Is alignment tape absolutely indispensable?

[Selvagem]

Hello everyone.

First of all I would like to apologize for bad English, I am using the Google Translate tool.

I'm Brazilian and new to the Reel to Rell world. I bought a used Akai GX-625 and want to leave the same effect just like the day it left the factory. When I received the same, I realized that the work will be arduous ... it was quite dirty and with several capacitors and bad transistors on the amplifier board, but fortunately this is all original, all the seals of the heads of reproduction / recording intact, I believe that never has been previously opened. Initially I did a nice cleaning and lubrication on the 3 motors and by all the paths where the tape goes.

After everything clean, I made the purchase on Ebay of this Kit here:

https://www.ebay.com/itm/PREMIUM-Re...07?ssPageName=STRK:MEBIDX:IT&_trksid=p2057872. m2749.l2649

My idea was initially to get this kit to only then start working on it, but anxiety did not allow me ... so I decided to use the BC 549C and general purpose electrolytic capacitors instead of the C458 transistors. I made the exchange of all the electrolytic capacitors that I will receive in the future (the seller sent a PDF with the position of the capacitors and the transisotres that need to be changed) and after the exchange the Akai came back to life!

Well, it is my experience in repairing a Reel to Reel and I am honest in saying that I do not have much experience in repairing audio equipment, I am more focused on repairing video equipment. I imagine I have everything I need in instrumentation for the correct repair (oscilloscope, audio analyzer, audio generator, etc).

Returning to the Akai, when connecting the audio generator via line inputs, at a frequency of 1Khz and 0dB and turning the key to Source it is possible to verify that the reading in the Vu is unbalanced, one channel is -1.5dB in relation to the other . Even so I did a recording test and it is possible to perceive a slight loss of treble in relation to the source signal (using music as source) and a small imbalance between the recording levels of both channels using the audio generator as signal source .

I wonder if it is possible to try to start fixing these problems without an alignment tape or if everything is wasted without it?

Thank you in advance.

 

[GPS16]

Hi Selvagem,

The loss of HF response may be due to the tape stock used during the recording. The "Record" set up of the machine will vary with different tape formulations. The whole HF response of the recorder will depend on the alignment of the heads to each other (Play Head to Record Head). To get compatibility from one recorder to another OR the correct HF Response from Pre Recorded tapes, the Azimuth needs to be set "Spot On" to 90 deg to the tape travel. By spot on we are talking Deg/Min/Secs accuracy. This can only be done with a calibration tape!!!

If you are familiar with Video (VCR), then azimuth is used on the video heads to "Force" heads to read their own tracks only without "Guard Bands" between them. For a HiFi Sound VCR this is taken a step further with Azimuth giving the Video/HiFi Audio track selection as well.

As you have the instrumentation, I would get hold of a service manual and try setting the machine up to new stock tape for recording purposes. LPR35 seems to be the tape of choice at the moment. You will still be left "hanging" as far as the playback side is concerned as the Play Azimuth will not be touched (you will be doing an "Internal" alignment only and setting the record head to the play head). The playback level cannot be done as this also requires the Reference Tape to give a calibrated magnetic level in nWb/m. So the record level will be "Internal" too.

Basically, without a Reference Tape, you can only set up the Record Side of the machine to the required tape stock and the "Current Settings" of the playback side of the machine which may be wrong in the first place.

It has been said elsewhere on the Forum, and personally I totally agree, there is no get around!!!! I have an MRL Tape for this purpose which is stored in a cool dry place away from any electronics. It stays there until required.

Sorry if this is not what you wanted to hear but "That's Life!!!"

Cheers.

GPS16

 

[Selvagem]

Thanks for the reply. I would like to supplement my previous information. At the moment I only have old tapes to test both the reproduction of these tapes and the recording made on them (I have some old virgin tapes as well). He did not want to touch any setting without first having the right material for a job well done. In my case now, without a standard test tape, I can not know if the problem is in the playback or the recording, because I must first make sure that the reproduction is perfect, and without the test tape this is impossible, correct?

As I mentioned, the difference indicated in the VU of the deck between the channels already indicates something wrong / misaligned. As I have bought and is on the way a kit of components of better quality for the PB / Record card I will wait for them to arrive and after exchanging I will check if this difference remains.

I believe that I will never use on this Deck a tape recorded on another Deck, because in Brazil these equipments are very scarce and I will not buy old recorded tapes, since they must be in the majority already deteriorated.

As I understand it, you could adjust the recording part without a standard tape, but in this case you would be performing the perfect recording / playback match only on this unit, correct?

I clearly notice that the sealing of the playback / recording head is intact, which is a good sign. Do you think that a new adjustment of azimuth (made with a standard test strip) could compensate for a possible wear of the head? Yesterday, for test purposes only, I recorded a test signal of 15Khz - 15dB and monitored at the line output the figure of Lisaujous and it was correct (in phase).

I imagine that if component wear does not affect the mechanical set up of the head assembly they would still be perfect and only bias adjustments, etc., will be needed. for the tape I'll use from now on, but if I do, I'll never be sure everything's perfect, right?

Another thing, since the tape used has a direct influence on the quality of the recording, you do not have to make any adjustments, I need to define and buy the tape that I will use for future recordings and on this tape I will perform all the recording tests, correct?

The tape that I have access here in Brazil to buy new is the RTM SM 468, is it a good option?

Best Regards.

 

[twiiii]

Absolutely, You cant determine what wrong quickly with out one.

 

[Selvagem]

Thank you for your help. I have already purchased an MRL 21T104 tape and now I have to wait for your arrival in Brazil. I also bought a demagnetizer.

 

[vwestlife]

Adjusting the azimuth by ear to a good-quality commercially pre-recorded cassette is good enough for all practical purposes. Sum the left and right channels to mono and then adjust it for the brightest sound (best treble response). Getting the azimuth set correctly will do wonders at improving Dolby NR decoding.

What a test tape does help with is adjusting the motor to run at exactly the correct speed. But again, you can get pretty close by using a known-good pre-recorded music tape and comparing it to the same song on CD.