A recent flea market finding: Philips N2204 cassette tape recorder. Bought it very cheap... honestly, to waste some time fixing it.
A Philips EL mechanism from late 1960s shows that this tape recorder has been made probably shortly after my EL3302, one of the first cassette tape recorders commercially available. The N2204, contrary to EL3302, has a bit better speaker and a built-in power supply (transformer based), as well as the wider level meter, auto-level and the tone adjustment. The transistor technology is still germanium. The power cord is like overgrown IEC C7 with rectangular pins, one horizontal, one vertical, so I had to add a replacement using typical slide-on connectors.
While in this model Philips used the typical cassette-in-lid approach (in EL3302 the lid was independent - you could play the cassette with a lid open or even absent), the mechanism is still Philips EL - the tank, which was developed as one of the first mechanisms so almost no wear-related research was done and most of parts were really solid. It means that lubricated properly, it can work well until the rubber parts get damaged, and the rubber in these mechanisms is good.
What cannot be said about a good rubber is the rubber used for two transmission belts. The transmission belt in the tape recorder may fail in one of 3 ways:
- First, the belt may just become loose. This belt can be easily replaced, and the belt still has some elasticity so it can be even used in some other device for a limited time. This is a typical damage in most devices.
- Second, the plasticizer component may dissolve in the rubber. This makes the belt hard and brittle, so it is needed to use a sharp needle to pick its parts from the wheels. These parts can be brushed easily and the belt can be replaced.
- The biggest problem, and the problem that was in my unit, was when the hardener dissolves. This makes the belt like a soft tar, and whatever it touches, it leaves black stains. This has to be carefully and patiently removed, bit by bit, into some paper towel or a toilet paper. Then, parts have to be washed - while metal parts like a flywheel can be easily cleaned in acetone, plastic wheels have to be cleaned using the denaturated alcohol many times to be clean from the remains of these belts. It took me about 4 hours of cleaning just to get rid of the old transmission belt. After drying and re-assembling, I put new belts. Contrary to the popular opinion in the Internet, the CD-ROM drive's tray mechanism belt is still too big as the "small belt" in the Philips.
After fixing the intermittent connection near DIN plugs which made the recorder stop sometimes, I found that it spins its wheels properly. Time for the lubrication - after cleaning the old grease, I found that, fortunately, the barrels used for the slider were not damaged. This is a weak spot of EL mechanisms - they must be lubricated well, or they will become polished on one side, and it will be more and more difficult to push Play. Cleaning the rewind direction roller made the mechanism work much more smoothly, and finally, removing about 2 cubic centimeters of an old dust from the inside of the tape pins finally made it work as it should.
After setting the motor speed again, I found that it plays very well. Tested recording using an original Philips microphone only to get no recording at all. Using a bit stronger 1970s microphone, I got something written to the tape, but this something was barely audible.
The typical drill in this situation is to clean the sliding play/record switch. Fortunately, Philips engineers used a switch which does not fall apart when serviced, so I had to remove electronics PCB, slide the switch PCB from its pocket, clean it with the alcohol and put it back. This completely solved the recording problem.
The record button and the cassette eject button look the same and they are near each other. Fortunately, the mechanism is cleverly made, so when You are already in playback, pressing Record will not erase the tape (record switch is shifted with the forward motion of the Play lever). However, trying to remove the tape I found that I can press Record much more frequently than I should be able to.
Yes, lost spring of the recording protection pusher. Fortunately, thanks to the construction of the mechanism it's not so dangerous, but first I tried to use a replacement spring, all of them were too strong, and I finally found the runaway spring on the speaker's magnet.
The thing they don't write in a service manual is that over an entire inside of the device, there is running a thin web of an exposed wire. This wire starts in unusual places, like wire lugs sticking from the screws or even some mounting brackets, runs around a few components and ends similarly, or to the ground plane in one of PCBs. While the entire chassis is grounded, this wire looks redundant, however, it is not. When I accidentally broken one of these, I got an entire set of 50Hz-like interferences, but only when my hand was near the eject button! Soldering the wire back did not fix the problem entirely, I had to put a new one, soldered to the points it was previously installed. Well, this was probably some clever design which was calculated using pen and paper that this and only this will minimize the buzz. On the other hand it is really easy to accidentally ground something to these wires during servicing.
Now the glue which I used to hold the speaker grill and some belts in its cover dries and I'll have to find a suitable power cable.
