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Atari 1050 drive "Boot Error"

P

powerlot

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Joined
Nov 20, 2021
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549
Location
Europe
Hi all

Now that I made my cable I've got the next issue:

One of the floppy drives I'm restoring does everything these drives do, but only results in continuous "BOOT ERROR" when trying to boot a DOS disk.

I checked and did everything one would usually do on a vintage floppy drive these days but it didn't help.

Thankful for any suggestions where to start, as I'm new to Atari floppy drives. In the mean time I'll study the attached manual.
 

Attachments

  • Atari1050service_jer.pdf
    1.2 MB · Views: 4
It's pretty quiet in the Atari section, huh?

I procured a second working drive and could exclude the drive mech and custom chips from being faulty. They all work when inserted in / connected to the board of the good drive.

Next I'll compare the waveforms in the manual with a scope...
 
LiqMatrix said:
AtariAge forums are great for Atari computer/console related posts.
Click to expand...
Thanks but I don't want to register to (yet) another forum only to make few posts and disappear again...

I tried to find any signal but it's just silent. I think the LM733 may be dead, as the other components around the read circuit don't look faulty.

Now to find one...
 
Replacing the LM733 didn't change anything. There's still some weird noisy output on TP5. I have no idea what could cause this.
1713510934616.png

Any ideas are welcome
 
I asked for support in the German neighbour forum, it took a while to find the problem but the drive is fixed now.

Summary:
- absolutely no signals from the amplifier when reading as written before
- eventually, we found out that one of the input voltages (pin 1 of LM733) was too low, where it should be symmetrical to the circuit connected to pin 14
1721373301414.png
- checking the passives and diodes on a multimeter didn't reveal any faults
- when trying to reflow all solder joints in the area between the R/W heads and the differential amplifier, diode CR1 burst open from the heat of the soldering iron
- replacing it fixed the problem

It looks like the diode CR1 was marginal. On a multimeter it read as a diode would with the correct voltage drop, but in circuit it partly failed and by sheer chance it revealed its flaw when heat was applied.

Anyway, happy to cross this one off the list
 
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