Uher Z124 charger

[TheReeler]

I'm having problems with this charger. When I record, the power isn't enough and the voltage drops and a "hum" noise appears. If I push the voltage BATT, it reads below 5V and the VU lights start to blink and the meters too.

I replaced the big cap and thw two small ones that are in a small boards and resoldered all solders again, but the problem stills being there.

The last test I did is to switch the voltage selector to 100-130V and connect the charger to an external transformer (220 down to 125) and with this configuration, all works fine, but if I try to plug it directly to the main supply (selecting 200-240V in the switch first), the problem appears.

Any helo would be appreciated.

PS: I can't find the Z124 schema.

[esla]

Hi Reeler,

the schema is now in your mailbox.

The only thing IMHO can be, that one of the two (where can I find this word in Englisch "Transformatorwicklung", ist "winding" allright?) is out of order and has an disruption. At 110 V both windings working parallel. At 220 V they working serial. Why shoud the charger working properly at 110 V and not at 220 V?

All users, who can better speak Englisch then I do... can anyone please help to translate?

Das ist ein simpler Längsregler und wenn der bei 110 V läuft, kann es meines Erachtens nur an einer unterbrochenen Trafowicklung liegen, wo irgendwie noch ein bischen durchkommt.

Gruß Jens

[TheReeler]

Hi esla, thanks for the comments and for the file. However the Z124 A-1 I think isn't the same than the Z124 because in the schema of the Z124 A1 there is only one capacitor and inside the Z124 there are at least three, two small and one big.

So in your opinion, the problem can be the transformer itself?.

[esla]

Now you should have the schma you've searched for.

The transformer may be the problem, so you should try to measure the two parts of the transformer (blue-yellow and green-red). Both windings should have the same resistance. Is it so?

Before that you should remove the voltage switch (110 V / 220 V). If the transformer ist okay, we should try to find the problem again.

Greetings Jens

[TheReeler]

Thanks!!!.

7.2 ohms in both cases. I've unsoldered all wires to try to find the problem. The is a wire, green with black bars that goes from a bottom part of the "-" diode bridge to a board, but is another different part of the "-" pin of the diode bridge, don't know what it is, but there's no continuity between that wire and the conventional "-" pin of the diode bridge.

Look:

Beginning of the wire...



... final route of the wire.



Is this normal or that wire must be in direct contact with the "-" pin of the diode bridge?.

Thanks.

[esla]

So I've opened my A124 once again and hope I can rebuild ist sometime.

The pin, with the arrow at this position is "8". This green-back wire ist soldered there. This definitvly one side of the diode-bridge, connectet to the positive side of C5. I've measured it. Your transformer seems to be okay, if you have 7,2 ohms in both cases. How much voltage can you measure over the big capacitator (C4). I have 11,5 V here (input voltage 230 V).

Greetings Jens

Edit: How much can you measure from one to the other pin für the AC-Plug? Here: 425 Ohm....

[TheReeler]

Can't measure now with tension... look, shot taken NOW:

The pin, with the arrow at this position is "8".

Don't understand that. I can't see a "8" in the schema.

This green-back wire ist soldered there. This definitvly one side of the diode-bridge, connectet to the positive side of C5.

I can't figure out whick exactly is C5... can you point me with my pics?.
Neither can't read the values of the two caps that I marked in my images. Are the simbols correct in my images or not?

Thanks in advance.

[TheReeler]

I've found the 8 in the board (my board seems to be unreadable). So the end of the wire was correctly soldered, but them seems than instead to be soldered to the "-" of the diode bridge, is soldered to the "+" of the diode bridge? Do you said that?.

[esla]

No no! Not the "+" or "-" side of the diode bridge! The positive pole of C5 must be connected with the red wire of the transformer. You can see it on the schema. It is one point at the AC secondary site.

I'll make photos of my adaptor later, it's just already opened now. But you don't answered my question: what resistance can you measuring from pole to pole in the AC-input (wich will go in the AC outlet in the wall )... you can try to search for an error, but if the primary site of the transformer ist'nt right, you'll never get an answer about it.

And as I said: 425 Ohm are allright there. It seems the transformer has an thermal fuse on it, but I'm not already shure.

Greetings Jens

[TheReeler]

103 ohms, but the output of transformer is unsoldered now, both red wires are without connect.

About the C5, I can't identify it... but anyway, the wire from point 8 (green with black bars) is the one that must be soldered to the red wire of the transformer?...

Thanks.

[TheReeler]

Here is a pic of the diode bridge:




The wire from the pin 8 (green with black bars) were soldered to the point marked with "?" in the pic, and measuring that "?" point between any other of the diode bridge, the impedance is always null, if I measure as a diode, that point againts any other of the diode bride, is always null too... so, is like that point went to nowhere.

Any thoughts?...

[TheReeler]

esla postete
And as I said: 425 Ohm are allright there. It seems the transformer has an thermal fuse on it, but I'm not already shure.

After rewiring completly the Z124, but WITHOUT soldering the wire that comes from "8" to ???, I get 420 ohms.

Now I need to know where to solder the wire that comes from "8"...

[TheReeler]

Another thing... the wire from "4" goes to the ~

That's correct?.

[PhonoMax]

Sometimes it's simpler to point than to explain:

https://tonbandforum.de/bildupload/Z124.pdf

Hans-Joachim

[esla]

It's the same as here - and shold be allright. The contact with the question mark, is in the diode bridge, but the fifth diode! Have a look at the schematic, there we have the four diodes für the "Graetz-Gleichrichterbrücke". But on the left upperside you'll find a fifth diode - and that ist this pin. Therefore the wire goes directly to the negative side of the capicator C5.

The wire from the pin 8 (green with black bars) were soldered to the point marked with "?" in the pic, and measuring that "?" point between any other of the diode bridge, the impedance is always null, if I measure as a diode, that point againts any other of the diode bride, is always null too... so, is like that point went to nowhere.

That can't be! If you are measuring "null" ohms, this diode is out of order. Replace the diode bridge and for these diode in the upper left try to solder a external diode. I've measured in the "Ohm"-Range always over 1 kOhm here from this pin to all other pins of this diode bridge. And she ist soldered. Or, try to replace only this diode, may be it works also. solder the green wire with black bars with the anode of a 1N4001 or so, and the cathode with Pin 1 of the the transformer (schema posted by Hans-Joachim). You must have 15 V over the "C5". It is only a, how can I tell it, a simply "help-voltage". But it must be there.



Greetings Jens

[esla]

PhonoMax postete
Sometimes it's simpler to point than to explain:

Thank you Hans-Joachim!

If you can better write in English than I can, then please try to translate:

Die einzelne Diode oben ist in Zusammenarbeit mit C5 doch nur eine simple Hilfsspannungserzeugung in Einweggleichrichtung. Der Hauptstrom kommt natürlich über die Grätz-Brücke. Was mir nicht klar ist, warum viel zu wenig Widerstand auf der Primärseite ist, das Netzteil aber bei 110 V laufen soll, bei 230 V aber nicht. Übergangswiderstände im Spannungswähler oder so etwas? Oder doch der Trafo?

Edit: doch eher der Brückengleichrichter (insbesondere diese Zusatzdiode) hin...

Gruß Jens

[TheReeler]

Hi again,

Yesterday I finally ended to rewire all inside the Z124. I replaced all old wires with newer ones, so I could check all things better, even the wires from the board to the transistor over the deck of the board.

I realized yesterday late night that the down pin of the diode bridge was the fith diode!!!, I measured it and it was right, so I solder from the pin 8 to there and protect it with a small piece of dielectric as was the original wire. I took lot of pics of all the process, but they are at home and now I'm at work.

After the job I tested it and works better than before, but I think the power seems to be not enough in some cases, when the machine is recording and with the light of the meters lighting.

It would be helpful it you could check the voltage in the lateral contacts (as it were used as a battery) while the Z124 is connected to the UHER with the DIN cable.

With the machine just powered on I get around 7.5V. If I start recording, the voltage starts to drop, and if even I turn on the light of the meters, it drops more.

[TheReeler]

Here the values of the voltage of the Z124 measured thru the external terminals while the DIN socket was plugged to the machine:

With the machine turned off: 7.55V
With the machine turned on, stop mode:7.45V
Playing:6.60V
Rewinding:6.73V
Fast forwarding:6.00V
Playing, with lights of the meters turned on: 6.33V
Recording: 6.00V
Recording with the lights of the meters turned on: 5.78V


During any transport function, if the lights of the meters are turned on, they light poor and when hit stop button, they light good.


Some pics of the rewiring process:












The bulb was burned, so I replaced it with a led:

[esla]

Hello,

I have three UHER Report (the third isn't here):

Uher 4400 Report Stereo - it has an A124 adaptor, Uher 4000 Report IC - it has the A124 A1-adaptor, Uher Report L - unknown adaptor

Now I took the 4400 Report Stereo and measurured the output voltage. If the machine ist powered on, I have here 6,05 V. When I start recording it drops down to 4,6 V! :oah: But this machine is not tested and had no repair. My Z124 connector also has to be repaired!! That's a fact. 4,6 V isn't normal.

Then I measured the Z124-A1 adaptor in the same machine. Power on: 6,00 V, then I started recording: 5,8 V. It seems normally. Can't use a DIN cable, but I've measurded directly the output contacts of the Z124 or Z124-A1.

Greetings Jens

[TheReeler]

Ok... mine is 4400 Report Monitor, maybe the power consume is greater than in other previous machines and maybe the Z124 isn't enough to give all the power needed. After the rewire the voltage is better, before that when I start to record, the voltage dropped below 5V and monitoring thru the speakers appears a big and rare noise. Try this in your 4400 Report Stereo while recording and tell me if that noise appears.

I replaced also the three electrolic capacitors, the big one for a 16V / 2200uF and the other two for 25V / 100 uF, all are capable for working at 105º. I tried also to solder another big capacitor in pararel to try to double the capacity, but it doesn't help.

Also the led consumes 20mA instead of the 40 mA of the original bulb... what I couldn't do is to solder the led to the original points of the bulb, because I don't know where were originally in the board. The schematic says that the original bulb is 5V, but I didn't find a 5V point in the board while measured it with the tester, so I soldered the led to a 6.5V with a resistor in serial.

[esla]

Hello,

today I've changed the rectifier bridge to a newer one. Now I have a stable output voltage:

UHER 4000 Report-L:

"off": 6,5 V
"on": 6,25 V
"play": 6,15 V
"record": 6,15 V

UHER 4400 Report Stereo

"off": 6,45 V
"on": 6,15 V
"play": 6,05 V
"record": 6,05 V

UHER 4000 Report IC

"off": 6,35 V
"play": 6,10 V
"record": 6,10 V

It's now much better than before (4,6 V!).

Greetings Jens

[TheReeler]

Inside my Z124 finally the main transformer was burned after more than 1 hour of continuous recording

After that I replaced the internal transformer with an external one but inside the unit something were hot, so finally discovered that the heat came from the diode bridge. I replaced it with a smaller and more modern diode bridge and soldered to it a 5th diode, because in the original diode bridge were another diode inside.

After that, now all works OK and the voltage is good even while recording. I get 6.2V then.