Another 130xe memory issue

[moonlight_mile]

Nothing that I can see.

I did check the voltage. Everything is getting a steady 4.90/4.89 volts. I am using the same power supply that I use for the other 130 and the 800 xl with the u1m so I am confident the power rails and power supply are good.

Will have to wait to see what happens when I get the new cpu.

[_The Doctor__]

the bank select lines should not have toned out the same... leave one bank disconnected and see if it boots with either of the banks connected as the primary bank,

[+scorpio_ny]

For some reason, I thought you socketed all the RAM. In the photo, it looks like only one bank was socketed and replaced with new chips.

[moonlight_mile]

Nah. I only replaced the second bank as that seemed where the issue was lying. I plan on replacing the other bank I was just taking it a step at a time. 
 

I am guessing to totally disconnect a bank is contingent on those two resisters I switched. Which resister should I totally disconnect to only allow 1 bank available?

 

thanks guys. 

[1050]

The way it was originally is left bank (unchanged) is the main system ram and the right bank only has to do with the extended memory talents. You've changed the wrong ram if you want to boot it. Might as well change it all out now? One bad chip effects that one bit of all 64K of memory BTW so you found one bad chip in the extended memory side and changed all of them out while resistors were swapped, and now it doesn't boot indicating a bad solder bridge/connection somewhere in the swapped ram section. It could always have been Freddie, they go south on occasion too. The resistors only swap memory in 64K chunks and only the system ram boots the machine, extended memory does nothing until you call upon it with ramdisk software for example. So extended memory resistor could be left one legged and the machine would boot up fine, but it will fail to function any use of the extended memory unless that resistor is attached. Not sure which resistor supplies /CAS signal to which column of ram, but if you've got a datasheet for your memory chip you can find that pin number and test it with a VOM meter to the resistor pad responsible for that column of ram chips.

[moonlight_mile]

Sorry guys that I haven’t been in contact. Been fighting headaches all week. Must be the Pennsylvania temp fluctuations.

Anyway. I haven’t moved the resistors back to see if it boots on the original bank of ram yet.

But I did order another set of 4164’s (Samsung brand) so I will be finishing the ram replacement. My new 6502 should be here tomorrow so I will pop that in before I move the resistors to see if the cpu may have been the culprit.

Just thought I’d let ya know. I really do appreciate all your help!

[moonlight_mile]

Ok got my 6502 and new 4164s (for the first bank).

I swapped the resistors to set it to the first bank. (That used to work) but now I get the red screen.

I don’t know if I will put in the new chips this weekend but when I have those in I will start popping around with my logic probe and see if I can narrow down the issue.

I have to check the resistors that I swapped. Those got kinda mangled so I will check the resistance on those see if they are still working or not.

I toned around to see if there were any bridges I couldn’t see on the sockets i installed. All seem isolated.

Now that the same issue is arising on the first bank maybe it isn’t necessarily the ram? I am still going to swap out all the mt chips but it does seem a little strange that now the first bank is doing the same thing.

Will keep ya posted.

[moonlight_mile]

Aha. R111 33 ohm resistor is totally dead. No reading at all (in circuit). R110 tests fine.

 

All I have are 510ohm resistors.

 

Is there any other value I can replace it with or do I need to order a few orange orange black gold resistors?

[StickJock]

5 hours ago, moonlight_mile said:

Aha. R111 33 ohm resistor is totally dead. No reading at all (in circuit). R110 tests fine.

 

All I have are 510ohm resistors.

 

Is there any other value I can replace it with or do I need to order a few orange orange black gold resistors?

 

You could just wire up 16 of your 510 ohm resistors in parallel.  That would give you 31.875 ohms.

 

?

[1050]

Just jumper them until you get some 33 ohm replacements. You might even get lazy and leave them in the package while using the machine. They were never necessary in the first place is the point. More on point some things are done for engineering "etiquette" and 33 ohm ram resistors are just that. Keep that pinky in the air kind of deal.

[moonlight_mile]

I ordered a little pack of 33 ohm resistors. Supposed to be here tomorrow. Hopefully they will be here sometime in the afternoon so I can pop ‘‘‘em in and see what happens. If not maybe I can sneak them in on Sunday between Mother’s Day stuff.

[moonlight_mile]

Ok. I replaced the resistors and I have a working computer.

I went and replaced the first bank of ram, so all ram has been upgraded.

I went and ran syschek reports ok. I ran xtended memory Check. All ok with the exception of it only showing 64k.

The resistors are back to stock.

Now my side2 and side3 carts now boot. Where they didn’t before the ram was changed. So something is working properly. I didn’t run the old chips from the first bank through my tester yet.


Below is a screen print from sdx but I am assuming it is still only reporting the main bank or am I all set?

[_The Doctor__]

 

[moonlight_mile]

1 hour ago, _The Doctor__ said:

 

Thanks!   I tried fake mode. Kept saying I had 4 megs but I am probably doing something wrong, but…..I tested dos 2.5 and spd 3.2 RAM disk. Both work properly, I can read and write to them no issues, so I guess my 13o is actually all fixed!  I couldn’t really get sdx on the side2 cart to set up the RAM disk. But I am guessing either I am doing something wrong or since the sd card pretty much has all the drive letters maxed out, that could be a reason. (I was just trying to use Rd.com)

 

thanks for all the help!!!
 

now to decide what to do with it. I already have a Sofia 2 and updated rom in my main 13o and u1m and Sofia 2 in my 8ooxl. 
 

any suggestions on what I could do with this one to make it different and worthy of keeping around with my other 2 8-bit units?

 

Also, my old 198os Archer (radio shack) solder is starting to dwindle down. What is the best solder to get that is currently on the market. Best by ways of: best for the type of work we all do on our vintage machines?

[chevymad]

VBXE. Also do you have both NTSC and PAL machines?  I converted my vbxe XEL machine to PAL. Nice to have both machines to try everything.

[moonlight_mile]

1 hour ago, _The Doctor__ said:

 

Thanks!   I tried fake mode. Kept saying I had 4 megs but I am probably doing something wrong, but…..I tested dos 2.5 and spd 3.2 RAM disk. Both work properly, I can read and write to them no issues, so I guess my 13o is actually all fixed!  I couldn’t really get sdx on the side2 cart to set up the RAM disk. But I am guessing either I am doing something wrong or since the sd card pretty much has all the drive letters maxed out, that could be a reason. (I was just trying to use Rd.com)

 

thanks for all the help!!!
 

now to decide what to do with it. I already have a Sofia 2 and updated rom in my main 13o and u1m and Sofia 2 in my 8ooxl. 
 

any suggestions on what I could do with this one to make it different and worthy of keeping around with my other 2 8-bit units?

 

Also, my old 198os Archer (radio shack) solder is starting to dwindle down. What is the best solder to get that is currently on the market. Best by ways of: best for the type of work we all do on our vintage machines?

[moonlight_mile]

9 hours ago, chevymad said:

VBXE. Also do you have both NTSC and PAL machines?  I converted my vbxe XEL machine to PAL. Nice to have both machines to try everything.

I have 1 pal Sophia and 1 ntsc Sophia. So I think I am covered there. 
 

Is there any real uses for rapidis?  I know rapidus and u1m don’t get along too well which is why I haven’t thought about that for my 8ooxl. 
 

I am holding out for the external u1m for my main 13oxe. 

[_The Doctor__]

;)

[+Stephen]

4 hours ago, _The Doctor__ said:

LMAO - been a long time since I had one of those solder reels.  Funny what things you can instantly remember though.

[moonlight_mile]

That is what mine looks like. Just smaller spool as it is pretty fine gauge solder.

[moonlight_mile]

[hueyjones70]

I just got a new (to me) 130XE. It has mt RAM chips. I had planned to put in the 320K RAM upgrade so I immediately took out the extended RAM bank and put in non mt RAM. I checked everything out and the computer booted successfully. A couple of days later it wouldn't boot; so I hooked up syscheck. Syscheck says RAM is good but it doesn't do the next step where you get the rainbow screen. Star Raiders boots but nothing else. I socketed the ROM and that chip was good. i socketed BASIC and that chip is good. I have to socket everything I need to troubleshoot so what is the most likely culprit that I should socket. I plan to replace the rest of the RAM once I get it working again.

[Beeblebrox]

It's a tricky one. TBH the chances that other ICs that were working a few days have gone bad I'd say are slim.  (Of course it can happen but I think rather than look to start socketing more chips I'd first suggest focusing on the work you have done to it so far. Triple check your RAM socketing work first. Do you have a RAM tester unit to pop out the RAM you have installed and test each one by one? (Just in case your replacement ram chips are bad).

 

Syscheck II is great but I've had situations where it didn't always pick up on failing RAM, or something else threw it out.

 

The problem is you could go for the usual suspects but you may find yourself socketing all the 40pin Ics (CPU, PIA, ANTIC, GTIA, FREDDIE,etc) and they'll all be ok - but here you are introducing the chance that in doing the socketing more issues could creep in. (Been there before).

 

What happens when you boot without Syscheck?  Can you upload a pic of the screen?  Is it just black straight away or do you see a coloured screen and hear a little pop beforehand?  If so what colour?

 

It helps if you have a CRT and when I am troubleshooting a non booting system I have the A8 hooked up to both my CRT and my LCD via my S-video splitter. On the CRT you see things onscreen intially that you don't see on the LCD as the latter displays the signal outpuy a few seconds after the A8 is powered on and you miss it.

 

Have the volume on your display turned up so you can hear any pop in audio.

 

My money is on the RAM still being an issue. Also might be worth checking out the MMU.

 

 

Edited January 15, 2023 by Beeblebrox

[moonlight_mile]

In my case I had 1 bad ram chip and while trying to troubleshoot the ram bank that was bad I toasted the one resistor. 
 

I would make sure all the ram is replaced by known good ram and check those two resistors. 

[TZJB]

13 hours ago, hueyjones70 said:

I just got a new (to me) 130XE. It has mt RAM chips. I had planned to put in the 320K RAM upgrade so I immediately took out the extended RAM bank and put in non mt RAM. I checked everything out and the computer booted successfully. A couple of days later it wouldn't boot; so I hooked up syscheck. Syscheck says RAM is good but it doesn't do the next step where you get the rainbow screen. Star Raiders boots but nothing else. I socketed the ROM and that chip was good. i socketed BASIC and that chip is good. I have to socket everything I need to troubleshoot so what is the most likely culprit that I should socket. I plan to replace the rest of the RAM once I get it working again.

Double check your work. Disconnect power and check continuity with an ohmmeter of all the address lines between the RAM and the CPU, also check for short circuits. Also that the RAS and CAS are continuous. It is possible that there may be a broken track or solder joint affecting the RAM. It happened to me and that's how I found it.