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First time repair on cassette deck

repairmanjack's picture

Hello all;
I have a very brief introduction to make....first of all, I work for Philips, in the Medical systems division, and do not have *any* experience working on audio equipment, but I have some slightly older philips equipment I bought back in the 90's I would like to keep, but needs repaired. This is my first post to this site, so if these types of service questions are not the sort of thing you do here, please forgive.

Also, I have downloaded the service manual for this unit. You guys have a GREAT resource here.

I have a Philips FC 930 double tape deck, and deck A will not play the cassettes. It starts to, then about 1 second after pushing play, the auto reverse mechanism kicks in and turns the play the other direction (on the B side of the cassette). After about a second or two on the "B" side, it does this again. This repeats three or four times, then stops. I have also noticed that the rewind and fast forward functions do not work either; they run for about 2 seconds or so then stop.

Bad motor maybe?

As a *complete* newb to this stuff, I gotta ask, where to start? If it was a Philips Xray machine, I'd know waht to do : ) Here, I'm in uncharted territory. Any help is appreciated!!!



Re: First time repair on cassette deck

I guess you know the direction change is triggered by the unit sensing no tape movement. I don't see the FC930 manual here, but some units may sense EOT with a optical sensor looking for the clearer leader area. I've always found it useful to have an cassette without any tape in it. Put the cassette in and remove cassette compartment front cover, so you can get a good look inside the tape compartment. Press play, does the pinch roller rise up and contact the turning capstan. Is the pinch roller turning, and in good condition? Pinch rollers can dissolve away completely or get hard and not grab the tape. You should be able to see the capstan press into the pinch roller slightly. Does the take up reel side turn CCW? The torque of the take up reel will be greater in fast forward than in play. Just press on it lightly with your finger to test this difference. A lot of units have a idler wheel that flops back and forth between the take up reel in play mode and fast forward , and flops over the to left side to rewind or reverse play. You may have to remove the back of the cassette compartment to see this part if you can't see it from above. In the FC931 manual it's shown on page 44 as part 165. Should have a black rubber tire on it. It should not be gummy, but s/b firm and not hard, about the same as a good pinch roller.

Re: First time repair on cassette deck

Does it have a mechanical counter? If it does, and the counter is not moving, it will engage the auto reverse. Either the counter is hanging up or the belt is bad.

repairmanjack's picture

Re: First time repair on cassette deck

sooooo......where does one find these parts? I have a philips part number, but have scoured what few resources I know of. Any ideas?

thanks!

repairmanjack's picture

Re: First time repair on cassette deck

no mechanical counter; this unit has a digital counter. Does that matter? The deck "B" is fine.

I'll try the belts, thanks for the tip!

repairmanjack's picture

Re: First time repair on cassette deck

Replaced the belt, no change in behavior. I noticed the smaller motor in the center of the cassette assembly does indeed switch from left right and turns the gears for the wheels of the cassette, however they don't last long, about 1 to 2 seconds in either direction.

Re: First time repair on cassette deck

Hi,

I don't know if it is possible with this deck but here is what I would suggest. Open the cassette loading tray. Now there should be a limit switch on the opposite side of the tape transport system (ie. the opposite side of the heads). Depending on the unit, there may be one switch for Record, one for tape sensor and one for detecting the type of tape (Chrome, metal, normal).

Try and find the one which is used to sense the presence of a cassette. Activate this switch and press play. Now try to turn the take up spindle with your fingers and observe the digital tape counter. It should move. If not, there could be a problem with the circuit that is sensing the counter wheel rotate or maybe the wheel itself is not rotating.

Normally, you will be able to see a small wheel which is painted with alternate patches of black and silver. As the wheel moves, the sensor counts the revolution.

Hope this helps.

Regards,

Balu

repairmanjack's picture

Re: First time repair on cassette deck

Interesting phenomenon now.

I have replaced the belt on the deck. No change except for one. After the comments about the counter, I noticed that although I do not have a mechanical counter, I do have an electronic one. I can only assume the very small circuit board behind the left hand capstan is the counter. Even though it will only rewind for about a second or two before the tape switches direction, I noticed the counter in fact does *not* change. Intermittently, however, the tape *will* play in the reverse direction, and the counter will change. Not really sure how to proceed from here. If its a bad counter circuit, I'm not sure how to find parts for it. And how the hell you get them capstans off??

Re: First time repair on cassette deck

An electronic counter is usually controlled by a Hall device, which is switched by an LED that shines on a black and reflective surface on one of the reel tables. You could have a bad Hall device, LED, dirty reel table or a problem with the circuit connected to the Hall device. There has to been some wiring to the Hall device (usually three wires). Could be a power supply problem to this circuit.

Re: First time repair on cassette deck

Cassette Decks with electronic counter: have two options, Hall element with a rotating magnet, or an opto-coupler with rotating disc like a fan blade. Check if the belt to this device functions correct.