Intellivision problems

[Billythegrape]

I have a model 1 intellivision. It was crusty, so I cleaned it thoroughly, including scrubbing the crap out of the cart port. I bought 4 used games: Night Stalker, SPace Hawk, Space Armada, and Donkey Kong. Disassembled the carts and scrubbed the contacts with silver polish. Then and only then did I try to use the damn thing, which gave me the black screen no matter what angle, level of insertion, or game cart I used. I know, this is not an easy or straight forward thing to address. The only "service manual" I've been able to find has instructions on using a diagnostic cart that, for all intents and purposes, doesn't exist.

 

Here's what I've done with the mother/daughter board:

 

- Checked voltages into and out of the power supply board per the intv website faq, all good.

- Replaced all polar caps on both boards.

- Replaced 2 2N3906 transistors as the board was brown underneath them. 

- replaced both voltage regulators on the PS board

- reseated and deoxit-ed the chips, scrubbed sockets with deoxit

- hardwired the ribbon cable as it was corroded AF

- tried piggybacking some of the 14 pin chips with ones I had from a C64 repair

- checked the RF module visually, seems ok.

 

Nothng made any difference. Yes, I have pressed the reset button. I have an oscilloscope, DMM, soldering station, and am pretty handy, but without any sort of diagnostic guide this is difficult. Does anyone have any suggestions? I have attached photos of the boards.

 

[+-^CrossBow^-]

With the scope or a freq counter, did you check that the clock signal is making it all the way to pin 10 on the cartridge port? I can't recall if that is with or without a cart though.

 

BTW there are a few different service manuals available online for the Intellivision with most of them even have diagrams using a 15mhz or better o'scope to check for various signals on the board.

 

Check out the console5.com tech wiki to access them.

 

https://console5.com/wiki/Category:Console

 

Another thing to check is to make sure the crystal is working. I've actually had at least one of those goes back on me in the past. Also had one that only gave a black screen until I started to adjust the C2 cap near the crystal.

 

[Billythegrape]

I will check both those and report back. How do you check the crystal?

[+-^CrossBow^-]

2 hours ago, Billythegrape said:

I will check both those and report back. How do you check the crystal?

I use my frequency counter and read what I'm getting at pin 10 off the cartrdige port with the system powered on. It should read right at about 3.57954Mhz

[walldog1]

I agree with Crossbow, you need an oscilloscope to check clock frequency & to check for wave forms at certain areas of the board. When checking clock Hz at pin 10 at cartridge, you do not need a game plugged in to test.

 

Also, when I zoom on pictures of backside of Logic Board, I still see some very weak solder joints, you can even see a hole next to the pin coming through.

 

There is also the possibility one ormore of the IC Chips is/are bad, several which can leave you with black screen. If you push the reset button while black screen is on, do you get some blips of color? That can tell me if there is at least a video signal getting to the RF Modulator and good chance of bad IC Chips. And speaking about RF Mod, you never know if someone has messed with the Video & Audio adjustment screws or it can just be bad. I have popped off the lid and all looks good but just can't adjust. I have a homemade tool to help me with that test.

Edited November 24, 2021 by walldog1
Addition to Crossbow reply

[Billythegrape]

Clock signal:

 

With my scope set to 1x, I don't get a waveform anywhere on the cart pins.

 

I get nothing when pressing the reset button.

[+-^CrossBow^-]

Pin 10 is one of the points specifically to check from the cartridge port. It is also present from Pin 15 off the color IC (U10).

 

After that, check the service manuals as I believe one of them (The Sylvania one tends to be the most clearly scanned in), has a chart of what voltages you should be getting from various pins off the ICs in the system. Although I will state that the actual listed voltages I feel are more of a guideline vs actual readings since most of mine tend to read differently than what the charts show.

 

 

[Billythegrape]

Ok will do.

[+Lathe26]

On 11/24/2021 at 11:42 AM, Billythegrape said:

Clock signal:

 

With my scope set to 1x, I don't get a waveform anywhere on the cart pins.

 

I get nothing when pressing the reset button.

This is unlikely to change things, but set your oscilloscope probe to 10x instead of 1x.  10x increases the impedance so the oscilloscope sees a smaller signal (the downside) but it also puts less load on the circuit-under-test and is less likely to alter the circuit's behavior (the upside).  Clock signals can sometimes be rather sensitive.