Coleco Adam troubleshooting - won't boot, no picture

[Lando242]

I picked up an Adam a while back and have been sitting on it until I could cobble together a power supply* as it does not have a printer. I put one together but the system doesn't appear to boot. I have it connected to a CRT TV using a single RCA cable and an RCA-to-Coax adapter. The TV and cable work fine with other computers and consoles of the era. I get no picture. Not even black, just snow. The light on the keyboard does not come on. The tape drive does power up though. It starts 'playing' even when no tape is loaded. What should I check first?

 

*The new PSU is a MeanWell RT-50A.

[Tekman]

You need to verify all voltages are present and in range first before any further troubleshooting is performed. Verify all voltages INSIDE the ADAM and not just at the external power supply terminals.

The keyboard LED is simply an LED connected directly to +5 and ground through a current limiting resistor and is a good indicator of no +5v present, a broken ADAMnet cable, or not using a proper ‘reverse’ ADAMnet cable.

It's also a good idea to disconnect all ADAMnet devices (includes keyboard), any internal expansion boards, and all data drives from the system to see if anything is holding the system down. With everything removed, the ADAM is still capable of booting to SmartWRITER.

 

ADAM DB-9

1 - +12v
2 - +12v
3 - +5v
4 - -5v
5 – GND
8 – GND

RT-50A terminals

+5      - Pin 3
COM - Pin 5 and 8
+V2   - Pin 1 and 2
V3     - Pin 4

[ChildOfCv]

8 hours ago, Lando242 said:

I picked up an Adam a while back and have been sitting on it until I could cobble together a power supply* as it does not have a printer. I put one together but the system doesn't appear to boot. I have it connected to a CRT TV using a single RCA cable and an RCA-to-Coax adapter. The TV and cable work fine with other computers and consoles of the era. I get no picture. Not even black, just snow. The light on the keyboard does not come on. The tape drive does power up though. It starts 'playing' even when no tape is loaded. What should I check first?

 

*The new PSU is a MeanWell RT-50A.

The next question (after power) is if you're on the correct channel.  Usually 3 or 4 for NTSC systems, or 3,4, 35, or 36 for PAL systems.  If you're sure you're on the correct channel, and if the cable is fine, the problem could be a bad connection on the ADAM's RF output.  Check if it wobbles, which would indicate that its press fit is loose.  Another possibility is that the connection from RF board to center pin has broken its connection.

[Lando242]

15 hours ago, Tekman said:

RT-50A terminals

+5      - Pin 3
COM - Pin 5 and 8
+V2   - Pin 1 and 2
V3     - Pin 4

Welp, there's problem #1 found. I went off a connector wiring guide that said pin 5 was for the ground. I dutifully connected that wire to the ground terminal on the RT-50A. I will swap it to the COM terminal and see what happens. Do I have to connect to pin 8 also or is that optional? The wiring guide didn't have anything connected on pins 6-9.

 

10 hours ago, ChildOfCv said:

The next question (after power) is if you're on the correct channel.  Usually 3 or 4 for NTSC systems, or 3,4, 35, or 36 for PAL systems.  If you're sure you're on the correct channel, and if the cable is fine, the problem could be a bad connection on the ADAM's RF output.  Check if it wobbles, which would indicate that its press fit is loose.  Another possibility is that the connection from RF board to center pin has broken its connection.

It is an NTSC system. I have tried both channels. If I have to crack open the case I will check the RF connector.

[Tekman]

8 hours ago, Lando242 said:

Welp, there's problem #1 found. I went off a connector wiring guide that said pin 5 was for the ground. I dutifully connected that wire to the ground terminal on the RT-50A. I will swap it to the COM terminal and see what happens. Do I have to connect to pin 8 also or is that optional? The wiring guide didn't have anything connected on pins 6-9.

I highly recommend you also have the pin-8 ground return like Coleco used. If not, you have a single return for all +5,+12, and -5, which is not ideal. Nothing is connected to 6,7, and 9.

Edited December 19, 2023 by Tekman

[Lando242]

Progress. I moved the wire from ground terminal to the common terminal on the power supply and now the system powers up. The LED on the keyboard lights up and I get a 'black' screen on the TV over RF. The TV also plays all kinds of crazy sounds and the screen is all sorts of rainbow static on the on top of the black background. I put in an old Sub-Roc Colecovision cart and reset and powercycled it a few times but saw no improvement. When I have more free time I will crack open the system and try disconnecting all of the internal cards and such to see what happens.

  

15 hours ago, Tekman said:

I highly recommend you also have the pin-8 ground return like Coleco used. If not, you have a single return for all +5,+12, and -5, which is not ideal. Nothing is connected to 6,7, and 9.

I am using 18 gauge, 4 stand wire, so I don't have a second line I can connect to pin 8. Would a jumper to pin 5 be sufficient since I'm using larger gauge wire than what the original had? I'm already using a jumper between the two 12 volt pins...

[Tekman]

18 gauge is perfect. If you don't have the ability to add the second ground wire, then at least jumper it to help make the best possible connection because it's so important.

 

Priority one is to read voltages inside the ADAM when you open it before anything else. You can adjust the POT on the supply until you read about 5.15v inside the ADAM. VRAM is usually the first to complain if the voltage gets low enough.

[chad5200]

On 12/20/2023 at 5:37 AM, Tekman said:

18 gauge is perfect. If you don't have the ability to add the second ground wire, then at least jumper it to help make the best possible connection because it's so important.

 

Priority one is to read voltages inside the ADAM when you open it before anything else. You can adjust the POT on the supply until you read about 5.15v inside the ADAM. VRAM is usually the first to complain if the voltage gets low enough.

Interesting that you mention to also run ground to pin 8... I will do the same as I don't see this mentioned anywhere else.

 

Question... for testing the voltage inside the ADAM, where do you recommend testing at internally?

 

[Tekman]

18 hours ago, chad5200 said:

Interesting that you mention to also run ground to pin 8... I will do the same as I don't see this mentioned anywhere else.

 

Question... for testing the voltage inside the ADAM, where do you recommend testing at internally?

 

Coleco didn’t make it easy to find an easy spot to verify +5v inside the console.

 

With only the three expansion slots and data drive connectors available, it’s easy to slip and short things out. Even trying to use the I/O expansion edge connector is difficult.

 

What I do is read across any easy to reach +5v decoupling capacitors on my MIB238-WiFi or 1MB RAM Expander boards. I’m assuming you do not have the luxury of having an expansion card inside your console.

 

The easiest method people use is to use a roller controller power tap adapter and read it from upper two widest apart female sockets. I still prefer to read the +5v further past this point because there is still more wiring from that point until it reaches the main Gamma PCB. There is still nothing wrong with reading it from the adapter for good results.

 

If you don’t have any of these, the two very top left and right fingers of all three expansion slot connectors are GND (left) and +5v(right). Just don’t press down too hard on the connectors and accidentally squeeze them together and short them out. The Meanwell itself has protection for that, but no reason to push your luck elsewhere.

Edited January 16 by Tekman

[chad5200]

On 1/16/2024 at 5:48 AM, Tekman said:

If you don’t have any of these, the two very top left and right fingers of all three expansion slot connectors are GND (left) and +5v(right). Just don’t press down too hard on the connectors and accidentally squeeze them together and short them out.

Excellent info.  Thank you!  Just built a new cable for my Mean Well RQ-50B power supply.

 

I used about 3 feet of this wire: DEKIEVALE 18 Gauge 6 Conductor Electrical Wire, 10FT 18AWG Black PVC Stranded Tinned Copper 6 Wire Cable, 18/6 Cord Extension Cable  https://a.co/d/eV3ZBAG

Also used this for the plug: DE-9 (DB-9) RS232 Female Socket Connector to Terminal Block Breakout  https://a.co/d/beYpJQd

 

Then dialed mine in so now it is measuring 5.15v internally.

 

Much appreciated!