Random RAM test failures on 800XL

[+Stephen]

1 hour ago, Forrest said:

I have had multiple computers made in the 90’s

Of which none are Atari 8bit machines, nor Atari 2600s.  I have dozens of amplifiers in my possession all working fine and un-repaired from as far back as 1969.  Again - shotgun replacing of all caps in old equipment does way more harm than good.

 

If my car was running a little rough, would I just haphazardly replace the entire engine because they go bad, or would I first diagnose the issue and replace only what was bad?

[Peri Noid]

There are some machines like late Amigas, where you either recap, or you have a piece of junk sooner or later. If not already. So generalization may be harmful. 

But I agree, that majority of Atari machines work quite well on original caps. 

[TGB1718]

1 hour ago, Stephen said:

I have dozens of amplifiers in my possession all working fine and un-repaired from as far back as 1969.

Apart from my Atari 8 and 16 bits which have had no need to replace caps, I also have a Technics full stack

HiFi system circa 1990, had a blown amp module when I got it for a song  not working, replaced the 

amp IC and it's been fine ever since, no cap replacements and compared to modern stuff this sounds

absolutely great

 

 

[+x=usr(1536)]

2 hours ago, Stephen said:

Again - shotgun replacing of all caps in old equipment does way more harm than good.

(Emphasis above mine)

 

This is the key part: shotgun replacement.  Just saying, "it needs caps," and replacing them without knowing what the actual problem is is an invitation to cause new problems without solving the one you were originally looking to fix.

 

I won't go so far as to say that Atari systems never have a cap go out - I've replaced them in literally a couple of machines where this had happened - but compared to many, many others, they seem to hold up well in this regard.  It's not something I'd necessarily be expecting to have to do when I open a machine up unless visual inspection says otherwise, or there was the distinct sound and smell of a cap popping off while I was using it.

 

It's your machine and you can do with it as you see fit.  Please understand that this is the spirit the advice is being offered in.

[Forrest]

(Edited)

I was right

Edited May 27, 2023 by Forrest

[+DrVenkman]

29 minutes ago, Forrest said:

(Edited)

I was right

LOL, not about A8 computers you're not.

 

And again - LOUDER FOR THOSE IN THE BACK - none of the caps in an 800XL will cause random, intermittent DRAM failures. 

[Forrest]

My statement was just a suggestion about 8 bit Atari’s - nothing more.

 

I have a much broader computing experience than 8 bit Atari’s.

Edited May 27, 2023 by Forrest

[+x=usr(1536)]

2 hours ago, Forrest said:

(Edited)

I was right

So what was the actual problem?

2 hours ago, DrVenkman said:

And again - LOUDER FOR THOSE IN THE BACK - none of the caps in an 800XL will cause random, intermittent DRAM failures. 

But firing the parts cannon at it means you're bound to hit something eventually, amirite?

[Beeblebrox]

Where can I buy a parts cannon from? I have a good selection of tools but this sounds ideal. 😋😁

[itripn]

I want to thank everyone for their passion (or lack of) for my Caps 🙂. A quick visual inspection showed no obvious leakage or bulging, and as others have said I've not seen this with any of my A8's. But it's worth a look and so I did.

 

I've also not found any obvious cold solder joints, and 5V/GND seem reasonably clean, to the best of my ability to test (oscilloscope newbie).

 

I am in the process of getting a Sys-check XL from @tf_hh in addition to the AVG cart (for other utilities) just to add to my toolbox for these kinds of issues. I am also working on getting a hold of some spare CPU's (Sally), CTIA, and ANTIC chips.

 

Have put this project aside for a bit until I get some of these things -- but I really appreciate all the wisdom folks have offered in this thread. If I get this thing working again, I'll be sure and post back the solution.

 

Cheers,

Ron

 

[Beeblebrox]

2 hours ago, itripn said:

I want to thank everyone for their passion (or lack of) for my Caps 🙂. A quick visual inspection showed no obvious leakage or bulging, and as others have said I've not seen this with any of my A8's. But it's worth a look and so I did.

 

I've also not found any obvious cold solder joints, and 5V/GND seem reasonably clean, to the best of my ability to test (oscilloscope newbie).

 

I am in the process of getting a Sys-check XL from @tf_hh in addition to the AVG cart (for other utilities) just to add to my toolbox for these kinds of issues. I am also working on getting a hold of some spare CPU's (Sally), CTIA, and ANTIC chips.

 

Have put this project aside for a bit until I get some of these things -- but I really appreciate all the wisdom folks have offered in this thread. If I get this thing working again, I'll be sure and post back the solution.

 

Cheers,

Ron

 

 

Good luck. BTW I assume you are in the UK? 

 

Also assume Ctia was a typo and you meant gtia?

 

 

 

 

[itripn]

Thanks! I’m in Portland, OR

 

Cheers,

Ron

[Ricky Spanish]

16 hours ago, x=usr(1536) said:

But firing the parts cannon at it means you're bound to hit something eventually, amirite?

also means you found the shittiest mechanic... like every ha-ha.

[itripn]

Thought I'd give a quick update here... Over the past few weeks I've obtained a Retro Chip Tester, an AVG cart, and a Sys Check 2. All RAM and LSI chips check out with the Retro Chip Tester. AVG Cart is cool, but as many suggested wouldn't be a game changer for this diagnostics effort.

 

Sys Check 2 arrived today, and like the built-in memory tester, it showed random failure across all RAM chips each time I run it. After reading @tf_hh's manual for the Sys Check, I started getting super suspicious of the power supply. I've been using an aftermarket power adapter because it's smaller and easier to deal with, and it's always worked great with my other XL and two XE's. So I dug out the original power supply from the closet and plugged it in, and Sys Check started passing. I've left it running for 30+ minutes automatically repeating the memory tests and all is well.

 

So, something about this particular XL is super sensitive to power. At least at this point I know all the RAM and main chips are good. 

 

Cheers,

Ron

Edited June 19, 2023 by itripn

[_The Doctor__]

2 hours ago, itripn said:

Thought I'd give a quick update here... Over the past few weeks I've obtained a Retro Chip Tester, an AVG cart, and a Sys Check 2. All RAM and LSI chips check out with the Retro Chip Tester. AVG Cart is cool, but as many suggested wouldn't be a game changer for this diagnostics effort.

 

Sys Check 2 arrived today, and like the built-in memory tester, it showed random failure across all RAM chips each time I run it. After reading @tf_hh's manual for the Sys Check, I started getting super suspicious of the power supply. I've been using an aftermarket power adapter because it's smaller and easier to deal with, and it's always worked great with my other XL and two XE's. So I dug out the original power supply from the closet and plugged it in, and Sys Check started passing. I've left it running for 30+ minutes automatically repeating the memory tests and all is well.

 

So, something about this particular XL is super sensitive to power. At least at this point I know all the RAM and main chips are good. 

 

Cheers,

Ron

many modern 'usb' type or buck type converters put out very unclean power, full of noise. They are bad for older machines and devices. Many of them pulse at high frequency and other such fun stuff. Older caps may not be able to shore up and filter the noise and pulses, and quite frankly even from new are not tuned to the specific spectrums from those types of supplies. Some weird video patterning, drive or sio devices not working properly etc and machines acting flaky have come down to these types or supplies and replacement 'regulators' a good number of times. Ditching these until companion filtration as well as noise suppression modifications are included is the best thing you can do. Sure they have met with some apparent and immediate 'success' but down the road it normally ends up be the mystery issue creator.

[Peri Noid]

3 hours ago, itripn said:

So, something about this particular XL is super sensitive to power. At least at this point I know all the RAM and main chips are good.

In such case it's good to replace the initial smoothing caps, the big ones next to the PSU connector. Although they are usually fine, they may get bad. 

Edited June 19, 2023 by Peri Noid

[TZJB]

13 hours ago, itripn said:

Thought I'd give a quick update here... Over the past few weeks I've obtained a Retro Chip Tester, an AVG cart, and a Sys Check 2. All RAM and LSI chips check out with the Retro Chip Tester. AVG Cart is cool, but as many suggested wouldn't be a game changer for this diagnostics effort.

 

Sys Check 2 arrived today, and like the built-in memory tester, it showed random failure across all RAM chips each time I run it. After reading @tf_hh's manual for the Sys Check, I started getting super suspicious of the power supply. I've been using an aftermarket power adapter because it's smaller and easier to deal with, and it's always worked great with my other XL and two XE's. So I dug out the original power supply from the closet and plugged it in, and Sys Check started passing. I've left it running for 30+ minutes automatically repeating the memory tests and all is well.

 

So, something about this particular XL is super sensitive to power. At least at this point I know all the RAM and main chips are good. 

 

Cheers,

Ron

 

That is good news as you found a way to fix your problem.

 

I use a switched mode 5V 3A power supply made by Tiger without incident. Most switch mode power supplies do have high frequency noise on their supply output, whereas the Atari inbuilt power smoothing is designed for the low 50/60 Hz mains frequency.

 

Of the eight 800XL that I own (I had to check my spreadsheet), I changed only one 470 uF capacitor that had bulged. I fitted a Panasonic FR 680 uF 16V 5mm pitch that I had ready for an Atari ST PSU.

 

So perhaps check/change the lone 470 uF capacitor, and upload some good images of your board to see if we can spot anything obvious.

 

A standard 800XL has the type of internal power smoothing below. The 5V A & B rails affect the RAM the most.

 

 

 

[Paul Westphal]

I'm in the Mt.Tabor area of Portland. Give me a shout if you need something :

https://www.eightbitfix.com/

Edited June 19, 2023 by Paul Westphal

[itripn]

 

Spent some time replacing all of the Caps today. For science, I did them one at a time, then tried Sys Check after each. Replacing the caps made no different, this specific machine still did not like the USB adapter I've been using with the other machine with no problem. But it's still stable with original power supply through many passes of Sys Check tests. 

 

@TZJB thanks for the extra info, I'll definitely use this in the future!

 

@Paul Westphal Thank you, I might take you up on the offer some day!

 

Cheers,

Ron

[Paul Westphal]

FYI - I have a factory Diagnostic station and it can be very useful in tracking down problems.

[ClausB]

On 6/20/2023 at 1:02 PM, Paul Westphal said:

FYI - I have a factory Diagnostic station and it can be very useful in tracking down problems.

Interesting! Are there photos posted?