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Type: Posts; User: Dwight Elvey

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1. Thread: IBM PC Floppy Drive Problem - Head can only move in one direction

by Dwight Elvey
Replies
15
Views
258

This part of the circuit can be tested with a...

This part of the circuit can be tested with a voltmeter and a piece of wire, you don't need a logic probe.
It will jump back if it is stopped before it advances again. The is not that it is trying...
2. Thread: IBM PC Floppy Drive Problem - Head can only move in one direction

by Dwight Elvey
Replies
15
Views
258

You need to trace the track00 circuit. 4F pin 11...

You need to trace the track00 circuit. 4F pin 11 should track the switch. Watch T8. It should not toggle when the head is moving away from track00 and should stay high.
Like wise 3D pin 2 should...
3. Thread: How to test M8655 serial board

by Dwight Elvey
Replies
8
Views
217

How about the handshake wires? Dwight

Dwight

by Dwight Elvey
Replies
63
Views
934

Great Dwight

Great
Dwight

by Dwight Elvey
Replies
63
Views
934

Without special setup, there is not much else you...

Without special setup, there is not much else you can do. The head alignment usually only aligns one head, assuming the other head was right to start.
Dwight

by Dwight Elvey
Replies
63
Views
934

Forget what I just said, you drive has three...

Forget what I just said, you drive has three pots.
Dwight

by Dwight Elvey
Replies
63
Views
934

With the disk out, carefully lower the head down...

With the disk out, carefully lower the head down by closing the door slowly. Most double heads have opposite flat sides such that only a narrow part overlaps ( the width of a track ). You don't want...

by Dwight Elvey
Replies
63
Views
934

It is also hoped that you measures the pots value...

It is also hoped that you measures the pots value before you adjusted it? The pot sets the write current.
With the tracking being a little off, it would read a disk formatted by by itself. The...
9. Thread: IBM PC Floppy Drive Problem - Head can only move in one direction

by Dwight Elvey
Replies
15
Views
258

It could be one of the XORs or 3D but my bet is...

It could be one of the XORs or 3D but my bet is still with the Zero switch. He didn't say it would step away from track zero when it was suppose to be stepping towards track zero, only that it would...
10. Thread: IBM PC Floppy Drive Problem - Head can only move in one direction

by Dwight Elvey
Replies
15
Views
258

Opps. I should have said 4F pin 10 stuck high not...

Opps. I should have said 4F pin 10 stuck high not low. When both pins of 4F were one, it would block the step pulse. Anyway, the same problem the switch is stuck or something in the switch path. 4F...

by Dwight Elvey
Replies
63
Views
934

Try a little more weight to see if it is still...

Try a little more weight to see if it is still contact issues.
Also check the rotation speed.
Dwight
12. Thread: IBM PC Floppy Drive Problem - Head can only move in one direction

by Dwight Elvey
Replies
15
Views
258

My bet is a stuck or broken track 0 switch. It...

My bet is a stuck or broken track 0 switch. It thinks it is always at track zero and that won't let it go any more towards track zero, it is locked out by 4F pin 10 being stuck low.
Dwight
13. Thread: "Weird" flip flop .. need some "pointers"

by Dwight Elvey
Replies
13
Views
390

It is interesting that different training makes...

It is interesting that different training makes one see things differently. When looking at logic diagrams, I don't tend to look a them in terms of positive or negative logic. I only look at them...
14. Thread: Altair 8800 restoration question

by Dwight Elvey
Replies
22
Views
504

Here is a manual for your board....

Here is a manual for your board.
http://www.s100computers.com/Hardware%20Manuals/MITS/88_4kdrb.pdf

Be careful about that extra regulator. It may be for the negative rails of the RAMs. You'll have...
15. Thread: Altair 8800 restoration question

by Dwight Elvey
Replies
22
Views
504

That is good and bad to hear. ( bad for the memory card )
With the boards removed, you can do a quick check data in lines by grounding them on the bus. It is a simple test to make sure when you have...

by Dwight Elvey
Replies
36
Views
2,165

I've used GeoffB17's method for years and never...

I've used GeoffB17's method for years and never had an issue. The key is to wipe the disk CLEAN with a strong magnet. Only format or write to is on the 1.2M drive!
Dwight
17. Thread: Hacking the VT100 keyboard

by Dwight Elvey
Replies
11
Views
617

What is the clock rate used by the keyboard UART?...

What is the clock rate used by the keyboard UART? Looking at the schematic, it isn't clear. That divided by 128 or 144, depending on which of stop counts are used would be the fastest half cycle you...
18. Thread: Altair 8800 restoration question

by Dwight Elvey
Replies
22
Views
504

When you reset, your video showed the address lights all lighting because of the buffers are going 3state. My question is that do all the addresses light in sequence when you increment the address....
19. Thread: Rockwell RM 65 Family (AIM 65) Development system?

by Dwight Elvey
Replies
12
Views
198

Here are some pictures of my machine: The last...

Here are some pictures of my machine:
The last picture is looking down into the rack. Notice that there are two long UCB strips. The large card strattles the two busses. The RAM card is 8Kb of high...
20. Thread: Hacking the VT100 keyboard

by Dwight Elvey
Replies
11
Views
617

The speaker is controlled by a bit from a uart...

The speaker is controlled by a bit from a uart data. The rate that you could toggle is controlled how fast you can send 8 bits of data over the serial. To complicate things, the serial is a...
21. Thread: Rockwell RM 65 Family (AIM 65) Development system?

by Dwight Elvey
Replies
12
Views
198

I wonder if it was able to switch between AIM65...

I wonder if it was able to switch between AIM65 controlling the bus and RM65 controlling the bus. The one shown was used with the AIM65 only controlling.
Dwight
22. Thread: Rockwell RM 65 Family (AIM 65) Development system?

by Dwight Elvey
Replies
12
Views
198

That was where I'd seen the RM65 FDC manual. It...

That was where I'd seen the RM65 FDC manual. It was apparently used with the AIM65 sometimes. I'd assume that they made an adapter to UBC or STD bus, from the AIM65, at sometime.
Dwight
23. Thread: "Weird" flip flop .. need some "pointers"

by Dwight Elvey
Replies
13
Views
390

I'm assuming this was for the Siemens system your...

I'm assuming this was for the Siemens system your working on?
Dwight
24. Thread: Rockwell RM 65 Family (AIM 65) Development system?

by Dwight Elvey
Replies
12
Views
198

The only manual I know of on the web someplace is...

The only manual I know of on the web someplace is the FDC manual. I don't know about the AIM manuals because I've not payed attention to them.
Dwight