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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 14th Oct 2020, 4:29 pm   #1
ben
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Default Making a midi system cassette deck standalone

I recently found a nice Sansui cassette deck (Model D-E970) next to some bins. This was once part of a top of the line system, it has dual 2-motor auto reverse cassette wells which can both record - not a feature one often finds.

Unfortunately the power lines seem to be a -30v for the digitron plus an AC 9v supply for the rest (there is evidence of internal regulators and rectifier). Not sure if that is used also for the digitron cathodes. I cannot find a cct diagram for this unit, so am working from what I can see on the boards.

My quest now is to come up with something from the junk box that would supply the voltages required to get this thing working.

I was thinking of harvesting a PSU PCB from things like DVD players, VCRs and older set top boxes that have a VFD. This DVD player (attached) has -24v output plus a couple of DC 12v lines which could probably provide a 9v AC source without too much trouble. I suspect a VCR might be a better option, as it would have greater current capability.

Has anyone attempted such a thing before? There must be stacks of these midi system components lying unused long after the amplifier/PSU has met its maker. In the past I did this with Sanyo and Marantz units that only needed a 12 or 24v DC supply. Turntables especially could always be given a new lease of life for the cost of a mains adaptor and a barrel socket. This, however is a bit more challenging!
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Old 14th Oct 2020, 8:57 pm   #2
Michael Maurice
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Default Re: Making a midi system cassette deck standalone

I wonder what the AC 9V supplies, it is probably +/- 12V but you'll also need a 5V supply and maybe even a -5V supply.
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Old 14th Oct 2020, 10:24 pm   #3
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Default Re: Making a midi system cassette deck standalone

Sorry I should have been clearer, the diagram I uploaded is of a PSU in a defunct DVD player I own and was thinking of using. I don't have the diagram for the tape deck. On its PCB near the proprietary connector are marked, amongst a few other things, the 9v and -30v lines (fortunately!)
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Old 20th Oct 2020, 8:50 am   #4
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Default Re: Making a midi system cassette deck standalone

I think obtaining a circuit is the way to go ,I have done similar in the past ,but not as complicated ,good luck with it ,love to see it working. Mick.
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Old 20th Oct 2020, 9:38 am   #5
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Default Re: Making a midi system cassette deck standalone

I don't suppose the schematics in the Service manual (hifiengine) for the single cassette model D-970 (which has integral power supply) would be of any use ?

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Old 20th Oct 2020, 8:51 pm   #6
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Default Re: Making a midi system cassette deck standalone

Thanks for the tips. Sadly none of the cassette decks listed there are close enough!

I have, however, studied the schematic from the system's amplifier and it seems that connector system control-1 is what goes to the tape deck I have. So am now trying to figure out the voltages that would appear on each pin 1-11. So far I have found:

1. GND
2. SSB TU (tuner controlled record remote?)
3. 9.1v AC phase
4. 14.5v AC (1)
5. 9.1v AC Centre Tap
6. 14.5v AC (2)
7. 9.1v AC 2nd phase
8. ? Rectified -29v?
9. ? -29v?
10. 5v?
11. 5v?

A further complication is that not al these lines are likely to be used by the tape deck , I think there was a graphic equalizer on the same connector. Will keep looking.
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Old 21st Oct 2020, 9:36 am   #7
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Default Re: Making a midi system cassette deck standalone

Hello Ben it might be worth a call to Ed Dinning on the forums who may be able to build a custom AC transformer for you if practical in terms of costs etc. Also when I was part of an Authorised Service centre years ago Kenwood indeed supplied all of the dealers with a master supply with 3 types of a connector to run things out of systems that were multi stacked as solo units with analogue audio output to monitor audio etc when required. It was a real help indeed, if i can find a picture of one on google I will let you know.
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Old 21st Oct 2020, 10:37 am   #8
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Default Re: Making a midi system cassette deck standalone

Now you know what supplies were available from the amp, and you can see where the rectifier and regulators are connected within the cassette deck, you could probably lash-up a bench supply to the main lines and see what (if anything) happens.
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Old 29th Oct 2020, 10:38 am   #9
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Default Re: Making a midi system cassette deck standalone

I have now come across a power supply PCB I think would cater for all the voltages in question. Before experimenting, however, I need to ask a favour. Perhaps some kind soul could cast their eye over the diagram in post 6 and check my interpretation of the voltages on that connector?
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Old 29th Oct 2020, 2:03 pm   #10
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Default Re: Making a midi system cassette deck standalone

Largely in agreement with you Ben, but see why you have some questions marks.

As from your Post # 6 with bold comments:-

1. GND - Agreed
2. SSB TU (tuner controlled record remote?) - SSB out from the microprocessor (active low), can see the other SSB out on IC3 which is driven by a Remote Control signal but not easily able to see if it is Tuner controlled ?
3. 9.1v AC phase - Agreed, yellow via fuse F2
4. 14.5v AC (1) - Agreed, green via fuse F3
5. 9.1v AC Centre Tap - Agreed, Black 1A
6. 14.5v AC (2) - Agreed, green 1.4A
7. 9.1v AC 2nd phase - Agreed, yellow via fuse F1
8. ? Rectified -29v? - Very Unsure about this, it connects to the +ve side of the mD4 bridge rectifier, with the -ve side of the rectifier at -43.5V, with the regulator transistor mQ7 emitter being at -29V. With the 30V Zener mDZ2 connecting the transistor emitter back to the +ve side of the bridge rectifier. There is also a 10 Ohm pull down (to ground) resistor mR80 connected to the +ve side of the bridge rectifier. On the one hand I thought pin 8 may be close to -29V because of the Zener but the 10 Ohm resistor to ground confuses me ?
9. ? -29v? - Agreed, via inductor mL100
10. 5v? - Unsure, 5VAC from transformer (Orange 0.3A) connecting through to the 5.6V Zener mDZ3 via 100 Ohm resistor mR15 but the Zener cathode is at -29V so unsure of final voltage ?
11. 5v? - Unsure, 5VAC from transformer (Orange 5V) connecting through to the 5.6V Zener mDZ3 via 100 Ohm resistor mR14 but the Zener cathode is at -29V so unsure of final voltage ?

David

Last edited by DMcMahon; 29th Oct 2020 at 2:10 pm.
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