Hammond Case Size Chart

I’ve been poking around at effects pedal enclosures again and thought it would be nice to have a chart to compare the actual sizes of the common Hammond-type 1590 series project boxes. So I made up a Hammond 1590-series Comparison Chart [PDF].

Hammond 1590 Comparison Chart

I used dimensions from Hammond and from a third-party lookalike (the boxes sold by Mammoth Electronics, in this case), unscientifically rounding dimensions to what seemed to make sense and then approximating those in Inkscape. The stated dimensions should be close enough, possibly 0.1″ off but usually less. The one exception is the height of the 1590LB boxes, which can differ almost 0.25″ from Hammond to others – I went with the larger 1.3″ dimension on that one. The actual size when printed should be close enough to actual size to get a good feel of how big it they are in addition to relative sizes.

The PDF will probably print more nicely than the PNG file, but both are full 8.5″x1″ letter page size – for dimensions to be accurate you’ll need to print at actual size, not scaled down to fit in margins at all.

Licensed under Creative Commons Attribution-NonCommercial – share and print for reference as you like, but please keep attribution intact or link back. Hope it’s useful!

B-52 Matrix 200 Master Volume Replacement

B-52 Volume Fix: Stock Unit Photo

A friend of mine has a B-52 Matrix 200 PA system he uses for small events and the volume pot busted. Adjusting the master volume would result in intermittent sound on, often way more on than wanted. Pity, as it’s a decent sounding rig for a small to mid-size room. 

In this case the master volume pot seems to have failed internally – probably from getting smacked at some point, but according to the internet these units seem to have various other quality issues as well. Rather to be expected with this bad a solder job – pretty crappy wetting on most joints:

B-52 Volume Fix: Lousy Board Solder

Anyway, nobody on the internet seems to have fixed this particular problem but it’s pretty simple: the Panasonic EVJ-Y15F03A54 is a drop-in replacement for the obscurely branded OEM part. The EVJ-Y00 and EVJ-Y10 series should also work – the Y10 is actually the exact match – but DigiKey didn’t stock it and you don’t need the threaded bushing in this application anyway.

Forgot to take good photos of the tear-down, but if you’ve been into gear before it should be pretty straight-forward:

  1. Remove the amp chassis from the case – screws on top (in the handle recess) and on the bottom.
  2. Unplug the ribbon cable to the DSP (effects) board
  3. Remove the six screws holding the edges of the front panel to the main chassis.
  4. Figure out how to lay the front panel on the workbench without yanking wires too much (or unplug the wires from inaccessible locations on the power board in the chassis – make sure you label which goes where, they’re both the same size plug)
  5. Take out all the screws on the front panel and remove the nuts from all the jacks – the front panel will lift off the circuit board so you can access the volume pot.
  6. Desolder the old pot (don’t overheat like I did and lift traces)

    The vias came out with it... good thing we didn't really need them.

    The vias came out with it… good thing we didn’t really need them.

  7. Solder in the new potB-52 Volume Fix: New Pot Installed
  8. Reassemble in reverse order

If you can’t get the Panasonic for some reason it should be possible to use a standard dual 50K audio taper pot, as long as it will fit between the front panel and the circuit board. (Measure carefully!) Make careful note of the pinout in the Panasonic datasheet – it’s not what I would have expected. I did a quick trace back to the closest op-amp to confirm pinouts were identical, here’s the schematic:

B-52 Volume Fix: Partial Schematic

The op-amps are standard JRC/NJM4558s but in SIP packages – took me a few minutes to find the SIP pinout.

So that’s pretty much it. It took me longer to find the replacement pot than it did to take the unit apart and replace it, and that was nearly more time with a screwdriver than the soldering iron. I also need to work on my desoldering skills, they ain’t what I thought they were.

Ruby Amp Build

Ruby Amp: Finished Cab without GrillOne of the things I have been wanting to do almost since I got an electric guitar – over ten years ago – is to build some of my own effects pedals. I decided earlier this summer (2012) that I am actually going to do that, by golly, and not just true bypass mods and control switchboxes like I’ve done in the past. Real analog effects circuits this time.

Then I realized that I wanted a way to test things at my electronics bench without lugging my mega-ton 112 combo up and down two flights of stairs and decided I needed a practice amp first. I could buy one of those, I guess, but I want to build stuff – why not that, too? And I managed to do it for practically free. Continue reading

Emergency Garage Release

We had a power outage a while ago, in the middle of which someone needed to get out of the garage and… couldn’t. The door that needed to be opened was, naturally, the one that wedges itself in slightly when it shuts, so it jams the electric opener’s emergency release.

Further investigation revealed that a good hard judo-yank will release it (with a bang), but not everyone can do that. So I made a release helper – because almost anyone can step on a lever. The pictures pretty much say it all – just hook the custom specially calibrated clothesline to the release pull and step on the board.

This is it.

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Drilling Holes Without Spewing Sawdust

This is one way to drill a hole without getting too much sawdust all over the place, even using a spade bit.

Fencing your woodchips with masking tape.

Fencing your woodchips with masking tape.

I normally reserve creating sawdust and messy things like that for the Shop For Big And/Or Messy Things, far away from my office/computers/electronics bench. However, the Shop For Big And/Or Messy Things is really cold in the winter and I was feeling wimpy.

Clean Drilling - Top View

Consumer Fake Out: Your Nightlights Are Lying To You

This past week I picked up a couple of cheap LED nightlights at Marden’s ($1.99 for a two-pack) and had to take them apart, of course, as I am a self-respecting geek, and because I was at one time mildy obsessed with running LEDs off line power. I guess that hasn’t quite worn off.

This all has led me to two conclusions:

  1. American consumers are suckers
  2. Chinese are either idiotic electrical engineers or brilliant social engineers, or both

Actually, both of those are not entirely deserved, nor totally fair, but read on for the full tear-down. Continue reading