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Old 07-17-2016, 12:46 PM
MHzTweaker's Avatar
MHzTweaker MHzTweaker is offline
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Join Date: May 2016
Location: Hillsborough, NC
Posts: 992
Numark TC4100 Tape Deck switcher I purchased and my repair efforts

Hello all

I found myself wanting an easier way to switch tape decks and found some old threads speaking to a rare Sony switcher, DBX 200 and 400X switchers and also a Numark 4 deck switcher.

A quick look on ebay turned up this link for several Numark TC4100 units:

I purchased one TC4100 for $69 and an extra repair kit that is included and also available separately for $35. So I have enough parts to replace the 100K pots twice. A pair of lamps also come with the unit.

I received the unit yesterday and tore into it to do the pot replacements. I did not receive the instructions with my unit so I was left to my own devices. The first thing I noticed was these are not 100% direct replacement parts. 4 of the 7 solder connectors will have to be bent and formed with pliers to fit pot to the PCB. Also the 6th "Test Tone" pot is a single and not a dual channel pot. I received all dual channel pots. After the seller responded and sent instructions I was told I would have to make a dual channel pot fit and work in the single channel PCB location. The pinouts do not remotely line up. I ended up running a jumper wire from one of the solder tabs.

Here is what I ended up with. New pots are on the left. The original Numark pots are on the right.

Last edited by Pacific Stereo; 07-17-2016 at 01:35 PM. Reason: Fixed title
Old 07-17-2016, 03:49 PM
Skywavebe's Avatar
Skywavebe Skywavebe is offline
Skywave Tape Deck Repair
Join Date: Jul 2008
Location: Bensenville, IL
Posts: 14,503
Good work fixing it up as this is a credit to your abilities. I was going to say the Numark unit may have a lot of nice features but then look out when they start to go bad. They were not known for an outstanding product but more on the name relabel type product that could be anyone's junk. Kind of like Mackie and Behringer having different mixers made with the pots and knobs exactly in the same place. Where do you think they were both made? China. The only difference is the face panel.

Often times the replacement parts are not going to be exact. This happens all the time and we have to get used to finding parts that almost fit but can be made to work. Might have been easier to spray the present pots with Fader Lub and see what you come out with. E bay repair kits are often full of Chinese parts and you can do a better selection of parts yourself. These people are only there to make money on those that do not know. They don't care about you after they have the money.
Best regards,

Sam Palermo, BSEE , ProSquad Member
Skywave Tape Deck Repair- Chicago area
(630)616-0932 Office/ Email skywavebe@sbcglobal.net
Past Teac/Tascam Lead Service Technician at Chicago Factory Service, Sony too still doing repairs.
Old 07-18-2016, 04:16 AM
MHzTweaker's Avatar
MHzTweaker MHzTweaker is offline
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Join Date: May 2016
Location: Hillsborough, NC
Posts: 992
Indeed.... I've found it can be beneficial to buy from the right person. Even on the best of days things have gone wrong and the person on the other end can be crucial in resolving issues.

I purchased the switcher and the replacement parts from the same person in Texas. He did all the legwork on the Numark. He has owned one since the 1980's. He had accumulated over a dozen of these TC4100 mixers as donors trying to keep a few running. As you say when these things fail..... He eventually got fed up and sourced compatible 100k pots and bought 100 pots to repair all the Numark switchers for resale. He decided the labor was not worth his time so he is selling off like 6 or 8 of the TC4100 units with the replacement parts and instructions.

I bought one with the replacement pots and lamps. I also bought an additional set of 6 pots should I ever need them. After the seller answered a few questions I was able to completely repair it in a couple hours.

I also purchased a DBX 400x yesterday for comparison

Last edited by MHzTweaker; 07-18-2016 at 04:20 AM. Reason: more info
Old 07-14-2017, 12:57 PM
eissmann's Avatar
eissmann eissmann is offline
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Join Date: Oct 2014
Location: Santa Barbara
Posts: 545
I decided to try one of these switchers and of course it's broken! So I ordered the repair kit on eBay. And I have a question....The replacement sliders will fit two ways. I tried measuring resistance from the various pins and I can't determine which orientation is correct. Is there a "correct" direction to orient these pots? How do I determine which way to orient them? Thanks in advance!

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