Fixing my BR-9

Another project for the list. My Gibson BR-9 lap steel has been really noisy, so I've been investigating the possible culprits.

Right now something is shorting out in the tone control, causing the tone control to act like a volume control. I thought this was the capacitor, but testing it out with the cap desoldered and bypassed with another capacitor still yielded the same problem.

So I ordered 2 new 500K pots, so I plan on rewiring the whole thing. Of course, for value purposes, I plan to keep all the original pots & caps.

The projects list

I have quite a list of little electronics projects to finish:

1. Build a new Champ Amp chassis: I have a board, components, transformers, pots, wire, etc. 
2. Build a Deluxe Amp clone
3. Finish "Old Ironsides"  (test transformers)
4. Repackage NPN Fuzz, and test with different components
5. Build GGG Shin-Ei Companion Fuzz kit
6. Build GGG Mini Mixer Kit
7. Build a few Craig Anderton EPFM projects

Boss HM-2 Repair - Part 3 (final)

So I got the HM-2 fixed, but it wasn't without its problems.

The pins on the DS-2 replacement pot are a little too short to get all the way through the board with ease. In addition, the replacement pot doesn't have board mounting tabs on the LH and RH sides, so the mechanical connection isn't as good. 

So first I unsoldered the old pot and saved it. 

Next I bent the pins carefully on the new with some pliers. Then I soldered the pot in at a shallow, slight angle, so that the pins could make a strong connection on the other side of the board. Finally I went to bend the pot flush with the board after it was soldered and I heard a crack: apparently the phenolic mounting wafer on which the pot is mounted cracked. I checked the pot values to make sure it was still working, and it was still in spec. I also spun the knob, and felt a tiny "tick", like a detent, in the action, about 1/2 way. 

Closed it back up, took it to the guitar lab and plugged it in, all good! I felt a little like the new pot didn't have the same range as the original; but then again I haven't use the paddle in many years so I can be sure. It seem like between 7 o'clock (zero distortion) and 9 o'clock, the sound goes from a heavy over drive to a mean growl. From 9 o'clock to noon, it gets funnier and deeper. From 12 o'clock to 5 o'clock though I can't tell much difference, I don't seem to hear much of a difference in sound. That may be because I was testing it out on my DG stop and it was very oversaturated.

The replacement knob is slightly brighter orange than the original 3 knobs, but that may change with time & grime.

Happy to have it all back together and working. 

Screaming Bird fix

I got my EH Screaming Bird pedal fixed today. Took some mucking around, developing a wiring diagram, testing... Jack Ormans LPB-1 schematic was the closest to the actual values in my Screaming Bird; the other common schematics used different transistors with  different values. 

Found some wiring photos of other LPB1 and Screaming Bird online and was able to deduce and test wiring through trial and error. 

Here was it in the testing stage, wiring here is wrong, but pretty close:

I had to replace a missing DPDT switch, which I found at Radio Shack a few weeks ago...nice that thy still carry parts!

Here was the final wiring diagram that worked, so I drew it up:

I think it's interesting that +9V runs to the Jack sleeve (traditionally ground!). The values in the diagram above are the actual ones I observed/measured. As in the other schematics I've seen, you could easily substitute the two caps for .002uF, or other more convenient values. 

Looks nice buttoned up, and sounds nice too!

Boss HM-2 Repair - Part 2

So I spoke to Leanna at Boss support today and was able to get  the "Distortion" pot for a DS-2 is Boss P/N 1327-9854, it's $4, $11 shipped. They had it in stock...hooray! Hopefully will get it next week. 

Got the Boss knob a few weeks ago, so I am back in business.

Boss HM-2 Repair - part 1

So I'm cleaning out my studio a few weeks ago and I come across the first Boss pedal I ever bought, a Boss HM-2 Heavy Metal pedal. A high-school acquaintence (Jon-Paul B.) sold me his Squier Bullet strat, a Peavey practice amp, and the HM-2. Finally I could make some real noise! I was super stoked.

Sometime in the 1990's I accidentally stepped on the pedal wrong and broke the Distortion knob off. Only a little nub of the potentiometer shaft remained, enough so I could adjust it.

Now reading online about the popularity of this pedal for Swedish Metal tones, and considering it's no longer in production, I decided to try to fix this problem.

Starting with the HM-2 Schematic (thanks to Hobby Hour) I was able to determine it's a 250K pot.

Today I called Roland support and spoke to a nice guy named Carlos. The Distortion pot for the HM-2 is no longer manufactured...BUT I was able to find a pot on another production pedal, the DS-2 Turbo Distortion. This is another 4-pot Boss pedal (so the pot dimensions should be about the same), and the value of the Distortion pots are the same on both pedals (250K), so I figure it should be a direct swap.

FYI, the "Distortion" pot for a DS-2 is Boss P/N 1327-9854. It's a 12mm pot. They don't have it in stock, so I have to call back in a couple of weeks when they do.

This Alpha pot might work too, but I'd have to buy one to see if it will fit. It's a good bit bigger (16mm), and without knurled shaft. Seems tricky to find a 250K pot, 12mm body, with a knurled shaft.

I was able to order a knob; that was about $12 shipped...steep, but fine for a vintage pedal.

So commence with the disassembly. Tools needed:

Philips head screwdriver

12mm socket 

11mm socket

Socket wrench

1. Unscrew the back case (4 Philips screws)

2. Lift out the back and corrugated plastic insulator. 

For reassembly, note that the ridges of the insulator go towards the PC board. 

2. Unscrew the input and output jack nuts using the 12mm socket, and reserve the washers and nuts. 

3. Set the knobs to zero (full counterclockwise) then gently pull off the 4 control knobs. This is a good time to clean off the dust and grime with a damp microfiber cloth. 

Then unscrew the 4 nuts on the potentiometers using the 11mm socket. They're not on there very firmly, they don't take a lot of torque to loosen them, remember for reassembly. Reserve the nuts and washers. 

4. Now you have access to the potentiometer "control" board. I didn't disconnect the switch and battery snap. For now. 

5. Then I set about measuring the pots. Screw shaft is 10.5 mm in diameter, base diameter is 12mm, knurled shaft height is 10mm (~3/8") from threads, knurled shaft diameter is approximately 4.6mm (3/16"). 

More to come!