NUMARK TC 4100 MIXER
Tone Calibrator
If you need to switch audio inputs and outputs for up to four tape decks, VCR's, CD/DVD players or recorders, or any other two channel audio player or recorder, you should have this device on your short list. You'll find in this model features that simply don't exist in other mixers. Considering the inclusion of two analog VU meters, a tone generator, signal level adjust capability, and complete input & output switching for FOUR DEVICES, the Numark TC 4100 stands above most of the other switching devices you could buy today.
There is one shortcoming with this model that I thoroughly addressed below.
A little history first-->>
I bought my first Numark TC 4100 in 1984. I still have it, and I still use it. At the time I had two reel to reel tape decks, a cassette deck, and a stereo receiver that would accommodate one stereo tape deck, having just one Tape Monitor circuit. I needed the ability to edit and copy audio tapes from any of my tape decks to any other, and the ability to record and play back from/to my receiver to/from any of the three tape decks I had. The TC 4100 did all of this admirably, with inputs and outputs to spare, and considering the built in VU meters and tone generator, added much more function and value than any of the simple minded tape switching units that were available at the time. That is still the case today!
After many years of use one of the channels on one of the inputs quit working. Later a channel on another input quit. And then another. After enough of that I bought a second TC 4100 right here on eBay.
And guess what?? It exhibited the same sort of failure...losing one or both channels from one or more in the four inputs, rendering that input(s) unusable!
So I bought another...and another. And most ALL of them had the very same problem to varying degrees. I was able to salvage parts from one of them to repair another to get one mixer that was 100% operational. But keep in mind here that I was replacing an old worn out part with another old, not quite yet worn out part.
Over time my needs changed and the number of TC 4100's I had on hand grew. I now have two of them in use in my vintage Quad system, another one in use in the Quad system in my office, and another two in use in the test bed in my shop where I repair Teac tape decks. (See photos.)
And then another nine or ten of them on hand! What I learned is that the level controls (most of them are dual potentiometers (pots) behind the sliders on the face plate) used in this machine regularly fail, a result of both use and time. Potentiometers like this often use a wire wound resistor. In the case of the ones used in this mixer that resistor looks more like a land pattern on a printed circuit board.
We are now 30+ years down line from the initial availability of this mixer. Based on my considerable experience with this model I would expect that eventually all of them are going to fail, and sooner rather than later. Most of the other two channel mixers & switchers that are available out there are also 30+ years old, each with their own shortcomings, typically, lacking features that are included in the TC-4100.
I developed a plan to buy used TC-4100's on the cheap, replace all of the pots with new parts to satisfy my own requirements and repair and sell the rest for a profit. Through a lot of research, trial and error, I eventually tracked down a suitable substitute part for the pots that is compatible both electrically and physically with the originals.
On the surface that seemed like a good idea. What I failed to consider is how much time might be involved in replacing all six pots, and how much the finished product would be worth. I'm happy taking the necessary time to repair one of them for my own use. But on balance, my time is much more effectively spent repairing a tape deck for resale than repairing one of these TONE CALIBRATOR/Mixers for resale. Having bought over a dozen of these, and about 100 pots as replacement parts, I find that I've actually repaired just four of them for my own use. And the rest sit on a shelf in my shop taking up room that could be better used. I don't see me taking the time to restore them all. Rather than continue to store them I'd much prefer to sell them off to the next user, and include the necessary repair parts with the sale.
(By the way, locating a useable part was not an easy search, to say the least. Finding a part with dual 100 K Ohm pots is easy (is that a logarithmic or a linear pot?). But there are many physical characteristics to consider beyond simple length and width, and overlooking any one of them will get you a part that you can't use!)
So, I intend to sell several of them, along with the parts (pots) that will eventually be needed, regardless of whether or not they are needed them today. If you can use a screwdriver, needle nose pliers, and a soldering iron, or if you know someone who can, this is a repair that can be finished on your kitchen table. I have not thoroughly tested these units but will guarantee the following: The unit will be complete, with both meters operational and illuminated, and with at least some of the inputs and outputs working correctly.
With a sale of this item I'll include a copy of a four page owners manual that came with my original unit. (Please remind me that I said this!) Interestingly, this document specifically warns against using "SPRAY CLEANER FOR ANY SLIDE CONTROL". This is precisely what someone would try given the failure I've seen over and over. I'll also include some pointers to help with the eventual replacement of the pots...things that I learned when I replaced them that I'm happy to pass on.
As noted, I have a lot of experience with this mixer. The only problem I've ever seen in 30+ years
of use with this model is the pots, and an occasional burned out meter
lamp. I've not had a problem with the
push buttons, power supply or the meters.
The unit you get may work fine upon arrival, in which case you will have
successfully stolen the device from me.
But regardless, it will eventually need the parts I mention. Anyone selling a similar item and claiming
that it works perfectly either has the one in a million machine that in fact
does work perfectly (I guess that's possible), or maybe just doesn't know how
to thoroughly test it. Personally,
having bought more than a dozen of them, I can say that the only one that
worked PERFECTLY is the one I bought new back in 1984.
Stated shipping is for the lower 48 states and includes insurance and packing material. Shipping outside of the US will be via the eBay Global Shipping Program. The photos are representative of what I have on hand and will not be the exact machine you receive. I won't sell you a machine that looks like a train wreck.
Please take a look at my feedback being 100% positive with hundreds of items sold. I've sold a few of these mixers with repair kit from this listing. A few of the feedbacks I've received on this item follow:
* Nice piece was easy to restore a pleasure doing business with you thanks
* Super fast shipping and well packed! We only need ebayers like this!
* alles bestens - vielen dank !!! (????)
* Thanks
* excellent comms, packaging, everything great. recommended
* yep works....
* thanks for the instuctions. great addition to my system
* very fast
* Nice, couple pots bad as described, installed new ones works great
* Arrived in good condition and w/ pots + instructions and printed user info,OKAY
* Nice piece was easy to restore a pleasure doing business with you thanks
I can maybe provide advice and council when you get around to switching out the pots. I'll start that advice by saying that once you have the mixer taken apart far enough to replace one pot you may as well replace all of them...even the ones not failing YET.
This item is being offered as-is with the potential issues noted. I'm listing it as not returnable but if the buyer discovers something that I haven't mentioned here please contact me. I'm a reasonable man and would think that we can work something out that everyone can live with.
Thanks for looking!