Cartridge pressure pad renewal

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centaur_qlf
ROM Dongle
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Joined: Sun Jan 23, 2011 8:52 am

Cartridge pressure pad renewal

Postby centaur_qlf » Sun Jan 30, 2011 11:23 am

Microdrive cartridges - failed pressure pads

The (presuably) foam plastic pressure pads deteriorate with age, making the cartridge un-readable. Is there a means of replacing these? I am used to delicate jobs and have replaced the, obviously felt, pressure pads on Philips dictating micro-casettes where the pad has been consumed by grubs; there isn't provision for making backups on dictating machines. These are low speed, but the QL are high speed, and seem to have a low friction coating, possibly PTFE. One has to be careful not to touch the tape with anything magnetic.


RWAP
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Re: Cartridge pressure pad renewal

Postby RWAP » Mon Jan 31, 2011 7:59 am

I have sent a pm to you with the details of someone who has replaced these for me in the past, although it is not an exact science especially as I keep finding particles of the pressure pad stuck to the tapes themselves!

I also quote another email I received some time ago from David Dolman:

The pads are used to keep the tape in contact with the reader head without causing any undue friction with the tape. Unfortunately in all of my tapes the pads it became apparent that they had corroded and this resulted in the pads being able to apply sufficient pressure for the heads to read the tape. To confirm this place the cartridge flat to the table, move the tape a little away from the pad and touch the pad with a blade. In my case even those that looked good fell apart when tested in this way. The solution, therefore, was simple, replace the pads! To do this I had to overcome two problems,

1. What to use?


I have investigated several alternatives and although I am still looking, the best material so far has been obtained from scavenged audio tapes. Get some of your old tapes and break them apart, recovering the pads. They are a larger version of the microdrive pads and similarly attached to a piece of sprung copper. Use a sharp blade, Stanley knife or such, I use a surgical blade, and remove from the copper pad. In some instances the pads may retain some of the old adhesive. In these cases make sure when you reuse them that this is the side to be glued to the microdrive “spring”.

Generally I've found that one audio pad cut crosswise will give two microdrive pads. They will appear to be too bulky, but should work.

2. How to actually replace the pad? Although my friend has described this part as more akin to surgery than computer repairs, it is still harder to explain than to do, so hang in there!

Using the flat of a blade carefully lift the cartridge tape so as to form a loop above the cartridge. This is to keep the tape clear and allow you access to the pad and should be no more than 1cm. Now holding the cartridge at a downwards angle of 45 degrees and slightly tilted towards you, use the tip of the blade to remove as much of the pad as possible making sure not to contaminate the cartridge or tape, but don't try to remove the glue just yet. I find that cleaning the knife and blowing on the cartridge every so often helps to keep it free of dirt.


Once you have done this hold the cartridge upwards, making sure the tape is still clear and gently ease the blade between the sprung copper and the cartridge casing so that the point is resting on both sides of the casing. I find a fairly narrow blade is best for this part. Then gently ease the blade forward and twist slightly. Usually this results in one side of the sprung copper “spring” coming free. If both come free and the "spring" comes away, providing it has not broken and I haven't broken one yet, don't worry it will be fixed. In fact this makes life easier, but I have not made a point of removing the "spring" as it can be repaired without compete removal.

Using the blade tip manoeuvre the “spring” such that the free end is now out of the casing. I find holding the cartridge upside down helps this part. When this is done hold the cartridge with one hand using your thumb to keep the loose end of the spring out of the cartridge, turn the cartridge upwards. Now you can clean the pad area completely clear of the old pad.

The “spring” is now ready to be glued. I use Super Glue with a small brush applicator. Glue the flat surface of the “spring”, taking care not to apply too much. I have over glued on a few occasions and then had to use my blade to release the “spring” from the cartridge casing. You should note that even this is recoverable.

Using a pair of tweezers pick up the cut down “audio” pad and gently position it onto the glued area. Again using your thumb to hold the “spring”, gently align the pad to the correct position.

It may be notable that the glue I use has been extensively used already and so may allow for more adjustment of the pad than with fresh glue. I cannot comment I afraid.

Once done use the flat of the blade to press down onto the pad and hold for several seconds. The new pad should now be fixed firmly to the “spring”. Remember;

AT ALL TIME ENSURE THAT THE TAPE IS CLEAR OF THE PAD.

Before you reposition the “spring” make sure that both sides of the “spring” are set at a 45 degree angle downwards from the pad. Without this they will not click into place and provide the pressure needed for the reader head.

They can go flat and will not click into place. To cure this, remove the “spring” and reset the sides to the 45 degree angle.

Now, using the tip of the blade, reposition the free side of the “spring” back into place. This does take a little patience, but is not too difficult. Finally, use the flat of the blade to gently “tap” the tape back into place.

Your cartridge is now ready for testing. To-date I have recovered 27 from 31 cartridges, however, I have no knowledge as to how long these repairs will last, but so far so good.


centaur_qlf
ROM Dongle
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Joined: Sun Jan 23, 2011 8:52 am

Re: Cartridge pressure pad renewal

Postby centaur_qlf » Tue Feb 01, 2011 9:52 am

Very helpful, Rich.

However, potentially magnetic items like steel should be kept well away from recording tapes; brass or plastic tools are needed.

If too much superglue is inadvertently used it may soak into the pad and harden it. For dictating tapes, I used a meagure coat of all-purpose solvent glue on each siurface.

In my initial post I suggested that audio tapes ran slowly, but I now realise that fast erase or copy are ofen carried out. This would be so for pre-recorded tapes.

Do the pads on audio tapes last better or is it that we have newer manufacture available, I wonder?



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