Teac A-6300 R2R For Repair

Since I've been hanging out in R2R forums while fixing the 4010SU, I've picked up quite a bit of info on other Teac decks. The A-6300 arm oscillation is mostly caused by tape wear on the right tension arm guide pin. The tape drags causing the arm to chatter.

Fixes can be filing or sanding the entire guide surface (edges and flat surface) then polishing smooth. Since this arm was bent up so badly and the tape guide pin was loose, I opted for a new part. They had the arm and pin so bent out of shape it was forcing the tape out of the head guides in reverse play resulting in tape skewing off the head and distorted sound.

Ebay had some used arms, but they wanted new prices. Teac Tascam in Canada has some parts available for the old decks and they had a new arm for $33. The old arm doesn't look too bad as I had it out and peened the guide pin and straightened the arm. It sounded better in reverse play, but the arm still chattered a bit.




I have to remove the capstan flywheel for clean/service and new belt. Having this out of the way makes changing the arm easier.



The right tension arm is drooping. It connects to a cam that closes two micro switches when it is lifted with tape run around the guide. If the switches are open, nothing happens when you press play. The droop is from a broken plastic limit stop. The limit stop prevents damage to the micro switch nubs when the flat part of the cam contacts them. Force it down a bit by accident and you’ll need two micro switches.






I have a used limit stop on the way, but I have seen guys fabricate them. I had some 1/8” ABS here and it was within a few thousandths thickness of the broken piece. I wondered if the ABS might be a bit more resilient than 49-year-old plastic, so I made one. I couldn’t locate the broken piece, so I used pictures of a whole part as a guide and snuck up on the final dimension. It fits and does what it’s supposed to.



Those pencil lines will allow putting the pinch roller solenoid back where it was.



Good fitting snap ring pilers are a must to prevent this ring from becoming a Jesus clip.






I have more reassembly before I see if it fixes the problem. If it doesn’t, it could be reel motor torque out of spec which will be checked regardless.

Got the used limit stop. I had already looked at videos of A-6300’s playing and filed the second stop on the fabricated one until the arm position clock position matched during play.

The flywheel had some oil inside the hub. I cleaned it and cut a narrow strip of felt and glued it in. Typically, you find foam or felt on capstan flywheels to catch any oil that may leak from bearing so it doesn’t get to the belt. The design of this one prevented a foam or felt disc around the capstan bearing hub area. The diameter of the bearing hub extends to the holes in flywheel.

Great results! Plays with no issues now in reverse. Good sounding deck. Now do I flip it and buy a better deck or totally recap it and keep it.

https://youtube.com/shorts/7aKpvWmfvF0?si=eFdJIivmjuYF-bzm






As an example, this is a capstan flywheel from the Teac 4010SU showing deteriorated foam replaced with felt. The 6300 used a rubber seal at the capstan end instead of foam like the 4010.

With my old eyes, I'm into 2 x 3 schematics now... 2 feet x 3 feet.

I removed some caps to test. Some are good, some are at 20% and some over 20% out of spec. I decided to recap it. Teac used Chemi Con caps. The electrolytics are mostly SL's, or general purpose, several LR's or low ESR and four CEKU which are really special. They measure spot on. There are some Tantalum and dipped Tantalum. I removed a couple, and they are well within value spec.



I found a source for Panasonic FC caps that will cover all values needed (with exception of a Muse bipolar). So, the general-purpose caps get an upgrade.



I was concerned about fakes, but they look real good and test well for value. (Sencore LC-53 Z meter used to test). Several were tested for leakage, and they passed. I test and write values down on tape or separate them in bags and plastic storage boxes. These are 10uf, (I didn't write decimal, 9.8, 9.9uf). It allows me to closely match R and L channels and I can trust the marked value when I install it. I test and record the removed caps as well.






First blood, PS done. There are way too many wires to desolder to get the boards completely out. One can cut zip ties, get some slack in wiring and move boards for best access possible. I take pics or notes to make sure polarity is correct. (The markings on the board may not be visible). I powered up and tested PS before continuing. All is well. No smoke or sparks.



The lower boards may be slightly easier.

Thanks! I like that it still works, except for the occasional misfires.

The Teac A-4010SU I re-capped had no board markings for capacitor polarity. The A-6300 does. The other curve ball was some caps in the 4010SU had the positive lead marked on side of cap instead of negative. So far, all caps on the 6300 are marked for the negative lead, except for one bi-polar. The other good thing about the A-6300 is the caps used on PCB matched the parts list, so easy ordering. The 4010 I had to double check each value due to all the revisions. Some values were different on the parts lists I had.





With the mic/playback EQ amp board done, I powered up and tested, ran through a quick calibration and playback to make sure all was well. Now I move on to the line out/phone amp board.

Removing the daisy chain grounds between boards and a couple of signal wires makes this one easier.

Clipdat wrote: »

These are really intricate and complex machines. They certainly didn't think too much about how they'd be serviced in the future.

Or maybe they did, and they just went with this design anyway because they had to meet a cost/complexity/formfactor etc. limit.

Either way, fascinating stuff. It reminds me of this one I saw an ad for recently: https://revox.com/en/tape-recorder/285/b77-mk-iii-stereo-tape-recorder

They thought this will make it more challenging! Imagine the assembly line of solder slingers attaching wires. In my limited experience, you find connectors used more in pro decks than semi pro decks. Like Ken once said, they had to keep them pro decks running so they need to be repaired quickly.

I was loaned an expensive tape to listen to, and even on a semi pro machine, yeah, I get it. I just don't have the budget for them.

Hey thanks Carl! Jupiter is missing you guys.

I thought I had all my caps in one box but found this small stash including Elna Silmic II and some Muse from the DAC build and mod days. I'll replace the small amount of LR and CEKU caps with the Silmic II. There are also a few LR and two CEKU on the line out board.

Aaron @ALL212 saves the day! Thank you, buddy! I was short four 33uf caps so he sent me some. He dug into his Gold reserves, Nichicon. All fini. Still works!