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Sharp RT-3388a solenoid/plunger not working

Florida21

Jul 11, 2022
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I’ve tested the paths of diodes, capacitors,Etc. And all check out good. solonoid tests good as well. I know I’m missing something and really needing some help. Thank you
 

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kellys_eye

Jun 25, 2010
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What about the supply to the solenoid circuitry? Can you activate the solenoid by shorting Q808 collector-emitter?
 

Bluejets

Oct 5, 2014
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5,883
I don't see any Q808.
Looks like Q802 would be the switch for the solenoid.
 

kellys_eye

Jun 25, 2010
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The image of the schematic looks to say Q808 - it's very blurred on my screen and could be different! It's the transistor with the collector connected to the coil.
 

ivak245

Jun 11, 2021
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When you say the solenoid tests good, do you mean you have applied power and seen it work? I am asking because I have seen solenoid windings heat up and expand, jamming the plunger, but they still check ok with a meter.
 

Florida21

Jul 11, 2022
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The image of the schematic looks to say Q808 - it's very blurred on my screen and could be different! It's the transistor with the collector connected to the coil.
Sorry for the blurred pics. These should be better
 

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Florida21

Jul 11, 2022
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When you say the solenoid tests good, do you mean you have applied power and seen it work? I am asking because I have seen solenoid windings heat up and expand, jamming the plunger, but they still check ok with a meter.
yes, I actually tested with a 9v battery and it worked. any suggestions?
 

Bluejets

Oct 5, 2014
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yes, I actually tested with a 9v battery and it worked. any suggestions?
It's a wonder you managed to get any movement out of it with 9v.
Supply rail appears to be 27v so is that ok...??
You say you shorted Q808 (which doen't appear to exist) but what about Q802, which, even though rather blurry, I think is the switch for the solenoid.

I too, have had solenoids jam as ivak245 says.
Might be a good move to post clear photos and some further detail from the power supply further down the schematics page.
All rather vague on the answers.
 

Florida21

Jul 11, 2022
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It's a wonder you managed to get any movement out of it with 9v.
Supply rail appears to be 27v so is that ok...??
You say you shorted Q808 (which doen't appear to exist) but what about Q802, which, even though rather blurry, I think is the switch for the solenoid.

I too, have had solenoids jam as ivak245 says.
Might be a good move to post clear photos and some further detail from the power supply further down the schematics page.
All rather vague on the answers.
I’ll check Q802 today. Also attached another pic of schematic. They all should be much clearer. Sorry for the piecemeal. And again, really appreciate all of your help and patience with this novice.
 

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Florida21

Jul 11, 2022
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I’ll check Q802 today. Also attached another pic of schematic. They all should be much clearer. Sorry for the piecemeal. And again, really appreciate all of your help and patience with this novice.
Just checked Q802 and shorted, plunger worked! I did replace Q802 with a spare board I bought on ebay but still nothing unless I short it.
 

Bluejets

Oct 5, 2014
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Cannot make out any detail on the new photo as it is too small to make out any detail.
Did you look at it when you posted it...???:rolleyes:

Q802 is ....(from what I can make out on previous photo #1 )... driven by Q803 via a couple of (what looks like) either R1 or F1 inputs.
Actually that is written in the text beside the schematic.
Any signal there...??
 

Florida21

Jul 11, 2022
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Cannot make out any detail on the new photo as it is too small to make out any detail.
Did you look at it when you posted it...???:rolleyes:

Q802 is ....(from what I can make out on previous photo #1 )... driven by Q803 via a couple of (what looks like) either R1 or F1 inputs.
Actually that is written in the text beside the schematic.
Any signal there...??
I don’t blame you for rolling your eyes, lol. I did look at it before I attached. I’ll try again. I’ll also check your suggestions as well. Fingers crossed on the pic. Huh!BA6C3D67-F5BE-4A3E-B332-B010909B47DD.jpeg
 
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Bluejets

Oct 5, 2014
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DOHHHH!!! ......:rolleyes:now it's upside down.......(Goto #12)
Did you look at it when you posted it...???:rolleyes:

Solenoid appears to get it's signal (whatever form that takes) from the control unit via either F1 or R1 (assume forward or reverse)
There is a "zero rewind" switch sw10 which would, I imagine, disable/enable that feature.
You may possibly need access to some form of a scope if the signals are pwm or similar pulses to determine if signals are indeed being generated.

Perhaps trace your main supplies and see if they are good. (12v ) you have determined you have 27v by the previous test #11.
 
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Florida21

Jul 11, 2022
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DOHHHH!!! ......:rolleyes:now it's upside down.......(Goto #12)


Solenoid appears to get it's signal (whatever form that takes) from the control unit via either F1 or R1 (assume forward or reverse)
There is a "zero rewind" switch sw10 which would, I imagine, disable/enable that feature.
You may possibly need access to some form of a scope if the signals are pwm or similar pulses to determine if signals are indeed being generated.

Perhaps trace your main supplies and see if they are good. (12v ) you have determined you have 27v by the previous test #11.
First if all, I’m really sorry for the pics if not coming out clear. My phone takes great pics but not sure why when attaching they are not clear. I have gone back and checked F1 and R1 for voltage which there is. Unfortunately I’m a real novice when it comes to this but always want to learn. At this point not sure if I need to throw in the towel, and don’t want to test all you wonderful peeps who have been helping me, your patience. I’ll take any direction if you still want to help me, but understand if not. You guys helped me on my 1st tape deck, but I’m running out of brain cells! Lol. Have a great day
 

kellys_eye

Jun 25, 2010
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Do you have the 3V regulated supply to the control unit via Q810?(Q819 - still can't see the details - need a clearer schematic) - maybe pin 7 of the control unit?

The 'multiple' faults you have mentioned all stem from the output(s) of the control module which won't work without that 3V? supply
 

Florida21

Jul 11, 2022
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I can’t seem to find the pin 7 of the control board since it’s that flat band. I also took a closer pic of the schematic and behind the control unit. I do have voltage at Q819 but not sure how to test for 3v at control unit. Also, the control unit does work ,the display, tape counter, etc.
 

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kellys_eye

Jun 25, 2010
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Do all the physical switches (mechanical) all work? Are they all in their correct operating position? Have the contacts been cleaned? Still can't read the damned schematic! but the solenoid is essentially activated from two inputs at the base of Q804? There re two 10k resistors attached to the base of that transistor and if you ground the 'top' end of either of them then the solenoid should operate - is this the case?
 
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