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  #1  
Old 03-20-2017, 10:00 AM
knownothin knownothin is online now
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TEAC A-6300, 2 O'Clock Position

Okay, teach me how to set the 2 O'Clock position.
See picture for the procedure below given to "real" technicians.

I don't have the Teac test tape.
Will the correct calibration tape be MRL's 1/4" / 7.5 ips / NAB / 250nWb/m for $129?
Thank you.
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File Type: jpg out01.jpg (70.7 KB, 39 views)
  #2  
Old 03-20-2017, 12:05 PM
earczar earczar is offline
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If you learn this technique your going to need to change your name. Do you have a millivolt meter,oscilloscope and function generator because that is the minimum that you will need to calibrate. The 2 or 3 oclock is an aproximation spot where your output dials would have sat indicating 0db when using the original teac test tape, but if your using 250 nwbs test tape then would indicate +3dbvu. Its a constant reference point that isnt moved after set. But that is not the first step, and skipping steps will run you into big trouble. What you need is someone here to walk you threw it, because personally just reading the manual doesnt cut it. This can get expensive just a heads up, and sending it off is generally cheaper and if your using technicians here on tapeheads then will yeild greater results. But i dont blame you for trying.
  #3  
Old 03-20-2017, 01:13 PM
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macman007 macman007 is offline
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The 2 O'clock position is approx the #7 on the 3 controls, Mic, Input, and Output. When setting the specified and maximum positions, you are setting the reference signals, once you have the settings correct at the 2 O'Clock position, you leave them alone, and do not move them during the rest of the procedures. Maximum level is set with the corresponding control all the way to the clockwise position. Once you set that, reducing the control to the 2 O'Clock position provides the specified level , you set and forget for the rest of the procedures. Some decks will provide the specified level dead on the 2 O'clock position (#7), others are to a hair either before or after the '7'.

Some decks will specify the 3 O'clock position in calibration, this would be the #8 on the dial, perhaps a c-hair before or after it...

Again, once you have the correct measured signal corresponding to the clock position, you do not move the control again for the duration of the reproduce AND record calibration procedures.

Hope this clarifies things a bit..
  #4  
Old 03-20-2017, 01:22 PM
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dhnash dhnash is online now
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The white arrow in the attached photo shows the 2:00 position.
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  #5  
Old 03-20-2017, 02:08 PM
knownothin knownothin is online now
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Please refer to the picture in the first post.
(1) How does one connect a 10K ohm load to the output jacks?
(2) What is used to measure the -2 dB and -8 db levels at the output jacks?
(3) Which is the correct test tape to buy for 7.5 ips? I use a lot of Scotch 207.
Thank you.
  #6  
Old 03-20-2017, 02:57 PM
earczar earczar is offline
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Heres a link to a leader millivoltmeter this is what easily measures db.
http://pages.ebay.com/link/?nav=item...alID=EBAY-ENCA

You connect a 10k resistor inline with the positive terminal, i wired mine within the meter itself. Personally i used a 7.5 ips 250nwbs mrl , but many suggest 200nwbs , because its easier to read the levels,meaning you just go by the manuals levels instead of accounting for the increase of +3db from using a hotter mrl tape. there's are also multi speed tapes which might be worth getting in case you want to do 15ips, if i get another i would buy two speeds. although you still can use the 7.5. To do the job.

Hope this helps
  #7  
Old 03-20-2017, 03:37 PM
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tapetech tapetech is online now
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Quote:
Originally Posted by earczar View Post
You connect a 10k resistor inline with the positive terminal,
"inline" indicates a series connection which is incorrect. You want the resistor in parallel with the meter input. (between the positive and ground terminals of the measurement meter)
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  #8  
Old 03-20-2017, 03:46 PM
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tapetech tapetech is online now
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Quote:
Originally Posted by knownothin View Post
Please refer to the picture in the first post.
(1) How does one connect a 10K ohm load to the output jacks?
(2) What is used to measure the -2 dB and -8 db levels at the output jacks?
(3) Which is the correct test tape to buy for 7.5 ips? I use a lot of Scotch 207.
Thank you.
Since you are using an old tape (207) to record, you should buy a 200 nWb tape from JRF and jsut follow the manual's instructions. pn for tape is 21T104.

Set the output knob to 2 o'clock, play the tape and adjust the play cal pots for -8 dB output. If you buy the meter on the link, use the bottom red scale to measure -8. No conversions needed if using the test tape indicated. That same tape should indicate zero VU on the tape decks meters. Always keep the out knob at 2 oclock when calibrating.
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Tim@MusicTechnology.com**** WWW.MusicTechnology.com
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  #9  
Old 03-20-2017, 03:58 PM
knownothin knownothin is online now
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This is great info, and I know it's been asked before, and you probably get tired of it too.

I just ordered an LMV 185A (supposedly working fine).
Now have found an older post and am reading that a 75K ohm resistor should be used instead of 10K ohm, and need to get a dual banana clip too.
Also need to take the plunge and get a test tape, the 200 nWb variety.
I have an oscilloscope, but have never turned it on or used it (yet).

Do I just take a 3' cable with RCA's at one end, and solder the loose ends to the dual banana clip and resistor?


Thank you.
  #10  
Old 03-20-2017, 08:21 PM
earczar earczar is offline
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Are you sure it wasnt 7.5k i think thats what Sam recomended because thats what i used, just found out though about the parrellel connection, i guess i misunderstood that part, thnx Tapetech. For your oscilloscope Check for xy mode or learn about it while you wait for tape, watch youtube videos on lissajous patterns. You need a function generator as well. Unless you mentioned having one. And good idea with the 200nwbs it will give you less headaches.

Last edited by earczar; 03-20-2017 at 09:53 PM.
  #11  
Old 03-21-2017, 12:10 AM
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Skywavebe Skywavebe is offline
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Quote:
Originally Posted by knownothin View Post
Please refer to the picture in the first post.
(1) How does one connect a 10K ohm load to the output jacks?
(2) What is used to measure the -2 dB and -8 db levels at the output jacks?
(3) Which is the correct test tape to buy for 7.5 ips? I use a lot of Scotch 207.
Thank you.
The 10 Kohm is a load that the deck is suppose to work into. It is a 10K resistor that is attached across the hot terminal and the ground on each RCA jack. The resistor can also be attached to the AC millivolt meter input so that any RCA you plug that cable into will have a 10K ohm load.

What do you measure the -2 and -8dBu signal on.? The above mentioned AC millivolt meter which I often times recommend the Leader LMV181A which is what I have on my bench. All benches have 1, 2 or more of these.

The correct test tape is the one closest to the original one that the manual recommends. That is the 200nWb/M flux density tape at 7.5 IPS. Getting the 250nWb/M is the wrong one as it is for 1/2 track decks plus using the wrong tape will require you to make offset calculations- this is a thing only an experienced guy will do as it will just complicate the procedure for you and you don't need that at this stage of the game.
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Past Teac/Tascam Lead Service Technician at Chicago Factory Service still doing repairs.
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  #12  
Old 03-21-2017, 12:18 AM
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Skywavebe Skywavebe is offline
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Quote:
Originally Posted by knownothin View Post
This is great info, and I know it's been asked before, and you probably get tired of it too.

I just ordered an LMV 185A (supposedly working fine).
Now have found an older post and am reading that a 75K ohm resistor should be used instead of 10K ohm, and need to get a dual banana clip too.
Also need to take the plunge and get a test tape, the 200 nWb variety.
I have an oscilloscope, but have never turned it on or used it (yet).

Do I just take a 3' cable with RCA's at one end, and solder the loose ends to the dual banana clip and resistor?


Thank you.
With many answers- they have to be used in the context of the question. I place a 7.5K resistor on a LMV181A input to reduce noise for the measurement of dolby test points for cassette decks and like deck of the X1000R points 14 and 17. This meter is not the one that I measure the deck output with. I use another LMV181A to each day calibrate the M826A Teac test set and then use that test set to measure the levels of decks- this is bench 2. This is the same test set I used at Teac on my bench there. On bench 1 I use an Audio Precision 1 plus unit with appropriate load. Teac decks are typically hooked to nominal loads a 47Kohm and are expected to drive a minimum of 10Kohm. So that is why in test set up they use the 10Kohm value which of course should be resistive and not inductive.
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Best regards,

Sam Palermo, BSEE and 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 still doing repairs.
http://s609729863.onlinehome.us/tape...uipment-repair
Now accepting MC, Visa, Amex & Discover Cards!
  #13  
Old 03-21-2017, 03:28 AM
knownothin knownothin is online now
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I appreciate the clarification.
In the link below there are pictures of a set-up with the resistors and cables.
Is this how it is done for the output testing of the left and right channels?
Oh yes, and the wattage of the 10k ohm resistor?
Thank you.

http://www.ebay.com/itm/Leader-LMV-8...MAAOSwnHZYgOEy
  #14  
Old 03-21-2017, 08:40 AM
knownothin knownothin is online now
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An excerpt from a supplier:

"These are NEW exclusive short test tapes, recorded for us by MRL, which contain all the tones you need to set up reproduce equalization ("EQ") head alignment and reference levels. Tones are 50Hz, 100Hz, 1kHz, 10kHz, and 16kHz for alignment, plus a section of white noise, recommended by MRL for fine azimuth and phase adjustment, and a 20hz-20kHz continuous sweep to test frequency response."

Why doesn't it include a 400Hz tone (per the procedure given in the first post, this is required)?
Why doesn't it include a 3000Hz tone for use with a wow/flutter meter to set accurate speed?
Thank you.
  #15  
Old 03-21-2017, 10:05 AM
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tapetech tapetech is online now
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Quote:
Originally Posted by knownothin View Post
An excerpt from a supplier:
Tones are 50Hz, 100Hz, 1kHz, 10kHz, and 16kHz for alignment,.
That tape is likely 250 nWb/m (ask the seller), so you would need to modify the calibration a bit: Play the 1KHz tone. Instead of adjusting play cal for -8dB on the external meter, you adjust it for -6 dB. And that same tone should read +2 the deck's VU meter.

And play the 1kHz tone to check speed as well. Measure the tone frequency with your DMM and see if it's within the published speed spec for the 6300 (+/- 10 Hz). BTW, there is no specific control in the deck to "adjust speed" (as you indicated).
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Last edited by tapetech; 03-21-2017 at 10:17 AM.
  #16  
Old 03-22-2017, 02:17 PM
knownothin knownothin is online now
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Okay, I am trying to get the 200nWb/m tape, but MRL has been down for a while redoing their machines.
So it doesn't matter then whether the test tone is 400Hz or 1000Hz to perform this task, I still try for -8 dB on the external meter and 0 on the VU, correct?
  #17  
Old 03-22-2017, 03:06 PM
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1000 Hz will work fine. Since 250 is now the "standard" operating level, MRL may not make or sell any more 200 nWb/m tapes. Instead of -8dB/"0" VU you adjust for -6dB/+2 VU (with the 250 tape). Pretty simple. Then you just follow the service manual exactly for the rest of the adjustments.
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Tim@MusicTechnology.com**** WWW.MusicTechnology.com
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  #18  
Old 03-23-2017, 10:19 AM
Audiomayvin Audiomayvin is online now
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Hi!
You say"Instead of -8dB/"0" VU you adjust for -6dB/+2 VU (with the 250 tape)."
Why? If you calibrate with the 250 tape at -8dB your machine will be calibrated for 250 nwB/m. What's the problem with that?
The 207 was 3M's answer to Ampex's 406(or was it the other way around?).
The 406 was the tape for 250 nwB/m.
There seems to be some confusion about the position of the o/p pot.
Over the years there were only 2 versions.
One was turn the pot to maximum(to give -2 dB) and then turn down the pot to reduce o/p by 6 dB. No actual position of pot was given.
The other version was to position the pot at 3 o'clock.
On a lighter note, the difference between a tapehead and a plumber is one letter-R
To quote "Also need to take the plunge"
All the best,
Leon(The Audiomayvin, Montreal(514)739-5403)
  #19  
Old 03-23-2017, 11:15 AM
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Scotch 207 tape may work with a 250 operating level. However, Scotch 207 will certainly have more distortion than today's "regular" tapes like SM911. If I were setting up the deck at my shop, I would for sure try a 250 op level for the 207 tape, but I would test distortion and saturation levels and make sure they are good before giving it back to the customer. The OP does not have the ability to test distortion and saturation levels. Also the OP will not know how to correctly set bias in his deck, so his distortion levels with 207 may likely be higher than normal. Telling the OP how to correctly set bias is beyond his capabilities right now (he's a beginner). Also we don't know the condition of the heads. If they have HF loss, then that can lead to more distortion in record (due to the OP underbiasing the 207 tape when attempting to set up the deck).

2 o'clock on the output knob is the "calibration" setting for that Teac model. That is where you leave the knob for calibration. The meter indications in play monitor will only be correct at that setting.
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Last edited by tapetech; 03-23-2017 at 11:29 AM.
  #20  
Old 03-23-2017, 11:30 AM
Audiomayvin Audiomayvin is online now
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Hi!
The 207 wil not "may" work but will absolutely work at 250.
All tapes that are specified to work at a certain level imply one thing. And that is that 9 dB above that reference point you are going to hit 3% THD.
Whether it is SM911 or 3M 207. That's how each tape's reference point is established. I have tested that and it is so.
All the best,
Leon(The Audiomayvin, Montreal(514)739-5403)
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