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Korg Polysix Battery Repair

Oh, the Korg Polysix.   A wonderful piece of vintage awesomeness, except for the unfortunate tendency for the on-board battery to self-destruct, taking the programmer board with it. I’ve done several of these in the past; this was by far the most challenging to work on.

This unit was not unusual in that the battery had indeed leaked, and I could immediately see several components were damaged. It was unusual in that not only did it have MIDI, it had an original Korg MIDI retrofit installed from the factory. I honestly didn’t know that Korg even made an interface for this. I also had no idea how difficult it was going to make the repair.

The first hint came in trying to access the KLM-367 programmer. The retrofit sits on top. Two of the larger CMOS chips that are normally on the programmer are instead installed on the retrofit, with ribbon cables leading back the the original sockets. There are also hard-wired (soldered) connections to the front panel controls, the key assigner, and the voice board. I pulled the ribbon cables, but had to leave everything else connected.

P6Guts

Factory installed by terrifying space monkeys.

When I first looked at it while the customer was present, the damage didn’t look too bad. With the board out of the unit, though, it was as bad any I’ve seen previously. One of the quad logic chips and one electrolytic capacitor were completely shot.  The cap would be removed for the battery modification, but the chip had to be replaced. In addition, many of the traces were bad.

These repairs are not normally difficult, just time-consuming. I removed the old battery and the damaged components, then cleaned the board. Using the component diagram from the service manual, I marked the traces that would need to be repaired. For the new battery, in addition to removing the capacitor there’s a resistor that has to be replaced with a diode. I also installed a socket for the new logic chip. Once all that was in place, it was time to start adding the wires to bypass all the bad traces.

P6TraceRepair

And this is why I’ve started wearing my glasses more often.
“Oh you need little teeny eyes for reading little teeny print…”

Double-checked everything, installed the new components, put everything back together, hit the power, and…success! Sort of.

The programmer seemed to be working. Kind of. The synth section, though, was not. There were several dead keys. Some of the controls worked and some didn’t. I could create a patch and it would store, but they all sounded horrible. Powered it off, pulled the board, and went over it again. I found one wire that wasn’t soldered correctly, and also noticed that the metal mount for the retrofit was shorting a couple of resistors. A quick dab of solder, a minor change of position, and after I pulled the keyboard and took care of the bad keys it  seemed to be working – almost.

This time, the synth section was perfect  and it sounded fantastic. The arpeggiator didn’t work, though, and while I could still store patches the behavior of the programming section seemed odd.  Realizing that the retrofit might be causing an issue, I tried to locate documentation. A web search turned up a user’s manual, but no schematics.  At least I was able to disable the external sync for the arpeggiator, so now the whole synth side worked as it should.

Ignoring the odd behavior, I tried reloading the factory patches from known-good WAV files. No dice. They’d partially load, but then I’d get an error. I ended up entering the missing patches manually. I also verified that not only does the MIDI interface work, but the additional patch storage locations are accessible.

In the end, the customer picked up the unit and was extremely happy, even with the quirky issue saving patches. It doesn’t affect playability at all, or patch selection. I told him that if I can locate the service information for the retrofit, he can bring it back.

And of course the other positive note is that after this one I’ll never be afraid of doing a Polysix battery repair again.

Synth Price List – June 2012

No major structural changes. More models and a few new vendors added.

As always, the “Range” column represents the year-to-date average taking into account the availability of that particular hardware along with the difference between the high and low prices. A wide range indicates either low sales volume or large gap between the high and low (or both).

Synth Prices – June 2012

Synth Price List – May 2012

Format is the same, for a change. Added a couple of new manufacturers and a bunch of new models. I have several manufacturers with just one or two models; I may add them primarily to use as filler to make the pages come out even.

As explained in a previous post, the Range column represents a range of prices based on the high and low to date, but also takes into account the volume of sales. If the range is really narrow, either the item is very popular or the prices are always pretty close. Wide ranges indicate either a big disparity between high and low or a small volume.

In either case, it’s reasonable to assume that if you want to purchase something, seeing a price somewhere close to that range is a good thing.

Synth Prices – May 2012

A Tale of Two Polys

About a year ago I got a reasonably good deal on a Poly 61 and a Siel DK-600. Both were described as “working, but need TLC”. That turned out to be, at least in the case of the Korg, a bit on the charitable side. (The Siel is a future project.) Note that the picture above is not the unit in question – I really need to make more of an effort to take “before” pictures. Trust me, though, it was a mess.

Problems were, in no particular order:

  1. Half the keys were completely non-responsive.
  2. Most of the keys that did work only did so intermittently.
  3. Pressing down on the center of the keyboard caused the whole thing to go nuts – LEDs went random, the sound jumped all over the place. There was obviously a short somewhere.
  4. Most of the screws were missing.
  5. The battery was dead.
  6. A good bit of the plastic laminate on the case was gone, and the case itself looked as if it had been attacked by angry beavers.
  7. The joystick didn’t work.
  8. Although this wasn’t immediately apparent, the mylar ribbon cable that connects the two main boards was only being held in place by gravity and good wishes – it was cracked in several places.
  9. It was filthy.

It did, however, power on.  All the major parts were present; all the panel buttons and LEDs worked. It did make noise as long as you played very gently and managed to hit any of the few keys that functioned.   I added it to my “to be fixed one of these days” list & stuck it in the closet.

A couple of months later, I found another one on Ebay that had no bids on it. The case looked to be in good shape, but the seller said the keyboard didn’t seem to work and all the patches sounded the same (dead battery).  It was yet another as-is sale, as  they had no idea if anything else was wrong. So, I picked that one up too.

With two semi-functioning units my initial goal was to combine parts to come up with one working synth, but the more I thought about it the more it seemed like a really bad idea to trash a piece of vintage gear. So, I went with plan “B”.

Since I no longer have a wood shop, or even just the tools, making a new case wasn’t on the table. However, veneering the old one seemed just as good a choice.

Again in no particular order, here’s what I did

  1. Rebuilt the keyboard – I’ve done enough crappy Roland keyboards to have this down to a (tedious) science.
  2. Replaced the battery.
  3. Cleaned & re-aligned the joystick.
  4. Removed the ribbon cable and connectors, and replaced with regular wire. This was Not Fun – I had to solder both ends of something like forty wires to the headers on the logic boards.
  5. Replaced missing screws and standoffs.
  6. Removed the rest of the plastic veneer, repaired the damage to the case, and veneered with red oak.
  7. Cleaned all switches and pots.
  8. Reloaded the factory patches – which also verified the memory and tape interface work.

A couple of the presets seemed to be incorrect, but I chalked that up to the dodgy WAV file I had to use to restore the factory settings. Entering those patches manually took care of it.  The bottom line is that now I have one functional synth in a pretty sweet custom case.

  

And the other one? The electronics weren’t as bad. I replaced the battery and rebuilt the keyboard on that as well. The only thing not working is the arpeggiator.  Normally, I would be hesitant to dive into that level of repair, but based on the way it’s acting I know what the problem has to be – I just need to see if I can use the crappy schematics to find the chip that needs to be replaced.

Even if I sell it as-is, though,  I’m sure I can get at least $100 for it, which means I got the other one for a song. A squelchy, buzzy, pitch-bent, impersonal and oh-so-cool song.

Synth Price List – March 2012

Commentary to come later, but for the moment here’s the list. As usual, it’s grown a little.

Synth Prices – March 2012

Korg DW-6000

Another fun one.

I’m a huge fan of under-rated, unappreciated keyboards. And this is certainly a sterling example of that group.

This was Korg’s first digitally controlled hybrid synth, released in 1984. It uses 8 sampled wave forms as a sound source, along with analog filters and envelopes. 6 voices, 64 patches, unison, polyphonic (!) portamento, joystick, noise source, chorus, and Korg’s ADBSSR envelope generators.The keyboard is neither velocity or aftertouch sensitive.

The back panel has jacks for MIDI In/Out/Thru, the tape controls, program up, portamento, headphones, and stereo outs. The program up is a welcome feature; it would be nice if this were available on modern keyboards. It simply allows you to advance the programs by just hitting a footswitch.

It’s essentially a Poly 800, with six more waveforms. Construction is solid, and the design is logical and well thought-out. Most of the panel real estate consists of a list of the presets, all the parameters, and graphic diagrams of the waves. At this point all of Korg’s new offerings utilized digital access controls instead of knobs and switches. Their implementation is, at worst, a little tedious, but by no means difficult to either understand or use.

Any discussion of this synth invariably starts by saying that the DW-8000 is a much-improved version, by virtue of additional waveforms, digital delay, aftertouch and velocity, and an arpeggiator. This, to me, is actually a philosophical argument. The additional features on the 8000 don’t negate the fact that the 6000 is a perfectly usable instrument.

Most of the presets are good, but as usual most can stand a little tweaking to make them excellent. Basses and strings are great, along with the strident digital organs at which all Korgs of this vintage excel. It takes little time to set up any number of luscious, swirling pads. Piano? Not so much. Which is fine, considering the lack of a velocity sensitive keyboard. Actually, considering the small pool of waveforms it’s remarkable that such a wide variety of sounds can be achieved.

My complaints are small. User programs will overwrite the presets, and there’s no restore feature. So to reset an instrument, you either need to dump from tape or reprogram everything by hand. It’d be nice to have a little more control over the chorus, and the keyboard action is really light. Considering it sells for two-thirds to one-half the price of it’s more advanced cousin, these complaints seem tetchy.

Pros: Solidly built. Good presets. Program up, MIDI Thru, and Portamento jacks.

Cons: Non-velocity sensitive keyboard. No dedicated user program locations. Heavy.

No demo for this one, I’m afraid. My last unit was a rescue; it was bought and sold rather quickly.

Korg DW-6000 Manual

 

 

 

Synth Price List – February 2012

As indicated – the full list. Since the list has grown quite a bit, I may just post this from here on out, instead of dedicated posts for each section.

Synth Prices – February 2012

Synth Prices February 2012 – Korg & Yamaha

The price displayed is the average selling price for that particular model for the month of February. The percentage is the difference between the current and year-to-date average, which is an indicator of the direction the price is going. As per the last column, that direction is either “-” for down, “+” for up, and “0” for staying (relatively) the same.

Model Price Chng Dir
Korg
DW-6000 $161.83 1% +
DW-8000 $273.24 8% +
Karma $533.36 0% 0
M1 $527.32 9% +
Microkorg $242.88 0% 0
Mono/Poly $1,299.00 -12%
MS-10 $831.33 11% +
MS-20 $1,768.80 0% 0
MS-2000 $512.86 4% +
MS-2000R $358.81 1% +
Poly 61 $200.00 0% 0
Poly 61M $320.58 -5%
Poly 800 $240.82 5% +
Polysix $827.80 15% +
Prophecy $385.00 6% +
Wavestation $237.50 6% +
X5/X5D $374.65 4% +
X50 $407.76 -1%
Yamaha
AN1X $504.33 9% +
CS1X $230.33 8% +
DX-21 $118.79 8% +
DX-27 $174.88 8% +
DX-7 $261.35 -3%
FB-01 $55.71 5% +
MM6 $374.22 5% +
PSS-120 $4.25 -61%
PSS-130 $26.37 3% +
PSS-140 $27.00 21% +
PSS-170 $16.80 -28%
PSS-470 $64.25 11% +
PSS-80 $14.50 -3%
RX-11 $54.14 -4%
SHS-101 $207.00 3% +
TYU-40 $22.99 8% +

No major surprises for Korg. The Micorkorg is still has the highest sales volume of any instrument, and the Poly 800 has gone up quite a bit in the last few months. Like the Roland SH-101, the MS-20 would seem to be more of a collector’s item than a utility instrument, based on the current price.

I’m in the process of changing some of the Yamaha models. At the moment, I have too many mini keyboards and not enough synths.

Synth Prices 1/20/12

Couple of days late on this one. Bi-weekly price update. N/S indicates there were no recorded sales during the time period. Percentage column shows the or decrease from the last period. The larger values here may not be reflective of actual trends, since there may have been only one sale in the period.

I’ve actually begun to track many more models, and can see average pricing over a longer period of time. If nothing else, it gives a good sense for whether or not something on Ebay or craigslist is fairly priced, or whether the seller is under the influence of pharmaceuticals.

Averages based on Ebay sales data from 1/2/2012 to 1/15/2012.

Roland
SH-101 $742.06 -1%
Juno 60 $933.09 16%
Jupiter 6 $2,110.50 -5%
JP-8000     $527.50 -3%
Juno 106 $582.42 9%
SC-55 $81.00 27%
Alpha Juno 1 N/S
D-50 $335.71 -20%

The SH-101 continues to astonish me. It’ll be interesting to see if the release of the Moog Minitaur and the Arturia MiniBrute have any effect on mono synth prices.

Korg
Polysix $385.00 -49%
M1 $461.39 -10%
Poly 800 $260.00 0%
Microkorg $237.78 -7%
X50 $406.50 5%
MS-2000 $503.17 -7%

The Polysix only had one sale; whoever it was got a good deal.  Although it’s still too early to be sure, the Poly 800 appears to be stable – another head-scratcher.

Yamaha
DX-7 $276.11 4%
MM6 $338.09 -5%
AN1X N/S
CS1X $235.63 89%
FB-01 $71.00 37%

The AN1X may not have been a good choice for this list. I like it, but the sales volume has been really low.

Moog
Minimoog $2,972.50 6%
MG-1 $566.33
Prodigy N/S
Rogue $517.50 -20%

Need to rethink this list, too. The MicroMoog has more sales than the Prodigy.

Casio
CZ-101 $144.08 -10%
MT-500 N/S
RZ-1 $107.38 6%
SK-1 $41.59 -8%
VL-1 $32.05 -52%

The VL-1 appears to have corrected; the average price for the past few months has been around $44.

This seemed like a good idea at the time, but I’ve found the 2-week interval is too short for some of the lower-volume keyboards. Instead of this, I may change to doing it monthly but with an expanded list of models. Again, if you have any suggestions let me know.

Synth Prices 1/3/12

Bi-weekly price update. N/S indicates there were no recorded sales during the time period. A couple of other units were suggested, which I added. Also added a column to show the percentage increase or decrease from the last period.

Averages based on data from 12/19/2011 to 1/1/2012. Overall volume was lower due to the holidays.

Roland
SH-101 $753.33 -7%
Juno 60 $804.33 -20%
Jupiter 6 $2,217.00 17%
JP-8000 N/S
Juno 106 $536.13 -18%
SC-55 $63.92 -35%
Alpha Juno 1 $219.83 6%
D-50 $421.84

Added the D-50. The Sound Canvas makes me kinda sad…I still love that pupster & use mine all the time.

Korg
Polysix $760.00 14%
M1 $513.24 23%
Poly 800 $260.33 73%
Microkorg $254.71 3%
X50 $386.71 -6%
MS-2000 $542.50 19%

Microkorg and X50 seem pretty stable. I’m still a little surprised by the Poly 800; I almost wish I’d kept the ones I’ve fixed over the years.

Yamaha
DX-7 $251.81 -12%
MM6 $355.72 4%
AN1X $478.67 15%
CS1X $125.00 -37%
FB-01 $52.00 37%

Although the price listed is based on just one sale, and isn’t therefore really statistically  relevant, the CS1X is still somewhat underrated. It’s a bargain.

Moog
Minimoog $2,800.00 -46%
MG-1 N/S
Prodigy $780.00 11%
Rogue $649.66

Added the Rogue. I’d include more Moog models, but the sales volume is so low that I don’t know if the numbers would mean anything. It also just occurred to me that the MG-1, Prodigy, and Rogue are all basically the same synth.

Casio
CZ-101 $160.67 -20%
MT-500 $47.77 -18%
RZ-1 $101.25 107%
SK-1 $45.28 -9%
VL-1 $66.25 68%

Another one I don’t get…what’s the appeal of the VL-1? It’s of historic interest, certainly, and cute, but at that price? If I found one at a yard sale for $10, yeah, but otherwise I’m happy to stick with the VL-1 VST.