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Priam V150 exploded part, can anybody identify ?

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SunDown79

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So as stated in the other post I am working on an Altos 886 and in it there was a big 5,25" full-height MFM harddisk.
Turns out its a Priam V150 that did absolutely nothing, which is rare for a drive, they usually make some noises.

So had a look at the PCB on the bottom, all seemed ok
Then removed all the screws and stuff to get to the PCB below that and was full of dust AND I saw that something on the corner had exploded but not sure what it was.
Anybody here perhaps have an idea ? Would be cool if I could just replace the part, clean it all up and perhaps still use the drive.

Pictures are here : https://flic.kr/s/aHsmTnfTQV

Thanks!
Stefan.
 
Looks like an over-heated resistor - high wattage. Probably need to consult the schematics and determine what over-loaded the resistor.
 
My guess, as an electronic noob, was that there was soo much dust between the PCB and rotating part that it was unable to rotate and thus destroyed something.
Or perhaps something stuck at one time in the drive itself (heads or something). It rotates freely now.
And well a schematic, ghe, ehmm, don't think that will be findable very easily ;)
 
I just worked on one of these, it's an inductor part of a power supply input filter.
The board failed I haven't checked to see if this is open.
Something was drawing a lot of power for yours to blow like thatpriam.JPG
About all you can do is board swap since there is no repair information on Virtex/Priam drives that I've been able to find.

There are tantalum caps all around there (the yellow cylindrical things) check if any are shorted
They fail a LOT
 
Last edited:
The other thing to watch out for is the power supplies in that whole product line fail a LOT
I have a stack of 586, et al that all need their power supplies rebuilt.
Before turning it on, you should make sure the supply rails are solid under load.
 
And lots of things to check but impossible for someone without electronic knowhow to check out probably.
Unless you could point me into the right direction ? As I also have a 986T that seems to be very dead (well the fan spins but thats it)
 
SunDown79 said:
I realised that later on, sorry
Click to expand...

Not all drive will damage the platters but some have a sharp edge on the back and will cut a chunk of the platter out. You'd need to replace the platters from a donor drive. The cut will cause the head to bounce.
As for the coil, it is likely one of those yellow capacitors. Those are tantalum capacitors and a common failure point.
It looks like it ran hot enough to melt the solder on the lead. It blew the thing off the board.
As a general rule, newer drives can be rotated either way. ST506 drives will be damaged ( don't ask me how I know ).
Dwight
 
Question (lots of posts after each other hehe); can you test the tantalum's while they are still on the PCB ? And will a standard multimeter work ?

Al Kossow said:
I just worked on one of these, it's an inductor part of a power supply input filter.
The board failed I haven't checked to see if this is open.
Something was drawing a lot of power for yours to blow like thatView attachment 65524
About all you can do is board swap since there is no repair information on Virtex/Priam drives that I've been able to find.

There are tantalum caps all around there (the yellow cylindrical things) check if any are shorted
They fail a LOT
Click to expand...
 
that's good news. you can temporarily just put a jumper (or a fuse!) where that inductor
should be to see if the drive spins up

good V150s are hard to find. you should back up the contents if you can, but the easiest way to do that is with dave gesswein's mfm emulator board
 
I bought a 50mb Vertex drive from an 886 off of eBay since my system was missing its disk
and was able to dump its contents, which appears to be Xenix.

Has anyone else successfully archived their drives, or managed to image the installation software?
There isn't much for the 886 out there.
 
SunDown79 said:
And yup, it shorted, beep beep goes my multimeter, the other ones around it all seem ok.
Click to expand...

One can tell if there is a short on the power line but you may not be able to identify which one. Don't depend on beeping as an indication of being shorted. Use an ohms scale and measure it! The beeping is just for circuit tracing and not a sure measurement of a short. Lift one lead of the capacitor and measure with an ohms scale.
Dwight
 
Dwight Elvey said:
One can tell if there is a short on the power line but you may not be able to identify which one. Don't depend on beeping as an indication of being shorted. Use an ohms scale and measure it! The beeping is just for circuit tracing and not a sure measurement of a short. Lift one lead of the capacitor and measure with an ohms scale.
Click to expand...
There's the opposite effect as well. I got some wet-behind-the-ears tech on a Data General service call and he wanted to pull the backplane AGA fuses (see next paragraph) and check their cold resistance. I told him that was useless and unsafe, and the only way to test for a bad fuse was to measure the voltage drop across the fuse in a powered-up system. He refused to believe me and before I could stop him, he grabbed a backplane fuse and pulled it. This was followed by a loud scream and an impression of an AGA fuse burned into his fingertips that he likely still has to this day (like the bad guy with the medallion in "Raiders of the Lost Ark").

The early Eclipse backplanes were festooned with AGA fuses in the usual metal clips. These are available in ratings up to 30A, and lots of the fuses were 30A ones. They can get quite hot if they develop slight resistance. And if those weren't enough fun, the DG boards were festooned with "picofuses" which look like a 1/4W resistor. These are designed to protect sensitive parts of the board, Edson and the gang never having heard the bit about a transistor sacrificing itself to protect a fast-blowing fuse.

My S/200 was an odd beast. It collected a bunch of odd hacks and a partial CPU swap from me, so it was essentially an S/230 in S/200 skin (but with WCS). It was full to the gills with memory (256KW of MOS memory, which required a homebrew interposer because part of the CPU / MAP still thought it was talking to core). That required kicking out all of the 4-port terminal cards and replacing them with a separate comm chassis with ALM cards. We also upgraded from a 4324 (rebadged Diablo 44 5-over-5 disk) to a 6061 192MB disk (like a DEC RP06). I also ordered a 4MB fixed-head paging disk normally used only with AOS and did a RDOS driver for it as the system boot device. DG pretty much gave up and decided "sell him anything he wants and let him figure it out". At one time I had a 64-terminal XBASIC system (yes, I'm THAT GUY who wrote the infamous "XBASIC can use any 32 terminals, as long as they're the first 32" STR).
 
See my other thread about restoring my 886, might be a better place to collect info, see http://www.vcfed.org/forum/showthread.php?78223-Altos-886-restoration-(some-questions-help-needed)

Al Kossow said:
I bought a 50mb Vertex drive from an 886 off of eBay since my system was missing its disk
and was able to dump its contents, which appears to be Xenix.

Has anyone else successfully archived their drives, or managed to image the installation software?
There isn't much for the 886 out there.
Click to expand...
 
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