Help needed with a Mattel Intellivision

[federicoangeloni]

Hi at all!

I have a Mattel Intellivision that is showing only the black screen. It was a little oxidated and i've cleaned it well, but it seems to be not working. I'd like to repair it and to check what are the parts that are not working. I've checked the power board and it seems to be working. I've opened the motherboard shield and i've cleaned every part. After that i've checked the voltages on the IC...generally they must have 5v on their corner pin. Three of those IC have an heat sink on top, and i'm not sure if they are installed in the right way. Beyond this, i've checked the voltages and some of them seems to be not good. I've made a picture with the board with the face down, where i've put the lines between the point where i've putted the multimeter and the respective value of voltage measured. Can you give me some hints on how to check what's wrong and where to check other things to exclude other issues?

 

[mthompson]

I was able to fix my Intellivision that was showing a black screen. It turned out to be a bad transistor (or two) near the CPU. But first I was able to verify that most of the chips were good by swapping them onto a working board.

 

This thread has pictures and other details about what I did to get it going. Several sharp minds on this forum helped tremendously. I'm sure you'll get some advice for your troubleshooting. Good luck!

[federicoangeloni]

I was able to fix my Intellivision that was showing a black screen. It turned out to be a bad transistor (or two) near the CPU. But first I was able to verify that most of the chips were good by swapping them onto a working board.

 

This thread has pictures and other details about what I did to get it going. Several sharp minds on this forum helped tremendously. I'm sure you'll get some advice for your troubleshooting. Good luck!

 

Thanks a lot for the hint. Now i haven't a working board, then I've just ordered the transistor...and i'll also replace all the capacitors on the motherboard with new ones. But...how can i know the correct orientation of the IC chip? the one without heat sink are easy since are all oriented in the same way, with the same orientation of the text on it. But for the ones with the heat sink on it? They have some text on the lower face, but how can i be sure that they are mounted in the right way?

[mr_me]

Are you able to see the semi-circular indentation on one side of the chip? That should tell you where pin one is.

 

edit:

A bad cartridge/slot connection can produce a black screen like there's no cartridge. Have you tested multiple cartridges?

Edited July 30, 2018 by mr_me

[HunterZero]

Corner pins eg pin 1 of the DIP40's are not always the Vcc pin or GND, there are no standards in the pinouts. The GI chips use some strange voltages, especially the CPU, so it's important the 5V and 12V rails are stable. The rail that runs around the edge of the board is common ground, you can use continuity mode on your meter to check which pins of each IC are ground. There is also a single blue wire 2-pin connector, make sure this is connected properly to the power supply.

 

Check continuity of your ribbon cable and be careful with it.

 

Eg, RA-3-9600 RAM chip has +5V Vcc on pin 9, and +12V on pin 10 and -3V on pin 11. Pin 31 is GND.

 

Eg, on the CP-1610 CPU, pin 34 is +5V, 35 is -3V and 36 is 12V. Pin 39 is GND.

 

NB, all the GI branded DIP40's have pin 1 (marked with a notch) on the end of the chip furthest from the cartridge connector.

 

Are you getting a flash when you press the reset button? Is the cartridge slot clean and has no bent pins? Does fully inserting and backing out the cartridge a hair help? Have you tried several cartridges with the same result?

 

The advice I gave on the linked thread apply here too. It definitely could be transistors Q1 and Q2. Definitely carefully clean and resocket all socketed ICs with Deoxit. Check for bad or corroded sockets.

 

Do you have a logic probe or scope? Can you confirm CPU-1610 pins 37 and 38 are pulsing?

 

I have found the SHOEI branded electrolytics on the mainboards of these systems are quite reliable, but it never hurts to replace ancient electrolytic caps. It's a good idea to replace the large filter caps and the 7805 and 7812 voltage regulators on the power supply board too.

 

If the Q1/Q2 replacement doesn't get it going, then the most common IC to go bad that can cause anything from crashing to black screen is the RA-3-9600 SRAM.

 

- J

Edited July 31, 2018 by HunterZero

[federicoangeloni]

Thanks for the answers. I've inspected well the board and i've discovered that some capacitors on the logic boards are not in good state. Since this i've replaced all of them.

 

I'll add some information for the users of the forum, i hope that could be useful for everyone.

 

For the ones that should do this work, these are the capacitors that you need:

 

Main PCB
C26 1uF 50v
C27 10uF 25v
C28 10uF 25v
C30 10uF 25v
C40 47uF 16v

Power Board
C1 10000uF 16v
C2 100uF 16v
C3 2200uF 25v

 

Note that there are different versions of the board, then the code could be different, but the capacitor values are these. Take care about the orientation of the capacitor pins.

 

I've ordered the C1 capacitors since i haven't it, then i'll recheck all the voltages after replacing the C1.

 

It's important that the power board provides the correct voltages. This are some tests that are on the service manual. If the voltages are the ones indicated here, then the power board should be ok:

 

 

The i'll check again my voltages after my C1 capacitor will arrive.

 

I've checked the continuity of a lot of lines, and it seems to be good. Since i must wait the Q1 and Q2 transistor too, i've made a picture with all the IC where i've indicated all the pins that could be useful to check the voltages. I've found the ground through a multimeter (as you've adviced, i've checked the continuity between the ground of the board and those pins) and i've also checked all the datasheets of those IC to check their correctness and the voltages of the other pins.

 

You were right!!! They have a strange pinout and also strange voltages!!!

NOTE: the black pins are the GND, and i've written the value of the Voltage near the red pins!

 

 

I'll give you other updates after the order of my components will come! Thanks!

[federicoangeloni]

Hi at all!!! Finally my components are arrived, then i've made some works on this intellivision. I've changed the remainder capacitors, and i've tested the powerboard with the reference of the image that i've posted in my last post. Well, it seems to be ok, and all voltages are ok, then this is working. On the logic board, i've changed the Q1 and Q2 and i've made a full recap. I've also cleaned all two or three times, and check the continuity. Now the situation is near the same before: i have a black screen, and it flashes when i press reset. I think after this work that the problem could be one IC (or more?). Do you have any advices about some other tests to do? I don't have an oscilloscope to check pulse...is there a way to know what ic could work and what not? Thanks

[HunterZero]

If you haven't already, check that all the DIP40 sockets and cartridge port are good (eg, for the chip socket, the top of the legs have continuity with the pad).

 

And try running the system with both the hand controllers disconnected if you haven't already and see if you can get to the title screen.

 

Make sure the bent over crystal isn't touching the reset button.

 

But I think it's very likely that you have a defective socketed IC. The best way forward is to find a donor parts board, and start swapping socketed chips one by one.

 

In order of likelihood, from my experience these are the chips that could cause black screen (coincidentally, the same order as in the service manual):

 

U2 RA-3-9600 SRAM

U4 AY-3-8900 CCIR STIC for PAL Intellivisions (note that the AY-3-8900-1 STIC is the NTSC version. Fun fact: If you swap to the NTSC STIC and swap the X1 4MHz system clock to 3.5795MHz, you get a PAL60 console!)

U1 CP-1610 CPU

 

- James

Edited August 10, 2018 by HunterZero

[HunterZero]

For reference...

 

 

There are some differences between board versions, but the large ICs are all in the same location.

Edited August 10, 2018 by HunterZero

[federicoangeloni]

Hi at all! At the end, i've found another working Intellivision, and i've tried all the ic on the first one. Well, the only one chip that was gone, was the CPU CP1610. The others works good, but adding the working cpu on the first board, it was not working. Since this i prefer to rebuild a perfect intellivision from the two that i've got and i've sell the other ones for parts. My advice is to buy another intellivision, since is really difficult to make hypotesis with only one faulty unit! Thanks a lot!

[HunterZero]

So was the only faulty chip the CP1610 CPU? It's not too difficult to get a spare for this.

[Gernot]

it isn't

 

but i can't tell if it still works i haven't tested it but it would be a sneeze.

further italy isn't 1000 miles away from my home.

[federicoangeloni]

So was the only faulty chip the CP1610 CPU? It's not too difficult to get a spare for this.

 

Yes this was the only one chip that was faulty. But i've faced that there were some problems with the board, then i've preferred to rebuild a 100% working console, and sell the other one for spare parts! Now i have a perfect and revised.