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Vintage Tape (Audio), Cassette, Wire and Magnetic Disc Recorders and Players Open-reel tape recorders, cassette recorders, 8-track players etc.

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Old 24th Feb 2021, 7:11 am   #21
Termorilis
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Default Re: Schaub Lorenz Music Center 5001

Thanks Dmc Mahon. I translate the English to the Italian language the contain of the old forum. I remember that I'm italian. The problem is very interesting. We update.
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Old 25th Feb 2021, 8:54 pm   #22
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Default Re: Schaub Lorenz Music Center 5001

through the old discussion I saw that to test if the pilot tone circuit works, you need to do a test: it consists of connecting the R833 and C831 of the record / playback circuit. This produces a loud hum through the speaker which should trip the relay (if the pilot tone circuit works). I would like to perform this test but I cannot read R833 and c831 because the schematic has too low a resolution. Do any of you have a higher resolution schematic?
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Old 25th Feb 2021, 9:39 pm   #23
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Default Re: Schaub Lorenz Music Center 5001

ok! Found! Through the manual.I'll take the test as soon as possible.
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Old 26th Feb 2021, 7:22 am   #24
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Default Re: Schaub Lorenz Music Center 5001

R833 and c831 are connected in series. I have shorted the c831 with a jumper but there is no hum. Playback of the tape stops. And anyway, there is no detachment and return of the tape. Is the test valid in your opinion?
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Old 26th Feb 2021, 11:36 am   #25
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Default Re: Schaub Lorenz Music Center 5001

Not sure as not familiar with the test and have had no time to view the circutry.

Maybe ricard (the author of the suggested test) can elabortae more.

David
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Old 26th Feb 2021, 4:21 pm   #26
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Default Re: Schaub Lorenz Music Center 5001

According to a schematic I'm looking at, R833 and C831 are already connected together....

I would have thought a low to medium level 50Hz input to C601 should trigger the relay, if not I would check the amplifiers circuit, T601, T602, T603 etc, the pilot tone switching voltage comes from the cathode of D602.

The 50Hz for the pilot tone on record comes into the Base of T801 via the junction of C801 and R800 and TA contacts 15 and 16....So far as I can make out.

Lawrence.
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Old 26th Feb 2021, 9:02 pm   #27
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Default Re: Schaub Lorenz Music Center 5001

It would take me to inject a 50Hz signal. But I don't know how to generate it and exactly where to inject it.
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Old 26th Feb 2021, 9:52 pm   #28
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Default Re: Schaub Lorenz Music Center 5001

Does the tape have known good pilot tone recordings on it? If so are they present at C601 when looking with a 'scope when playing back?

Lawrence.
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Old 27th Feb 2021, 2:55 pm   #29
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Default Re: Schaub Lorenz Music Center 5001

Quote:
Originally Posted by Termorilis View Post
It would take me to inject a 50Hz signal. But I don't know how to generate it and exactly where to inject it.
Page 14 of the manual says to feed in a 50 c/s 25mV signal into the input of the pilot signal amplifier (signal generator at C601 and ground) which should energise the rls 601 relay.

David
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Old 27th Feb 2021, 3:01 pm   #30
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Default Re: Schaub Lorenz Music Center 5001

Been trying to see how/where the internal 50Hz pilot signal is generated/derived from.

In the manual section 4.8.0 b it explains that the 50Hz is obtained from the voltage divider R401/R402 off the 6V supply (ref Fig 80), partially also shown on Fig 5.

David
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Old 27th Feb 2021, 3:13 pm   #31
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Default Re: Schaub Lorenz Music Center 5001

A 390 Ohm across R402 should give a near enough test voltage from the potential divider, so far as I can make out the bottom end of the potential divider that's connected across the 6 volts AC supply is connected to the +ve 18 volt rail when TC is selected.

Lawrence.

Last edited by ms660; 27th Feb 2021 at 3:24 pm. Reason: extra info
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Old 27th Feb 2021, 4:31 pm   #32
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Default Re: Schaub Lorenz Music Center 5001

I tried with the oscilloscope with a 20 millisecond time base corresponding to 50Hz. I inserted the probe into the positive pole of C601. At the end of the recording I have a very flattened sinusoid. This is when the recorded song ends. After 2 3 seconds I have a straight line. The pilot tone appears to be present. Confirm?
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Old 27th Feb 2021, 5:24 pm   #33
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Default Re: Schaub Lorenz Music Center 5001

So far as I can make out there should be 50Hz at point 53 for a couple of seconds when switching from record to stop and there should be 50Hz at point 83 in playback for a couple of seconds after the finish of the recording that's being played back if a pilot tone was recorded after that recording.

Lawrence.
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Old 28th Feb 2021, 6:39 am   #34
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Default Re: Schaub Lorenz Music Center 5001

Quote:
Originally Posted by DMcMahon View Post
Maybe ricard (the author of the suggested test) can elabortae more.

If you're referring to this post https://www.vintage-radio.net/forum/...3&postcount=13 I was just translating the indicated passage from the German text referred to in post 10 of the same thread manual into English. No other relationship to this machine (although it's one of those devices that keeps entering my frame of consciousness from time to time; I first read about it in a book about tape recorders written in 1970).
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Old 28th Feb 2021, 8:04 am   #35
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Default Re: Schaub Lorenz Music Center 5001

I did the test with the oscilloscope you suggested and at point 83 of the circuit in playback mode at the end of the piece of music I have a sine wave for 2-3 seconds.
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Old 28th Feb 2021, 2:51 pm   #36
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Default Re: Schaub Lorenz Music Center 5001

Quote:
Originally Posted by ricard View Post
Quote:
Originally Posted by DMcMahon View Post
Maybe ricard (the author of the suggested test) can elabortae more.

If you're referring to this post https://www.vintage-radio.net/forum/...3&postcount=13 I was just translating the indicated passage from the German text referred to in post 10 of the same thread manual into English. No other relationship to this machine (although it's one of those devices that keeps entering my frame of consciousness from time to time; I first read about it in a book about tape recorders written in 1970).
Yes
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Old 28th Feb 2021, 2:56 pm   #37
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Default Re: Schaub Lorenz Music Center 5001

If the amplitude of the pilot tone at point 83 is sufficient, the next test I would do would be to monitor the DC voltage with the 'scope set to DC between the Emitter and Collector of T603, when the recorded track is playing it should be approx 18 volts and at the end of the track during the two second pilot tone the voltage should fall to very low.

A brief explanation so far as I can make out from pilot tone detection through to rewind.

Note: In the schematic the relay and solenoid contacts are shown in the rest position.

When working normally in play, contacts rx6 & rx7 of relay RX are closed, contacts rx8 & rx9 are open, when the voltage between the Collector and Emitter of T603 goes low due to the detection of the pilot tone the relay Rls601 is energized and it's contacts open, that disconnects the power to the energizing coil of relay RX and contact rx6 breaks from rx7 and makes with contact rx5, that results in relay R being energized, amongst other things that results in contacts v6 & v7 of relay V opening which causes the tape drive idler solenoid KMV to be de-energized causing it's contacts kmv2 & kmv3 to make while at the same time, due to solenoid KMV being de-energized, the tape drive idler is released. Meanwhile, getting back to relay RX, contacts rx8 & rx9 of relay RX close, thus energizing relay RH which results in the contacts rh7 & rh6 of relay RX being closed, that in turn causes solenoid KMR to be energized, thus bringing the rubber drive wheel on the rewind motor into contact with the rim of the tape supply spool and the tape is rewound (fast) The motor is turned on by contacts kmr4 & kmr5 of solenoid KMR.

Any errors then guilty as charged.

Lawrence.

Last edited by ms660; 28th Feb 2021 at 3:24 pm. Reason: extra info
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Old 28th Feb 2021, 3:32 pm   #38
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Default Re: Schaub Lorenz Music Center 5001

It works !!! I adjusted the trimmer near the 500 microfarad capacitor connected to the mercury relay. Problem solved. Since there are many unrecorded tracks, the automatism clicks many times. It had been deliberately deactivated to prevent it from snapping so many times. Then I have some small keyboard problems left to solve. We update.
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Old 28th Feb 2021, 3:40 pm   #39
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Default Re: Schaub Lorenz Music Center 5001

Quote:
Originally Posted by Termorilis View Post
It works !!! I adjusted the trimmer near the 500 microfarad capacitor connected to the mercury relay. Problem solved. Since there are many unrecorded tracks, the automatism clicks many times. It had been deliberately deactivated to prevent it from snapping so many times. Then I have some small keyboard problems left to solve. We update.
Good result.

Lawrence.
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