Tuesday, September 10, 2019

2015 iMac Display Replaced

The new display is here and working just fine but I was in for a big surprise when I took the cracked one off. The adhesive had "set up". The display was now firmly attached to the case! I had to use the pizza cutter tool again to take it back off. ๐Ÿ˜ฎ

I'm out $446. OTOH, I'm going to upgrade to a 2019 and a close friend has offered me more significantly than the current eBay value for this 2015 so I'll break even.

Sure would like to have that $446, though. ๐Ÿ’ธ

Wednesday, June 19, 2019

2015 iMac Disaster

Well gang, it wasn't long before the repair/upgrade of my 27" 2015 iMac came to grief. I got up, walked in the room and there before me was a computer with its display lying on the edge of beloved Herman Miller Ferrari-colored computer chair. I was so horrified that I didn't even think to take a picture of that appalling tableau. No, no one else will ever have the sadly-missed golden opportunity to co-experience such an exquisite non-rush.

I stood there in a daze for some time. Reality itself was beyond my capacity to entertain. ๐Ÿ˜‘

I finally came out of my stupor. As I gingerly lifted the display up and turned it over I beheld cracks aplenty:

Full screen (click to enlarge)

Right end

Needless to say the video and back-light cables were no longer in their sockets on the logic board. Having worked on aluminum iMacs numerous times I immediately assumed the worst. That is, all surface-mount connectors ripped clean off the PC board. Amazingly, the backlight connector had no damage at all. The embedded DisplayPort (eDP) connector only had its ends bent.

Backlight connector
eDP connector
There was virtually no adhesive residue on the back of the display except along the bottom which was still quite tacky and one small spot about an inch wide elsewhere. The frame was also tacky but not as much as it should have been.

We wiped everything down with IPA before we put the new adhesive strips on. Perhaps we rubbed the strips too hard while we were putting them on the case. I'm sure this is a pressure-sensitive adhesive so that may have made it start to cure before we got the display on. OTOH, we may not have rubbed things together as tightly as we should have after the display was on. At this point I don't know what to think.

Better pictures to come when we take it apart again to replace the display. ๐Ÿ˜ท

Thank "Bob" it didn't reach the floor. At least it's still working.

๐Ÿ–ฅ

Thursday, June 13, 2019

Eldorado 325A Frequency Counter

My latest acquisition from eBay:

From the seller's photo (heavily retouched by me)
Works perfectly down to 1Hz. I haven't tested the high end yet. I had a shoot all set up but as usual a disaster cropped elsewhere. I'll update this post with more pictures later if I have the chance.

$67. I was the only bidder.

The next day a model 224 with only four settings went for $65. ๐Ÿ™„

Friday, June 7, 2019

Systron Donner 6052 Frequency Counter

This is a work in progress...

Here is an HDR image:
Click to enlarge
More to come

Friday, May 31, 2019

Systron Donner 8350 Reader/Generator

Here's a lousy shot of my Nixie tube timecode generator/reader:

Click for a much better view!
I'm not sure what tubes are in it but the envelopes are only about 2" high. The thumbwheels set the starting time for generator mode so it can be used as a Nixie clock. The entire case is only one unit high.

Note the two missing keycaps between "Hold" and "Power". The plastic has become so brittle that the ears snapped like twigs with I pulled them off to replace the light bulbs. Not only does it look stupid but without the caps in place the switches can't be actuated.

I saved the pieces. I suppose they could be glued back together with a thin, springy piece of steel reinforcing the joint and making it flexible enough for them to be put back on again.

If I had new, blank caps I could reproduce the text with decals. If anyone has a fix please message me.

Perhaps later I'll have time to take a better picture and get some interior shots. And get the part numbers on the tubes.

Thursday, May 30, 2019

2015 iMac Teardown and Second SSD Installation

A few months ago my iMac 17,1 made some very scary noises. It sounded like a loose plug in an AC socket arcing away accompanied by some hissing. There was no magic smoke, no smell.

Last week we tore the machine all the way down to inspect it. The power supply had no visible damage or odor. The AC socket and wires were OK. The mystery remains a mystery.

While we had it open I installed a second SSD in the HDD bay. Because the machine shipped with an Apple SSD on the logic board and no hard drive in the HDD bay I didn't know if the mounting brackets were installed. I found conflicting reports online. What I knew for certain was that the SATA cable to the HDD bay was not installed so I purchased a new one.

I also purchased an SSD installation kit from OWC which included a 1TB SSD, 3.5" to 2.5" adapter, "pizza cutter" tool for detaching the display (which is glued on), a thermal sensor and the adhesive tapes for re-attaching the display.

I got lucky—the drive brackets were there along with a lot of dust:

Thank you Apple
The only thing I didn't have were the pin-shaped screws that go into the grommets on the HDD brackets. We managed to fasten the drive adapter in place with some regular drive screws. They fitted snugly in the grommets and it's very unlikely that any of them will vibrate loose.

New SSD in place
(Note that I installed a 500GB Samsung EVO 850 that I already had on hand. I'm saving the OWC 1TB SSD from the kit for an external enclosure.)

There was one heart-stopping moment when the display slipped out of our hands and the bottom landed about 1/16" above the lower edge of the housing. We very carefully pulled it loose without breaking the glass and put it back in place correctly.

I held my breath again as I pushed the power button. The machine chimed, the fan spun up, and the display came on. What a tremendous relief. I spent weeks researching every aspect of the project and in the end it paid off.

Next up—install Mojave on the second internal SSD and find out how much of the software I use on a regular basis in El Capitan is broken. I'm going to buy a 2019 iMac as soon as refurbs start turning up in the Apple Refurbished Products store. Then next generation iMac will require macOS 10.15 Catalina (or later) which will no longer support any 32 bit software so a 2019 could be my last Mac purchase for a long time. No new Mac Pro and 6K Retina display for me even if I could afford them.

So that's my story. I've used it for months since the scary incident with lots of heavy gaming sessions cranking the cores and the GPU up to the max without any problems. Fingers crossed.

Finally, I could never have done all this by myself! I can't thank my buddy Bogart enough for his help.

Saturday, July 28, 2018

Scintillation Probe Kit

Prologue: A New Geiger Counter...

With the arrival of a new Geiger counter with a x1000 scale it was finally time to assemble the scintillation probe kit I purchased from Iradinc in 2014. The probe only required 900V so the stage was set.

The first hassle was to clear off enough space on my decrepit workbench.

The Kit: Some Assembly Required...

The pieces of the puzzle (click to enlarge)
Left to right: 3" diameter 2.25" plastic crystal; Hamamatsu R6233 Photomultiplier tube; tube cap; BNC connector; voltage divider parts; silicone grease; huge diameter heat shrink tubing.

Additional materials (click to enlarge)
Isopropyl alcohol, spray adhesive, electrical tape — all as recommended by the GeigherCounters group brain-trust. I still haven't found any 99% isopropyl alcohol locally but I did get some 90%...

The first step was to wire up the resistor string on the base of the PMT. My eyesight has been going downhill for years and this was somewhat of a challenge. The markings on the tiny resistors were very hard to make out. I was very nervous about plunging in and naturally I managed to scratch the insulation off of one. Tom was kind enough to send me some spares so I dodged that bullet.

PMT voltage divider complete (click to enlarge)

BNC connector attached (click to enlarge)

At this point it was time to glue the cap to the PMT. Unfortunately, the silicone rubber I had bought turned out to be the type that gives off acetic acid while curing. This damages electronic components.

I had specifically searched for and bought what I thought was "neutral cure" but somehow managed to screw that up. Yet another delay as I waited for the correct adhesive to arrive (once again I couldn't find any locally).

Cap glued to PMT (click to enlarge)
The plastic crystal is highly fluorescent and glows beautifully under 365nm UV light.

Crystal fluorescing. In a dark room it's quite bright. (click to enlarge)

Perfect fit (click to enlarge)
I did not bother to polish the crystal. I was too nervous at this point to be able to without mucking things up even more. A voice of experience told me not to sweat it so...

Next up was attaching the crystal to the PMT. I carried the bag of silicone coupling compound to the workbench, went to get something else, sat down and... the silicone grease was nowhere to be found on my cluttered workbench. AUGHHH!

Fortunately I had some more in another PMT wiring kit but my nerves were wearing thin. I proceeded with taping the crystal to the PMT and quit for the night. The next day I wrapped the entire assembly with layers of electrical tape and glued the front scrim on.

I took everything into a windowless bathroom and sealed the door. I powered up the Geiger counter and was highly relieved to hear lots of background counts. The relief was well-earned.

Taped and working. (click to enlarge)

It took me a couple of weeks to reach a point where I was ready to finish things up with the very large piece of shrink tubing. My job was a bit sloppy but I was satisfied with the result when I heard background counts again. Mission accomplished.

Heat shrink shrunk. (click to enlarge)

By the way, if you happen to see a small plastic bag labelled "Silicone" anywhere please let me know.

A big thanks to Tom Hall for this kit and his support. A very special thanks to K0FF without whose help none of this would have been possible let alone gotten done. Bravo.

[postscript]

I found the missing silicone grease. It was on my workbench all along amidst the bubble lights. Look closely. Very closely.

Closer. Closer... (click to enlarge)
Right there the entire time. I told you my eyesight is deteriorating.