Tip from some one who has been maintaining R2R machines for 35 years. With A/B 77s & PR99s, indeed any other pro-sumer machines. Lay them on their back to do the adjustments. It means 1. The load on the bearings is even around the bearings and the pinch-roller pressure is not fighting gravity: Means better W&F - will help that flutter (evident by the characteristic L to R waveform shake relative to the triggered waveform on the scope - common in lesser spec machines) you see on the scope and will aid setting the azimuth up. 10kHz is my preferred frequency for azimuth. I then drop the sig gen to 1kHz to check I have the right peak and am not 180 degs out of phase. I also tweak the hf prior to azimuth to get the amplitudes of the signal the same - again aids line-up. Once azimuth is done you can go back and do a level/freq response adjustment in the normal way.
Thanks for the tips! When i switch from sine wave to square wave on the signal generator, the phase between channels changes a lot (given i already aligned them with the sine wave). Why would it be? thanks
I would appreciate a more detailed video on the azimuth taking into account all comments so far but do not forget the novice people with some basics to electronics. They fight to understand those vital issus of callibration and allignment. Thank you again to all of you that share your knowledge.
All I can say is, if ever I needed my hi-fi system fixing, your the man for the job, because I have complete confidence in your ability. You just know this stuff! lol, and Im not being sarcastic here, I really am impressed by not only your electronic knowledge, but your garage equipment too. It looks a proper workshop, strange looking gear everywhere, but only to a layman like myself..ha ha keep it up, I enjoy your work. Paul.
Its easier and accurate to set the azimuth with the X/Y-mode on the scope. Correct phase is shown as a line leaning 45° to the right. The more out of phase the more circular and leaning to the left.
Usually, you go for the level first on the waveform scope and then fine-adjust the phase with a Lissajous figure as best as you can. Because if you simply go for the 45° line, you might just be in relative phase but could still be off by a complete wave cycle which would reduce the level. You can see level in the Lissajous, but if your scaling is set to auto or something, you might not realize it. And the higher you go for azimuth alignment (as an example, Nakamichis are adjusted with a 16 kHz full track cassette), the greater the risk for errors.
Hi. Great video. Can you describe the AF Signal Generator? What other signal generators do you use? Plus, show how you plug in the oscilloscope to the Revox for people new to electronics. Thanks.
Now I wonder how you would adjust the azimuth for a variety of different reels I am looking to digitally transfer, I have a large collection of second generation safety copies that were recorded on around twenty different machines all with different azimuth adjustments. I would have to somehow test each and every reel to find the best setting, but the question would be how? In my case I could not use a single tone, what do you feel my best option would be?
Hi Simon, Regarding the bias HF signal, it's seems rather high in my opinion. Although I'm not sure what the relative amplitude of your test signal is? I'm in the middle of servicing my A77, and the 120Khz bias 'carrier' (as I call it), is about 100mV/160mV peak to peak (at CHI/CHII at line out) for a full 0VU modulation at 1Khz. I think they are ideally supposed to be circa 50mV (rms)? I did examine and tweak both bias traps - for the record amp, and for the playback amp. So mine seem okay. I did upload my work on my blog, but took it down until I finalise all the major work. Regards. PS: apologies if folk have already mentioned this, I haven't read the other comments.
I know this is 3 years ago. But I've been studying all I can about reel to reel tape head alignments. I agree that azimuth is a crucial alignment. I have found that one doesn't need all the very expensive eqipment but have good reliable equipment. O scopes and the like. I gathered some good information from your video. Thank you.
If you have a decent enough sound card in your computer capable of at least running 96 kHz, you can use software oscilloscope tools like AudioTester 3 to do a lot of the work. Then all you need is reference alignment tapes and a good true RMS volt meter.
@@svenschwingel8632 interesting information, how would you connect the RTR to your soundcard to measure the azimuth settings? Just via line outputs of the reel to reel straight into the soundcard? Cheers
@@brendanryan6363 I use test tapes with a full-track 10 kHz tone and connect the RTR or cassette deck to the PC's sound card via its line inputs. Then I use the software oscilloscope's X/Y setting to display a Lissajous figure. It is very easy to set the proper phase (which is the angle of the PB head) that way. Just aim for maximum output first and then finely tune the azimuth screw so the Lissajous figure gets as close to a 45⁰ line as possible.
Hello Simon, your work is really interesting, ask, do you inject a 16Khz hf signal from the function generator to the Revox input and compare with the tape output? Thank you
When you go to the playback head did you rewind the tape and playback the recorded 10khz signal. Also did you turn off the signal generator at the same time.?
That is not as service manual describes to do it. Service manual says use a 8kHz tape and adjust to get the maximun level at both channel. I do prefer a tape with blank noise recorded. Of course with a well recorded tape to test it.
Is it possible to perform this calibration without a test tape ? If a 10kHz signal is fed into it, can the record head azimuth be adjusted 1st and then the playback head azimuth ?
You need to set playback head to a reference first. If a three individual hed machine is being aligned , you could set the record head to pmatch the playback azimuth. But playback really would still needed to be done first to ensure good results on other machines.
You need the replay alignment set correctly in the first place. This can be done with a reference tape from a known good deck. This record alignment is to match the record head azimuth to the playback head.
For replay you need an LU tape. Once the replay side is lined-up you use a sample of your preferred tape for the rec side line-up. Tape type for azimuth isn't critical but for rec level/freq response and bias adjustment it is.
I've done this for various cassette decks, inc dual capstan machines. Indeed there is always this phase shifting between left/right channels and so taking the best center spot is something to aim for. Of interest is the noise here - appears to be the bias frequency on your 16 Khz signal/carrier? Personally, I like the two-sinewaves method over the lissajous figure method. Interesting video, thumbs up! ;o)
Interesting about the phase shift. That would ruin stereo imagery as it would be like having a speaker out of phase? I assume the level rape in definitely recorded in phase?
@@SoddingaboutSi Apologies for the late reply: We won't notice phase shifts at high frequencies. I'm not sure where we would begin to notice this, and where it ends. I'm guessing at say 30Hz ... 5Khz? At 10Khz and over? ... I don't think so, and in any case HF are usually transients.
@@SoddingaboutSi No, not American, I commented that because it reminded me of the anti-Christ. Could we call him the counter-Christ as well? And he's not bad at all, just revolves his thoughts in another direction as in counterclockwise. He'll be as wise as Christ too, that's for sure!
Tip from some one who has been maintaining R2R machines for 35 years. With A/B 77s & PR99s, indeed any other pro-sumer machines. Lay them on their back to do the adjustments. It means 1. The load on the bearings is even around the bearings and the pinch-roller pressure is not fighting gravity: Means better W&F - will help that flutter (evident by the characteristic L to R waveform shake relative to the triggered waveform on the scope - common in lesser spec machines) you see on the scope and will aid setting the azimuth up. 10kHz is my preferred frequency for azimuth. I then drop the sig gen to 1kHz to check I have the right peak and am not 180 degs out of phase. I also tweak the hf prior to azimuth to get the amplitudes of the signal the same - again aids line-up. Once azimuth is done you can go back and do a level/freq response adjustment in the normal way.
Wow,beautiful explanation.Makes perfect sense...Thank you very much
Thanks for the tips! When i switch from sine wave to square wave on the signal generator, the phase between channels changes a lot (given i already aligned them with the sine wave). Why would it be? thanks
Great video! Azimuth is so important, and not everyone maintains it properly!
I would appreciate a more detailed video on the azimuth taking into account all comments so far but do not forget the novice people with some basics to electronics. They fight to understand those vital issus of callibration and allignment.
Thank you again to all of you that share your knowledge.
Yes, this is a very useful video. Thanks!
All I can say is, if ever I needed my hi-fi system fixing, your the man for the job, because I have complete confidence in your ability. You just know this stuff! lol, and Im not being sarcastic here, I really am impressed by not only your electronic knowledge, but your garage equipment too. It looks a proper workshop, strange looking gear everywhere, but only to a layman like myself..ha ha keep it up, I enjoy your work. Paul.
Thank you for this.
Greetings from Russia. Thanks for the video. Soon I will head to adjust A77
Its easier and accurate to set the azimuth with the X/Y-mode on the scope. Correct phase is shown as a line leaning 45° to the right. The more out of phase the more circular and leaning to the left.
Usually, you go for the level first on the waveform scope and then fine-adjust the phase with a Lissajous figure as best as you can. Because if you simply go for the 45° line, you might just be in relative phase but could still be off by a complete wave cycle which would reduce the level. You can see level in the Lissajous, but if your scaling is set to auto or something, you might not realize it. And the higher you go for azimuth alignment (as an example, Nakamichis are adjusted with a 16 kHz full track cassette), the greater the risk for errors.
Hi. Great video. Can you describe the AF Signal Generator? What other signal generators do you use? Plus, show how you plug in the oscilloscope to the Revox for people new to electronics. Thanks.
Now I wonder how you would adjust the azimuth for a variety of different reels I am looking to digitally transfer, I have a large collection of second generation safety copies that were recorded on around twenty different machines all with different azimuth adjustments. I would have to somehow test each and every reel to find the best setting, but the question would be how? In my case I could not use a single tone, what do you feel my best option would be?
Very helpful. Thanks for sharing.
Hi Simon,
Regarding the bias HF signal, it's seems rather high in my opinion. Although I'm not sure what the relative amplitude of your test signal is? I'm in the middle of servicing my A77, and the 120Khz bias 'carrier' (as I call it), is about 100mV/160mV peak to peak (at CHI/CHII at line out) for a full 0VU modulation at 1Khz. I think they are ideally supposed to be circa 50mV (rms)? I did examine and tweak both bias traps - for the record amp, and for the playback amp. So mine seem okay.
I did upload my work on my blog, but took it down until I finalise all the major work.
Regards.
PS: apologies if folk have already mentioned this, I haven't read the other comments.
I know this is 3 years ago. But I've been studying all I can about reel to reel tape head alignments. I agree that azimuth is a crucial alignment. I have found that one doesn't need all the very expensive eqipment but have good reliable equipment. O scopes and the like. I gathered some good information from your video. Thank you.
If you have a decent enough sound card in your computer capable of at least running 96 kHz, you can use software oscilloscope tools like AudioTester 3 to do a lot of the work. Then all you need is reference alignment tapes and a good true RMS volt meter.
@@svenschwingel8632 interesting information, how would you connect the RTR to your soundcard to measure the azimuth settings? Just via line outputs of the reel to reel straight into the soundcard?
Cheers
@@brendanryan6363 I use test tapes with a full-track 10 kHz tone and connect the RTR or cassette deck to the PC's sound card via its line inputs. Then I use the software oscilloscope's X/Y setting to display a Lissajous figure. It is very easy to set the proper phase (which is the angle of the PB head) that way. Just aim for maximum output first and then finely tune the azimuth screw so the Lissajous figure gets as close to a 45⁰ line as possible.
Hello Simon, your work is really interesting, ask, do you inject a 16Khz hf signal from the function generator to the Revox input and compare with the tape output? Thank you
Its helpful. thanks!
Could you create a video on how best to calibrate a capstan motor speed?
I guess I missed the connections ....one probe on a output channel... and the other on a input?
Thanks Paul, it's very basic stuff in the scheme of things. I plan to to a full alignment on this machine once a calibration tape arrives from Russia.
Depends on the machine and what exactly needs doing?
When you go to the playback head did you rewind the tape and playback the recorded 10khz signal. Also did you turn off the signal generator at the same time.?
Playback head is kinda intrinsically involved in this process...
That is not as service manual describes to do it. Service manual says use a 8kHz tape and adjust to get the maximun level at both channel. I do prefer a tape with blank noise recorded. Of course with a well recorded tape to test it.
Is it possible to perform this calibration without a test tape ? If a 10kHz signal is fed into it, can the record head azimuth be adjusted 1st and then the playback head azimuth ?
You need to set playback head to a reference first. If a three individual hed machine is being aligned , you could set the record head to pmatch the playback azimuth. But playback really would still needed to be done first to ensure good results on other machines.
you need to first adjust replay alignment with a test tape, no?
You need the replay alignment set correctly in the first place. This can be done with a reference tape from a known good deck.
This record alignment is to match the record head azimuth to the playback head.
For replay you need an LU tape. Once the replay side is lined-up you use a sample of your preferred tape for the rec side line-up. Tape type for azimuth isn't critical but for rec level/freq response and bias adjustment it is.
Did you ever figure out what was causing the wave distortion ? I have similar issue. Thx
Yes it's basically wow and flutter and imperfect tape to head contact. If the head are warm it will be worse that shown here. Use a good unworn tape .
I've done this for various cassette decks, inc dual capstan machines. Indeed there is always this phase shifting between left/right channels and so taking the best center spot is something to aim for. Of interest is the noise here - appears to be the bias frequency on your 16 Khz signal/carrier?
Personally, I like the two-sinewaves method over the lissajous figure method.
Interesting video, thumbs up! ;o)
Interesting about the phase shift. That would ruin stereo imagery as it would be like having a speaker out of phase? I assume the level rape in definitely recorded in phase?
@@SoddingaboutSi Apologies for the late reply: We won't notice phase shifts at high frequencies. I'm not sure where we would begin to notice this, and where it ends. I'm guessing at say 30Hz ... 5Khz? At 10Khz and over? ... I don't think so, and in any case HF are usually transients.
Can u do this for cassettedecks to?.
John Kerkhof sure, for cassettedecks, 8 track tape, reel to reel and all devices with tape head.
@@gbrl_ht01 I don't recommend trying to do this with helical 🤣
hy i have revox a77mk4 and i have a problem, the vu meter in play mode not working, only in record mode working, so why?
Normal from memory. They are record level VU meters.
Oh I see, the tone you're using for the adjustment is played on a speaker, and your camera microphone pics up the sound...
Anti-clockwise? Never heard that term before.
That's because your a Yank!
@@SoddingaboutSi No, not American, I commented that because it reminded me of the anti-Christ. Could we call him the counter-Christ as well? And he's not bad at all, just revolves his thoughts in another direction as in counterclockwise. He'll be as wise as Christ too, that's for sure!
If you say so lol.
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