Well now that the pickup has been repaired, we’re ready to put this baby back together.
Firstly, we scrape out all of the crud left by extra lacquer, rubbing compound, etc., before fitting the tremolo:
Then we make new holes, since the old stripped ones have been plugged:
Before fitting the tremolo, I wanted to mount a ground wire to it, but I wasn't too happy about connecting it to the base, since I wasn't sure how the signal would transfer from the main block/drum. After thinking about several options, I noticed that the threaded hole that holds the arm lever on the top goes all the way through the drum (although it's not actually threaded all the way through).
So I tapped a thread a little bit into the bottom and connected the ground wire there:
And here's the tremolo system all fitted back in:
And from the top. You can also see the ground wire coming through into the control cavity, which I've also shielded with shielding tape, just like the back of the scratchplate:
The neck and strap buttons attached (apologies for the shaky photo):
Finally, the pickguard/scratchplate holes are marked and re-drilled, so that it too can be re-fitted:
And here it is all back together:
I did a quick sound demo of the guitar. It's pretty basic, but hopefully you can at least hear more or less how it sounds. I had to record it on my camera in low light, so, you know...
Apologies in advance for the crap video quality/sound quality/accent/playing/background mess.
Well that's the end of the Hofner Colorama restoration. If you happened to stumble upon this post and haven't seen the whole process, feel free to click on part one here: http://diystrat.blogspot.com/2011/09/hofner-colorama-ii-restoration-project.html, and follow the whole story by clicking on "Newer Post" when you reach the bottom of each part.
P.S. Here's a guy showing what these old Hofner Coloramas can really sound like:
… was the volume pot for that particular pickup, I was hopeful that after cleaning it out with contact cleaner, the sound would come back. However, after plugging the whole thing in, it became apparent that there was another problem.
The (working) neck pickup measures a very healthy 4.9kohms.
And this is the bridge pickup:
Which is my multi-meter’s way of saying infinity ohms (or in other words a completely dead pickup).
Well, I did say a long time ago that part of the reason I was doing this restoration was to learn new things. I guess this latest problem might as well go in there too, so today's (unplanned) blog post will be about how to repair/rewire/rewind a guitar pickup.
After quite a bit of research, it seems that two copper wire thicknesses were used over the years to wind these particular Hofner "Diamond Logo" pickups, namely AWG 43 and AWG 44. AWG 43 is slightly thicker than AWG44, making it more difficult to fit enough on the (very small) bobbin to achieve the required resistance. Nevertheless, I decided to go with AWG43 because it is less likely to break during the winding process (even AWG43 is considered pretty thin for pickup winding).
What you see in the photo above is a pedometer, some wires, a reed switch and a couple of magnets. In total, it cost around NT$89, two quid, three bucks, or whatever it works out as in the currency you are acquainted with.
Shown below is the inside of the pedometer. It's a very basic mechanism, which I'll try to explain as simply as possible. The metal bit at the top is a rocker arm that bounces up and down with every step you take, making contact with the piece of metal just below it each time. You can also see a really thin piece or wire (which also acts as a return spring), which maintains electrical contact between the rocker arm and the other piece of metal at the bottom of the pedometer circuit. The rocker arm and the spring can be removed very easily and the two new wires can be attached directly to the two metal contacts instead. The other ends of the wires are connected to the reed switch, which will close the circuit each time a magnet passes close to it.
A drill is held down extremely tightly to a workmate bench with velcro straps. The pedometer/counter is clipped onto one of the straps and the reed switch is taped onto the end of an old toothbrush handle and located as close as possible (without touching) to the magnets, which are taped onto the drill chuck, with a bit of rubber padding behind them to stop them from magnetizing the whole chuck and confusing the reed switch.
A bolt passes through the bobbin and is held on tight with a nut and washer before being clamped into the chuck.
I've also clamped a piece of metal with a hole drilled in it to the workmate. The diameter of the hole is the same as the internal width of the bobbin and acts as a kind of lateral movement limiter (does that make sense?) Basically it's to stop the thread going too far in either direction, causing it to fall off the side of the bobbin.
The drill is variable speed and is set on a slow speed (I went with approximately 200rpm in the end). I've uploaded a video of the dry run to make sure everything appeared to be working fine here:
Finally I leave the new spool of thread on the ground and pass it over my finger before then passing it through the hole and onto the pickup bobbin. I can control the tension by gently pressing down a little with my thumb. I have to say, though, this thread is extremely fragile, so most of the time I was more concerned about it sticking to my finger without any help from my thumb at all. It did actually break after about 170 turns and I had to start again, but luckily that was the only time.
I was hoping to get to 5000 turns, so I stopped when i saw this:
Note that at 200rpm, getting to 5000 turns took 25 minutes.
The bobbin's pretty packed here, but it really needs to be to get close to being balanced with the bridge pickup:
The bridge pickup isn't potted, so I'm not going to pot this one either. Instead, I quickly wrap it a couple of times with PTFE (plumber's) tape. I use this rather than sticky tape in case I need to remove it for any reason. It's not particularly pretty, but it does the job and it'll be hidden inside the cover anyway:
Once back inside the case I measure the resistance. I was hoping for something slightly north of 5K and it came out just about right (5.17K):
Well, it happens. You have a lovely finish on your guitar and then you drop it, chip it, scratch it, or whatever. In my case I got a bit overly energetic while polishing it and this happened:
It probably didn’t help that the lacquer hadn’t completely cured so was still a little bit soft. I’m sure there’s a term for this, but I can’t for the life of me remember what it is. The long and sort of it is that I friction burned it, causing the lacquer to melt and shift.
First things first, I decide to scrape off the raised lacquer with one of my favourite new tools, the razor blade:
This leaves us with the following:
Next, I carefully sand away any remaining effects left by the original melting using 400 grit paper wrapped around a wine bottle cork:
This leaves us with this (you know that expression about things getting worse before they get better?)
Next, we go over it with 600 grit paper, again wrapped around a cork (800 grit would be better if you can get your hands on some):
Leaving us with the following:
Now I decide to go with wet sanding (you could do this on the earlier stages if you wish too), using 1200 grit paper:
Now it’s starting to not look so scary:
And lastly, as far as sandpaper’s concerned, I wet sand it with 2000 grit sandpaper:
Leaving us with this:
Luckily I had enough lacquer on there that even after all the sanding, I never broke through to the paint. Had I done so, I’d need to do a bit of painting/lacquering and a little bit more sanding to get to this stage, but it would still be perfectly do-able.
Finally, it’s a case of using the rubbing compound to get the shine back (being a little less zealous this time around):
And the final result. It’s almost like it never happened:
The whole body was then wet sanded with 400 grit paper wrapped around a rubber sanding block.
This left us with a clear view of any imperfections that were either small divots that were missed at the time of filling, or where the filler didn’t stay in place during pre-paint-application sanding.
Rather than applying hundreds of coats of paint until these were filled in, they were spot-filled instead. To do this, we sprayed some of the red paint from the same rattle can into the rattle can lid, left it to thicken up for 10 minutes or so, and then applied it with a small paint brush (the paint brush can be cleaned afterwards with mineral spirits (turps) and live to see another day).
The filled-in areas were then sanded back again.
After this, another full rattle can of paint was applied and after waiting a couple more weeks, any remaining imperfections (much fewer than before) were again drop-filled:
However, this time they were carefully scraped flat with a razor blade:
The whole body was again wet sanded back with 400 grit paper as before, and was now ready to receive lacquer/clear-coat. About two and a half rattle cans were applied and thankfully there were no runs:
The guitar was then left a full month and this is how it looked after that:
To remove the “orange peel”, the guitar was again wet sanded with 400 grit sandpaper wrapped around a rubber sanding block:
Getting there:
Done:
After that, it was wet sanded with 600 grit paper, again wrapped around a sanding block, and making sure to sand in a different direction to the 400 grit paper. This is to make sure no marks left by the 400 grit paper were missed.
Then the next available grit was used (in my case 1200 grit [something like 900 grit would be preferable as an in-between grit, but I just couldn't locate any at the time]), again changing the sanding direction:
Followed yet again by the next available grit, which in my case was 2000 grit (again not ideal to jump grits this quickly, but sometimes you just have to work with what’s available):
Finally rubbing compound was rubbed in with a clean, fairly soft rag and the finish was polished up by hand:
Leaving us with this:
The camera flash is really showing the micro-scratches left by the rubbing compound in this photo, but to the naked eye they're not very visible at all. I'm going to wait another month or two before finally polishing them out, since it's become evident that the lacquer is still a bit too soft (more on that in the next post).
