Colored sql

Status

Thanks to Alexey Kalinin for his grc profile which colorizes mysql.
You also need grc, which is super easy to install by hand (directions in INSTALL worked like charm)

Good stuff!  Below screenshot is from cathode, an OSX terminal program that emulates old terminals (note the scan lines and slight curvature).  It may be trite, and a little hipster, but I get a kick out of it.

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Simpson 476 Mirrorscope: Success!

Finally got a trace!  Turns out that the open cathode resistor I replaced that I thought was supposed to be a 2.7k was actually supposed to be a 39k, so after rectifying that (with a 33k), and replacing the incorrect bias resistor, it lit up like a charm.

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After that, I put a sine in the X & Y, and fiddled with the bias controls until I got maximum linearity.  The sweep & trigger is a little wonky, so I think I’ll run some tests with an external sweep generator to dial the amp sections in first, before I tackle the sweep.  Besides, Benton (who’s scope this is) mostly only uses X/Y mode, so that’s more important.

There is some burn-in visible on the CRT, I may poke around eBay to see if there’s a replacement that’s available and inexpensive.  The filter caps in the power supply are shockingly good, but I may replace them anyway, at least the paper ones.

After a congratulatory sip of Bourbon (4 Roses, one of my faves), I realized that all the troubles in this scope stemmed from bad 39kΩ resistors. I wonder if there was a bad batch, or they were all just under spec’d?  In any event, I’m going to replace them all, and probably up the rating to 2W, just to be sure.  I may also replace the 68k resistors that have drifted as well.

Here it is triggering on a 100kHz square wave, not bad!

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Simpson 476 Mirrorscope – continued adventures

So I took Benton up on his offer of giving me the 2nd working scope, and it’s been super helpful in having a unit to compare to.  It’s hard to diagnose this thing without real schematics – the ones from the 480 are different enough to be more of a source of confusion.

Before I got the second unit, I took the face place off in order to get better access to the components.  Unfortunately the face plate is what holds a lot of the unit together, so it’s in a very fragile state right now.  This thing was not made for easy service.  I have it on a plywood square that lets me move it around and spin it more easily.img_7016

There’s some alligator clips to keep parts of the circuit grounded that were otherwise grounded through the face plate.

I also grabbed the FLIR One from the office and took some temperature measurements.  Here are the two hottest components:

A resistor in the vertical bias sectionimg_7007

A resistor in the power supply:
img_7003

Both ALARMINGLY hot.  (pardon the mixed units, switched to Celsius 1/2 way through).  The FLIR is a really useful tool – the only issue is that at these close ranges, the visual and thermal layers don’t quite line up due to the physical spacing of the cameras.

I started checking values and taking measurements and noticed a few things:
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Unlike in the 480, the 2nd section plate resistors are different between the horizontal and vertical sections.  Horizontal are the same 68k, while the vertical is 39k.  All have drifted high, and in some cases out of tolerance. These are 1W resistors, according to the manual.

R109, 2.7k 1/2W, that connects the cathode to ground, was open.  I replaced it with the closest thing I had, a 2.2k.  After that, I could make tiny adjustments in the vertical position, but the beam shape went to shit.

Shortly after that, Benton dropped off the second unit.  I removed it from it’s case, and started taking measurements.

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For starters, those resistors don’t get nearly as hot, so I started to get more confident that the problem was in the vertical biasing section (that bit with the pots hanging off the back)

Finally, I noticed the smoking gun:

img_7064-1

That piggybacked resistor pair?  That’s R98, called out as a 39k 1W in the schematic, but that there’s a 270Ω in parallel with a 330Ω, for a total of 150Ω !!.  But wait, It gets weirder.  That same resistor in the ‘working’ unit, is color coded as a 39k, but measures at 260k!  W.T.F!?.  When I place a closer value, 33k in the bad unit, I start to get a little more range, but the beam is still fuzzy.  When I replace it with the 260k resistor, I get tons of range, but still a fuzzy beam.

Meanwhile, on the horizontal side of the bad unit, that 39k resistor (R97) has been replaced with 3 50k in parallel, for 16k.

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Time to order a bunch of 1W resistors, I guess.

 

Simpson 476 Mirrorscope

Up next on the bench, a Simpson 476 Mirrorscope.

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This example belongs to Benton Bainbridge, an NYC video artist.  He’s got two, and this one needs the most help, so I figured I’d get it on my bench and get it working again.  That’s the hope, anyway.  As can be seen from the photo, the CRT points upward, and the operator views it through a 45° mirror, that flips up as the top of the chassis.  This yields a benchtop oscilloscope at an unheard of depth of only 8″.
It turns out, the manual for this beast is no where to be found.  I’ve reached out to Dave at Arktek manuals to see if he can dig up something.  I’ve gotten hard-to-find manuals from him before, so hopefully he can work some magic.  I also reached out to Steven Johnson, who’s got a great page and manuals for sale.  The Simpson 480 Genscope is approximately one of these mirrorscopes with a signal generator on either end.  I can’t even begin to imagine how unweildly that is to work on, but at least there’s a manual available.

I met Benton at his place, and we started comparing the “good one” and the “bad one”:

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Sweet DJ rig, yo

The problem seems to be in the vertical amplifier section, made up of (2) 6K6 twin triodes. One the good unit, the signal to the deflection plates varies between 170 – 240v while on the bad unit, they’re pegged at 350v, which appears to be full anode voltage.  Tubes were tested, and swapped, to no avail.  I brought my Heathkit TT-1, which Benton got a kick out of – it’s such a fun instrument to operate.

There were a few ground connections that appear to have been severed, but reconnecting them didn’t solve the issue.  There are a number of resistors that are running hotter, so much so that they’re discolored; however when measured cold, they appear to still be in tolerance.

There are a few differences between the 480 and the 476:

  • The 5Z4 rectifier is absent in the power supply.  This appears to power only the oscillators, so no surprise there.  The power supply consists of 2 6X4s, one for the CRT HV, at about 900v, and one for the rest of the circuits, at about 350v.
  • There’s an extra 12AU7 not present in the schematics for the 480.  I suspect this might be a pre-amp for the vertical input.  The 476 has more rages than the 480: 4 steps from .5v to 500v as opposed to ‘low / high’ on the 480.  Alternately, it’s a part of the sweep / trigger circuit?  I know that this is scope is capable of ‘synchronized’ operation, but I can’t for the life of me see how this thing triggers by looking at the schematic.
  • Some other component value differences.

Here’s the relevant part of the 480 schematic.  simpson-480

Benton offered that I should take both, to have  good one to compare with.  I declined, only wanting to bring two additional cubic feet of oscilloscope into my apartment, but I may take him up on it if I can’t get this figured out.  On old gear like this, I immediately suspect old caps in the power supply, but since the horizontal sections seems to be working (ish), that doesn’t screen out as the culprit.  I think I’ll just start checking / changing out caps in the PS for good measure, as I familiarize myself with this unit.

The other thing I’m definitely going to do is grab my boss’s FLIR One to scope out any really hot (or suspiciously cold) components.

But before I do anything else, I gotta order some more caps, my HV Electrolytic stock is almost depleted.  I kind of like running out of parts, it means I’m keeping busy.

Heathkit H89A – Continued boot failures

So I’ve tried just about everything, and the consensus is that I’ve just got bad disks.  A bunch of people on the SEBHC Board has been super helpful, a few even offering to send me boot-disks.  I took one gentleman (Ken) up on his offer, so hopefully that’ll get me up and running.
Lee suggested some lines on the floppy connector to probe, which I’ll get to tomorrow.  May even sick the 7D01 on this…
This manual has me convinced that the BIOS is correct. It’s a newer one to go along with the floppy controller card, which just isn’t referenced in any of the printed documentation I have.
Ken confirmed my understanding that the floppy drive is a fairly dumb device, and it’s the controller that determines sector firmness, track count, & density.  He’s even shared wiring instructions to get 3.5″ drives.  I’m eager to try some newer drives and disks once I get up and running.

Heathkit H89A – floppy config & attempted boot

I’ve tried every disk in every drive with what I thought was the working configuration, to no avail.  Every failure is the same: hitting ‘b’ to boot, getting ~5 seconds of disk activity, and failing with ‘? Boot Error’.  Heads appear to be in impeccable condition, and the disks look clean.  Here’s a closeup of the heads on the hard sector drive:

Floppy drive head closeup

And here’s the collection of disks I’m working with:

img_6437 img_6439

SW501,4 controls which card to boot from:
0 = H88-1 Card at P506/P512 (the right most slot), I/O Port 174
1 = Z89-37 Card at P504/P510 (the left slot of the right bank, I/O Port 170

I’ve tried both; 0 boots to the internal, hard sector disk, 1 boots to the 1st drive in the H-37 enclosure, a 96tpi soft sector drive.

The internal drive is set to Unit Zero (or DS1) for use with the H88-1 card
Screen Shot 2016-08-14 at 3.45.36 PM

But wait, we can also use this drive as a soft-sector drive on the the Z89-37 controller.  Note that the drive settings are different:
Screen Shot 2016-08-14 at 3.45.44 PM

Yes, it’s backwards.  My predecessor was nice enough to not cut the links, but to simply bend the pins of the package out.  unfortunately, they’re super fragile, and a single attempted bend broke the pin, several times. I ended up using a portion of the original package and some wire.

Note that J4-J7 needs to be set correctly on the Z89-37 card.  It’s now set to J4, meaning the single drive ID’s as DS1 plugged into P3 (the top port on the card) is Drive 0.

As I was shuffling connectors and moving the board around, this happened (took me a few minutes of failed boots to spot):
img_6436

I temporarily crammed it back in, and got to the H: prompt.  Still won’t boot to a disk.

I wonder if this is noteworthy:
Every boot attempt seemed to take the same amount of time to fail (3-4 seconds), regardless of which configuration or even if a disk was present.  When I jump J4 on the Z89-37 (what I believe to be the correct config), an attempted boot without a disk tries indefinitely and never fails.

 

 

Heathkit H89A computer, first repair attempts

I’m just jumping right in –

I acquired the following from Ray (WA1FFT) in NJ.
  • Heathkit 89A
  • Complete set of spare boards from H89A (different mb)
  • H17 Dual hard sectored 5 1/4” floppy drive
  • H77 Dual soft sectored 5 1/4” floppy drive
  • Box of hard & soft sectored disks.
I was really just after the H17 to go along with my H8, but $30 for all that? No brainer.
Ray warned me that two caps popped on the main board,  and indeed C508 & C515, 2.2u tantalum caps, failed violently.  We’ve got to see what other damage they did; tantalum capacitors are like the suicide bombers of the electronics world.
IMG_6388
They were replaced with 10u caps I had in inventory (close enough):
IMG_6394
I found Herb Johnson’s 2016 adventures in Heathkit H89 rebuilding while surfing around, and his page is a great reference.  As I got a spare set of boards as well, I figured I’d first just swap them out.  No go.  The boards are slightly different, and that difference includes the power supply connectors.  According to Lee Hart, the key’d power supply molex connector indicates a late-model H89A.  That would be the 2549 board
I’m assuming that also took out U585, a 79M12 and U565, (only have a heath part), as there’s no -12V & +12V on the output of those regulators.  I also have a spare, earlier model board to compare with (and possibly steal parts from if I’m impatient), but I’m noticing more and more inconsistencies between the two boards, and with the documentation.  Here’s where it gets (more) annoying:
U515 is a 71M12C, your run-of-the-mill -12V regulator.  OK, terrific.  Same on the old board as well, and consistent in all docs I have.
U567 only has a heath part#, 442-674.  It’s in parallel with U568, they both feed separate +12V supplies.  Here’s where it gets squirrelly:
  • In the docs, it’s called out as part 442-663
  • The pinout labeling is different (common pin center, whereas board image & earlier board call common pin as the left one)

Here’s the old board (85-2208-1) incorrectly marked pin-outs, but check out that sexy ceramic ram chip:
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Here’s the documentation for the newer board, but the pin-outs are still mis-marked:
FullSizeRender

Here’s what I’m left to deduce, and can confirm after some metering:
  • The earlier board silkscreen and artwork in my manual (for the later board) are both wrong for U567 & U568
  • U515, a negative regulator, indeed has it’s common (gnd) on the left; it’s input and output are swapped from positive regulators.
  • U567 & U568 are almost certainly 7812s (+12V regulators), as they are on the earlier board.  They are only silkscreened correctly on my newer board.  The new board artwork illustration, and the old board silkscreen are both incorrect.
GRRR….
OK, well U515 seems to be working well out-of-circuit, but there’s almost no resistance between ground and it’s output in the circuit.  Suspecting C509 & 511 next.  Lifted both, no dice. I’ve got to be careful with the desoldering gun, the traces are easy to lift.
So what else is connected to the -12V line?  Besides the 2 -5V regulators, and the card bus, I’d imagine it’d be the built-in UART used to communicate with the terminal board, since for whatever reason, it’s full blown RS-232 between the two.  Yep, sure enough there’s a quad EIA-232 driver. Nope, there’s still a short with that removed.
So it’s the -5V regulators?  Nope.  Forgot about C513.  Yep, it’s shorted.  It’s always the last place you look…
Next up – replace the regulators and attempt to power up again.

Heathkit H89A, First Light

Progress continues.  I tested the regulators and they were fine.  I ultimately traced the problem to C513.  It was shorted, and has been replaced by a comparable ceramic cap.

After bringing her up on a variac, I’m greeted with an H: prompt!

I ran a memory test, which is one of the routines in the monitor ROM.  A full test would take over 2 days, so I just let it run for a bit after quitting.

IMG_6407

377377 is 64K in octal.

There’s a routine you can enter manually that prints characters to the screen:

IMG_6410

Finally, there’s a routine to run a drive speed test.  Using a tweaker to adjust to 200:

IMG_6424

Unfortunately, I can’t get it to boot off any medium I have, either hard sectored on the built-in drive, or soft sectored using the external H77 drive.  Not sure what to try next…

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