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Slow/defective 1050 drives with lazer upgrade

1050 slow lazer

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#26 Nezgar ONLINE  

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Posted Thu Jun 14, 2018 2:35 PM

Another source I came across for new belts for 1050's with Tandon mechs:

https://console5.com...indle-belt.html

#27 E474 OFFLINE  

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Posted Sun Jun 17, 2018 7:25 AM

Hi Nezgar,

Thanks for the link on drive belts. I've sprayed the belt with dressing fluid (a couple of days ago), but it is taking ages to try, so haven't tried it in the defective drive. I've just tried a belt from another drive, and unfortunately the drive still isn't ok. I did an RPM test, and I just got "error can't read" all the time, and the drive sounded exactly the same as before - sort of irregular speed sound. I don't think it is the 1050 board that is giving problems, the original mechanism from this drive works fine in another drive, and the mechanism that isn't working was originally from a drive that is working fine with another mechanism.

I can try taking apart the upper spindle, and lubricating that (I don't think I have anything left to lose with this mechanism), but I can't think of anything else to do with the drive. Do you have any ideas on what else I could do, or what might be worth investigating next?

#28 Nezgar ONLINE  

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Posted Sun Jun 17, 2018 9:56 AM

Just re-reading what you've tried before - you said you swapped the bad mech to a known good drive's controller board and the problem remained? (Confirms problem is mech, and not controller board)

Did you confirm that a known good mech works in the drive that had the bad mech?

This really narrows down that the issue is the mech. The only failure points here to cause irregular rpm are the motor itself, the belt, and the spindles.

I'm wondering if the motor itself is shot. Do you hear irregular speed from it even with no belt attached? If no, how about if you add a little resistance by pressing on it while spinning?

#29 E474 OFFLINE  

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Posted Mon Jun 18, 2018 4:20 AM

Hi Nezgar,

The drive mechanism was originally in another drive, and didn't work there. I swapped the mechanisms between drives, and it didn't work in the current drive, but the mechanism I swapped out worked fine in the other drive. So both drive boards are working fine, but one mech isn't working. I've tried putting in a drive belt from a working drive, but it still won't pass an rpm test, and there is the same irregular spinning sound. I'm going to try and lubricate the upper spindle assembly, but don't have time for the next couple of days. I will try running the motor without a belt (I think I tried this before, and I think it made a clacking sound).

#30 tf_hh OFFLINE  

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Posted Mon Jun 18, 2018 11:49 PM

there's a lot of wiring to a small upside down IC on top of the CPU, maybe it's RAM for lazer mode.

 

I´m pretty sure the 8K trackbuffer RAM is soldering below the EPROM as shown in one of the first pictures.

 

I´ve done such updates in my bad years also with the Speedy 1050 :ponder: 



#31 E474 OFFLINE  

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Posted Wed Jun 20, 2018 6:23 PM

Hi Nezgar,

 

    I have tried the defective mechanism with the belt treated with belt dressing fluid, but that didn't fix the drive (I got the same error message when I used the Lazer rpm test).

 

    I removed the upper spindle, and tried to take it apart, but only managed to remove the first C clip, the inner C-clip was too difficult to remove.

 

    I made a video of the drive spinning without the upper spindle, but there is the same sound if you listen carefully to the audio (I have down-scaled the video to 480p).

 

    I then removed the belt on the defective drive, and recorded the audio (defective_motor.mp3). Then I did the same for a working drive (good_motor.mp3). The audio sounds quite different, so I think that the motor itself is the problem. At this point I figure the motor needs replacing.

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#32 E474 OFFLINE  

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Posted Wed Jun 20, 2018 6:55 PM

Hi Jürgen,

 

   I'd always assumed that the Lazer code was in one EPROM, and the Doubler code was in another EPROM, and the switch selected which one was active. I didn't upload a picture of the switch, but I'll upload it for completeness (you can see which pins the red, white and black wires go to, and how the switch is wired up).

 

   If it's a single EPROM that holds all the code I have no idea how the switch would determine which code gets executed, but I appreciate this is your area of expertise.

 

   I'm not sure if the upgrade was put together this way to save the cost of making a circuit board (though I imagine assembling it must have been fun), or if it was to deter people from trying to copy it, but I am very reluctant to do anything to it. My hardware comfort zone is somewhere between a breadboard and soldering wires to bi-directional logic level shifters.

 

   I was playing round with the Lazer utilities, and they use SIO command 'r' to read from the Lazer memory (sector number seems to correspond to 16-bit memory address), so I think it might be possible to dump the EPROM (or at least the Lazer part) using software, but I haven't tried this yet.

Attached Thumbnails

  • drive_OS_switch.jpg


#33 Nezgar ONLINE  

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Posted Wed Jun 20, 2018 11:20 PM

I agree the defective item here seems to the the motor itself.  The 'sound' of the bad mech is slower. SO.. Looking back though, I don't think you mentioned if you actually tried adjusting the RPM? This is done using the VR2 pot near where the mech's wires connect to the controller board.

 

Some relevant info in 1050 Field Service Manual: http://www.atarimani...vice-manual.pdf

 

Page 1-7 (PDF page 10): The DC motor includes an internal Tachometer, whose output is monitored in the Tach Feedback circuit. The Tach Feedback circuit senses changes in current and maintains a constant motor speed.

 

Page 4-9 (PDF page 22): "When speed pot VR2 is adjusted, the voltage on Pin 10 of U5 increases or decreases. This causes a corresponding increase of decrease in the frequency of the AC signal on the motor control lines, Pin 8 of U5 and Pins 11 and 5 of U5."

 

Silkscreen of the controller board is on Page 5-6 (PDF page 36) of the document, so you can see where VR2 and U5 are. (right next to each other)

 

I'm curious if you have a multimeter if you can check the following on the jumper block where all the wires from the mech connect - Numbering 1 to 17 front to back.

 

Ground the neutral probe (black) of the multimeter somewhere on the drive mech, there's a couple holes that it seems i can let mine stand, better if you have aligator clips.

 

Pin 11 (red) measures about 7.2V DC with a disk inserted on my drive, and 6.8V without. Drive is maintaining RPM with higher current draw -( disk friction) You can test this by pressing your finger on the spindle cone or motor to increase friction. The drive will compensate by increasing voltage to maintain RPM. I can make mine peak over 9V DC. ( I presume 12V is the max)

 

Pin 8 (grey) I measure 3.44V AC, which is the tach feedback coming from the motor. This AC voltage tells the controller the speed the drive is actually turning.

 

Both of those measurement readings will go up or down in response to adjusting the VR2 pot.



#34 Nezgar ONLINE  

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Posted Wed Jun 20, 2018 11:38 PM

As for replacing the motor....a Tandon mech of mine uses a Copal LC-177E, a WST mech has a Copal LC-177H.

 

A quick search online I found these pages:

https://www.ebay.com/itm/350618532123LC177 Copal JAPAN 12V DC Stepper Tachometer Pm Motor LC-177P
https://www.ebay.com/itm/370814531100LC-177 COPAL 12V DC Stepper Tachometer PM Motor w pulley LC-177J 5400rpm
http://www.oddmix.co...al_lc_177b.htmlNice descroption of Copal LC-177B + detailed specs.

Not the best deals, and not sure what the letter designation at the end means... But maybe this will help in sourcing a part, or someone more knowledgeable than me knows other replacement parts that will work or has an otherwise dead mech that the motor can be salvaged from.


Edited by Nezgar, Wed Jun 20, 2018 11:47 PM.


#35 Nezgar ONLINE  

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Posted Thu Jun 21, 2018 1:12 AM

 

I´m pretty sure the 8K trackbuffer RAM is soldering below the EPROM as shown in one of the first pictures.

 

I´ve done such updates in my bad years also with the Speedy 1050 :ponder:

 

I just came across this directory on pigwa: http://ftp.pigwa.net...e Made Upgrade/

 

The pictures there look a LOT like the mod in E474's drive, but there's no description... there is an 8KB ROM there too. Maybe that's the Lazer ROM


Edited by Nezgar, Thu Jun 21, 2018 1:13 AM.


#36 tf_hh OFFLINE  

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Posted Thu Jun 21, 2018 3:43 AM

I just came across this directory on pigwa: http://ftp.pigwa.net...e Made Upgrade/

 

The pictures there look a LOT like the mod in E474's drive, but there's no description... there is an 8KB ROM there too. Maybe that's the Lazer ROM

 

Indeed. I´m sure it´s the same. The file "1050 Home made upgrade pic 3.jpg" shows the EPROM from bottom side, and the chip below the EPROM is not an EPROM, it looks like a standard 6264 chip - 8 KByte trackbuffer.



#37 Nezgar ONLINE  

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Posted Thu Jun 21, 2018 8:46 AM

In E474's drive, the switch goes straight to pins 1 (red, VPP +5VDC), 14 (black, GND), and 26 (white, N/C to EPROM, but probably to chip underneath) on what is according to the pictures on pigwa, a 2764 EPROM.

So.. the switch does not seem to bank select anything in the EPROM, it seems to be for something else. If the 8KB '1050 Upgrade.rom' is what's in use here, it has no trace of US Doubler code in it, but I do see the Drive ID to switch mappings at the end of the rom: '3241' starting at 1FF4.

The RED and WHITE wires seem to connect through a resistor on the centre pole of the switch, so some reduced voltage will go to pin 26 on the eprom/underneath chip at all times. And then the switch toggles none or the reduced voltage going to the black wire to GND on the EPROM... I don't understand this...


Edited by Nezgar, Thu Jun 21, 2018 8:46 AM.


#38 E474 OFFLINE  

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Posted Fri Jun 22, 2018 3:49 AM

I always thought it was two EPROMs, and the switch toggled between them, but could it be a single EPROM, and the switch changes the address for the RAM chip under the EPROM? You always need ROM at the top of the address space for a 6502 to boot (or at least something to supply the boot code address), and I guess you could code a test to see which address has RAM, and act accordingly?

#39 E474 OFFLINE  

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Posted Wed Jul 4, 2018 5:20 AM

Hi Nezgar,

Thanks very much for the info on checking the motors, and also the links for new motors/mechanisms. I was fairly convinced the motor was to blame, so I took a chance and ordered 3 defective drive mechanisms from www.rewindgames.eu. Fortunately I managed to get one mechanism to work, which left me with my original defective mechanism, and 2 untested mechanisms, which I will have a look at when I have some free time. So that's now 3 out of 3 working drives, plus some left over mechanisms for the future.

Regarding the actual mod in the 1050, I am fairly reluctant to try to dump the ROM using an EPROM programmer/reader as the mod was made sometime during the mid-eighties. Fortunately the ROM passes the Lazer diagnostic test, so is probably not suffering from bit-rot, though I always wonder if the diagnostic program has been hacked so it always says "PASS", though I have no evidence this is true. I tried dumping the ROM using a short assembler routine that sends SIO commands to read data from sectors >= 720/1040, which returned data from $8000 - $9FFF (IIRC), but it looks like the code on the 1050 Lazer mod won't return data from anything over $A000. I have a copy of UnHappy.exe, which is supposed to upload the original 1050 ROM, and think that could be hacked to include code to dump the ROM, and do other things, but I don't have time to do anything with it yet.

#40 Nezgar ONLINE  

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Posted Wed Jul 4, 2018 7:44 PM

Maybe if you can dump what you can via software, it can be compared to the ROM here:
http://ftp.pigwa.net...e Made Upgrade/

#41 Nezgar ONLINE  

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Posted Tue Jul 24, 2018 6:24 PM

So was browsing my new-to-me BEST electronics catalog, and saw

FC100520 1050,Indus Drive Motor ... $18.00 (price may have changed since printing)

#42 E474 OFFLINE  

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Posted Sat Jul 28, 2018 6:56 PM

Hi Nezgar,

Thanks for the info, I know I need at least 1 drive motor, but I have two other mechanisms that I haven't had time to test yet, so I will check those first. Also need to get a couple of mylar layers for the 130 XE's that I am trying to revive, and probably a few other items, so I will put together an order, hopefully in the next few days.




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