Hi Michael,
The data sheet in your link does not show how they number the pins. This is a datasheet that does give this information. The middle pin (2 on this datasheet.) is ground. The middle pin in your manual (And some manufacturers datasheets.) is pin 3. I think that regulator is a good choice.

Les.

 

The new Microchip MIC29300-12WT, 3Amp regulator is fitted.

Motor 1, one solenoid valve/relay is working, the one that operates when inserting a cassette.
Press play, fast forward, rewind, second solenoid valve/relay and motor 2 does not work.

These are the working voltages I have on Board U302 Connection block;

3. -6.6v

5. -17.8Mv

6. -11.59v nearly correct

7. -17Mv

8. -17Mv

17. -0.455v

18. -17Mv

19. -0.548v

22. 370Mv

23. 352Mv

25. +27v this one is correct

26. -11.75v

27. -11.90v nearly correct

28. -17.4Mv

Thank you Les; you are getting there, kind regards Michael

 

Hi Michael,
First check that that the voltage on pin 15 of the power supply board is +15 volts with respect to ground. Check that the voltage between pins 8 and 9 on the power supply board is 6 volts AC.(Checking all the power supply rails is always a good place to start fault finding.) I am assuming the two lamps that this supplies are to illuminate photo detectors that detect that there is tape in the path or that some part is in position. (They may only be to illuminate part of the control panel.) Am I correct in assuming that motor 1 drives the capstan and motor 2 drives the reels ? You talk about solenoid valves. I can't think what they would be used for in a cassett recorder. Can you explain ? If these two voltages are correct then I suggest following the flowcharts on page 22 of the manual. I think most of the ICs they refer to are on the drawings on page 21. The signal levels will be on the output of the gates. I suggest that you start following them for the wind or rewind button. (If you press the play button the pressure roller may push the tape in contact with the capstan and wear it through as the tape is not moving.)

Les.

 

Use correct symbols , Mv is MEGA , mV is MILLI ,

I think you need to use mV...

Your problem is no +15V output , so you need a LM7815 regulator.

https://uk.farnell.com/on-semiconductor/mc7815ctg/ic-v-reg-15v-7815-to-220-3/dp/9666117

 

One thing you could check before using the flow charts is to check that the voltage on the collector of TS457 is about -11.8 volts with respect to ground. A cassette MUST be inserted in the deck for this test.
(This is the negative supply to the 4000 series ICs. What is normally the positive supply (Vcc) is at ground potential.)

Les.

 

First check that that the voltage on pin 15 of the power supply board is +15 volts with respect to ground. Check that the voltage between pins 8 and 9 on the power supply board is 6 volts AC.(Checking all the power supply rails is always a good place to start fault finding.) I am assuming the two lamps that this supplies are to illuminate photo detectors that detect that there is tape in the path or that some part is in position. (They may only be to illuminate part of the control panel.)

These are the working voltages I have on;

Board U302 Connection block; 15. -00.9mV (how did I miss this one)

Board U402 Power Supply across 8 and 9, 6.13v~ (ac), these two pins supply the power to the two bulbs on the two recording strength meters 21 and 24 on page 2 of the manual, some people/techies call them VU meters. (incidentally; I have found this app to be the best so far to translate the Dutch in this manual to English) https://play.google.com/store/apps/details?id=com.microsoft.translator

Am I correct in assuming that motor 1 drives the capstan and motor 2 drives the reels ?

Yes you are quite right about motors 1 and 2.

You talk about solenoid valves. I can't think what they would be used for in a cassette recorder. Can you explain ?

The solenoid valves/relays; I haven’t studied what the lower one does, the top one if you look at the photo, you can see it would push the connecting cam and bring in to motion some of the surrounding gears. The manual calls them relays (I am used to seeing similar ones on oil burners which are called solenoid valves these are operated via the magnetic coil to move a stem/rod of the valve, you can hear a click when they come into operation, Danfoss ones I am very familiar with).
Kind regards Michael

 

Use correct symbols , Mv is MEGA , mV is MILLI ,

I think you need to use mV...

Thank you Dave for the education; yes you were quite right about that millivolt abbreviation (Mv) I will alter my consistency from now on to mV lower case m and upper case V.
Kind regards Michael

 

I have just realised; looking on Board U402 Power Supply, F427 has a 4amp fuse and I have just fitted the new regulator (Microchip MIC29300-12WT) with a specification of managing up to 3amp!

I have some voltage readings taken a while back (I don’t know if these are still correct) for IC430 µA78M15

Pin 1. 27v

Pin 2. 15v

I need to recheck these!

 

I have no idea what the significance of your voltage reading on pin 15 of board 302 is. I can't even find it on the schematic. I asked you to measure the voltage with respect to ground on pin 15 of the POWER BOARD (Board 402) As I (And Dave.) have said before verify that ALL the power supply output voltages are correct before following signal paths. (If your car would not start would you start replacing parts of the engine before checking that there was some petrol in the tank ?) I think you are confusing solenoid valves with solenoids. Solenoid valves control the flow of fluid (Liquid or gas.) In post #28 you say the voltage on pin 2 of IC430 is 2.15 volts. This is the same point as pin 15 on the power supply board. So assuming that voltage reading was with respect to ground you have no + 15 volt supply. You need to replace IC430 as Dave has said in post #24. If IC430 is getting very hot it's output could be being dragged down by a short. If its is getting very hot the tell us and we can suggest some more tests. Don't worry about F427 being 4 amps. The RMS current through it will be higher than the DC output current of the regulator and it also has to withstand the charging surge of C730.

Les.

 

These are the working voltages I have on Board U402 Power Supply

Pin 15. 15v

IC430 µA78M15 (confirmed)

Pin 1. 26.45v

Pin 2. 15.10v

I have taken a temperature measurement after 20 minutes of power on circuits; from both these regulators that use the metal heatsink IC430 is 30°c and IC431 is 31°c, taken as close to each regulator as possible?

In post #25 you kindly asked; for a reading on the collector of TS457 on board U302 the reading is -11.74v

My apologies for the errors in post #26 measurement from the wrong board and post #28 of which I have amended.

Kind regards Michael

 

Hi Micheael,
I have just looked back through the posts and now realise I misread the the voltage on the output of the 15 volt regulator in post #28 as 2.15 volts ( Rather than Pin 2 15 volts.) The comments about temperature are not relevent now as it is giving the correct output voltage.
The voltage of -11.74 on the collector of TS457 is OK. (This was to check that there was power to the 4000 series logic ICs.) The next step is to follow the flow charts as I suggested in post #23 I tend to be lazy following a signal from source to destination. I would start about half way down the signal path. (Half way down the flow chart as this follows the signal path.) If the signal is correct at that point I would jump to about three quarters the way down the signal path and so on. If the signal level was wrong I would jump back to about a quarter of the way down the signal path. This way keeps dividing the area where the fault is located in half.

Les.

 

Is my understanding correct?

I will be starting halfway down the Wind chart SK15, say, IC435b it has an L after this which indicates (low state -12v) will be the initial reading?

My connection will be on the output of that gate, pin 4. it’s identified on the schematic drawing as the pin nearest to the downwards exit from this gate/switch?

Pres the SK15 and this will connect the previous IC435d H and alters the reading to 0v, if this gives this reading, it is correct and move forward to say IC431a hatched L (with delay in low stat), pin 3. or pin 6. on the PC connection block, the reading will be 0v and pressing SK15 it will read -12v?

I need to write these readings down so they can be later examined by all as progress continues.

Individual pages; Flow Charts a and b and U301 Logic Control board can be seen on my OneDrive, for easy access.

Kind regards Michael

 

There is information on the meaning of L, H, shadded L and shaded H at the top left hand corner of the flowchart page. When I said that I woulf start in the moddle of the signal pathe I had not looked at the flow charts. Looking at the "Wind" flowchart it is quite short so it should not take long to follow it from the begining. Note the flow chart splits off in different directions to produce signals that have different functions. The first one I would follow is the one that ends at the wind indicator LED. You will probably have to look up the data sheets on the 4000 series ICs to find their functions. Just for a start IC438 is a MC14071 which is a quad OR gate. It might be a good idea to print out the flow charts and the schematic as you will be looking from one to the other at most steps in the flow chart.

Les.

 

It was more efficient to record all the pathways of the SK15 integrated circuits (IC’s) voltages at the same time; which hopefully gives a better understanding of the faults.

As you kindly advised; I have recorded all the IC voltages as shown after CUE (play + WIND) and under SK15 out of the flow charts b, I used the SK15 FF/Wind button, to record the second voltage, it is under the column called Sv, the first voltage is called initial and is under the column called (Iv), I am confirming the related SK15 LED does work.

I have noticed that there is a lot of millivolt readings on these; on the U301 schematic drawing at the finishing end of the board pin 6. it gives an expected voltage of, 0v this is the initial voltage, my reading is -17mV, with the button pressed it gives an expected voltage of, -12v, my reading is -11.55v, nearly correct?

I have transferred all these voltages into a dedicated table; it can be seen here on my OneDrive, the file is called, N5748 Upper relay and motor 2 does not work 28Dec18.

https://1drv.ms/f/s!AuQDAPiShOjc9RoD2G3xlbzfvUuQ

Your help with this is very much appreciated, kind regards Michael

 

Back tracking from IC431a; the first one I suspect is IC435, (I do find it difficult to keep track on this, even though I have my voltage reading to refer to)?

I could undertake a further recording of voltages without causing a cassette tape to foul SK13 REW/Rewind; I think doing this would not help to identify ones outside this area that could be damaged and it would be best to renew all 15 IC’s and save much time, what do you think, we can see voltage deficiencies from the readings?

Michael

 

The controll signals to board U302 seem to be correct for rewind at the IC outputs on board U301. Check that these signals on connections 6 and 8 where the enter board U302 are correct when you press the wind button. Check the following voltages with respect to ground on board U302.
TS433 emitter. (It should be about -11.8 volts)
TS434 collector (It should be about +25 volts)
IC455 pin 1 (It should be about -11.8 volts)
If these voltages are correct then the fault causing the slide solenoid not to operate should be in the block of components under the title "ELECTROMAGNET SLIDE".

Les.

 

Board U302 connection block; with SK15 Wind pressed for pin 1. and 8. voltages only.

Pin 6. -35mV ?

Pin 8. -11.55v ?

TS433 emitter -11.2v
TS434 collector 26.8v

IC455 pin 1. (centre) -11.20v

I don’t know what pins 6 and 8 should be?

All voltages with respect to ground.

Kind regards Michael

 

Just above and to the right of the pin numbers on the schematic of U302 it shows the transition waveform when the wind button is pressed. Pin 6 goes from low to high (-12 to 0 volts) and pin 8 goes from high to low (0 volts to -12 volts) which is correct. Connect your oscilloscope to the junction of R533 and R534 and check that you get a negative going pulse (I would guess about 10 milliseconds long.) This should make TS427 conduct and TS429 not conduct. (These two transistors form a bistable.) You will have to trace the reason why this part of the circuit is not actuating the slide solenoid. You will have to do this yourself as every test result will decide what to test next.

Les.

 

Connect your oscilloscope to the junction of R533 and R534 and check that you get a negative going pulse (I would guess about 10 milliseconds long.

Only have a multi-meter's

 

Test that TS427 goes from non conducting to conducting when the wind key is pressed.

Les.