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Member Since 11 Apr 2010
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#4085868 1088XLD - Custom A8 Computer in 1050 Drive Case

Posted by BillC on Sun Aug 5, 2018 3:23 PM



If you are running into issues with what can fit in the drive bay opening you could use a custom faceplate similar to the one in the post below for the MEGA Speedy, which would allow use of the entire front edge of the main PCB. The upper port area could be enlarged as well if desired.



#4082516 Faulty RAM on 800XL - what ram to buy

Posted by BillC on Mon Jul 30, 2018 5:27 PM



The important things about the right RAM chips are already told.


But... How is your experience with Atari 8-Bit? If you´re doing the first technical steps with such an old system, it´s better to do it step-by-step. First fix the defects, then think about expansions. There are a lot of new developments, some useful, some not. You will find a lot of infos here at AtariAge :)

True, but there is no point in purchasing replacement 4164 chips if considering a 256k upgrade. The 41256 chips are backward compatible with standard 4164s if pin 1 is grounded, and are often the same price or less.

#4077111 Identifying upgrades in an 800XL, labelled "256KB and RS232"

Posted by BillC on Sun Jul 22, 2018 10:02 PM

I pulled out an 800XL that I had in storage which I have looked at before. On the underside was written “256KB and RS232”. Hoping this was a RAM and SIO upgrade, I opened it up and took some photos.

The Satantronic RAM testing utility only recognises 48k and fails on some tests.

Does anyone know about this particular Ram upgrade is (labelled “JWG 86” in the photo) or what the RS232 upgrade might be?


Sent from my iPhone using Tapatalk

This PCB is likely a variation of Claus Buchholzs' 256k upgrade for the 800XL.


The ICD RamboXL, Wizztronics 256k, and Newell 256k were commercial versions, this one could have been done by a local users group.


There are 2 versions of the ANTIC chip, this PCB appears to be a simpler version which will only work with the later? one.  Support for the other version of ANTIC requires a couple extra logic chips.


The first think to check would be the ribbon cable connection to the PIA chip, which you haven't shown, this is required for bank selection.



The RS232 mod could be an internal R-Verter interface connected to the SIO port.

#4071969 SIO Maximum Current Draw?

Posted by BillC on Mon Jul 16, 2018 1:47 PM

The 800XL schematics show the SIO 5V supply line directly connected to the 5V supplied by the external power supply, so 1.5A....working on a similar SIO device, and had the same question.



The limit for external +5V current on the SIO port would NOT be 1.5A, it would be the maximum the power supply could deliver minus the current needed to run the computer.

#4069166 Atari 130XE video cable

Posted by BillC on Thu Jul 12, 2018 5:26 PM


It's pretty easy to find this cable does S-video and composite



8-Bit Classics does too, selling both Commodore 1702 and s-video versions. The cables are good quality, the prices are lower, and for USA/Canada shipping should be lower as well.



#4069129 New owner needs help :(

Posted by BillC on Thu Jul 12, 2018 4:07 PM

Yes, I used that book extensively.  Other than a couple of mistakes I figured out (R148 isn't marked on the schematics, just a resister symbol without the numbers,) it was quite helpful in attempting to track down the signal loss.  Would have done me more good if I had an oscilloscope instead of just an analogue volt-ohm meter.  Even a more modern digital multi-meter would have been helpful :(


From the same page, I pulled the SAMs service manual & the Field service manual for the 800 as well.

Even when the parts value isn't listed in the schematic, it can usually be found in the parts list near the back of the Field Service Manual. The image below is clipped from page 201.



#4066204 I bought an 800XL on ebay and when I powered it up...

Posted by BillC on Mon Jul 9, 2018 1:38 AM

A 68766 is a direct drop-in if you can find one to burn ver.C on.

Or get an adapter which allows the use of a 2764 compatible chip, which are less expensive and much easier to find.





Some models of the 600XL have 2 jumpers which already allow the use 2764 EPROMs for internal BASIC, the socket must be converted to 28 pin also.

#4066179 Some new (not really) hardware made by tfhh

Posted by BillC on Mon Jul 9, 2018 12:57 AM

Makes sense, thanks for confirming. I guess I've just never seen it before, and even my old 320K 130XE must have Rev B then.

AFAIK only the 400/800 OSs were referred to by letters, A or B. Versions 1,2,3 were for the XL/XE, Version 4 for the XEGS, and Version 10,11 for the 1200XL.

#4064575 1050 drive issue

Posted by BillC on Fri Jul 6, 2018 8:15 PM

atari does not use the index hole

The 810/1050 don't use the index hole, but I believe the XF551 does.

#4064238 1050 drive issue

Posted by BillC on Fri Jul 6, 2018 11:26 AM

I tried to fix it tonight. Broke off the pad that presses the disk against the head. Anyone know if/where I can get one?

Best Electronics lists it in their catalog addendum, I don't know if it's the complete part or just the pad.

They do have a minimum order of $20 + shipping, and Brad can sometimes be difficult 



810 / 1050 Felt (Rabbits hair) round pusher pad for the upper head assembly arm.   CO17511 $3.00

#4063372 I bought an 800XL on ebay and when I powered it up...

Posted by BillC on Thu Jul 5, 2018 1:03 AM


I held down the option key at power up and sure enough it tested 48k just fine.  I couldn't find an 'A' series Basic chip (probably cause I pitched it)

so I used a 'B' series chip and the computer booted up just fine.  So as oracle_jedi and R.Cade said, "this is just normal procedure."  My thanks to all for their input!



There was no 8k Revision A BASIC chip. Revision A is the brown label BASIC cartridge which contains 2-4k ROM chips, and was for use with the 400/800/1200XL.

#4059163 Where to buy an A/V cable for 800xl?

Posted by BillC on Thu Jun 28, 2018 3:17 PM

When I was searching for a cable I ran into a lot of this kind of information. I have no idea what chroma is it why I would want it. If audio+composite will give me sounds and a color picture on my tv then that's what I want. ;-)

Chroma + Luma(AKA s-video) is normally better quality video than composite. 8-Bit Classics sells several video cables for the Atari8, with 2 giving the option of composite & s-video, the chroma/luma output can be mini-DIN4(normal s-video) or dual RCA(Commodore 1702 monitor)


Their cables including s-video only cost $2 more than their composite only cable, and allow the option of getting the better quality video if you connect chroma to the monitor port of your 800XL.


Composite + dual mono audio: $9.99 + S&H

Composite + mini-DIN4 s-video + dual mono audio $11.99 + S&H

Composite + dual-RCA chroma/luma + dual mono audio: $11.99 + S&H

#4056575 Antic and Analog disk-of-the-month archives?

Posted by BillC on Mon Jun 25, 2018 9:07 AM

I don't know if all of them are there, but ATRs of most are on the 3rd Holmes CD and are available from the pigwa ftp site.

#4051296 Troubleshooting CPU board on a 400

Posted by BillC on Sun Jun 17, 2018 11:50 AM


OK, I see.  I can't figure why I'm only getting +5.5VDC maximum.  I pulled R308 and it tested at 330K OHM.  However, with power the voltage out from R308 is only +5.5.  Should I just replace R308?  

There are a few possibilites for low voltage between R308/R309.

1. The +12V power supplied is too low, with the resistance values given it would be about +9.1V if they're accurate.

2. The resistance across the potentiometer is too low, if the +12V supply is good I calculate it to be about 280k instead of 500k.

3. The capacitor(C305) is failing, allowing DC current to ground which increases the voltage drop across R308. I believe it would only take 5 micro-amps current thru C305 to cause the lower voltage. (This would make it equivalent to a 1 to 1.1 meg ohm resistor)


If the symptoms are caused by item 2 or 3 replacing R308 with a lower value(150k or 180k) may resolve the issue for now, but the capacitor or potentiometer may degrade further causing the problem to re-occur.


I think R309 is the most likely culprit, with C305 being the second most likely. The +12VDC supply being low is less likely as this would probably cause other problems(4116 RAM chips require +12VDC, but if the RAM has been upgraded to 4164 chips this wouldn't be an issue)

#4047391 Atari 800XL custom bios switch questions

Posted by BillC on Tue Jun 12, 2018 1:39 PM

Sounds line a common switch between 2 OS ROM's. Usually between the stock XL OS, and the other for compatibility with 800 OSb.

Sounds like yours has a 3 position switch, where the centre position is not connected. red/yellow screen is a common symptom of a missing/bad OS ROM, which the centre position would simulate.

Inside I expect you would see a 2nd chip soldered on top of the first. With the switches' wires connected to the power pins of each.

I don't immediately recall a particular OS that used a black background. Maybe you could run a utility to dump the OS to a file, and upload here...

This machine could have a RamrodXL which has sockets for 3 individual OS chips, this upgrade uses a 3-position switch to select the active OS.