Mega-cart issues?

[azog]

It's been a long time since I played with my VIC-20, so I broke everything out and wanted to dive right in with the Mega-Cart. But I seem to be having issues...

When I select an image, it never loads and just sits there forever. It does matter which image, or what kind (tape or cart), it never actually loads. I'll attach two images.

One is trying to load HESMon. I can select any configuration (expansion RAM, etc) with the same behavior. I've let it sit at this screen for like 30 minutes and it never actually loads.

Another image is trying to load the Control menu (press CONTROL while power on); I thought I saw somewhere that I can reset NVRAM, but I also get the same behavior. This time, the only thing that appears is the Mega-Cart logo, and nothing.

Since it's been a while since I last used everything, I tried some other carts just to make sure it's not the VIC itself. You can see my VIC-Rabbit cart in the image. It's not an auto-starting cart, but it works. I also tried Omega Race and Radar Rat Race, and they work. Both are original carts.

Any suggestions on where to start? Thanks

[beamrider]

Try to...

How to clear preferences and restore default factory settings

In case of a problem, or you if you simply want to delete your settings quickly, it is possible to clear all preferences and restore the Mega-Cart to default factory settings.

Please remember that the preferences contain such settings as your favorite items, custom Early startup menu items, filters (Categories, Publisher, System, etc) plus other things. So, when you clear preferences you lose all these settings!

Firstly, you need to enter the Service menu. In order to enter this menu, hold down the CTRL key when you turn ON or reset the Vic-20.

Next, select "RESET PREFS". The Mega-Cart will restore default factory settings and open the Menu Music selector screen that allows you to select a favorite menu tune.

Once you have selected the menu tune, the Early Startup menu comes up automatically with the default settings.


Source: http://www.retroisle.com/commodore/vic2 ... hp#restore

[azog]

Firstly, you need to enter the Service menu. In order to enter this menu, hold down the CTRL key when you turn ON or reset the Vic-20.

Look, I'm not trying to be snippy, but since you didn't read my post, you will see that the second photo shows what happens when I try this, e.g., it does not work. I cannot get into the service menu either.

[beamrider]

fair enough, only skipped through.

You can try unzipping and running the attached mega-cart repair program on the Vic. Can't remember where I got it, but it has rescued mine a couple of times.

[azog]

You can try unzipping and running the attached mega-cart repair program on the Vic. Can't remember where I got it, but it has rescued mine a couple of times.

Thanks for the repair program. Unfortunately, when I say "nothing works", I mean that literally. I can't even get the VIC to load unexpanded BASIC while the Mega-Cart is installed... sadly, I guess this is one for the recycling bin, doubly sadly, since they don't seem to be available any more.

15 minutes later:

[beamrider]

I believe you should be able to prevent it from AutoStarting by using a cartridge port extender that allows you to turn it off? Then you could try switching it in and running the program again?

[tokra]

It could always be a bad connection. That other carts work does not say much, since the MegaCart may well use different memory-areas and pins than the standard game-cartridge. Have you tried plugging the MegaCart in and out a few times (at least 5?). This may improve the connection. I know my MegaCart sometimes does crazy things when the connection is bad, but this is always gone after a few times removing and reseating the cart.

You could also try cleaning the contacts of the cart and especially the slot with isopropyl alcohol.

But never, I repeat NEVER throw a MegaCart in the recycling bin! Even if it is defective there is always the possibility to repair it one day.

[azog]

I've not necessarily written off that it could be a faulty connection in the VIC. After all, these things are ~40 years old. I did spray it with contact cleaner and also used a fine grit sandpaper to to try "polish" the contacts. But I've tested pretty much every other cart I have (half dozen or so), so it's gotten limbered up.

Good idea about the cart extender. I don't have one so I'll have to see if any are listed on ebay or find if anyone is producing contemporary versions. My VIC-Rabbit has a "passthru" cart connector, so I'll play with that too, see if it helps.

I have another VIC-20 in unknown condition. It's one of the older two-prong power units...

[beamrider]

Good idea about the cart extender. I don't have one so I'll have to see if any are listed on ebay or find if anyone is producing contemporary versions. My VIC-Rabbit has a "passthru" cart connector, so I'll play with that too, see if it helps.

If you can't get any joy with the "VIC-Rabbit" then you could fashion something from two 44 pin jamma connectors wired straight through with an isolation switch on the address select line for block 5. Another solution would be to swap the kernel ROM (easier if it's socketed) for one that doesn't look for the auto-start signature.

[Mike]

...

The errorneous display suggests to me that there might be some issue with the Mega-Cart's built-in reset circuit. I.e. it probably still maps in all relevant RAM or ROM, but fails to send a reset pulse to the VIC-20 to start the mapped-in cartridge dump (or alternatively, go into the BASIC start-up message with the selected RAM expansion).

Do you have any means to monitor the reset line on the cartridge port (pin X)?

[azog]

...

Do you have any means to monitor the reset line on the cartridge port (pin X)?

Yes, I have a Rigol DS1202Z scope. What should I be expecting?

And funny how you mentioned the reset, because I forgot until just now. The physical reset button the cart actually doesn't work. I wonder if they're related issues... Anyways, I'll hook up the scope and see what I see. Thanks

[Mike]

What should I be expecting?

/RESET is active low, so upon either a press on the Mega-Cart reset button, or leaving the Mega-Cart menu into a game/tool or the BASIC start-up prompt you should see a low level pulse (less than 0.8 Volts) on the order of maybe 10s of milliseconds, and a high level signal (more than 2.0 Volts) at all other times.

[azog]

What should I be expecting?

/RESET is active low, so upon either a press on the Mega-Cart reset button, or leaving the Mega-Cart menu into a game/tool or the BASIC start-up prompt you should see a low level pulse (less than 0.8 Volts) on the order of maybe 10s of milliseconds, and a high level signal (more than 2.0 Volts) at all other times.

Well, looks like the reset is staying high at all times. When I select an image, it never goes low...

[6502dude]

MegaCart has both hardware reset via push button switch as well as software reset via internal logic.

If MegaCart starts up ok to main menu, but games, utilities, etc can not be selected, it is likely fault within software reset logic.

Send me a PM and we can discuss repair options.