Calibrating and tuning a CS50 (and I assume the other nearest siblings) is an iterative process. There are pitfalls at every step, and when you finally reach the end you get a nice easter egg -a tuned 4 (or more) voice synth! In the last post I quickly diagnosed why my CS50 didn’t make a sound -having the TU (tuning) voltage jumped to ground. This post is about other problems. The CS50 circuitry has a lot of functions that are distributed among a couple of boards, so you may find you have a tuning problem originating in your SUB board, or a portamento problem originating from your PRA board. Well, I had a TU problem coming from my SUB board – no matter what I tried, I got 6.5 volts at the TU terminal -trim pots had no effect… this terminal is supposed to be 4.000 volts. Lots of head scratching and component replacement later I decided to just order a CS50 SUB board from synthparts.com -a handy side effect of CS50 voice boards being worth $400 – $500 each, making the CS50 worth about 2x it’s ‘complete working’ value in parts is that CS50 specific parts are CHEAP. I got a complete front panel and lower chassis in like new condition for $150 while I was at it. Too much money probably, but not bad really if you just want to fix your cheaply obtained synth that just happens to be worth more as parts.
Part way through a power supply recap. I am told the small value green caps don’t really tend to fail, and to leave them alone. After the recap it’s a good idea to look at the rail voltages again just in case. Continue reading
For those mad enough to attempt a repair or god-forbid restoration of their PolyMoog, here is a running list of parts I have/will/need to replace. This will be updated as I get stuff.
Power Supply has had its capacitors replaced. Note the 4700uF is a radial -they were out of axial capacitors in the rating I needed.
P o w e r s u p p l y : : : : : .
3x 470uF x 35V axial capacitors
2x 1000uF x 35V axial capacitors
1x 4700uF x 16V axial capacitor
3x LM723CN chips (not sure if these need replacing, but they are 33 years old and replacements are $0.65 each.)
Few synthesizers have such a bi-polar reputation. Amazing sounding and tedious to maintain, much less restore are the two poles of this equation. Moog churned out a few of these – I am guessing a little over 4000 since this fellow is serial number 4021 and I’ve never found a reference to a later one. Gary Numan famously used the Polymoog and so did a list of other luminaries if VSE is correct, but there isn’t anyone recent on that list. I’m excited to fix this to see what it can do in a modern setting.
It just happens sometimes. You mention you have an X you are looking to get rid of, and a friend says they have a Y they’d like to get rid of. A little cash one way or the other sweetens the deal. In such a way this complete, clean, low mileage, semi-functional Polymoog joined the menagerie.
I decided to be ‘one of those guys’ and placed an ad on Craigslist looking for an ARP Odyssey (really want one!!), anyway -responses were thin and expensive except for a ‘broken Yamaha CS50’. I went for a look and hey-ho next thing I knew I had a $600 CS50 in the back of my car. Considering perfect ones sell for $1200 – $2000, the price was probably high for how little worked on it, but I decided to take a chance since I like a challenge. It came with a lid and legs.
A good looking specimen. All slider caps are present. The keyboard is in great shape. Not too many scratches. Even came with the legs. The LFO control board has a bunch of paint loss in the lower left corner -like the PO played with a metal band watch on.
This is my Moog The Source. It was a lovely all original piece in great working order. In a fit of ‘I’ve got too much stuff’ a while back I sold this fellow on eBay and ended up having one of the worst selling experiences I’ve ever had. I used this synth lightly in the studio and everything worked, even after several hours being on. The buyer complained about lots of little things that frankly I suspect weren’t there, the aim of which was to get a partial refund. After two weeks of having the money I got for this tied up in ‘item not received as described’ Paypal limbo I sent the buyer $50 and told them to ship it back. They used about half the bubble wrap I sent it in and to round out the bad experience it showed up as you can see below.
Cheek took a pretty good hit. Fortunately it still worked perfectly. Shame about the original finish on the original wood… Continue reading
One of the downfalls of products from the early 80’s is the crap plastic they made a lot of stuff out of, and the putrid shades of slightly green beige it turns over time as the fire retardant bromine migrates out of it. I bought this Piano Plus 11 off craigslist while I was restoring the Juno 60 to steal the key bed and maybe some buttons, sliders and other components out of. I got it home, spent some time horsing around with it, and decided I just couldn’t kill such an interesting thing, so I just swapped its perfect key bed for the slightly glitchy one in the Juno 60. What’s so interesting about it you ask? Well, it has built in drum patterns, bass accompaniment and a kick-ass arpeggiator – all with a din sync out to drive other stuff.
This did 18 months of solitary confinement in my closet while my wife’s pregnancy progressed and then while the boy grew as I did late night/early morning diaper shifts. One day I came across it while looking for some shoes and realized this would be a great first keyboard for a kid, so I pulled it out and sized it up. The plastic cheeks -similar to a Juno 106 and JX-3P were offensive, so I decided to get some wood cheeks made.Here’s the nearly finished product. The wood cheeks make the cream colored panel a lot more acceptable. Yes, that’s a VP-330 under it, more on that later. Continue reading
The danger with inexpensive synthesizer projects is it’s easy to justify spending money on them once they are in hand, and frequently end up being more expensive than if you just went out and spent eBay retail on the same board. I can type the sentence, I can say the words, but when a $200 Prophet 600 was listed on Craigslist, you know I just had to make a play for it. The seller responded to me by calling about 6 hours after I sent my ‘Is it still available’ email -which seems funny because I asked that question about 7 minutes after it was posted. All the seller could tell me was that it didn’t power on and had some broken keys. We met up the following morning and a deal was struck. JD was a stand up guy for being true to his ‘first to come’ statement -even after receiving a lot of emails.
In the car. I’ve seen worse. I’ve started with worse. My big fear was that the voice chips were missing, so I opened it up before buying. All chips were in place, as were a lot of debris and mouse turds.