Akai X5000L Reel Machine - left side sounds dull

[canidoit]

I have been playing around with tape and it's really brought back some life into making music. I can really see the potential of loving the sound of tape except my tape deck and reel to reel are having issues.

I picked up the Akai X5000L from an old Reel to Reel collector over 10 years ago and now I have decided to start experimenting with it. I noticed the stereo image was off and after listening further, noticed one side was duller than the other side, causing the shift in center.

Do you think this is a simple fix, maybe clean the heads or demagnetise? I did notice a bit of corrosion on one of the heads, but I felt it with my hand, and it was smooth to the touch. Should I sand this down with ultra fine sandpaper, so that the heads does not damage my reel tapes?

Where would you get the parts for this type of machine? I would hate to give up on this unit.

 

[CalavoBob]

The tape to head contract is critical in getting high frequencies both into and back off of tape. First try cleaning the heck out of those heads with 99% alcohol using the old style paper stem Q-tips (not wooden stems). The tape to head contact can also vary across the head if it is not perfectly parallel to the tape so get out the jeweler's loupe and the alignnent tape to check that.

It is possible to relap heads if they are grooved from long term tape use, however due to the limited depth of the gap it can only be done once or maybe twice. Keeping track of the screw, washer, and wiring sequence, remove and unsolder the heads. Using approx 6 oz of pressure you can go through a sequence of wet sandpaper from (depending on the depth of the grooves) 220 grit to 330, 400, 600, 800, and 1000, finishing off with felt and Wrights silver polish for about 10 minutes. Continually observe the grooves, and scratches using a jeweler's loupe during this whole process. Move up the grit numbers as you observe the grooves and scratches disappear. This is a very delicate procedure in which you gently sand (with a little water) in 3-4 inch circles on a pane of glass, while rocking the head slowly back and forth while circling. Then turn the head around 180 degrees and continue. Try your best to maintain the parabolic shape of the original head contour. You need to very carefully replace them back into their correct position using a combination of pre-dissasembly close-up photos, and then marking their faces with a black sharpie marker, running tape (discard this tape afterwards) and observing the wear pattern through the black marker. Get the wrap, height and azimuth visually, then clean them up with 99% alcohol, demagnetize them and use an alignment tape from 1kHz through 15 kHz to finish the alignment. If slightly pressing the tape on either side of the head increases output, then the head is not centered on the tape. The polishing procedure takes about an hour per head, but getting them back into the head assembly and aligned properly can take a couple of hours.
Its amazing how good they can sound after doing this., but its a tedious procedure.

I've been doing some reading in old recording magazine articles about studies of head geometry affecting the countour effect (head bumps). Sharp discontinuitites across the face of a playback head are known to increase the level of the peaks and valleys in bass response. Studer tape heads have a very gentle arc to them with no sharp outside edge where the tape leaves the head, and these macines famously have a neglible contour effect of about 1/2 dB. Machines like Teac 3340s have a narrower parabolic shape, with an almost square edge at the sides, and the playpack heads are seen to have contour peaks of 2 to 3 1/2 dB. Because of this I have recently lightly rounded the outside edges of heads on these during relapping and have found a slight improvement of about a dB in their contour effect. Has anyone out there done this too? What kind of results have you gotten? I'm curious.

 

[CalavoBob]

I found that article about head geometry. Its by Peter Butt in the Dec 1975 issue of REP magazine. He had a lot of experience optimizing high speed tape duplicating machines, but he also researched about pro tape decks. He also talks about gap scatter, azimuth tables, and fringing effects. With respect to head relapping he said that if you can minimize the wrap angle, it reduces the contour effect (head bumps). He suggests that sharp edges of the head contour should be removed, even if they don't contact the tape. I try to do this when I relap heads. If you're looking for a reliable pro to relap your heads, contact John French at JRF Magnetics.

 

[RoadrunnerOZ]

Relapping heads requires a lot of time and patience, progressive microscope checking and the right materials. The final finish in a professionally done relap is at 1 micron (equivalent to 14000 grit). You can get lapping film but it’s expensive and only works for a few passes unlike wet and dry sandpaper. The last stages of a relap are approx 2000grit (1800 is 9 micron) 4500 (5 micron) and these are available as wet and dry - then 1 micron (14000 grit) lapping film