Sunday, October 30, 2011

I received a test source of electroluminescent panels for the T4 build yesterday, General Electric night lights. Now, if I can source some GE resistors this thing will be 100% same source! Hahahaha, just kidding. These night lights were made in China, so the only same in the source is the name.

Plugged it in and it fired right up, I was so excited I forgot to take a picture, sorry.

Disassembly is pretty easy, there's already a groove where the front and back case half meet. It was just a matter of running a knife around the groove until I could shear the three connection pins, then it opened right up. What you see is what you get, the two contact pads at top of the element are press fit to the metal studs in the back half of the enclosure which taper into the blades of the plug. 120 volts AC (in my neck of the woods) right across the element, it's that simple.

My initial hope was to cut the element down so it could lay directly atop the CdS cells which would be pointing "up" in relation to the octal plug base. However, it appears that one electrode runs the perimeter of the field and to cut it down at all would sever that conductor and potentially render the panel useless. Being that this entire assembly is built on something like acetate, there is flexibility, so my current line of thinking is to roll this like a tube to line the inside of the can and situate the CdS cells in a periscope type fashion.

Sunday, October 23, 2011

Huge stretch of images ahead.

So a friend, who will remain nameless in these chronicles unless he (that's the only hint you'll get) wishes to be named, has been keeping an eye on an equipment recycling drop point near his beaten path. Occasionally something of interest or use appears, and if we're quick it is harvested (as opposed to recycled). I stand by my position that reuse is more efficient than recycling; and, for the record, I understand we are sanctioned to harvest materials from this point - just don't ask me for my papers.

Anyhow, word of some transformers passed along the wire so I grabbed the van to do some picking. Amidst the pile of stuff was this decommissioned Rigaku something or other, which, in addition to the 5U modular frames which were admittedly the eye catching aspect is built upon a very well constructed steel frame.

Very solid and as far as I can tell, pretty precise in terms of a level plane up top. This has become my first choice in base for the languishing CNC build, effectively putting a bit of wind in my sails.

Current line of thought is to put the computer in the lower 5U rack bay (which faces the fan panel to left) and build or rehouse the 24 volt linear power supply for the stepper motors in the top bay. I believe both my large rack mount PSU are too tall to simply slide into the case as is, but measurement will be double checked before I go much further.

The 5U frames are just the icing on the cake.

Here's some of the stuff pulled from the frames...

Backplane connection buss.

Socketed solid state relays.

Headers on the back side of this.

This all hails from 1992.


Curious if the liberal use of ADC means analog to digital converter, might be some fun stuff socketed in here.

Those black-dip parts claim to produce 250 Vac from 5 Vdc. Perhaps some day I'll put that claim to test.

Through hole logic central. Guess that statement can apply to most of these boards.

I'm happy a fair margin of these ICs are socketed.

Some contained switching supplies pulled from the unit (not counting the ones in the PSU box still installed in the frame as seen above). A couple 5A +5, a 2.8A +5/0.5A -5/0.5 A +12 and a 7A +24. One of the potted 250 Vac 10A mains noise filters seen to the right will wind up in my Tektronix R 556 (if it will fit), since I've been dragging my feet on procuring that part. Thinking the +5 supplies will be a workable foundation to a Lunetta type build.

Which brings me to this. Digital logic ICs from 1977.

Also amidst the wiring in the Rigaku were this cool AC mains wires.

Oh yeah, transformers. That's what lured me out in the first place.

C core power transformers, some (most) of which have multi-tapped primary windings labelled 200-210-220 volts. At least one of these will be wired up as a non isolated step down transformer providing a 115 and a 110 tap from the 120 volt mains supply for my older tubed equipment built for 110-117 volts. Such fine tuning of the wall supply will prolong tube and component life.

Tuesday, October 18, 2011

Received my General Electric B-46 photoconductive cells yesterday. After struggling with the 40 year old blister pack I stuck this part across the leads of a meter..

1.26-1.71 K under ambient light in the living room (no idea what angstrom I'm working with) and 160-200K after 5 seconds of cover, which puts it right in line with the Clairex CL505L that is the heart of the early T4 optos.

13th week of 1969 would be my guess. With the octet I concluded hastily that, should all fall within spec I can roll four T4 clones; I'm now leaning on slapping a range similar modern CdS cell to drive the meter, since that leg is out of the audio path and there is no benefit to a period correct part there. I tend to ignore what the meter is doing anyway..

Now to source the electroluminescent part, I'm pretty sure I can find a 2.2 meg resistor in a bin. There's also the matter of enclosure, but I do have some things I can cannibalize.

Monday, October 17, 2011

Here's a quick size up of the connection blocks on the Ramsa 8210. I've decided to retain stock set-up to expedite getting on to the next project, but hopefully the photos here give a good idea of what can and cannot be done without getting deeper into metal work:

The holes punched for the RCA jacks are a good fit for 1/4 panel mount, though the gauge of metal may allow flex.

Spacing on the vertical is workable, side to side not so much. The send/receive would naturally allow a conventional TRS set up, but the SUB input would have to be engineered in else-how. Maybe retaining an RCA would allow for the most versatility?

Of course, that leaves needing to mount the XLR, which is mounted on the plastic block that would be ousted with a jack change. There's also the trifling detail that while the block has a center hole for mounting, the mixer metalwork does not, so something's going to either flap or be drilled.

All in all, not an out of sight project, the depth of the 1/4" plug should be allowed for with ease, given the depth of the stock plastic mount. I'm just opting to choose my battles here.

Saturday, October 15, 2011

Public Service Announcement: If you are going to bolt Chatsworth two post aluminium racks together, the hardware you need is 1/2" 20 threads per inch.

At least that's what worked in my set up. I made two trips to the hardware store today, because my admittedly brief search on the subject turned up no hard data. 1/2" 20. Fortunately the center rack is a cheaper knock off, and as such is not threaded at those holes (which are placed at the correct points). This made bolting the three racks together easy, once I had the right part.

I've also had the opportunity to assess condition/damage on a few long neglected devices. The beat up RCA BC3C has shot into total restore/rebuild territory. Ugh, ugly. Mice. Gives me a focal point to hinge my activities this winter.

It'll need more than a tweak on the hum balance pot, that's for sure.

Friday, October 14, 2011

Continuing contemplation of the Teletronix LA2A as I shift and shuffle the new workbench into a useful state. Here's an early revision schematic I found at The Bottle Garden studio site, the absence of a LIM/COMP switch points to a first revision so far as I can tell.

Signal path: From the input transformer signal passes through cascading halves of a 12AX7 and into a cathode follower built on stacked halves of the 12BH7 feeding the output transformer (through a DC blocking cap).

Supporting electronics: Input signal is split into a strapped 12AX7 voltage gain stage which feeds the 6AQ5 which drives the luminescent panel of the T4 through a DC blocking cap. The T4 then, when fired, illuminates the CdS cell which decreases resistance, effectively draining more signal to ground before it hits the grid of the very first gain stage of the signal path.

So, the resistive drain of the CdS cell will always be in circuit, before any signal amplification. I'm making the leap to the conclusion that the CdS element has a tremendous impact on overall voicing and characteristic of the device. I'm also shooting down the statement of relief in my previous post regarding mica dominoes in circuit. They are not, unless you believe subtle frequency nuances of the side chain amplifier driving what amounts to a light bulb are going to play much of a sonic role. Which brings me to the electroluminescent element, it makes sense that the characteristics of this are going to play a large part in actually driving the CdS cells into their lower resistance state.

I bought this octet of NOS General Electric CdS cells at auction, I'm hoping that with the ability to play with series/parallel configurations I can come somewhat close to the static response range of the Clairex CL505. Since there was no data sheet I could find, this does amount to a shot in the dark.

Sunday, October 09, 2011


Been breaking my back lately, since one of my current primary focuses is to set up the studio at the new abode. I think the last time I had it close to properly set up was in 2006. This, coupled with the fact that I am planning to record the band Stalagmite sooner rather than later, prompted me to end a long term loan of my Teletronix LA2A to my friend Ty at Sublevel9. So what follows is essentially a refamiliarization as opposed to sheer speculation, and for the record, this unit is probably cleaner now than when I initially lent it out, so no laying blame for any seams of crud perceived in the following pics.

Spartan good looks, I defy you to make a grab for the wrong knob on this device.

It was built with a hinging front that will allow access to the guts even while powered on. I love gear designed with an inherent trust of the operator such that they don't automatically conclude that the operator is an idiot that will likely kill themselves due to such a servicing convenience. You simply can't get away with that today... perhaps the people are actually honestly less intelligent?

Moving to the rear, we see your typical back mounted tube and transformer set. Note pre-UREI label of manufacture. I do believe "Studio Electronics" was a Bill Putnam endeavor however, this unit appears to be a rev 2, with HA-100X input transformer and compressor/limit switch and T4A designator. As you can plainly see, the T4 opto slot is populated by something decidedly homebrew (thanks to my uncle for the opto build, and the unit). I have fuzzed out the serial number, which is low four digits.

I've always preferred everything in duplicate, being fixated on stereo. Having kept a loose eye on the going rate of complimentary UTC HA-100X transformers, I am planning instead to build a clone utilizing something I already have in the input iron pile, hopefully I can come close, I'm sure I can achieve 'useful'. Looks like a 50th week of 1964 to me, indicating they were running through existing stock on their way to rev #3, A-10 inputs.

Here's a shot of what's going on inside the current opto element, simply a switched VTL5C4/2 allowing for fast/slow decay. I'm planning on rolling a closer to stock arrangement with luminescent panel coupled with photoconductive cells when I get a chance. I did have to assert focus to avoid trying to dig up the box with old stock photocells in it while moving stuff from the old storage set-up to the new room. They are there, somewhere, and perhaps some of them will come close to operating within the range of the original Clairex CL505L elements used in the T4A & B (so far as I can tell).

Spec attached, for what it's worth.

I do plan on recapping this, as it appears that everything is original. However, my replacement frenzy will NOT include these, only the electrolytics. Frankly, having recalled mica "dominoes" inside, I was a bit dismayed that they are not in the signal path. Oh well, at least it will contain enough carbon comp resistors to convince most electrical engineers that I am a mindless savage.

Pretty neat layout, and the relatively low parts count makes for a nice wide open layout. I believe the part at left is a variable mica capacitor, the Aerovox center appear to be date coded 20th week of 1966, the domino cap at right is across the "FLAT" trimpot, indicating it may have a say on overall frequency curves and as such is probably carrying a bit of signal. Well, I can rest easier.

Continuing on the datecode front, the UTC A-24 output transformer looks coded 44th week of 1966.

The Sprague 40-40-30-30@450 can cap is dated 4th week of 1967, pretty sure that one needs to go. I'll probably slap a new production CE Manufacturing twist-lock at 40-40-20-20 and make up the 10uf internally if the 20s cause problems, which I doubt.

28th week of 1968 seems as close to build date (without going over) as I can get. I'd say late 1968 origin, since I haven't been able to find a serial number to date of manufacture cross reference.

This is for you, Nigel Tufnel.

Sunday, October 02, 2011

The rains have hit, prompting the end of my procrastination regarding the windshield wipers on the van. The original system entailed a mushroomed stud that was press fit into a hard plastic cap that pressed into the actual linkage arms. I use the term "press" lightly. I had the original set-up fail on me, and the replacement plastic pivot joints essentially amounted to garbage that failed on me again in a very short number of years.

Pictured here is my roadside fix. A short length of gas hose and a clamp on the motor side (left) and a wrap of bailing wire on the right. Recently I saw a similar vintage Tradesman advertised really cheap in operable condition... except the windshield wipers. I find it very easy to believe this is a common point of failure.

I pretty much never want to have to work on the wipers on the side of the road in a downpour again. Pictured here are the parts of my fix, and examples of the original linkage in various states of disassembly. The hole for the pin was a lot smaller than I had expected, and I'd already bought the hardware, so much of the following modifications are in fact unnecessary (I simply didn't feel like another trip to the hardware store). If I have to do this again, I'll tear down the linkage prior to buying hardware. Smaller gauge stuff is cheaper.

After learning the shaft was smaller, I did away with the circular nibbling of the mushroomed rivet.

Best approach with the motor end of the linkage was to cut the stud off with a hacksaw. In retrospect, that would have been a quicker way all around.

I had to drill out the linkage arms as well, in order to accept the collar of the plastic grommet. This was a messy business as my clamping capabilities were not up to the task of the bent rods and the drillpress I was using is essentially cheap junk and has terrible radial play. I think I have a line on a superior tool, which will allow me to tear this thing apart and see what I can do. But I digress, no pictures were taken of this as the quality of work was substandard. It'll carry the load set out for it, but it's not worth advertising.

The connection on the left was a bastard to break free, since I was still in the mindset of dealing with the mushroom end of the stud. Anyone recreating this work is HIGHLY advised to simply cut the original stud off with a hacksaw. Unless you really feel the urge to punish yourself, then you can work the mushroom down with a punch and pliers like I did. (seriously, just cut it off)

Not bad. A bit of Loctite on that nut and it will be ready to go. I should mention that the plastic bearing collar was cut down, it still sits proud a bit, to prohibit the two arms from touching, but the original dimension would have built in a lot of slop (and minimized available thread for the nut).

I also tore down the motor housing and transfer box, cleaned and lubricated everything and now it's just a couple bolts (aluminium, one sheared at teardown) and it'll be ready for new blades, which are sure to be a real PITA.