I thought I'd killed my 65XE. Now I'm not so sure.... help?

[electrotrains]

Hi All,

 

I've been doing some experimenting with DIY cartridges (probably best left for a different thread), but managed to kill my 65XE yesterday. Power LED lights, but screen is black.

Had it for 20+ years, so was feeling pretty down yesterday night.

 

I had put +5V (from a breadboard supply) into cartridge slot RD5, with the cartridge slot GND connected to breadboard GND. +5V from the cartridge slot was not connected. Atari was off initally, then powered on.

 

The Atari powered on to a black/dark red screen. I disconnected everything, but I now just get the dark red (almost black) screen when I power up. Don't really see why what I did was a problem - maybe somebody can tell me why I'm stupid....?

 

Anyway.. today I notice that most of the time I get the red (solid) screen, sometimes I get a bright green (solid) screen, but very occassionally the atari boots normally to a READY prompt and seems to work normally!!

 

So... can anyone help me? Any idea why I've managed to zap it into a state where it only boots sometimes?

 

Robin

 

[Rybags]

GTIA usually has some registers in randomish state on powerup, usual is dark brown/red or green. Not changing from that indicates the OS isn't starting up at all.

 

Machine randomly working - possibly you've fried the MMU but it still has signs of life. These things are easiest diagnosed if you have another machine so can test swap components into it.

So really, might be MMU, CPU, OS Rom , PIA or maybe even Antic. Or might be something else like a passive component.

[electrotrains]

Thanks for the reply Rybags.

 

I had looked at a schematic and saw the MMU was first in line from RD5 on the cartridge port, so was already wondering if it might be that. Although it boots normally one time in five or so without a cartridge, it never seems to boot with a cartridge plugged in.... so that perhaps points towards the MMU also????

 

I guess I might have to buy a dead 65XE from ebay and start swapping parts....

 

Robin

Edited March 3, 2015 by electrotrains

[Rybags]

You might be able to buy an MMU on it's own.

Also, 65XE has many common parts with 800XL. Although most 800XLs don't have the Freddie chip which replaced lots of individual logic ICs.

Additionally, early 65XE used the 1 bit Ram ICs same as 800XL but later ones used 4 bit Rams.

[Rybags]

It's usually the case of being more economical to just buy a replacement machine that works then keep the faulty one for parts.

[1050]

Don't really see why what I did was a problem - maybe somebody can tell me why I'm stupid....?

Ouch, too harsh on yourself there Robin. Problem was in dual supplies and that's never a real good idea in the first place, try to avoid if at all possible. You left the MMU trying to supply the Atari with power and it's not designed for that. Next time get your power for the breadboard circuit from the Atari at least when you have the breadboard circuit ready to be hooked up to the Atari. Then officially divorce the breadboard supply for the time it's hooked to the Atari. The school of hard knocks never closes.

 

Although I won't bad mouth advice for a second unit for parts purpose anytime since it's such a good idea, I would get an MMU alone just the same. They can be burnt on your side of the pond using a GAL16V8 and most entry level eprom burners. If you were looking for a reason to get one this is it? Just be sure this device is covered in the manual for it.

 

http://www.atarimax.com/jindroush.atari.org/achmmu.html

[electrotrains]

Thanks for the advice. Appreciated.

 

I've emailed B&C Computer visions to get a quote for a MMU + postage to the UK. The part is only $5 so that's probably the cheapest way for me to get back up and running (assuming it is actually the MMU I've killed).

 

I had already considered getting a cheap programmer and some GALs to play with for my cartridge experiments. In the end I settled on the XC9500XL CPLD series from Xilinx since they are a bit more flexible (more pins) and almost breadboard-able in PLCC+Socket form. May yet revisit this, since a programmer would allow me to program flash chips and eeproms too rather than my current mess of wires when doing this from an arduino.

 

Robin

[electrotrains]

Just a quick update - tonight I replaced the MMU on my 65XE with a new one and my Atari is alive again. Hooray!

Everything seems to work fine, so it looks like I simply blew the MMU.

 

So, thanks to Juergen from ABBUC who sent me a new MMU from Germany for a very reasonable price, Rybags and 1050 who correctly diagnosed the problem.

 

Robin

[Van]

Ouch, too harsh on yourself there Robin. Problem was in dual supplies and that's never a real good idea in the first place, try to avoid if at all possible. You left the MMU trying to supply the Atari with power and it's not designed for that. Next time get your power for the breadboard circuit from the Atari at least when you have the breadboard circuit ready to be hooked up to the Atari. Then officially divorce the breadboard supply for the time it's hooked to the Atari. The school of hard knocks never closes.

 

Although I won't bad mouth advice for a second unit for parts purpose anytime since it's such a good idea, I would get an MMU alone just the same. They can be burnt on your side of the pond using a GAL16V8 and most entry level eprom burners. If you were looking for a reason to get one this is it? Just be sure this device is covered in the manual for it.

 

http://www.atarimax.com/jindroush.atari.org/achmmu.html

I've wanted to be able to prog GALs for a while but reluctant to buy another tool (have a Williem ATM for EPROMS). Can you recommend a reliable burner for 16V8s?

Yogi

[Van]

Just a quick update - tonight I replaced the MMU on my 65XE with a new one and my Atari is alive again. Hooray!

Everything seems to work fine, so it looks like I simply blew the MMU.

 

So, thanks to Juergen from ABBUC who sent me a new MMU from Germany for a very reasonable price, Rybags and 1050 who correctly diagnosed the problem.

 

Robin

Good to see you patch her up! Just saw your breakout board thread, wish I had seen it earlier but oh well. Will have to do a board run soon, just what I've been looking for

Yogi

[1050]

Can you recommend a reliable burner for 16V8s?

Yogi

Not with first hand knowledge, the Superpro Z I got for under a hundred well over a decade ago is no longer offered at any price. But I see similar units on FleaBay starting at the $40 - $50 range. As stated just be sure you have access to a device list before purchase and the device you want to work on is in there. Yours, which I couldn't find, seems to be similar to a SP-8 which is NOT a universal programmer as it seems to do mostly eproms and eeproms. Universal means it does a lot more than just a few TYPES of chips, one or two types don't count even if the list is huge. I suspect you simply misspent your money on the Willem, although at the time I got this programmer it was the cheapest around with this much talent, so no blame on you if you just didn't know there were better units to even be had back in the day. I was stunned by the talent VS cost of mine at the time. Today $43 gets you what $100 used to is the good news.

 

Reliable aspect can't be known by me, mine works is all I can know about.

 

The G540 appears to the same deal as mine only in a USB version where mine connects via old school printer port. And this forces me to keep a 98 box viable, but I have other reasons to do so as well. 5.25 drive B that talks directly to my US Doubler and older DOS mode software that just won't fly on NT.

http://www.ebay.com/itm/281406972914

[Van]

Thanks for the input 1050

 

 

Not with first hand knowledge, the Superpro Z I got for under a hundred well over a decade ago is no longer offered at any price. But I see similar units on FleaBay starting at the $40 - $50 range. As stated just be sure you have access to a device list before purchase and the device you want to work on is in there.

Actually, this topic has spurred me a little. I've got an old Alta Engineering Pro2000 PCB I got 15 yrs ago but never finished building. For the longest time lately, I've thought is was a hopeless cause, the Alta web site is long gone, BUT just did some Wayback Machine digging and viola! Got the old Win95 software/drivers and PIC Firmware files. So I'll buckle down and complete it (seems like it was the reason I opted for the cheaper Willem board years ago, 'Don't need the PAL programer' Ha Ha Ha).

 

 

 

The G540 appears to the same deal as mine only in a USB version where mine connects via old school printer port. And this forces me to keep a 98 box viable, but I have other reasons to do so as well. 5.25 drive B that talks directly to my US Doubler and older DOS mode software that just won't fly on NT.

Have looked at this but was concerned by reports that it was hit or miss with older 16b EEPROMs, witch is more important to me for the most part.

It's a shame that we lost the HW level control of the Parallel port with Windows upgrades. There were allot of interesting devices that relied on it. Like you, I still have a couple Win98 boxes just to run outdated software and hardware.

Yogi

[MrMartian]

The TL866CS, also a $50 programmer, does fairly well and does basic GALs..