in on the above picture you can see why they put the masking tape on the top right of the before pic. The power rail is right next to the ground the shield sits on. A bit of rubbing and it could wear through the silk screen causing a short via the shield. Bit of poor layout work when it comes to that trace! That said, it's a massively better laid out PCB than the PAL 7800... I think they were drunk when they tackled that.

Very nice @juansolo and @marauder666 - really enjoy reading about these repairs.

 

Can you explain a little more about your methods replacing the power jack? Also how does one power a US NTSC machine in the UK - do you still require a transformer/converter from 110v?

[juansolo]

8 hours ago, mksmith said:

Very nice @juansolo and @marauder666 - really enjoy reading about these repairs.

 

Can you explain a little more about your methods replacing the power jack? Also how does one power a US NTSC machine in the UK - do you still require a transformer/converter from 110v?

The US and UK machines have the same power requirements. So a UK PSU will work on a US machine and vice versa.

 

We use either LiteOn or Cisco branded PE-1170-1SA1 5V 3A PSUs (https://www.ebay.co.uk/sch/i.html?_from=R40&_trksid=p2334524.m570.l1313&_nkw=pe-1170-1sa1&_sacat=0). We use them for most things that need 5V DC (MiSTer, PiCade, XL/XE, etc), they're great PSUs and have plenty of poke for most applications.

 

Bugger, posted the wrong PSU, that's the 5V one we use, you want a 9V one for the 7800. We use a Mean Well 9V DC Power Supply, Mfr. Part No. GS15A-2P1J (https://uk.rs-online.com/web/p/desktop-power-supplies/7212092/?relevancy-data). It's early morning here... Cleggy (who PM'd me) is obviously more awake than I am right now!

 

The DC jack is very specific and fits very snugly. It's made by Würth Electronik, part no: 694106402002. We get them from RS (https://uk.rs-online.com/web/p/dc-power-connectors/1224880/) but they're also available from Digikey (https://www.digikey.com/en/products/detail/würth-elektronik/694106402002/5047523).

 

There's a bit of a trick to getting it right, which if I remember I'll document photographically next time I do it. It fits almost perfectly in the cutout already there (you might have to file the case a fraction out of the sides. Sometimes you do, sometimes you don't). Once that's done I solder in a bit of solid core into the ground pad from the original jack (we use the original pads), but I don't solder it to the jack, I cut it short enough to go in, leaving a little for adjustment. Then I dry fit it in the case until it lines up. Once I'm happy it'll all fit it all comes out again and I solder in the power wire. Again solid core, but this time sheathed. Dry fit again and cut to length. Finally I'll assemble it in the case, line up the socket in the hole, and use a cable tie around the jack and through the original sockets mounting holes. Once in position this gets pulled tight as possible, then it's out with the board again and only then do I solder the wires to the jack. Once done the ground wire is probably only a couple of mm long and helps anchor it. It along with the cable tie and the sides of the case make the whole thing suprisingly secure. Easily as strong, if not stronger than the original jack.

 

I've asked Cleggy to take some close ups, I'll post them up when he sends them over.

Edited June 11, 2021 by juansolo
Whoops, wrong PSU... I'm not good when it comes to mornings.

[+mksmith]

1 minute ago, juansolo said:

The US and UK machines have the same power requirements. So a UK PSU will work on a US machine and vice versa. We use either LiteOn or Cisco branded PE-1170-1SA1 5V 3A PSUs (https://www.ebay.co.uk/sch/i.html?_from=R40&_trksid=p2334524.m570.l1313&_nkw=pe-1170-1sa1&_sacat=0). We used them for most things that need 5v DC (7800, MiSTer, PiCade, XL/XE, etc), they're great PSUs and have plenty of poke for most applications.

 

The DC jack is very specific and fits very snugly. It's made by Würth Electronik, part no: 694106402002. We get them from RS (https://uk.rs-online.com/web/p/dc-power-connectors/1224880/) but they're also available from Digikey (https://www.digikey.com/en/products/detail/würth-elektronik/694106402002/5047523).

 

There's a bit of a trick to getting it right, which if I remember I'll document photographically next time I do it. It fits almost perfectly in the cutout already there (you might have to file the case a fraction out of the sides. Sometimes you do, sometimes you don't). Once that's done I solder in a bit of solid core into the ground pad from the original jack (we use the original pads), but I don't solder it to the jack, I cut it short enough to go in, leaving a little for adjustment. Then I dry fit it in the case until it lines up. Once I'm happy it'll all fit it all comes out again and I solder in the power wire. Again solid core, but this time sheathed. Dry fit again and cut to length. Finally I'll assemble it in the case, line up the socket in the hole, and use a cable tie around the jack and through the original sockets mounting holes. Once in position this gets pulled tight as possible, then it's out with the board again and only then do I solder the wires to the jack. Once done the ground wire is probably only a couple of mm long and helps anchor it. It along with the cable tie and the sides of the case make the whole thing suprisingly secure. Easily as strong, if not stronger than the original jack.

 

I've asked Cleggy to take some close ups, I'll post them up when he sends them over.

Ah great thanks! The PSU is a switching power supply (110-240v) yeah?  I've been tempted to try and get a NTSC machine for development purposes eventually so that is very helpful!

 

The pins on my original PS are starting loose proper connection so I do need to mod the power soon. My last attempt to fit a temporary jack nearly ended in disaster for my spare machine!

 

[juansolo]

Input is 200-240v, so it'd be no good used in the US. Pretty sure Oz is the same as the UK (240V 50Hz) so you'd be fine with those PSUs if you can source them locally.

 

EDIT: Now I've posted the correct PSU, that one is actually 100-240V input so could be used worldwide.

Edited June 11, 2021 by juansolo

[+mksmith]

Just now, juansolo said:

Input is 200-240v, so it'd be no good used in the US. Pretty sure Oz is the same as the UK (240V 50Hz) so you'd be fine with those PSUs if you can source them locally.

Cool - wasn't sure whether there was US 110v required. Thanks mate!

[juansolo]

12 minutes ago, mksmith said:

Cool - wasn't sure whether there was US 110v required. Thanks mate!

It's not neccessary to use the supplied 110V PSU with most machines with an external power brick. Just find out the power requirements of the machine and find something that decent that meets that.

 

In some instances you can't get around the external brick or it has an internal supply. For those you'd need a step down transformer. Either 110V for US or 100V for Japan. Usually you can get away with using a 110V step down for Japan, but ultimately you are overvolting the power so if you can source a good quality 100V one, in those instances it'd be better. Don't use cheap Chinese eBay stuff if you're doing that, get something decent.

[juansolo]

Bugger, posted the wrong PSU, that's the 5V, you want a 9V one for the 7800. We use a Mean Well 9V DC Power Supply, Mfr. Part No. GS15A-2P1J (https://uk.rs-online.com/web/p/desktop-power-supplies/7212092/?relevancy-data). It's early morning here... Cleggy (who PM'd me) is obviously more awake than I am right now!

 

Edited original post.

Edited June 11, 2021 by juansolo

[juansolo]

Piccage from Mr Clegg (@marauder666)

 

 

As with all the pics on this thread, much zoomage is available if you click then click to open in new window, then click again to zoom in.

Edited June 11, 2021 by juansolo

[juansolo]

Also if you're doing this it's worth swapping out the ferrite ring for a diode as @-^CrossBow^- suggested:

 

On 6/7/2021 at 5:24 PM, -^CrossBow^- said:

And as you are adding in a barrel jack to replace out the current power jack, remove that ferrite bead just before the main filter cap and replace with a standard 400x series rectifier diode for some polarity protection in case someone decides to plug a Nintendo PSU into that thing or something.

 

[+mksmith]

3 hours ago, juansolo said:

Piccage from Mr Clegg (@marauder666)

 

 

As with all the pics on this thread, much zoomage is available if you click then click to open in new window, then click again to zoom in.

 

3 hours ago, juansolo said:

Also if you're doing this it's worth swapping out the ferrite ring for a diode as @-^CrossBow^- suggested:

 

 

Awesome thanks for the pics - much appreciated!

[juansolo]

UAV purchased for £30.79 delivered. We'll see how much it's total is once HMRC and the Post Office are done with it!

[+DrVenkman]

13 minutes ago, juansolo said:

UAV purchased for £30.79 delivered. We'll see how much it's total is once HMRC and the Post Office are done with it!

The RF on my NTSC 7800’s is terrible. Just rotten. The improvement from composite through the UAV is amazing, and the S-video is even better. Not sure how much difference it will make on your test systems but I’m looking forward to seeing your appraisal.