this instructable assumes that you have basic electronics skills and above average mechanical aptitude. disassembly and reassembly of a mechanism will be required and maybe simple soldering. instructions given here are tailored to early philips / norelco machines only.
a little history..
2013 marks the 50th anniversary of the compact cassette, known as "cassette" by most folks. few consumer products have a 50 year run. in it's 50 year lifespan, the cassette dethroned the reel to reel as a portable consumer audio recording media, made taking your music with you a convenient reality, spawned the birth of the walkman, and thus the creation of the portable entertainment industry as we know it. all this caused by a lowly cassette recorder brought to market in 1963 by the philips company.
in europe, these early cassette recorders were sold under the philips name. in the USA they were sold under the norelco name. philips was sued by philco and couldn't use the philips name in the american market. philips / norelco = same thing, different market.
initially, philips / norelco machines where the only ones on the market but eventually other brands started showing up. its not uncommon to find early recorders of this type that had a philips mechanism inside and a different brand name on the outside.
Step 1: ID'ing philips mechanism machines
in the first pic you will see the underside of three old philips based recorders. those machines from left to right are norelco, telefunken, norelco. the first two are the later models. the machine on the right is one of the very early models. note on the first two there is a small circuit board on the bottom left of each machine. that is the speed regulator board. the earliest of machines didn't have them and were more prone to speed variations.
that little board makes a huge difference in their ability to be used for any reasonable playback of music. the earliest machines lacked this board thus making them only suited for voice at best. speed fluctuations are common with all early cassette portables but its particularly bad with the earliest philips machines that lacked that regulator board.
as mentioned earlier, some manufacturers used a philips chassis in their own housing. despite the different external appearances, there's some notable traits all philips machines have that can help you ID what mechanism is really lurking in that old cassette recorder. the pics show you these traits.
1) all early philips machines have 2 DIN plugs for audio in / out
2) all early philips machines use one control lever that moves front / back and left / right
3) all early philips machines use 5 C batts
4) all early philips machines have two volume controls, one for playback and one for record level
5) it seems that the earliest of the actual philips / norelco branded machines did NOT have a tape viewing window in the door. these very early machines are of historical importance as being the first of their kind in the world but they are also the ones that lack the speed regulator board. this rule doesn't apply to re-branded machines. ampex for example offered the micro 10 which had a solid black door and the voltage regulator board.