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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 27th Jun 2021, 12:46 pm   #1
DMcMahon
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Default Grundig C 411 Automatic Cassette Recorder Check Out

My first look at this late 1970's mono cassette recorder that I purchased a while ago. It is the silver coloured top fascia version of the all black C 403.

Cosmetically looks reasonable condition, a quirky looking unit, feels robust and is heavy for its size. It was sold as working on batteries but not tested on mains as no mains cable.

It has a 9 pin DIN for inputs and outputs including external microphone, it has an internal condenser mic, also has a 2 pin DIN for external speaker.

This link provides a good overview.

https://www.petervis.com/gallery/Vin...and-c-411.html

Connected mains cable but unit completely dead so need to look at the power supply. On batteries it powers up and mechanically everything appears to work well, but zero sound (nothing at all) on playback, so investigation required into that as well.

Opened up and checked the internal 630mA fuse on the mains transformer secondary output, all OK. Been trying to measure the power supply voltages but difficult to identify the correct connections, so have partially removed the combined power supply + output amplifier board to check out the power supply artwork connections.

David
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Old 27th Jun 2021, 12:50 pm   #2
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Default Re: Grundig C 411 Automatic Cassette Recorder Check Out

Haven't seen one of those for a long time! There was one, tantalisingly locked away in a glazed bookcase, in our classroom at school in the late 1980s, which never got used AFAIK.
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Old 27th Jun 2021, 2:00 pm   #3
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Default Re: Grundig C 411 Automatic Cassette Recorder Check Out

Quote:
Originally Posted by DMcMahon View Post
My first look at this late 1970's mono cassette recorder that I purchased a while ago.

David
Correction, my late 70's reference was me getting mixed up with another cassette unit I am about to have a look at, the C 403 / C 411 / C 430 (Stereo version) came out around 1975.

David
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Old 27th Jun 2021, 7:50 pm   #4
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Default Re: Grundig C 411 Automatic Cassette Recorder Check Out

These suffer from the disintegrating gears. 3D printed replacements are available online I believe.
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Old 27th Jun 2021, 7:53 pm   #5
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Default Re: Grundig C 411 Automatic Cassette Recorder Check Out

Hi Ben, yes I had seen them (3D gears) online and wondered why, hopefully mine will be OK.

David
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Old 28th Jun 2021, 11:26 am   #6
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Default Re: Grundig C 411 Automatic Cassette Recorder Check Out

Checked out why it would not work with mains cable plugged in. Found that the changeover switch in the mains socket was open circuit when mains cable plugged in.

Switch was making a loud click when cable plugged in and opening the battery contact of the switch but totally open circuit on the other side of the changeover switch (that switches the DC power supply output to pin 5 of 9 way connector).

Removed the 2 pin mains connector (figure of 8 type) not really expecting to be able to do anything, but was pleasantly surprised to find that the changeover switch was removable from the body of the socket assembly.

Visually the contact was making but must have been heavily oxidised. Cleaned both contacts with fine wet and dry followed by contact cleaner. Switch is working fine now and now able to power the unit from the mains.

Next to investigate why no sound. First will scope the input to the output amplifier while playing a tape, if a signal there will look at the output amplifier board, if no signal then will look at the pre-amp board. If pre-amp board will see if can gain access to component side (presently can only see the artwork/track side) of the board to make fault finding easier.
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Old 28th Jun 2021, 11:35 pm   #7
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Default Re: Grundig C 411 Automatic Cassette Recorder Check Out

After retesting, sound now works fine, strange did not do anything to fix it ?

The playback sound sounds rather good with plenty of volume.

Removed the tape chassis from top cover to clean the heads etc. The plastic gears as far as I can see look to be undamaged. Now need to check out recording.

David
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Old 29th Jun 2021, 12:16 pm   #8
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Default Re: Grundig C 411 Automatic Cassette Recorder Check Out

Possibly spoke too soon about plastic gear wheels not being damaged.

After playing a few cassettes it has suddenly started making a loud knocking/clicking sound (on any cassette or without cassette fitted).

Initially thought the noise was coming from the rotating flywheel, investigating this found that the drive belt from the motor pulley to the flywheel is somewhat slack and the belt comes off quite easily when disturbed. But traced the noise to the Take Up spool area, looks like (difficult to see) that there is a plastic gear driving the Take Up spool somehow (cannot see what is driving the gear or what the gear is actually driving).

Noise only present in Play not in FFD or RWD.

So need to do a strip down to investigate further, at same time will replace the slack belt.

David
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Old 29th Jun 2021, 12:25 pm   #9
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Default Re: Grundig C 411 Automatic Cassette Recorder Check Out

What I like about all Grundigs, whatever type, they always fitted the largest loudspeaker possible.
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Old 29th Jun 2021, 1:25 pm   #10
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Default Re: Grundig C 411 Automatic Cassette Recorder Check Out

I had one of these many moons ago (probably still do but well buried), and I seem to remember that the tone and volume sliders gave me a lot of trouble, including no sound. If I recall, the tone slider isn't gradual. I think it just operates contacts underneath at the extreme ends of its travel.

One thing that did impress me was the determined and very fast wind (or was that rewind, perhaps both).

Shame if the gears disintegrate though.

Best of luck.
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Old 29th Jun 2021, 3:19 pm   #11
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Default Re: Grundig C 411 Automatic Cassette Recorder Check Out

Yes somewhat unusual tone slider with the middle setting being I guess the Flat setting and the outer settings (where contacts are operated) being max treble and max bass.

Touch wood no obvious issues with the operation of these sliders.

Yes the fast wind in both directions is good, no latching down on those keys though.

David
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Old 30th Jun 2021, 9:09 am   #12
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Default Re: Grundig C 411 Automatic Cassette Recorder Check Out

Oh yes I forgot about the non-latching keys.
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