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I'M Back, PDP 11/40..

Hi All;
I have Finished the Maintenance Board, and it helped me find my first Bad IC.. See my other posting under 74H74..
I am now Wire-wrapping (for me) a universal UniBus Display Card, it will be able to plug in either a UniBus or a Modified UniBus slot..
I will take the extra four or so signals from under the Backplane of the UniBus slot and run them thru a 16 pin Plug In for the signals that I need for the UniBus signals that are unique to it.. I have D00 L wired and it shows that my circuit is correct.. This time I am using 74ABT540's instead of 74LS04's for my Drivers..
THANK YOU Marty
 
Hi All;
Well, nothing like a minor/major screw-up to help pull my head out of where it should not be..
When I looked that the Schematic for the UA11 it shows CA1 and CB1 as connected together, So, I wired up instead CU1 and CV1 which put +15 Volts on the AC LO lines, and I heard some chips that were NOT HAPPY, and let out their Smoke Signal and Smell to let me know..
Needless to say, I am Tracing the AC LO line out to see what all the Damage is that I did.. Nothing like Counting from the Wrong end.. Hopefully the Damage was only One IC in, but it could have travailed farther.. This is where my sheets that I made come in Handy !!
THANK YOU Marty
 
It's very brave of you to be so frank about these issues. I find it most commendable. It is very healthy for novices in the future, who might come upon your thread, to be confronted with these accounts - their causes and consequences.

Too many collectors enter this hobby unaware of the damage they can bring about before understanding the nature of these errors. Even simple misplaced cards in a backplane can be the cause - not just homebrew hardware.

Thank you and keep up the good work.
 
Hi All;
RSX11M, Thank You for Your Encouraging words, Especially after making a Mistake like This..
I have Replaced two of the IC's in the Status Board, or I should say right now there is Power on the Status Board and Front Panel Only.. I have Not put in the Replacement Ic's, as I an going to check about three Ic's deep from the chips first line of Damage.. And it is easier to check the next in line IC With out the previous Ic, There are three Ic's to check, maybe four.. A 74H04, and two or three 74123's.. At present there is Nothing else on the Board that is getting Warm or Hot.. Hopefully, that is a good Sign.. Also, the Wire-Wrap Board Now pulls Down the 5 Volt Power Supply to 1.32 Volts when Inserted, So Now somewhere on the Board Something is either Shorted or Partially Shorted, I have pulled All of the Ic's and Pull-Up Resistors off of the Board and it still has the problem.. I'm hoping its a Wire-Wrap wire too close to something else.. And Not a Cap that is on the Board that has Shorted Out..
"Even simple misplaced cards in a backplane can be the cause - not just homebrew hardware." I have Done that and I have been Lucky that I haven't Blown up even more things..
THANK YOU Marty
 
Hi All;
It looks like at least two of the 74123's are Ok, tomorrow, I'll Check the other three 74123's just in case..
I am not so sure about the 74H04, So, I'LL recheck it tomorrow, it does go up and down, its just not at the level that I would expect, it may be Weak, from the Voltage surge..
THANK YOU Marty
 
Hi All;
I got the Short taken care of on the Wire-Wrap Board..
After taking One side of ALL of the caps off of the Board, and previously removing all other components, IC's etc.. And still having a short, between +5 Volts and Ground.. I did like I had to do on the Front Panel Board On my Old Imsai (Which I do not have any more), and that was Short all pins except Ground to +5 and I would hear a Tiny Crackle or Pop and the short would be gone..
Since I no longer have that brute force Power Supply, But I have my 6 Volt Electric Car Batteries.. 400 Amp..
And that did the Trick.. I no Longer have a short on the Wire-Wrap Board.. I think that some Boards develop Little shorting "Hairs" between different pins and they need to be taken out, What I have found is that they do grow back, IF it is a "Hair" and not some surface short or dirt.. Now Back to the STATUS Board..
THANK YOU Marty
 
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Now thats an interesting way of removing a short :), Im fortunate and have a thermal imager, just slowly increase the voltage and look for the bit that's getting hot, not as dramatic as zapping it with 400amps though
 
Dangerous game. I can usually find those with a good ohm meter - one that reads in 100'ths.

You might want to ohm out power and ground to the important device locations before re-populating.

Just a thought.
 
Hi All;
Rsx11M, I would normally agree, But when the WireWrap Board has Hundred of Heavy Connections to Power and Ground, it seemed the Only way to go, Worst off, it would smoke a Trace, and With Nothing else on the Board, nothing else could have been Damaged.. And I took the Board Outside, not the Whole Computer..
I wouldn't Have done it that Way, IF it were a Regular Populated Board.. But Being a Wire-Wrap Board with Everything taken Off, there was little chance of Blowing anything of Importance up..
The Board has been Put back in the System and left on for a while, No Problems Now..
If it were a populated Board I would Do it Differently, One is use No more than 4.75 to 4.95 Volts and check Polarity..
THANK YOU to Everyone for Your Concern and Warning to Everyone Else reading this Post..
THANK YOU Marty
 
The "Dangerous" reference was not intended as criticism. I've had to do the same thing myself - for shorts that resulted from metal migration through the G10. (though I usually resorted to a 1.5v dry cell in dimly lit conditions so I could see the flash and track it down)

Using a 1.5v source capable of high currents has many benefits. Mostly that semiconductors won't destroy themselves with such low voltages - at least not silicon ones. Even electrolytics can sustain it for a short time. You removed all the components so the only real danger was blowing out a heavy trace with a really big short. (which you'd have likely found first by other means)


It's good to talk about these techniques enough so that others will understand how to employ them appropriately. (and safely)
 
Hi All;
I am Warming up the iron and Taking out the DD11-CF BackPlane and Putting in the DD11-CK.. The DD11-CK has No Hand wiring it is Done on the Board. Trace style, and I am afraid that something Could have been wired Wrong before I got it.. And so to Eliminate that possible problem I am switching BackPlanes..
Since that BackPlace was what the Board that caused the original problem and Blew up in the First Place.. This latest setback, It might have Blown up the Ic that what taken out on the Timing Board from Before same Ic, or at least it smells funny at that location.. Of Course that could the smell left over from before.. I will find out when I get to the Timing Board and Re-Check its Ic's.. It also looks like the Data PATH board has a section that also smells funny as well, and there was No Connection to AC Lo on that Board.. Lots of things to check Out..
THANK YOU Marty
 
Hi All;
RXS11M, I had thoroughly Gone thru the Board, with a Magnifier, Ohm Meter and Touching any possible Solder Connections, So Yes this was a last resort.. I do Like Your Idea of using a 1.5 Volt Battery, I will remember that..
"It's good to talk about these techniques enough so that others will understand how to employ them appropriately. (and safely)"
I Totally Agree, Especially for any New Comer, who might not understand what Our Purpose was or is And Blow up a perfectly good Board..
I am Glad Someone Else has had this kind of Problem, and I thought I was the Only One..
THANK YOU Marty
 
Sorry - I'm not familiar enough with the distinctions between those backplanes to offer any comment. I'll just take it on faith that after all this hassle - you'd have checked it out before making the change. Hopefully someone else will be knowledgeable and offer comment.
 
Hi All;
RSX11M, As far as the information that I have the CK is the newer Version of the CF..
They Both are the UniBus on slots 1 and 4 and Modified UniBus on slots 2 and 3..
Any Way Thanks for You Help and Suggestions..
THANK YOU Marty
 
Marty said:
Hi All;
RSX11M, As far as the information that I have the CK is the newer Version of the CF..
They Both are the UniBus on slots 1 and 4 and Modified UniBus on slots 2 and 3..
Any Way Thanks for You Help and Suggestions..
THANK YOU Marty
Click to expand...

Not quite right -- not specifically a "newer version". Same logical backplane, but with a different power harness for a different variant of the BA11 workhorse chassis-family. All of the -Cx are logically equivalent, as are all of the -Dx.
 
Marty said:
Hi All;
RSX11M, As far as the information that I have the CK is the newer Version of the CF..
They Both are the UniBus on slots 1 and 4 and Modified UniBus on slots 2 and 3..
Any Way Thanks for You Help and Suggestions..
THANK YOU Marty
Click to expand...

I just noticed the backplane engineering drawings weren't on bitsavers. I've uploaded the 9-slot one to dec/unibus
and will upload the 4 slot if I can find them. From memory, the CK came out the same time as the 9 slot DK
 
Hi All;
AL, Your the Man, Thank You for Your clarification, and Uploading of the File, I will DownLoad it..
Do You have Any other Hidden Files that would be of Help for either of my current working on Machines, PDP 11/40 and PDP 11/04 ??
I have a nice large set of Schematics for the '04 which have ATEX on them..
THANK YOU Marty
 
Al Kossow said:
I just noticed the backplane engineering drawings weren't on bitsavers. I've uploaded the 9-slot one to dec/unibus
and will upload the 4 slot if I can find them. From memory, the CK came out the same time as the 9 slot DK
Click to expand...

found the drawings...

"Note: DD11CK assemblies are electrically incompatible with DD11-CF assemblies.
A DD11-CK will work in BA11-L and BA11-K boxes. A DD11-CF will work in BA11-F
and BA11-P boxes only."
 
Hi All;
Al, I am a little confused, my normal..
Is the Wiring Hole Order, the Same between the two, CF and CK, Since I just took out the DD11-CF and Wired in the DD11-CK, The holes for wires look like they are the same, I will ohm out the different connections, that I need.. Ground, +5 volts, + and - 15 volts, AC LO, DC LO..
THANK YOU Marty
 
Marty said:
Do You have Any other Hidden Files that would be of Help for either of my current working on Machines, PDP 11/40 and PDP 11/04 ??
Click to expand...

Probably. I'll check if there is a better set of 11/40 CPU drawings and that all of the CPU option drawings (EIS,FIS,MMU,Stack Limit) are uploaded.
It would be nice to get the pinouts of all the CPU cards that you made at some point. As you said, it's handy to have them
when looking at the backplane.
 
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