Wednesday, May 9, 2012

Moving somewhere where I'll have a small audio and music studio space, and a more open workshop which I'll be sharing with a friend working on automobile projects. Time to pack up and sort through all the hanging projects in my shop, finishing up anything that I can. I'm not too into the idea of hauling too much useless junk into the new house.

This module is from a Re'an patchbay that I carelessly dropped a few months ago. Supergluing it together is one thing, but in order to get it actually functional, something more substantial is necessary.

Obviously I can't trust that glue joint to take a lot of pressure, but it should last  plenty long in a well dressed rack.

There's this pretty little thing that I picked up in Portland. I'm pretty sure that it works - I mean, every now and then the light blinks, and if you have headphones there's a click - but I don't have any radioactive material around to help me confirm.

It's a good thing, I suppose, that I don't really NEED this for anything. Here's a half a dozen potentially leaky caps and a selenium stack in a fun little rat's nest. Don't really have time to dig here, so this one is just going to have to sit until the apocalypse.

Just for your info, if you plan on building a tube gieger counter one of your own.

Meanwhile, at work:

We're finally getting the new soundsystem we've been dreaming of, but first I have to trace all the conduit coming in and out of these pinblocks. The wiring dates back to the 60's and 70's for the most part. While it's very neat and tidy, it's drastically overbuilt by today's standards, and not in a particularly useful way.

I'm hoping that by pulling some speaker wire (actually loose 16 gauge) I'll free up enough conduit to our recording booth to help along a clean install.

Wednesday, April 18, 2012

Crate PA-B8350

I roadside rescue, picked up on my way home from a gig a few months back. This PA head  has been taking up my guitar workbench the entire time since. While I'm occupied with digging out, it's time to finally see what's going on with this thing.

I came for the brightly colored knobs, but I'll stick around for the built in spring reverb and effects loop.

Obstacle number one. While I often see devices that have had their power cords cut to keep people from using them due to some perceived or actual danger, the wear pattern here suggests a violent and unexpected disruption of power, i.e. an accident.

Nothing unusual inside, and no evidence of prior tampering. Everything seems in good order on visual inspection, but one of the three fuses fails a continuity test.

Not exactly burned out, but certainly not operational. Searches for schematics, parts lists and the like don't turn up anything that doesn't cost money, so I'll assume that the 1/4A 250V label on this (and the other non mains power fuse) is accurate, which is an easy thing to fix with a trip to the hardware store.

I also grabbed some crimp-on connectors to replace mains using an old IEC cable, but failed to realize that I didn't actually have the appropriate crimping tool, as I had thought.

Not optimal, but okay for now.

Nice big pop on power on, and the transformer hums like a beehive, but it works well enough to consider it salvageable. Since these guys are around 20 years old now, I'm gonna take a wild guess that electrolytics are at least part of the answer. Without a schematic, I'll need to just poke around and write down everything I see to make an order. Luckily there's not too much, really just the big guys in the power supply.

Monday, March 26, 2012

Does this dude talk about stuff other than chipmusic gear?

Yes,  I swear I do. Tube amps and more oscilloscopes on the way. Also putting off my re-do of the last post's gameboy EL backlight until tomorrow or so. Spoiler alert: when drawing power from a different place, it's even more awesome.

But for now, a quick update on something exciting (to me anyway).

That's 8 SID chips, fresh off the boat from Denmark.

I've been enjoying my sammichSID quite a bit since I built it, but I've lamented having only one older 6581 style SID chip. There are a ton of subtle differences between the two types, but the not-so-subtle difference is that the envelopes on the older chips leak profusely. At stage performance volumes, it's a big problem.

But now...

Two 8580 chips. I am very, very pleased to say the least.

Saturday, March 24, 2012

Kitsch-Bent electroluminescent gameboy backlight

The mighty kitsch-bent sent me an as yet unreleased electro luminescent gameboy backlight to try out. This was partly a successful experiment in shipping them longer distances (it arrived perfectly safe and sound), but also a favor - I've been waiting for these things for a very long time.

I've also been waiting for quite awhile to get my hands on a blue "play it loud" gameboy, which are rare in the US. Behold:

I figured what better way to celebrate than to install my brand new EL backlight in this much awaited blue gameboy.

For those unfamiliar with backlighting gameboys, you should know that the most difficult part of the process has not changed, and never will change - the polarizing sheet adhered to the back of the dot matrix screen must be scraped off so that the screen itself is perfectly clear. This is a somewhat difficult skill which takes practice. The real danger here is damaging the two thin ribbon cables that control the screen itself. I have heard of issues with the screen cracking, but I've applied quite a bit of force and never had that problem, so I'm afraid I can't speak to that.

What is often a hassle is the adhesive not coming off clean. That happened in this case, and the solution is usually rubbing alcohol and a soft cloth. In addition, I re-clean my screens repeatedly with a glasses cleaning cloth to make sure nothing rests on the screen that might scratch it. Anyway, you can see this one worked out fine.

Now let's open up the EL kit.

What you're seeing here is actually the back of the EL panel - the front is pink. The two metal contacts are what kitsch was worried about in the first place - he was concerned that they may detach, but they arrived securely fastened. The two white pads are salvaged from the original polarizing sheet, by Justinthursday's suggestion. The issue is that unlike traditional backlights, the EL panel is nearly as thin as the original polarizer, so it shoudl require the padding to keep the screen from rattling around. This wound up not working so well for me, but we'll get to that later.

Here is the panel fully installed. I should have taken more photos, but I found that I needed to cut away very little of the plastic frame surrounding the screen in order to fit the cables. It was a very comfortable fit.

There is a capacitor just beneath the screen which can be bent out of the way to make way for the two pin power connector to squeeze through. Pulling the cable up to the top of that hole and pushing the cap back into place makes for a comfortable fit.

Now that the front half is done, it's time to address the power inverter and the back half. First thing's first:

Looks like the battery contacts in this little guy have seen better days. The spring on the upper contact has disconnected entirely, and was actually hanging out near the speaker magnet. Typically I make an effort to clean these things, since there is a finite supply. I'll get around to it, but I've got a sleeping baby upstairs, so I'll just pull from a donor.

Much better.

This little heat-shrink-wrapped guy is the power inverter, wired up pulling power from the regulated 5V feed to the cartridge (and ground straight to the battery terminal). The inverter comes with a black and white cable pair for DC voltage input; typically black is used as ground and white as positive, but in this case the plug fits in either way at the inverter. The two input pins are different lengths, and the shorter pin is intended as ground, which is the opposite of the normal logic - typically connectors are designed to connect ground first as you insert them, to help avoid an unexpected shock when something is mis-wired. It's a minor oversight, considering that the amperage on this side of the inverter is negligible, and you're unlikely to be plugging this in while it's powered anyway.

The other side of the inverter has two identical pins to carry AC voltage out. If the inverter is powered without these pins attached to the cable hanging off the EL panel, there is a theoretical risk of burning out the regulator on the board. Kitsch says he's tried pretty hard, and failed to burn it out. I'm willing to believe him! Considering that there is a risk of shock from the more lively side of the regulator, it's probably best to keep it hooked up anyway.

All assembled. I'm really happy with how it looks, and I'm extremely happy with how not gawdawful bright it is - I've always felt that the LED backlights were unnaturally glaring in a dark setting, and I've always preferred the brightness level of a frontlit gameboy color, or the SP or DS. LED backlights have gotten brighter and brighter only as an attempt to even out the light by adding more LEDs - and while it's possible to dim them by changing resistor values, this also results in a less even light. The EL backlight is much more in my preferred territory in this regard.

There's been much question of noise added by running the EL backlight. The inverter definitely adds some noise to the internal speaker and the headphone output. In fact, when I tested the game boy with an AC adapter (which I usually do initially), there was a ridiculously loud (and sortof awesome) noise coming from the speaker. Batteries are much better, but there is a distinct hum, even with the volume turned down.

edit: what I described as a "hum" is really more of a high pitched whine, presumably at whatever frequency the AC runs at. It's honestly quite irritating for making music. That being said, I've discovered that the speaker in this gameboy is completely shot anyway, so while I'll probably remove it, I will test it out with an alternate known working speaker first, just in case.

re-edit: Kitch clarified a couple things for me, and you can expect an update to this post with the changes I'll be making to this install. In the meantime, I should mention that the place I took 5v from is not the ideal, and a lot of the noise problems are apparently alleviated by taking power directly from the power supply PCB.

What to do? Removing the internal speaker comes to mind - this offers some extra modding room as well. Additionally, "prosound" modding the gameboy is a necessity, as an output that bypasses the headphone amp should bypass the noise. I believe Justin has already confirmed this, and I'll be trying it with an ASM Retro panel mount pro sound within the next few days.

The other issue is that of the pressure points on either side of the screen. They are obviously caused by the white spacers on the back of the EL panel. Unfortunately, I'm upstairs with the baby and my tri-wing is downstairs in the basement, so I won't know until tomorrow or so whether removing the pads or loosening screws is the solution.

All in all, a great looking product, and an exciting step forward for the gameboy. I'm not entirely sure about recording with this guy until I get the prosound line in, and unfortunately I can't see using it as a home composition tool because of the noise. I'd need to disconnect the speaker to not be annoyed by it, and I do often work with the speaker  to lay out the basics of songs.

As a stage unit however, it will be fantastic - it's a much more comfortable light level, and results in a much easier to read screen. This is perhaps not so necessary for an act like The Glowing Stars where I'm taking only quick glances at my gameboys, but in an act like Matthew Joseph Payne where I'm doing more and more live mode stuff, I could get very comfortable with this. I'm excited to play with it more! Thanks again to kitsch for this opportunity!

Tuesday, March 6, 2012

A friend has a Fender Twin sized road case, and would like to trade it for an oscilliscope. Time to dig through the pile and assess workability.

First up is a Heathkit IO-104. When I first tried to search the internet for this guy, I misread the model as "10-104", which resulted in some confusion. The difference between I and 1 now seems pretty obvious, but to be fair the difference between 0 and O in the chosen font is only one of magnitude.

Simple, and attractive. Unfortunately, this model is single trace, so it probably won't be a trade candidate. Already on the desk, and extremely easy to open up (facilitated farther by a missing chassis screw), so let's see what's going on inside.

Quite clean, for something that was probably built as a kit. The electrolytics are clearly past their prime, although there's no actual leakage or burnouts to be seen. This came from a school with some money, so it's probably been sitting on a shelf for quite a long time. I've chosen not to apply power today.

This certainly tells a story. I don't know the storage history of this particular unit, but I do know that they built a new science building around the turn of the century, which probably meant some time spent in some kind of storage container during construction.

Either way, this particular brand of corrosion is everywhere, including on actual components. I've never seen this sort of thing on ceramic resistors like that, so I guess that tells a bit of a story. I can't imagine its good for the casing on those caps.

Although I love the color of copper oxidization, it's a bummer to see this happen to such a beautiful piece. Either way, this is quite an expensive way to shield a transformer - I'm not sure what inspired them to do this.

All in all, while I think this unit would be pretty easy to get running (new power supply caps would be a fine minimum, although I suspect it would need more work in order to stay calibrated), this guy is destined for some more time in storage.

Next up: Tektronix 561B. Blurry photo, oops.

Cosmetically, a work of art. Some strange design decisions though; this is a modular scope, and although the 561B was the first solid state design in the series, no solid state modules were ever designed. Apparently the design features amplifiers living entirely on the plug-in units rather than on the frame, which results in a direct tie-in to the CRT. The result is a scope which must be calibrated at every use.

Tubes in the dual-trace plugin. Lots of dust. This was after compressed air.

This got me pretty excited - these electrolytics, just short of socketed on their ceramic rails, were clearly designed for replacement. I realized soon after that based on their even 1.0, 0.1 and 0.01 values, they exist for calibration, not for any power purposes. Still a useful feature, but nothing that will help me get this beast running.

You can see the real power supply caps in the side shot above - multi-cap cans, everybody's favorite. This is a 60's unit which basically guarantees dry capacitors = no power until that's sorted, so back into the heap she goes.

A quick glamour shot of the onboard circuitry...

And a comparison of the connector pins on the two modules - after all these years, the modules slide in, connect and lock without a hitch, which is great overbuilt design - but why is one connector super grimy, while the other is spotless and shiny?

Saturday, February 25, 2012

Orban/Parasound 111B dual spring reverb

I'm going to start with the result here, then jump back to the beginning and work my way forward again. I just watched an episode of Star Trek: Voyager where something like that happened, so hopefully I won't get as confused as Janeway did.

Although I figured I'd leave my Sunn Beta preamp in the shot for posterity (it's the only one I've encountered), what we're really talking about here is the Orban/Parasound dual spring reverb. I found a detailed manual online, tucked in Orban's unlisted FTP site. There are extensive mounting notes, adjustment procedures, etc etc. Which is great! But I'm taking a slight shortcut, and just opening the sucker up for a quick visual diagnosis.

And here we have confirmation of my first assumption - leaky power supply capacitors - or at least one, but we can assume here that the twins are in similar shape, since they're in identical packaging with identical date stamps. Nice looking blister on that guy! Finding exact package replacements would be difficult and time consuming, so I'll settle for radial replacements for these axial bad boys.

And here we have their upright cousins, fully installed. Would have been tough to find something that would for sure fit snugly underneath the power transformer mounted to the chassis there. I had a photo of one of the other smaller audio line electrolytics but decided against taking up unnecessary space - you can barely see one in the lower left of this photo. Suffice it to say that they appear newer and in better shape - they probably aren't actually newer, but I'm giving them the benefit of the doubt for now. The parts list in the manual is dated 1/86, so they're roughly within safe limits.

Now for making connections. While I've always understood the logic of this setup, I still roll my eyes when it comes to actually hooking it up - especially on the workbench. I would up taking the cheap route and using the unbalanced "mixed" output for now. Digging through piles of old RCA stereo cable to make tails works well enough, at least for a test.

First attempt: failure. While the left side (white) is intact, you can see the crumbled remains of the right (red) side's coating there between the wires. Thank you Sony, for your humble attempt to make the wires identifiable, but something is wrong with your red dye 40+ years later, causing the plastic to break down. To the garbage bin with ye.

Although I have no more photos to offer, a second attempt has proven more fruitful, and I made some ghetto input tails as well. A successful install indeed, and now I finally have stereo spring reverb in my humble home recording rig. I'm excited to hear what this sounds like on my stereo gameboy signals, and I think the adjustable midrange on the EQ in these guys will be a fun tool.

Tuesday, December 20, 2011

Today I modified my Rock Band 3 keytar that I use in The Glowing Stars. Unfortunately the project wound up significantly more limited than expected. The keytar controller has three big issues from a performance MIDI perspective (the perspective from which I approach it) that I went into this aiming to fix:

1. Backwards pitch bend ribbon (towards the keyboard is bend up)
2. pitch bend ribbon is set to modulation control by default - only by holding down the adjacent button will it output pitch bent info, but holding down the button makes your hand nearly useless in the process.
3. No damper button.

Not knowing what to find, I venture forward.

Straight ahead disassembly, but the final screw is hidden under this rubber stopper which must be pried out. Presumably somebody decided that if you're vain enough to be playing a keytar - even in a video gaming session - you would care about hiding only this one screw - but no more.

While I'm at it - if you disassemble one of these yourself, take note that the screws on the keyboard edge of the unit are shorter than the rest. I wasn't paying attention and almost drove a hole right through the plastic...

These tiny screws are held up from the board by a variety of slightly different spacers. If you don't get them put back together correctly, the "whammy bar" or whatever button won't correctly. The goal here is to bypass that button anyway, but why make things uglier than they need to be? Besides, it's a minor puzzle.

A close up of the well labeled solder points that are connected when the front panel button is pressed. Here (and in the previous shot, which was shown out of order), they're already wired to a submini switch which I'll install on a drilled hole in the case. When the switch is closed, it puts the ribbon controller in permanent pitch bend mode, and returns the unit to normal operation when it is open.

The final result. Relatively innocuous modification. I decided to place the switch here because it is out of the way, but still available while playing.

As for the other things I had hoped to fix;

The ribbon controller seems to consist of about 8 touch pads and a micro controller which I'm assuming generates data based on which touch pads are pressed. Not a particularly high resolution device. I wasn't willing to get into it on my only keytar, but once I grab a spare, I have hopes for cutting all the traces on the PCB and re-connecting them in reverse to fix the pitch bend. A little bit obnoxious, but I don't see why it wouldn't work, as long as I can avoid burning out the SMD chip.

The keytar does provide an 1/8" jack for control pedal functions. According to the manual it can handle one analog expression pedal (no details provided) and one "digital stomp switch" which functions as a damper pedal. Now if there's a standard for "digital stomp switches" I'm not aware of it, maybe someone can enlighten me? But for the moment, I find my hopes of a damper control on the back of the handle (similar to Roland's AX series of keytars) dashed.