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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, 7:51 pm   #1
TerryB44
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Default Help with R2R Head

I have a record/play 2 track mono head that has 4 connections on the rear. Normally mono heads only have 2. Has anyone come across this before and how should I wire it up as my recorder only has 2 terminals to connect to. Is it that the record and play functions are on separate coils and if so should I just join the two sets of pins together so they are both fed from the same wires.
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Old 24th Feb 2021, 8:02 pm   #2
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Default Re: Help with R2R Head

There will only be one magnetic core if it's R/P and not separate R and P. You'd see the separate pole pieces if it was that.

So it's likely that there are two separate windings one on each half of the core. Most probably the manufacturer wants you to wire them in series (and get the phase right!)

It's likely that the core is in two halves and has a back gap. So both halves are made and wound identically and one is loaded upside-down compared to the other.

David
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Old 24th Feb 2021, 8:09 pm   #3
ms660
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Default Re: Help with R2R Head

Some heads had two windings that were then connected in series to form a tap for the bias feed.

Lawrence.
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Old 24th Feb 2021, 8:38 pm   #4
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Default Re: Help with R2R Head

Okay. So how do I identify which pins should be connected to complete a series circuit as there are no colour codes on the pins! The pins are arranged top left top right, bottom left bottom right. I only have multimeter and that can magnetise the head if I use that to test for continuity. Do I have to connect both windings or it will work with just one? Could I just fit the head and then play around with the different combinations of connection and see what happens?
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Old 24th Feb 2021, 8:40 pm   #5
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Default Re: Help with R2R Head

If you post a couple of photo's of the head, someone might be able to recognize it and what it was fitted to.

Lawrence.
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Old 24th Feb 2021, 8:42 pm   #6
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Default Re: Help with R2R Head

Connect one link diagonally and connect to the unlinked pins.
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Old 24th Feb 2021, 9:00 pm   #7
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Default Re: Help with R2R Head

Thanks Barry, I'll try that tomorrow and report back.
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Old 25th Feb 2021, 2:48 am   #8
jamesperrett
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Default Re: Help with R2R Head

I have one machine here that uses two windings on one head. It connects the segments in series for playback and in parallel for recording.
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Old 25th Feb 2021, 6:27 am   #9
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Default Re: Help with R2R Head

An unusual record/play head was the Ferrograph for the valve models which had a low impedance coil for playback (but stepped up with a transformer for feeding the valve preamp) and a high impedance coil fed directly from the valve record amplifier.

With potted head designs it's not possible to see what's going on inside. With Revox heads for A77/B77/PR99 etc it is possible to open the can and with some care remove the glued on cover to reveal two separate coils on both the record and play heads (3 head design) but connected internally (in series I think). I suspect it was/is convenient from a design POV to place one coil on the left side and one on the right side because, of course, they cant be placed across the front or rear gaps. I suspect it's the same for many other makes of tape head including cassette heads. If nothing else it seems an efficient use of very limited space inside the enclosure.
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Old 25th Feb 2021, 9:11 am   #10
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Default Re: Help with R2R Head

For deciding on the connection phase, measure the inductance of the windings in series. Go with the connection with the greatest inductance.

The symmetrical construction with two coils may also give a small reduction in sensitivity to external hum fields.

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Old 25th Feb 2021, 9:40 am   #11
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Default Re: Help with R2R Head

Hi, as is mentioned in post 6 I would begin by linking two of the pins diagonally and take the head wiring to the machines' amplifier section from the other two pins. I've seen this method on many two - track models which use the BSR TD2 deck.

Andrew
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Old 25th Feb 2021, 1:37 pm   #12
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Default Re: Help with R2R Head

Thanks Andrew, someone else suggested similar which is what I've done this morning and connected like this it works fine. It sounds much better now with plenty of high frequencies that were absent with the old makeshift head I had used as a stopgap until I found something better like this one. Cheers everyone who contributed.
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Old 26th Feb 2021, 9:38 pm   #13
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Default Re: Help with R2R Head

You were right Andrew, I found this picture of BSR Majestic heads in situ. You can see the wire connecting the pins diagonally.
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