Apple Disk ][ Controller

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Apple Disk ][ Controller

The disk ][ controller from another Apple IIe I own has decided that it is no longer working. It worked for a short while, in the sense that plugging in a floppy drive seemed to work fine. At one point by disconnecting and reconnecting the floppy drive (with the computer off) when I turned it on again, I smelled an unpleasant smell coming from the controller. I turned everything off. When I turned it on again, the floppy red LED stayed on with the engine running, everything seemed normal, but inserting a floppy disk it does not start automatically and even typing command PR#4, it seems that the floppy no longer receives the input from computer. What could have happened to the controller?

 

Thank you very much

GianDO

 

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The LS05 and LS323 are known

The LS05 and LS323 are known to go bad...

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PR#4?  Normally people put a

PR#4?  Normally people put a floppy controller in slot 6.  But that shouldn't cause the problem you are experiencing.  What usually causes failures is the floppy cable being attached backwards or one row off.  Although that normally blows out the 74LS125 on the Disk ][ analog card inside the drive, it can also blow other chips on the analog card or the floppy controller.

 

Beware that if the 74LS125 blows it is not uncommon for the drive to erase the track under the head wherever it might be.  If you open up the drive, quite often when the 74LS125 blows it will have an obvious burn mark or even a little chunk blown out of the top.

 

If the controller is bad, see if you can identify the part that was eminating the smell.  It may have a burnt spot or just your nose may be able to determine which chip or part it is.

 

Another thing that can happen on floppy controllers is just due to age the capacitors can go bad, especially the electrolytic at C2.  Look for signs of leakage on that.

 

Do you have another floppy drive and controller you can test with?  To eliminate which is the problem?

 

If you've blown a chip on your Disk II Controller Card, hopefully it is not one of the PROMs because those are unobtanium.  Only source for them typically is another card since the MMI 6309 (or other compatible chip) BiPolar PROMs haven't been made in years and few people have programmers these days that can handle them even if you find blank PROMs.  Also because they are expensive there are fakes out there and a lot of the ones coming out of China, etc., are e-waste recycled, meaning they are used.  And since these can only be programmed once, that means they are unusable.  Caveat Emptor (buyer beware).

 

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jeffmazur wrote:The LS05 and
jeffmazur wrote:

The LS05 and LS323 are known to go bad...

 

In fact I intend to replace them. L05 is quite easy to find, while LS323 is sadly hard to find.

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GianDO wrote:jeffmazur wrote
GianDO wrote:
jeffmazur wrote:

The LS05 and LS323 are known to go bad...

 

In fact I intend to replace them. L05 is quite easy to find, while LS323 is sadly hard to find.

 

 

74LS323 isn't that hard to find, but usually a lot more expensive than other similar chips...  Usually 2-3x the price of more common ones.

 

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DiskIICintroller.jpeg
softwarejanitor wrote:

PR#4?  Normally people put a floppy controller in slot 6.  But that shouldn't cause the problem you are experiencing.  What usually causes failures is the floppy cable being attached backwards or one row off.  Although that normally blows out the 74LS125 on the Disk ][ analog card inside the drive, it can also blow other chips on the analog card or the floppy controller.

 

 

It happened to me once that the LS125 broke on the floppy drive board. It was enough to replace it to get the floppy drive working again. In this case, the floppy drive board is intact and free from unpleasant odors. I clearly felt the nasty smell was coming from the controller because  computer chassis was open when it happened.

 

Unfortunately I have other drives, but I don't have another controller.

 

I attach the photo of the controller. The only IC that has two suspicious specks appears to be LS05, but I'm not sure.

 

DISK ][ CONTROLLER

 

 

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GianDO wrote:jeffmazur wrote
GianDO wrote:
jeffmazur wrote:

The LS05 and LS323 are known to go bad...

 

In fact I intend to replace them. L05 is quite easy to find, while LS323 is sadly hard to find.

 

My local supplier in Bulgaria has them in stock. They ship anywhere in the world: https://store.comet.bg/en/Catalogue/Product/351/

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I'd replace the 74LS05 first then...  Next the 74LS323.  Then the 9334, 74LS32 and 74LS174, probably in that order.  I normally keep spares for all of those chips except the 9334.  I might have one extra.  But I've got several Disk II Controller Cards and the newer ones with the DB19 connector, so I can swap chips to test.

 

As far as checking the P5/P6 chips...  You can look at the ROM code by going to the monitor with "CALL -151" then do "CX00L" where X is the slot.  You should see reasonable looking code if you list a few pages.  If it is a bunch of garbage or lots of 00's or FF's, the boot PROM may be bad.  You can find the actual code listings online if you want to check byte by byte, but usually it's either good or way off and obvious.

 

Little known is you can actually check the state machine PROM by swapping the chips and listing and comparing the data to the known good data.  It won't give a coherent disassembly because it isn't 6502 code, so for that one you need to know what you are looking for.  Just don't forget to swap the chips back...  and I HIGHLY recommend marking them so you know which is P5 and P6 if they aren't already marked with an Apple part # as many are.  Your picture they aren't marked, are they replacements?

 

Typical Apple markings are something like "(C) Apple 341-0027-00" for the P5 and "(C) Apple 341-0028-01" for the P6.  Your card doesn't have the typical red Apple 16 sticker either, so it is also possible your card was originally a 13 sector card that someone burned new P5 and P6 PROMs for.

 

Oh...  and for what it is worth...  one time back in the day I ran into a card that swapping out all of the chips wouldn't make it work...  turned out to be one of the transistors.  I don't remember which one, I think it was Q1, but it might have been Q2 or Q3...  That was 30+ years ago.

 

 

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CVT wrote:GianDO wrote
CVT wrote:
GianDO wrote:
jeffmazur wrote:

The LS05 and LS323 are known to go bad...

 

In fact I intend to replace them. L05 is quite easy to find, while LS323 is sadly hard to find.

 

My local supplier in Bulgaria has them in stock. They ship anywhere in the world: 

 

Thank you for suggestions.

 

Unfortunately there is not a 74LS05. I would like to buy all the ICs that are needed in this case, but unfortunately I can't find an online shop that has all the components in stock.

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softwarejanitor wrote:I'd
softwarejanitor wrote:

I'd replace the 74LS05 first then...  Next the 74LS323.  Then the 9334, 74LS32 and 74LS174, probably in that order.  I normally keep spares for all of those chips except the 9334.  I might have one extra.  But I've got several Disk II Controller Cards and the newer ones with the DB19 connector, so I can swap chips to test.

 

As far as checking the P5/P6

 

 

Sorry,  74LS32 or 74LS132 ?

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Sorry, typo...  it's a

Sorry, typo...  it's a 74LS132.  Go by the markings on the board, they're correct.  Sometimes chips found on the board are equivalents with slightly different part numbers.

 

 

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GianDO wrote: I would like to
GianDO wrote:
 I would like to buy all the ICs that are needed in this case, but unfortunately I can't find an online shop that has all the components in stock.

 

That's a tall order these days, even if you go with the 74HCT series instead of 74LS. Also consider AliExpress. If you do, my suggestion is to get at least 2 of each and always ask for refund if some of them don't work. That way you also end up building a nice reserve of spares.

 

When I was sourcing the chips for the Dan ][ Controller I even had a case when I ordered 3 AT28C256 EEPROMs and only one of them worked. But they sell them so cheap, refund the broken ones and ship them for 50 eurocents, so it's still totally worth it.

 

These days they also sell brand new chips labeled 74LS that are actually 74HCT, which will work just fine. The easiest way to tell the difference is by their heat signature, but you need to treat them with respect in terms of static, because they are CMOS.

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GianDO wrote:Unfortunately
GianDO wrote:
Unfortunately there is not a 74LS05. I would like to buy all the ICs that are needed in this case, but unfortunately I can't find an online shop that has all the components in stock.

 

Have you tried Unicorn Electronics and Jameco?

Between the two of them you should be able to find all the logic chips on your list.

Avoid Aliexpress if you can.

https://www.unicornelectronics.com

https://www.jameco.com

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Jameco doesn't have the

Jameco doesn't have the 74LS232. Unicorn Electronics has everything, but they have a $30 minimum order requirement. Once you include the shipping and the customs fee it will be over $50 and at that point you might as well get a replacement Disk ][ Controller from eBay.

 

For Europe AliExpress is an amazing deal and I don't see why you would avoid it. I've gotten so many retro chips from there in perfect working condition that would have otherwise gone straight to the furnace.

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The 74LS323 is availble on

The 74LS323 is availble on eBay.  AliExpress can be a good source of a lot of things, but it has the down side that it can be very slow and on vintage chips it can be hit-or-miss.  Lots of fakes and re-marked chips.  I've gotten some good chips there but I've also had some I had to get re-funds on and others on the online forums have had much worse luck than me.

 

Customs fees and shipping costs to Europe change things for sure.  If I didn't already have some 74LS323 on hand I'd probably order from eBay.  I found some for around $5 plus $3 shipping from China or $10.95 with free shipping from a US seller.  These are both sellers I've bought from in the past so I am more confident that i will get what I'm paying for.  I've never had to pay any extra taxes or import duty on small purchases like this.

 

The reason I have extra stock of things like 74LS323 is that when I order from places like Unicorn I usually buy additional stuff to fill those minimum orders or make the shipping charges worthwhile.

 

However...  I also see a lot of merit in your advice just to get another Disk ][ Controller Card.  It isn't like they're hard to find or expensive.  And then he'll have spares of most of the parts save the one that is actually faulty.

 

 

 

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I was able to find all the

I was able to find all the components at a shop an hour and a half from my house. I could not believe it. In this shop they had all the ICs that are on the controller and I bought some. After replacing them one by one following the order suggested by softwarejanitor I located the defective component, the IC 9334. In appearance this IC didn't seem damaged, its plastic case is still intact and I didn't notice any signs of overheating either on the socket or on the pins (when the unit has stopped working it just smells bad).I replaced IC 9334 with IC SN74LS259N and the controller started working normally again.Thank you all for the advice you have given me.

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GianDO wrote:I was able to
GianDO wrote:

I was able to find all the components at a shop an hour and a half from my house. I could not believe it. In this shop they had all the ICs that are on the controller and I bought some. After replacing them one by one following the order suggested by softwarejanitor I located the defective component, the IC 9334. In appearance this IC didn't seem damaged, its plastic case is still intact and I

 

 

Glad you got it working.  The 9334 doesn't fail often, but I have seen bad ones.

 

 

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