CT-F1000 problems

[hazydavy]

Hi all,

I bought a CT-F1000 tape deck about 10 years ago along with some other spec era gear. It's traveled with me from Seattle to Newcastle in the UK. It didn't work when I bought it and it doesn't work now ;-) For some reason, I decided that today was going to be the day to try and get it going. I bought one of WJOE's belt kits back in 2007 (!) as I thought it just needed new belts. I opened it up today and changed the belts but there's something more wrong with this.

As soon as you turn on the power, a solenoid starts "firing" every ~4 seconds to reset the switch mechanism. It does this irrespective of whether any of the buttons are pressed. Nothing spins :-(

I took a quick video showing the symptoms:

Any ideas?

Thanks in advance.

Dave.

 

[markthefixer]

edit: simply expressed. 100% of the time whenever the hall effect tape movement sensor sees no tape movement it's surrounding circuit generates periodic reset / stop pulses. Other circuits prevent that reset / stop signal from actually progressing and DOING anything. That could be anything from a defective hall element (which we'll discount for now) to bad component. Hall effect can be tested by just spinning the movement sensor and seeing if the solenoid stops clicking.


It's in the q201 - q205 area.
Q201 through c202 amplifies the Hall Effect tape movement sensor's input.
Q202 with C204 forms a pulsar circuit
and Q203's input from "logic" from elsewhere in the deck shorts 2.3k ohms across C204 perhaps to stop it from charging.
These send parallel signals to q204 which is performing as a logic element. An AC logic element because of the capacitor coupling into the collector and base of a PNP transistor.
Q204 signal goes to q205 which actually drives the solenoid, although d204 may be implementing other complex "logic" / analog functions at the base of q205.

So, how would I recommend a DIY tech to fix this without going nuts?
#1 I would test or just plain replace every capacitor (c201 - c207) in that area of the circuit
all are just garden variety (cea) capacitors - no trouble prone or special caps in that area
one 2.2uf, three 22uf and one 47uf cap
note: DON'T depend upon THIS post, the schematics OR the BOM for correct cap values as I have run into enough discrepancies to MANDATE a visual inventory of each capacitor position and it's capacitance value.
#2 I would remove and test q201 through q205 OUT OF CIRCUIT
#3 I would test out of circuit d201, d202, ZD201(6.1v) and D204.

Haven't figured out d204's function yet - could come back to bite me in the butt.
So if all the above doesn't clear it, open up d204 and just turn on the power - DO NOT put in a tape or operate the buttons.
This is to address the reset solenoid pulsing when JUST the power is on.