Help Pls = Grundig TK64 Motor Not running

[Phantomrose1999]

Hi All,

I am hoping there are some experts here on the Grundig TK64 Reel to Reel

I have spent a lot of time restoring one, see video link

https://www.youtube.com/watch?v=y_OZ3kFOh9Q

But after it was used for about 3 hours, i noticed it was quite hot, but perhaps normal. THEN THE MOTOR JUST SLOWED AND STOPPED !

The Motor wont start. The schematics dont show the color coding of the wires used, so i have taken photos. I guess the motor cap may have gone, but its impossible to get to (and there are two motor caps, in between the chassis and electronics, virtually impossible to access) it, so a cut and bypass is needed.

BUT i cant figure out the wiring to do this.. please see the voltages measured.

GRUNDIG TK64 is voltages at motor tag strip

0 AC

127 AC

133 AC



I tested a Grundig TK40, and measuring across the 3 pints, i got

119 AC

315 AC

285 AC

Any help to debug the motor not running appreciated and tips to cut and bypass the internal motor start caps greatly appreciated.

[Phantomrose1999]

Well, its another day and i spent most of on this Grundig TK64.

The problem is i cant find a schematic with motor connection diagram to match the unit i have. So some guess work.

PLEASE SEE attached details of me tracing the wires and substituting another cap in the place i though it should go, but still no luck..

1) Is the attached diagram / photos accurate ? its based on me tracing the wires

2) Where should the cap be connected ? from the middle wire to the Relay side OR the mains fuse side ?

3) I tried to connected a new cap between the middle motor wire (after isolating it) and the Relay side input power, but it still would not start the motor.

If i knew exactly which wires from the motor matched the schematic, i would just make some direct connections and bypass the 50/60 hertz switches.

[Lucien Nunes]

It is a long time since I had one of these, and the schematic in your post isn't clear enough to read, but to the best of my recollection the motor operation is quite conventional. It is a 'permanent split capacitor' type, where the capacitor is permanently in circuit to shift the phase of the current through one winding. I.e. the capacitor is a 'run' cap, not a 'start' cap.

A supply is taken from a tapping on the mains transformer primary via the relay contacts, into one winding of the motor ('left' lead). The other end of that winding returns to neutral ('right' lead). The third terminal is fed from one or the others via the capacitor, to provide a phase-shifted current through the second winding. Which side the capacitor connects to will depend on the specifics. On the TM schematic it looks like there are alternatives, depending on something (motor version, frequency etc). The capacitor value may also be dependent on frequency, e.g if there is a large cap and a small one, the frequency selector probably parallels them for 50Hz.

With the middle lead disconnected and the power off, I would test the resistance from left lead to right, and middle to right, to confirm that there are at least two circuits through the motor. That is not conclusive but if either is showing open circuit, there is definitely a winding fault. I would make sure that the transformer tap voltage (is it 120?) is reaching the two outer leads with the power on, and then briefly connect a substitute cap (value equal to larger original cap) from the middle lead to one of the outers. If it does not turn, try the other. If you can read and confirm the markings on the TM schematic outer leads that might help understand which of the outer leads is correct.

Note that as per your TK40 readings, the voltage at the capacitor winding can be in excess of supply voltage. For consistency, if you are taking voltage readings, it's convenient for them to be with respect to neutral / right lead. So the left lead will always be at the voltage present on the transformer tap / relay contacts, and the middle lead is the one of interest.

[Phantomrose1999]

Hi Lucian,

Thank you for the reply, i agree with everything you said, the problem being i cant identity which wires do what on the motor because there is no visible color on the wires.

However i have traced them and thus can assume which leads go where. PLEASE SEE ATTACHED DIAGRAM

What is baffling is the left most wire on the motor tag, is connected to a frequency switch, which IS OPEN FOR 60HZ and closed for 50hz. there are NO OTHER Wires from the left most tag on the motor.

I understand switching in an additional cap for 50hz, but i cant see anything connected to the left most wire on the motor tag (which is assume is the centre tap of the motor on the schematic) when in the 60hz position, meaning there is NO Cap in the 60hz position.

I did connect a new cap from the (Assumed middle wire) to the motor wire that goes to the relay, no joy.

QUESTION: Can the capacitor be connected from the (assumed) middle wire to ANY of the two supply lines ? or will it only work in one position.

My motor part number is 7882-032. according to the schematic, i should have connected the motor cap to the fuse / transformer side, not the relay side.
QUESTION Does it matter which of the two supply line the motor cap is connected to ?

[Michael Maurice]

There is no attachment but you'll probably find that there are two capacitors in one can say 2uF and 0.5uF (just guessing in which in the 50Hz mode the smaller one is switched in.

Can you post a picture of the motor run capacitor and its markings.

[Lucien Nunes]

Perhaps the machine is not equipped for 60Hz operation and the switch is redundant, with the 50Hz cap being made up of the two caps permanently connected in parallel to the 50Hz position.

It would be helpful to get resistance readings from the windings of a known good motor for comparison. I used to be aware of a typical ratio of winding resistances of the windings of Papst Außenläufer motors, but have long since forgotten and I'm not near any at the moment to check.

[Phantomrose1999]

Dear Michael, i have not found a schematic anywhere for my version of TK64, that has a frequency switch shown, or the TWO capacitors i can see.

These two motor capacitors are sandwiched inbetween the drive unit chassis and the metal chassis of the electronics. Impossible to see, but one is big and one is small. It will not possible to replace these, so instead i will just bypass the middle motor wire directly to a new run capacitor.

I cant believe where they put these capacitors, right in the middle of the sandwich..lol

Lucien, yes, i was thinking the same, that this is in fact NOT a frequency switchable unit, as its set to run on 50hz and thats what we have in Australia.

Can i connect the new motor cap, from the middle to EITHER Side of the supply ? or will it only work when connected to the the correct side ?

I did connect a cap from a TK40, from the middle wire to the relay side, it did not work. Perhaps the cap needs to be connected to the Fuse side. PLEASE SEE SCHEMATIC

[Lucien Nunes]

Whether the cap connects to yellow or red depends on the specific model of the motor. According to the schematic, yellow for version -024 and red for -012 and -032.

It is important to connect it to the correct side otherwise the torque may be reduced and the motor may overheat. But for a brief test to see whether it rotates, I would expect it to be OK connected either way.

Resistance measurements of the motor windings would in instructive. You will probably find the ratio similar to that of the good motor in the TK40, even if the actual resistance values are different.

[Phantomrose1999]

Thanks Lucien, I will buy a 5uf 250vac motor start cap and try connecting it to either side of the supply, (relay side and fuse side).

Just remember, there are no identifiable colors on the motor wires of my TK64, they are unlike the TK40 which has clear color coded wires, the TK64 has different shades of brownish tans..lol

Unfortunately i am about to drive from Sydney To Queensland for work and wont be back for at least a week, hate having to leave with unfinished business, but work pays the bills, ha.

[Phantomrose1999]

Hi All,

Finally back into the restoration.

I bought an expensive 5uF capacitor, and connected it directly to either of the input rails to the motor, and its STILL DEAD !

1) There is about 127vAC between the main two input leads.

2) I connected one end of the new 5uF cap to what i think is the middle wire of the motor, and the other end of the cap, to EITHER of the power input wires, but its STILL DEAD.

3) measured voltage between input and the middle motor lead is 6vAC.

4) I measured the resistance between the middle wire and one motor wire, and it is about 80ohms. Between the middle wire and the other motor wire, its about 26 ohms. IS THIS NORMAL ?

I have spent about 5 weekends rebuilding the electronics and its working perfect, it just needs to start spinning !!

The motor number is 7882-032. What is the chances of getting another motor ? Hoping to be able to remove the motor without splitting the chassis, is this possible ?

Any suggestions appreciated.

David

[Phantomrose1999]

SOMETHING VERY INTERESTING.

This attached photo is from a TK60. The motor looks identical to my TK64 motor. It has the 3 terminals on the back of the motor.

The photo from the TK60 service manual, shows there is NOTHING connected to the 3rd terminal. But in my TK64 there is (what i am assuming) is the center tap of the motor, which i am connecting to the capacitor and its not doing anything.

As i mentioned previously, if the 50/60hz switch is set to the 60hz position, the (what i assume is the motor middle wire) is OPEN and not connected to anything.

I have assumed the 3 wires and tags on the back of the motor are, 2x for power in and one being the centre tap.

I cant find a schematic for a TK64 with 50/60hz switching and TWO motor capacitors sandwiched between the chassis and electronics.

[Phantomrose1999]

Better Pic of the TK60 motor wires from the manual. only 2 wires !

[Phantomrose1999]

Here are all the voltage and resistance tests

The tag strip in the motor is:

Left goes to the 50/60 hz switch which I assume is the middle motor wire

Middle is going to the relay for power then to the transformer to get the 135v

Right is going to the fuse and mains neutral line in

Please see all the resistance and voltage photos

[wd40addict]

Is the motor actually mechanically free to turn?

If this is a typical single motor machine with a drive belt system a la Philips can you remove the belt and see if the motor starts with no load?

[Phantomrose1999]

Hi, As you can see from my 1st post, containing my youtube video after its electronic restoration, the motor was working very well.

The motor is free, and i have tried it with no load. It also has all new belts.

After about an hours operation, the unit was quite warm / hot, and then the motor just lost power and slowed down to a halt, while playing.

[Phantomrose1999]

Well, I opened a TK40 with nice coloured motor wires. Measured the resistance across the 3 known leads

End to end = 51 ohms
Middle to ends = 234 / 286 ohms.

Now I measured the TK64 motors with unknown coloured motors

End to end 29.8 ohms
Middle to either end 82 ohms

I traced some of the wiring and only got more confused It not match my understanding or the TK40 wiring. In the TK40 the main power input is across the lowest resistance, but not in the TK64. Please see photos.

I have tried connecting a new 5uf between C and A, and between C to B, after isolating C from existing circuitry. Still no life.

The wiring I traced seems to indicate I understand the motors wires. But the resistance test and comparison to the TK40 has got me very confused

Am lost now. The resistance measured does not match the expected wiring. But I can’t trace all of it anyway.

Any experts ?

[Phantomrose1999]

Originally Posted by Lucien Nunes

Whether the cap connects to yellow or red depends on the specific model of the motor. According to the schematic, yellow for version -024 and red for -012 and -032.

It is important to connect it to the correct side otherwise the torque may be reduced and the motor may overheat. But for a brief test to see whether it rotates, I would expect it to be OK connected either way.

Resistance measurements of the motor windings would in instructive. You will probably find the ratio similar to that of the good motor in the TK40, even if the actual resistance values are different.

I did this and only got more confused about the wiring and the problem

[Phantomrose1999]

Well progress at last

I split the chassis to trace the wiring

I found there are two wires going from the motor to a 4.3uf large capacitor and a smaller one being switched in for 50 hz. This explains why one of the selector 50/60hz switches is open for 60 hz.

The wires run from the motor directly to the 4.3uf cap in the middle of the chassis sandwich. Impossible to see or modify if you don’t split the chassis

In addition these two motor cap wires run to the motor internally and to the tag strip on the back of the motor. The cap is connected to A and C as well as the motor coil

This also explains why the TK60 and tk30 only have two power in tags on the motor. It’s because there is a direct connection from motor to cap in the middle of the sandwich

Finally I removed the 4.3uf cap and measured it, looks open. I measured the new 5uf cap and it reads 4.3. See photos and my YouTube video

https://youtu.be/vQTPYFB_KBU

Will reassemble tomorrow and test. What concerns me is that I did actually connect the new cap to A and C previously with no joy.

The motor config seem like a 3 phase delta config. With everything disconnected I got about 99 ohms no matter what I measured.

I bought a TK60 to investigate and possible steal the motor but it’s a 165v unit whereas the TK64 is a 135v unit. But I only measure around 110.

[Phantomrose1999]

WELL ITS FIXED !! YAY

I split the chassis and removed both the 4.3uf and 2uf motor run capacitors.

The new one i had was 5uF and the motor had written on it 6.3uF for 50hz.

So i used my new 5uF in parallel with the old 2uF (which tested ok) to give me a total of 6.6uF. Close enough the required 6.3uF

Put it all back together and it works wonderfully !!

- New bridge rectifier with 1000v 3A diodes, + 100 ohm 10W resistor
- 2x German 50uf+50uF main caps replaced.
- 99% of the wax capacitors replaced
- All new Belts from Germany
- And finally a new 5uF motor run cap (in parallel with the original 2uF)

She SINGS AGAIN !! and will no doubt last longer than me..ha.

Hope all this info helps anyone trying to restore one of these.

Splitting the Chassis is not that hard.. tips
- Remove the Record switch, and push through the hole, no need to disconnect any wires
- Remove the record head two screws and push through the chassis, no need to disconnect the wires
- The pause button and magic, eye assembley, comes out of the way, with 3 screws. Just take the top two screws and one lower down, and disconnect the gear from shaft, and push it out of the way
- Unsolder the motor wires from the tag strip, the motor will lift with the chassis
- move the power amp out of the way, remove the power amp 4 main screws where the heat shied is, and it just moves out of the way. Unplug the main connector, but leave the fat red cable to the input din sockets.
- Remove the 4 large screws holding the chassis togethers
- Remove the 4 screws and metal plate that holds the record switch.

It actually looks worse than it is. With all the above done, you can lift the chassis enough to remove the motor and replace the motor caps. You get about 3-4inches gap, more than enough.

Good luck.

[wd40addict]

Amazing, well done! So the 4.3uf must have failed after being woken from its slumbers. Suprising that the 5uf alone wasn't enough to at least get motor turning even if at low torque.