The UAV Rev. D Video Upgrade Thread

[+DrVenkman]

51 minutes ago, Heatvent said:

so not sure the differences between this board and the Ben Heck Drop In board,

Go to the first page of this thread and follow the link to Bryan’s original thread where he announced and discussed what became the initial public version (Rev C) of the UAV, and then go back to this thread and read the improvement made for Rev D. The board could certainly have been made to plug into the TIA socket but #1) the UAV was originally designed for A8 computers, not the 2600; and #2) not all 2600’s have socketed TIAs - desoldering a 40-pin chip without damaging it is substantially more challenging than doing so for a smaller 4050 socket if necessary. And it’s not even necessary to use a 4050 - you can wire the LUM signals directly to the UAV, which is how I have one installed in one of my 2600’s. When wired up correctly, you should get results as good - more likely better - than just about any other readily-available video mod. 

[Heatvent]

5 minutes ago, DrVenkman said:

Go to the first page of this thread and follow the link to Bryan’s original thread where he announced and discussed what became the initial public version (Rev C) of the UAV, and then go back to this thread and read the improvement made for Rev D. The board could certainly have been made to plug into the TIA socket but #1) the UAV was originally designed for A8 computers, not the 2600; and #2) not all 2600’s have socketed TIAs - desoldering a 40-pin chip without damaging it is substantially more challenging than doing so for a smaller 4050 socket if necessary. And it’s not even necessary to use a 4050 - you can wire the LUM signals directly to the UAV, which is how I have one installed in one of my 2600’s. When wired up correctly, you should get results as good - more likely better - than just about any other readily-available video mod. 

All fair points.  Also, good to hear that the UAV is superior in other ways.

 

On the grounding, I didn't have time to desolder / fix but just to troubleshoot I took a jumper cable and connected the "-" pad on the UAV to C204 for ground and it cleared up the audio noise and the picture (no more rippled edges).  Not sure if a bad ground connection is part of the issue rmzalbar is having but the pics of the video issues look very similar to the ones I was having.

 

 

 

 

[Heatvent]

Ok, classic case of one step forward two steps back.   I desoldered the 4050 chip tonight which was a bit of a struggle because when I soldered the IC socket on top, my sloppy soldering soldered the top of the legs to the top pads as well. With some patience, desoldering tool an desoldering wick, I was able to get the chip freed after a lot of fiddling.  I soldered the IC socket into the 4050 location and did a test with just the UAV installed.  No distortion although there is still a bit of hum/buzz coming through.  Altogether an improvement.  I was testing with the Combat cartridge and started the game.  Player 2 started firing repeatedly.  I quickly remembered the 4050 chip was not installed at it does some timing for the fire button (this is an older six switch).  I haven't figured out how I am going to mount everything so I thought I would just put the 4050 in the IC socket with the UAV disconnected and try via RF.  The RF picture seemed slightly worse than before but still ok/good. I started Combat and player 2 started firing repeatedly.  So not sure if I fried the 4050 chip in the process of desoldering.  I reflowed the IC socket and checked pins for shorts against each other and everything looks fine.  I ran out of time but I will check each leg to the pads on the bottom of the board to make sure they are all getting good connections.  Couple of things I also noticed as I was fixing this..

•  I think its a Transistor at O202 (right next to the 4050).  I removed this when I did the common AV mod.  I had put it back but I think I forgot to solder the legs.  This may have been my feedback / ground issue? 
• Strangely there was a nearby capacitor (that I did not previously remove) that also looked like it wasn't soldered.  

I fixed both of the above and in my stupidity didn't test the effects before moving on to desolder the 4050.  One day I will learn to do things one thing at a time.

 

Anyway, any thoughts on my misfiring tank opponent?  Is this definitely a 4050 issue?  Any troubleshooting tips?

 

I do have a 4050 on order so when it comes I can at least try a replacement and either confirm or rule this out.

 

 

 

[rmzalbar]

1 hour ago, Heatvent said:

Anyway, any thoughts on my misfiring tank opponent?  Is this definitely a 4050 issue?  Any troubleshooting tips?

 

On the 6-switch, there is a pullup to +5V from resistor R225, then through 4050 noninverting hex buffer into pin 7 and out of pin 6, then to TIA pin 35. Pressing firebutton grounds input line of 4050 dropping this entire path to zero volts.

 

So when firebutton is NOT pressed:

4050 pin 7 (input), 4050 pin 6 (output), and TIA pin 35 (input) should all be +5 volts. If you don't have +5 volts on input side of the 4050, pluck it, and check for 5V at the socket pin 7 to confirm pullup is OK and no short to ground. There is also capacitor and (sometimes) a zener diode to ground for protection between the joyport and the 4050. A failed diode can short.

 

If input of 4050 is OK and output is not, make sure 4050 has good +5 volt supply and ground.

Edited October 17, 2020 by rmzalbar

[Heatvent]

So pins 6, 7 and 35 are all low.  If I take the 4050 out, pin 7 is high (4.82v).  So it seems there is a short somewhere. It's getting late so I will try again tomorrow.  Maybe check the joyport for shorts?

 

Any other troubleshooting help would be appreciated .... thanks so much!

[+DrVenkman]

7 hours ago, rmzalbar said:

There is also capacitor and (sometimes) a zener diode to ground for protection between the joyport and the 4050. A failed diode can short.

 

6 hours ago, Heatvent said:

So it seems there is a short somewhere.

Check the capacitor and diode (if there is a diode installed). If one or both are shorted to ground, you’ll have issues. If those are both fine, then verify continuity of of the fire button signal all they way to TIA pins (pins 35 for player two, pin 36 for player one). If the 4050 is fine, if you don’t find a shorted cap or diode on the line, then something is amiss with your TIA. 

[Heatvent]

For the cap/diode.  Is this the service tip on C236 and C237?  Mine just has ceramic disc capacitors ... no zener diodes.

 

No continuity from either of the fire pins to the TIA pin 36/35.  I did check to see if the fire button has continuity to the 4050.  Not sure if it should but the fire pin on player 2 has continuity to pin 7 on the 4050. The fire pin on player one does not have continuity to any pins.

 

 

[Heatvent]

So doing some more checking and pin 35 TIA has continuity to pin 7 on the 4050.  Pin 7 has continuity to the fire pin on the P2 joyport.  But pin 35 on the TIA does not have continuity to fire pin on the P2 joyport.  Not sure if that helps identify the issue.

[Heatvent]

Correction pin 6 has continuity to pin 35 on the TIA

[rmzalbar]

All of your continuity checks are normal. Fire button should have continuity to pin 7 of 4050. Pin 6 of 4050 should have continuity to TIA pin 35. None of these pins should have continuity to ground. With the 4050 removed, you have 5v at pin 7, and 0v at pin 6. Normal.

 

What is NOT normal is that when you have everything plugged in, you no longer have 5v at pin 7 of 4050. I believe the 4050 is bad: It should not be sinking that 5v firebutton signal to ground on its input. That's the joystick's job (when you press the button.)

 

To visualize this - all the 4050 does is take a signal on its input (pin 7) and replicate the signal on its output (pin 6) before feeding it to the TIA. It just acts as a buffer to protect the TIA from static electricity or other tomfoolery that could otherwise arise from allowing the public to plug stuff directly into the expensive and sensitive TIA via the joystick port. It also standardizes the signal to a well-defined 0v (low) or 5v (high) signal, boosting it if necessary, in case the signal coming from the joystick is weak or iffy. But the input to the 4050 is high resistance - plugging it in shouldn't drag your 4.8v firebutton line down to zero all by itself.

 

The TIA lines that handle the joystick input are "active low" meaning 5v is "off" and 0v is "on."

 

The input lines for each of the joystick directions and button from the joystick port sit at 5v normally when they are not being pressed - the 5v is being trickled into the line through a current-limiting resistor, this is called a pullup. The 4050 sees the 5v voltage at its input, and accordingly puts 5v to its output to the TIA. When you press the button, you are connecting the line to ground, overwhelming the small resistor and draining the 5v down to zero. The 4050 sees this, and accordingly drops the output to the TIA to 0v. The TIA sees pin 35 change from 5v to 0v, and knows the firebutton has been pressed.

 

 

Edited October 17, 2020 by rmzalbar

[Heatvent]

I was just going through the schematics and seeing if I could follow things through...

 

Player 1 (Left) Fire - P1 fire connects to pin 9 input, pin 10 output on the 4050 and goes to pin 36 on the TIA. 

• I get continuity from P1 fire to pin 9 on 4050 and from pin 10 on 4050 to pin 36 on TIA.
• With CD4050 removed: 4.945v on pin 9    0.300v on pin 10    0.410v on pin 36 of the TIA
• With CD4050 installed: 4.944v on pin 9    3.592v on pin 10    3.590v on pin 36 of the TIA
• All appears normal (assuming ~3.6 on pin 10/36 is OK).

Player 2 (Right) Fire - P2 fire connects to pin 7 input and pin 6 output on the 4050 and goes to pin 35 on the TIA.

• I get continuity from P2 fire to pin 7 on the 4050 and from pin 6 on the 4050 to pin 35 on the TIA.
• With CD4050 removed: 4.945v on pin 7     0.300v on pin 6     0.481v on pin 35 of the TIA
• With CD4050 installed: 0.724v on pin 7     0.000v on pin 6    -0.002v on pin 35 of the TIA
• Seems like an issue when the CD4050 is installed.

 

My options at this point (unless there are some other checks I can do) is swap out the 4050 which I should have one before Wednesday.  Or, I have another 2600 that I could transplant the TIA chip (I don't really feel like desoldering another 4050 right now) and see if it is possibly the TIA chip.  Although, not sure if this poses any risk of damaging the TIA if there is an issue somewhere on the board or with the 4050 so I think I would rather wait until I get another 4050.

 

Edited October 17, 2020 by Heatvent

[rmzalbar]

I'd say it's the 4050. It's clear enough that the input side of the 4050 is dropping close to 0v when plugged in, when it should be near to 5v. Problem is not on the TIA side.

 

The 3.5 volts you are seeing on the output of the side that "working" is unusual. It seems the 4050 is not putting out a strong enough signal on its output there either. 3.5 volts is high enough to still be seen as "high" by the TIA, but it really should be close to 5v.

 

You shouldn't be able to damage the TIA in your testing, even with a failed 4050 because the only voltages available to the 4050 range from 0 - 5v, which the TIA is designed to accept on its inputs. The issue is that it's not getting the voltage levels you want it to get from the 4050. You should try to remember to take static electricity precautions, though. Touch your finger and your probe tip to ground just before you touch probes directly to the TIA pins, for example, to make sure you're not carrying a high voltage static charge along with you to the sensitive TIA. We know it doesn't have very good input protection, because there is a service bulletin to add a zener diode shunt to ground on the firebutton input line for the later models of 2600 that eliminate the 4050, running the firebutton straight to the TIA.

 

Zener diodes do nothing unless a voltage exceeds a limit, say 6 volts, and then it basically conducts all voltages more than that to ground, safely dumping any static charge and preventing the line from rising above 6v. This is what that diode is doing that you see on your schematic, but it's only protecting the input of the 4050.

Edited October 17, 2020 by rmzalbar

[Heatvent]

Super helpful ... thank you for explaining how this works.  I was trying out different joysticks at one point so maybe I fried the 4050 when I did this. Sounds like I should plan to add the diode/cap fix.

[rmzalbar]

Yes, the zener is shown on the schematic but with a note saying it was implemented later, and see page 3-3 of the service manual for how to install it by soldering it across the existing capacitor. They specify an Atari part number instead of the value of the zener, but any zener diode rated between 5.5 - 7.5 volts would be fine. High enough that 5v won't trigger it but low enough to clamp the voltage down to within safe limits of the 4050 for brief zaps.

 

When you solder a diode you have to keep it relatively cool. Pinching the lead with needlenose pliers between where you're soldering and the diode, or doing something similar to that, will serve as an adequate heatsink.

 

Another way is if your iron is hot enough to touch the joint for no more than a second and get a good melt, that would be OK too as there won't be time for heat to build up and travel along the lead. Then blow on it.

Edited October 17, 2020 by rmzalbar

[Heatvent]

Quick update...

 

I got the new 4050 yesterday and tried it.  The P2 fire button seemed to be working fine, however, strangely the P1 fire button was constantly firing.  I measured the voltage on the pins on the 4050.  Pin 7 was at 4.94 v and pin 6 was somewhere around 3.5-3.6.  Pin 9 was floating a bit between 4.8 and 4.9x (which I think was causing the firing to happen) and pin 10 was something like 3.5-3.6.  With the game running and P1 firing, attaching the probes from the multimeter seemed to stop the firing and then it stabilized above 4.9v which seems to be the high/low trigger point on the TIA chip.  I didn't have time to spend on it so it was a quick once over and I could be missing something but a couple of questions..

• Any ideas on the floating pin 9? What could cause this?
• The 3.5-3.6v on pins 6 and 10 seem strange to me ... any ideas if there is something else I should be looking at like I have a short or bad component somewhere?

I will try to spend some more time on it tonight, I did this late last night.

 

Thanks

[rmzalbar]

38 minutes ago, Heatvent said:

Quick update...

 

I got the new 4050 yesterday and tried it.  The P2 fire button seemed to be working fine, however, strangely the P1 fire button was constantly firing.  I measured the voltage on the pins on the 4050.  Pin 7 was at 4.94 v and pin 6 was somewhere around 3.5-3.6.  Pin 9 was floating a bit between 4.8 and 4.9x (which I think was causing the firing to happen) and pin 10 was something like 3.5-3.6.  With the game running and P1 firing, attaching the probes from the multimeter seemed to stop the firing and then it stabilized above 4.9v which seems to be the high/low trigger point on the TIA chip.  I didn't have time to spend on it so it was a quick once over and I could be missing something but a couple of questions..

• Any ideas on the floating pin 9? What could cause this?
• The 3.5-3.6v on pins 6 and 10 seem strange to me ... any ideas if there is something else I should be looking at like I have a short or bad component somewhere?

I will try to spend some more time on it tonight, I did this late last night.

 

Thanks

Floating pin 9: Pin 9 is the trigger line coming from the joystick port, which is always fed +5 volts from a pullup resistor. It should be near 5v when firebutton is not pressed. 4.8-4.9 is fine (there will always be some losses, which is why you'll not see the full 5v anywhere distant from the power supply). It shouldn't be "floating" as it should be actively fed 5v through a resistor, which you can see on your schematic. Do you mean that the value drifts around? Make sure you have a firm connection with your probes. You can confirm presence of ~5v at this pin with 4050 unplugged.

 

3.5 - 3.6 volts on pins 6 and 10: The 4050 should be capable of feeding enough current to raise the outputs to close to the input, i.e. it should be near 5v when 7 and 9 are 5v. These lines go straight to the TIA.

 

A multimeter adds some parasitic load (a few milliamp) and some capacitance. This can only matter if the circuit is not actively fed or drained, so leakage currents cause the voltage to passively float up to some level, easily drained away by your multimeter. However, the output of the 4050 can only be at +5v or ground, so there can be no float on the outputs while that chip is powered up and functional. Again its looking like the 4050 isn't strongly pulling the output circuit high or low. Check the socket for good contact on all pins. You should be getting a strong +5v power supply to the 4050 on pin 1, and a good ground on pin 8.

 

You can prove the TIA is working by jumping +5 volts over to pin 10. Firing should stop immediately. Its trigger point, by the way, should not be anywhere near 4.9v, it should be much lower. I can't find a spec on the TIA logic levels, but the trigger point should be somewhere between 0 and 5v, but closer to the middle than near one of the extremes.

Edited October 21, 2020 by rmzalbar

[Heatvent]

On 10/21/2020 at 11:24 AM, rmzalbar said:

A multimeter adds some parasitic load (a few milliamp) and some capacitance. This can only matter if the circuit is not actively fed or drained, so leakage currents cause the voltage to passively float up to some level, easily drained away by your multimeter. However, the output of the 4050 can only be at +5v or ground, so there can be no float on the outputs while that chip is powered up and functional. Again its looking like the 4050 isn't strongly pulling the output circuit high or low. Check the socket for good contact on all pins. You should be getting a strong +5v power supply to the 4050 on pin 1, and a good ground on pin 8.

So it looks like the issue is my CD4050 has only 3.6V on pin 1.  The 7805 has 5V coming off of it and I get 4.9V in the CD4050 input pins so I will have to try to figure out why the low voltage on the CD4050.  I assume when I fix that, the output pins will go up to 4.9V rather than 3.6V.

 

I also went back in this thread and noticed some comments that the UAV can replace the CD4050.  Although I am a bit confused unless there are PCB versions with a CD4050 but the fire buttons don't buffer through it.  I tried just using the UAV in place of the CD4050 and both players were firing since the 4.9V wasn't being passed to the output pins. Wondering if one option is just to bypass the CD4050 altogether and use the UAV for video and put diode/caps on the fire pins.  Here is the original post I am referring to:

 

 

 

Edited October 22, 2020 by Heatvent

[rmzalbar]

23 minutes ago, Heatvent said:

So it looks like the issue is my CD4050 has only 3.6V on pin 1.  The 7805 has 5V coming off of it and I get 4.9V in the CD4050 input pins so I will have to try to figure out why the low voltage on the CD4050.  I assume when I fix that, the output pins will go up to 4.9V rather than 3.6V.

Oh, crap. The 4050 gets its power from a voltage divider composed of resistors R231 and R232, with a result of 3.6 volts. So that is normal. I'm sorry I didn't check this earlier. So it looks like the purpose is to intentionally level-shift the 4050's output to TIA to a range of 0v - 3.6v. I'll think about this a bit more..

 

[rmzalbar]

It looks like a common issue with the 6-switcher models using the 4050 to buffer the firebuttons. The reason 4050 is set to 3.6 volts must be to set the video levels, which is mostly what that chip is concerned with. The firebutton doesn't need to be level shifted, though. A few people "fixed" it by bypassing the 4050 with the firebutton lines (which is fine, as the 4-switch models did simply that.) Why is 3.6v not good enough to prevent firing in the first place? Not sure, but possibly an aging TIA chip or still a marginal 4050 or socket.

 

Here's the thread on the issue:

 

 

Edited October 22, 2020 by rmzalbar

[Heatvent]

Yes, I saw that thread and the fix was to pull up or cut off pins 6/7 and/or pins 9/10 legs for the offending fire button and jumper the pads together to bypass using the 4050 and pass the 4.9v directly through to the TIA.  This is in part the reason for my question on the UAV being able to "replace" the 4050 and just plug-in to the socket (which is mentioned by Bryan in post #12 as well as in the instructions / features of the plug-in version of the UAV).  However, I don't think the UAV plugin version can simply replace the 4050 on a light sixer like mine where the fire buttons are going to the 4050 (unless it passes through pin 7 to 6 and 9 to 10)?  I know I at least tried running Combat with the 4050 out and the UAV installed and both P1 an P2 started firing repeatedly. This makes sense if the UAV is not shorting these pins since pins 6 and 10 and would have no connection/voltage.  Correct me if I am wrong but there are no jumper settings on the UAV to do this and with just the UAV installed the fire pins are essentially cut off. 

 

I could probably solder the pins together either on on the UAV or the underside of the board to accomplish this and not need a 4050 installed.  This may be a good option since I don't plan to use RF and if I bridge the pins on the UAV, this would easily be reversible by simply unplugging the UAV and plugging in a 4050.

Edited October 22, 2020 by Heatvent

[Heatvent]

I think I may have a faulty IC socket.  I noticed some intermittent voltages on pin 9.  The socket seems to have good continuity to the board but the connection with the leg of the IC chip seems a bit flaky. This is likely my issue with the voltage dropping for the P1 fire button.  Not sure if the UAV pins deformed the IC socket connectors which are fairly cheap.  Bending the connectors back a little seems to have improved the connection.

 

I have been struggling with a plan to mount the CD4050 and the UAV.  I didn't really like the IC socket soldered on top of the CD4050. Mainly because it was difficult to remove without desoldering the CD4050.  I would rather have an IC socket in the motherboard rather than soldering / desoldering these old pads/traces.

 

If I had another IC socket I would probably socket both the CD4050 and then solder a second IC socket on top of the CD4050 because it would be easier to service if needed and the 4050's are very cheap. 

 

I also considered mounting the CD4050 on top of the UAV above the jumpers which the instructions mention as an option.  However, the legs on the CD4050 don't seem long enough to clear the jumpers and make contact to the UAV PCB board pins.  Not sure if there is something different about the jumper pins on mine like they are taller or the legs on the CD4050 that I have are shorter, but there is a good amount of distance (1mm or so) between the legs and the solder joints on the UAV.

 

Another option I saw was to mount the CD4050 on the underside of the board and solder to the legs of the IC socket poking through the board and cut off the legs on the CD4050 (I think this is called the dead bug approach).  I didn't really like this approach because, again, this seems like it would be difficult to desolder and I don't want to risk damaging the board if I need to do so (especially given that this seems to be a bit of a trouble spot on the light sixers). 

 

The CD4050 on top of the UAV sounds the best option since I could just leave it on the UAV (I don't plan to change the jumpers), unplug and plug in a CD4050 to the IC socket.  Maybe I will look into removing the pin jumpers and connect these permanently so the CD4050 can be mounted on top of the UAV.

 

Not sure what others have done.

Edited October 23, 2020 by Heatvent

[manterola]

I have installed the UAV on top of a cd4050 by soldering only the 4 pins or 5 pins needed signals to the shoulders of the cd4050 pins. Another option is, as you mentioned, soldering the cd4050 on top of the UAV. You can get rid of the pins and jumpers of the UAV and create the jumpers directly in the UAV board using solder and/or wires so the jumpers are now hardwired and at UAV board level. That way the cd4050 will have enough clearance.

 

 

 

[Heatvent]

Just to close the loop...

• My issue was originally the 4050.  When I replaced it, Pin 9 on the IC socket was flaky.  I reflowed the solder on that pin and my issues seem to have gone away!
• I ended up cutting the jumper pins on the UAV about half way down to make room for the CD4050 above.  I slightly bent the pins that needed to be jumped for a 2600 and soldered the tips together, then mounted the 4050 above.  So now the UAV is an all-in-one plugin option.

Thanks for all the help!

[rmzalbar]

Nice, thank you for coming back to post the solution.

[Blues76]

On 12/23/2016 at 7:39 PM, Bryan said:

The latest version of the UAV (Ultimate Atari Video) board is finally ready for production. I am currently working on a run to ship in mid-late January.

This board is compatible with the 2600, 5200, 7800, and all Atari 8-bits. Most of the information in the previous thread is still relevant, but I'll be incorporating the important stuff into this thread.

http://atariage.com/forums/topic/246613-new-video-upgrade-coming-soon/

Differences from Rev C:

1. The adjustable delay circuit is improved and allows a ~40-45ns shift in the relative Chroma/Luma phase. The pictures below show the composite output when the UAV is set to the XE's Red/Blue and the 800XL's Purple/Green. As before, the two artifact colors can be swapped with a jumper. See this post for more info on machine specific colors.

2. All inputs now have current limiting resistors. This reduced noise slightly and makes the board a bit more goof-proof.

3. The jumper positions are different from Rev C and there's now a plug-in setting for the 2600.

4. The NCS2553 video amp is now a NCS2563. The new amp is intended for high-def purposes and doesn't have the 8MHz NTSC filter. All filtering is now done on the board and it looks a bit better. IMO the composite output now approaches the look of S-Video on a good monitor.

5. There is a spare pad on the board for attaching the TIA input on the 7800 (Tcol).

The pricing is slightly higher than Rev C since I'm paying for partial assembly and a couple of the new parts are a little more than the ones I previously used.

As before, I will offer this board in 3 configurations:
1. Plug-In - A Plug-In unit for the CD4050 socket ($25 + shipping)
2. Basic - A basic version that must be wired in (missing the pin-headers and green terminal strip) ($22 + shipping)
3. Kit -A basic version with the components to make it a plug-in version for custom installations. ($25 + shipping)

If you want to get on the pre-order list, please send me a PM.

Use this post to decide which boards to order. If you have a 2600 with a CD4050 chip, you can now use the Plug-In board (the Rev C Plug-In board lacked jumper settings for the 2600).

I'll be adding more info to these first couple posts over the coming days/weeks.

 

Hi. What is the difference between this and Sophia C? For the 1088 XEL, I see options for VBXE, Sophia B, Sophia C (two modes) ... but not this one... https://thebrewingacademy.com/products/mytek-1088xel