Yamaha C-70 replacement for ALPS tone control switch SW503 replaces P/N KA902820

Description

Up for sale - newly designed replacement for the Yamaha tone control switch SW503 (Yamaha P/N KA902820) used in the Yamaha C-70 control preamplifier.
The original solenoid driven switch assemblies are getting old and once they fail, your C-70 could experience channel output problems. And, of course, they are impossible to find! If you have the original Yamaha (ALPS) switch in your unit, its contacts have degraded over time and the contacts cannot be adequately cleaned without dis-assembling the switch. Even then, the contacts are worn and the whole thing should be replaced. That's where my device comes in!
I designed this device to be a 'drop in' replacement for the original S301 solenoid direction switch in the Teac X-2000R reel-to-reel tape deck. This device is the same as the SW503 used in the Yamaha C-70.
I used modern, high reliability, hermetically sealed components.  Replacement requires only basic soldering and de-soldering skills. Step-by-step instructions, solder and solder wick are provided - everything you need except basic hand tools and a soldering iron.
P
lease note that the  instructions I provide are for the  Teac X-2000R, so these instructions are just a rough guide for the Yamaha C-70 unit.
Please see these comments on this device sent to me by my customers and on popular equipment repair posts:
The first 2 paragraphs are from recent buyers who used the device in their Yamaha C-70. The rest of the paragraphs are from customers who used the item in
their
Teac X-2000R reel-to-reel tape decks.
"After removing the
moving pieces of the contacts (in the original solenoid switch), I saw how flimsy they are I'm sure my cleaning and reassembly will fix the switching problem but how long will it last? I don't want to come back and repeat this process. I decided to search for
replacement switches
or possibly better contacts. To my surprise, I came upon a post on a reel-to-reel Teac repair web site. The repairer had a similar problem to me with his Teac tape deck and the faulty switch was an ALPS switch that looked identical to mine. The really cool part though was that the restorer had built a drop in replacement part for the ALPS
solenoid switch
. The replacement part uses individual, sealed relays instead of a solenoid driving a set of mechanical contacts. The replacement part should be more reliable and a heck of a lot more durable. The replacement switch is designed so the original ALPS metal cover can be re-used. However, the cover is not necessary as everything on the new part is sealed. I am happy to report that this replacement switch works great and my
C-70 is back to full operation with no problems whatsoever. To me it is worth spending the money on the new replacement part. Especially as part of a full C-70 restoration
. This is really a great
Yamaha
preamp
."
"I found the new replacement for the tone control switch [SW503 in the Yamaha C-70 preamp]
for the parametric controls Yamaha p/n KA902820 for about .00.
It took about 30 min to change the switch and what a difference it made, the bass is more real, the mids are
cleaner and the highs are sparkling its like having a new preamp.
Give this switch a chance you won't regret it."
Below are comments from customers who used the device to repair their Teac X-2000R reel-to-reel tape decks:
"I ordered and installed this switch that a guy named Kurt built up and is selling on eBay. I installed it and the deck  works perfectly again. I think this switch is better than the OEM switch. It uses less current and is almost silent. He says the relays are rated at a million cycles. The relays are sealed. It was a perfect drop in replacement! Lets hope these switches are available for a good while! Personally I think if I was tuning up any X-2000R , it would get this switch. The old switches just work like a resistor in the signal path as they age."
"I bought one of these reversing switches from eBay to fix the same problem the author of this thread was having, dropping out of the left channel in forward play. It has fixed that and then some. I never planned on it making a difference in the sound quality the way it did. Both channels are now clear and the sound is so pure and clean sounding. It has never sounded this good before so I wrote to the maker of the switch and asked him what the contacts were made of and he said “The contacts are silver alloy with gold alloy overlay and have initial contact resistance of 0.075 ohms max! My device also has hermetically sealed components for long life - longer than the original switch....” No wonder it sounds so good after listening to the OEM switch with its dirty, corroded, worn copper contacts! If you have a X-2000R I highly recommend getting this high quality switch, you will find none better and its better than what TEAC made. He might not be selling these next year."
"I got the same results that you did. I have never heard my X-2000R sound this good. Ever. My original switch could not be repaired because one of the sliders was toast. But that said, after replacing the switch with this new one, as I went through the alignment I noticed a stability to the settings that I had never had before. Switching from forward to reverse and back again, and the A/C meter would be dead on. It is very repeatable. The top end on my X-2000R is like never before, in a good way. And I am getting a nice big sound stage that is steady. The switch is an improvement over the original switch even if the original switch was new in my opinion. The signal from the heads goes through this switch. I am so glad this guy built up these switches! I was so impressed I restored the rest of the deck, the deck sings like never before. "
"I did not have a problem with my original switch, but I wanted to get this beautiful and rare silver X-2000R working as it did when it was new.  I started by checking the recording performance of my X-2000R.  Before I replaced the switch, I measured the VU meter drop while recording a 1kHz signal.  I noted about a 4-4.5VU drop in the signal.  I performed the same test after I replaced the switch.  I noted only 2-2.5VU drop in the signal.  This is great news as I wasn't even aware this was a problem and my signal was being degraded with the old switch.  While I had the old switch on my bench, I removed the cover to inspect the contacts.  I noticed only a very small portion of the wipers were making contact.  The new switch improves the contact and results tremendously.  I am ordering 4 more for my other X-2000Rs!  Great job on the design, thorough instructions, and packaging.  Other eBay sellers, take note
."
"For those who own this machine (TEAC X-2000R) there is a weak part in it called S301 which is the solenoid ALPs direction switch. Once this starts to go bad you can try and spray it with Deoxit but that might not even work given the tiny and poorly made switch design. The correct answer is to put a properly designed switch in by [the designer] which is sold on eBay. This fellow has done some homework and has made a correctly made part that should have been put in the deck of this price in the first place. I, as a past Teac Lead Technician recommend this part!"
If you are restoring a Yamaha C-70, this is a great opportunity to replace the old SW503 with this new modern part! It's only a matter of time before the original part fails... I believe that any C-70's performance will be significantly improved by installing this switch.
If you are considering this device to repair your C-70, please perform appropriate troubleshooting to determine that your original SW503 switch has failed and requires replacement prior to purchasing this device. I guarantee that this device will function as a superior, drop-in replacement for the SW503, but
I cannot guarantee that this will fix your C-70 unless failure of the SW503 is the cause of your C-70 failure.
NOTE: The metal cover pictured is not included. This item is designed to accommodate the metal cover from the original SW503 device, if desired.
Thanks for looking and if you have any questions, just ask!
SHIPPING quoted for US48 ONLY
Please note:
I can
NOT
currently ship to Russia. eBay's global shipping program is not supporting this properly at this time. I don't know why eBay has Russia in its list when they will not provide shipping costs for that country. Sorry for any inconvenience. Please contact eBay for assistance/comments.