Reel To Reel Servicing

Discussion in 'Tape Recorders' started by NewMedia, May 14, 2006.

  1. NewMedia

    NewMedia Active Member

    I'm in the process of refurbising my Pioneer RT-909 Reel to Reel tape deck, either myself, from the service manual, or maybe I'll ship it out to an experienced technician who is familiar with this unit, but have searched and searched and Googled to no avail for a Service facility.

    Anyone know where I can find a reputable outfit to calibrate and tune up my Pioneer 909 ?


  2. RemyRAD

    RemyRAD Member

    Oh I'm sure I can help you out with the Old Pioneer? Are you actually in or near Ocean City Maryland? Either way, I can personally direct you how to tweak your machine up and/or refer you to Protech services in Wheaton Maryland.

    Tweaking an analog machine requires a head demagnetizer, calibrated alignment tape, volt meter and/or analyzer, maybe an oscilloscope?

    Generally you can only adjust the record section of any tape recorder for only a single tape formulation from a single manufacturer. Switches that select between different tape formulations are never on the money. But when all is said and done, generally most any tape recorder should be able to deliver a response of 50 -15,000 hertz + or -, 2 DB, with about 45 DB signal to noise ratio (without noise reduction) with reference to a peak recording level of 3% total harmonic distortion at 1000 cycles. Generally tape manufacturers will indicate how many DB over bias at 10kHz (depending on the head gap and impedance of the head) they feel presents the optimum compromise for their formulation.

    Remember never to adjust the low-frequency equalizer's on your playback cards to the low-frequency tones on the calibrated test tape. You can only do that if your particular calibrated test tape has been compensated for "head fringing effect". Otherwise you only adjust the playback low-frequency equalizer's while doing your record calibrations, only then adjusting the low-frequency equalizer is accordingly. An innocent and frequent mistake made by some of the best technicians out there. Yup, it's true.

    If you happen to use some of those old "latest generation" hot recording tapes made by companies like Ampex, Scotch, AGFA, and if you happen to be using that kind of stuff, you may notice that your tapes do not seem to fully erase. Unfortunately that scenario happened to many tape machines that could not develop enough erase head current to fully erase the tape! We had just that problem at Scully in the early 1980s with our 280B! We tried numerous other heads made by other manufacturers but still no luck. I believe we did discover that the only head that would function was the "Wolke" full track width head. The same head used by our competitor at MCI, that we never employed at Scully. So we only recommended the older formulation tapes.

    Still, it's fun and gratifying to tweak your own analog machines as there is no exactly right way to do it. There are at least 3 popular ways to adjust record bias with only a volt meter or even just your ears! you can even use the tape recorders own VU meter to adjust record and play back! The coolest thing about analog is: You can optimize it for different musical genres. That's the Art of it.

    A tweaker from way back
    along with final test technician and quality control manager at Scully 1980
    Ms. Remy Ann David
  3. NewMedia

    NewMedia Active Member

    Hi Dooby <g>,

    Wow, I had no idea that one could make recording adjustments using just a voltmeter. I do have an oscilloscope, but no tone generator but could pick one up on eBay cheap I'm sure, that is, if more than the voltmeter would make a huge difference.

    If however I can achieve some decent results with just a voltmeter that's even better.

    You said you could elaborate, or is this info already archived somewhere I could see it?

    Many thanks in advance.

    Ocean City, New Jersey

    p.s. maybe I should send out the unit, but on the other hand I'd love to tweak on my own (no pun intended, or innuendoes) ...with the voltmeter, that is! <GG>
  4. RemyRAD

    RemyRAD Member

    The information may in fact be archived somewherehere @

    Now let me see if I can give you a little bit of enlightenment?

    1. De-magnetize all of the heads and tape guides, taking care not to scratch the surface of the heads. Pulling the de-magnetizer away from the heads very very slowly until the de-magnetizer is at least 6 feet from the heads. No clean the heads with a soft cardboard sticks Q-tip with 91% Isypropel alcohol, not common rubbing alcohol which is only 70% and includes skin oil and stuff.

    2. Load your appropriate speed test tape on the take up side of the recorder and rewind it onto your empty take up reel. At 7 1/2 and 33/4, you will observe a full volume level set tone. Your volt meter should agree with the VU meter, as per the manufacturers specified output voltage.

    3. All slow speed alignment tapes of 71/2, 3 3/4 IPS run their frequency response tests at -10 DB with reference to 0 DB so as not to saturate the tape. Only alignment tapes manufactured at speeds of 15 and 30 IPS run their frequency response tests at full 0 VU. This is assuming that you are using one of the older generation reel to reel tapes that record 0 with a reference of 250 NanoWeber's per meter. Indicating that the tape that you are recording on is capable of over recording 3 DB over older standard formulations.


    5. During the extended 10kHz azimuth adjustments tone, connect your single bold leader to both left and right output channels and adjust the azimuth our greatest output level indicating a perfectly perpendicular track to the tape and adequate in phase response.

    6. Now it's time to monkey around with the record settings. Load up a real of your favorite brand and formulation of recording tape. Keep in mind that when you adjust the recording response of the machine is only for that brand and formulation of recording tape. You're settings will be inaccurate with any other brand or formulation of recording tape. This is all assuming that you have already completed playback alignment with a calibrated tape and volt meter.

    6. Either utilize an actual hardware oscillator or you can use your computer sound card and software to generate your sinewave tones. Yes that's right. Start with a 1kHz sinewave. It would be preferable to know what the output level of your sinewave is? Is it 1.25 volts or .3 volts? Input that tone into both of your input channels of your analog tape recorder and set your analog tape recorder to input monitor source.

    7. Make sure that the meters are indicating 0 VU on both meters. If not adjust the appropriate input volume controls so that they match.

    8. Now role record and switch your recorder's monitor switch to tape monitor. You may not see the same volume level playing back as you are recording. You may also be hearing some of the analog artifacts such as hisss and "bias rocks"?

    9. If you can locate your recorders internal record level controls, you can now set them so that the playback level equals the input source level. Very good.

    10. Bias adjustments will affect high frequency response adjustments as they are interactive. The key here is to adjust for the best compromise for your type of music. To properly adjust the bias first, lower your recording level to -10 observable on the recorders meter. Make a note of the 10 DB drop on your voltage on your volt meter. It is at this -10 DB that we will adjust the bias and record frequency response.

    11. Now set your oscillator to 10kHz, making sure the input level is still at the -10 DB level. Now locate that channels bias miniscrewdriver adjustment . Start turning the bias adjustment from full counterclockwise to full clockwise while watching the VU and/or the volt meter. You will discover a peak in level at a certain point in the rotation of the bias adjustments screw. Go back to that peak. Now increase the bias adjustments screw until the 10kHz tone drops by 2 DB. This was the general excepted setup procedure for tapes made by Scotch and Ampex with formulation numbers of 206/207 by Scotch and 406/407 by Ampex. They're hotter mastering tapes frequently required a 10kHz over bias by 3 to 4 DB which were Scotch 226/250 and Ampex 456/996. Ditto for the AGFA 468.

    12. Now that you have adjusted your bias for 7 1/2 and 3 3/4, you can now go back to your 1kHz reference tone and run your frequency response test up towards 20kHz. Adjust your records high-frequency equalizer's or as flat a high-frequency response as you can get.

    13. Now you are ready for your low-frequency playback equalization adjustment! Start recording at your 1kHz reference tone. Sweep the oscillator down towards 100 hertz and from there down towards 20 hertz. It is within that range that you will adjust the low-frequency playback equalizer's to provide the flattest record to playback response.

    14. If you decide to make fees adjustments at 15 or 30 IPS you will make all adjustments at 0 DB.

    This is the basic alignment procedure and I could go into finer detail here but I won't. So now you have all the information you need to truly screwup your reel to reel recorder. With any luck, you may even have trouble noticing the difference between input source monitoring and tape playback?

    Makes me almost want to do it again myself?
    Ms. Remy Ann David
  5. NewMedia

    NewMedia Active Member

    Hi Remy Ann,

    Wow, you really (Reelly ;-) went the extra mile here to share your wisdom and procedure. I am printing this out and saving it as well to my PIM/CRM as invaluable notes. One thing you say, without even beginning the overall outlined procedure was your step number 9 (...number 9, number 9, number 9) as you sate the following:

    9. If you can locate your recorders internal record level controls, you can now set them so that the playback level equals the input source level. Very good.

    I already have observed, but did not realize it's importance, that when I adjust my recording levels to average between say -3db and 0, and my peak record levels to max at say +3db (all this per the owner's manual) that upon pressing the "tape/source" toggle push-button on the R2R that the playback levels are dramatically lower on the VU readout, way way down around -20 to -10 or so!!! The really strange thing however is that to the ear there does not seem to be any difference in volume or in sound quality. Could it be I've attended way to may live rock concerts and sat in the front rows, been body-shaked by the deafening throttling at the funny-car drag races, lit off way to many M-80's against the surgeon generals warnings, passed around way to many ro@ch clips, downed lethal doses of the beloved 714's, and raced motocross the first half of my so called life to know better? Maybe all that wonderful flanging FX I think I'm hearing is all in my head, lol, I don't know. The secretary will disavow any knowledge of this mission <g>. But on the face of it, this huge difference in VU seems odd.

    OH, HOLD ON. Just had a wake-up reality check <g>. You know what, it's my stupidity factor again. Just realized upon confirmation of all the above that the playback VU readouts are fully controlled by the "Line Out" pot, LOL. Oh well, at least I caught myself, i.e., after all no huge diff between record and playback VU as the playback VU is simply a function of the output level pot. LOL. Never mind, lol.

    One unarguable fact however still remains Remy Ann. That is the kind and committed effort with which you penned your comprehensive and detailed reply explaining to me (all of us) the general procedures for preliminary calibrations of the heads. You have certainly succeeded in challenging me to the task. I'll have to study your outline, set aside a few uninterrupted hours, and tackle this worthy endeavor. Many thanks for you dedication to this forum and to my questions. I clearly owe you one or more. Paybacks are hell, but considering all that Karma I still have to work off in my more or less still a little rebellious adult life, could end up down there if I don't balance out all the mischief from my teen years by helping others today as an elderly 51 year old still wild to the core <g>.

    So 'nuf said, and have digressed, but wanted to reply to your wonderful post in at least equal dignity, even though my ranting is of little value compared to your vastly informative volume of such helpful information.

    I'm looking at my beautiful beast as I type, the Pioneer 909 as exemplified for posterity here: R2R 909 A.jpg
    ...against the picturesque sky background.

    It calls out to me to grasp the NAB reel hubs, perfectly sized for the human palm to gently spin forward and back while monitoring via my amp to hear those incredible time-warped slow-mo hand-turned forward and back sounds. How cool indeed. You don't get this visceral exhilaration any other way I know. Cuing the reels by hand and actually hearing the beautifully altered sound out. Wow. It's so surreal. A beautiful thing. Can't get this off my hard drive the same way. I can't even touch the hard drive, let alone spin and cue it by hand!

    So I digress, but still love this wonderful machine. It's so fascinating to me that a mechanical device could and still can yield such sounds, all without integrated chips, ram, no moving parts of today's electronics! It was the height of engineering of the day and quite an accomplishment of the reel to reel world.

    Oh well, back to setting up my cube as pictured here:
    ....and my PowerMac outputs to my Gemini FX mixer which is eagerly awaited from the UPS truck any day now, I can hardly wait!


  6. RemyRAD

    RemyRAD Member

    John, yes those were beautiful machines and few people will notice the dual capstan Drive! And if my memory serves me correctly, I believe both pinch rollers engage regardless of whether the machine is rolling forward or in reverse? Making that a closed loop drive, sort of like the 3M iso-loop system. That made for more consistent head alignment and wear.

    One thing to keep in mind is that there were really 2 popular ways to align a machine. One was the cheap fast and dirty way of relying on the machines own meters along with an oscillator, a test tape and nothing else. Then there was the more competent method of utilizing a third harmonic distortion analyzer, not a "THD" analyzer. Along with the other requisite volt meter and calibrated alignment tape. When I worked for Media Sound in NYC, we didn't have time to bother with the more sophisticated alignment of the multitrack machines before each session. We just didn't cheap, dirty and fast method of the onboard machine meters. It was good enough for rock and roll! Besides, Kool & the Gang, Barry Manilow, Maynard Ferguson and others didn't seem to mind?

    I never much liked recorders that had a non-calibrated playback level control! Sure, you could scribble upon the electronics for the proper calibration point but it never quite stayed there. That's why all of the professional machines all had a detent calibration position along with the variable capabilities. Or just the internal controls that had to be accessed by "Little Greenies" (by Xelite) within.

    I could have gone into greater detail as well but since I am a lazy bitch, I didn't.
    Ms. Remy Ann David
  7. NewMedia

    NewMedia Active Member

    Thanks again RAD for your great insights, hindsight, and foresight!

    Much appreciate hearing from someone like you that really knows her stuff.

    You are truly a great asset to this forum.

    A million thanks!
  8. RemyRAD

    RemyRAD Member

    That is a great picture of Mr. Windows! Looks like a picture I had taken around the age of 18 or was that 40? Maybe both?

    Combustible concoctions confusing critters
    Ms. Remy Ann David
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