reel to reel tape recorder

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Old 09-08-14, 05:09 PM
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reel to reel tape recorder

For those of you who are old enough to remember these things I need to ask for help. I am making one from my large spare parts pile. I am mixing and matching parts from various machines. My issue is that in PLAY mode both motors must turn in opposite directions, which is not an issue, but must also turn slower than when in WIND speed. If not there is a chance the tape will stretch and break. I know I can use a VARIAC but they are large and heavy. What I need is either a simple transformer with a 110 primary and a 50 volt secondary. The transformer would only be needed in that mode. An alternative would be a simple small speed control. The motors are 4 pole eddy current fractional horse power cap start/cap run. In the past I have used a transformer. Can a light dimmer be used in this instance? These motors will run on any ac voltage from about 6 to 110, hence the variac in the past. I have one being used for testing as I write this. I do not have a dimmer handy. That would be a simple solution. Advice please.
 
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Old 09-08-14, 05:37 PM
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Welcome to the forums.

That's quite an undertaking. It can be extremely difficult to keep the tape tension proper.
My issue is that in PLAY mode both motors must turn in opposite directions, which is not an issue
Actually they appear to turn in different directions but it's actually the way the electronic braking works. I assume you're talking about the reel drives. The problem is that depending how much tape is on the reel is how much back tension you need and it varies.

I'm a DIY'er and I've serviced those machines for years but to build one.... I dunno. A tough job.
 
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Old 09-08-14, 05:50 PM
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I'm just kidding, but I would get in touch with Jimi Page or maybe Frampton, they have mastered the art of tape recording.
 
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Old 09-08-14, 05:57 PM
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These are cap start/run 4 pole eddy current. In the past I have used a simple transformer, 110 primary, 50 secondary. The motors are large enough that torque is built into the motor. That is only an issue in WIND mode. In PLAY mode both motors rotate at half rpm in opposite directions. It is the roller against the capstan that overcomes back tension to move the tape. The supply motor provides enough back tension to keep the tape tight against the heads. In Wind mode the leading motor rotates at full rpm and the trailing motor rotates at half rpm to create back tension. Either motor could be the lead. Since you have serviced these. perhaps you could provide me with the appropriate transformer or info to one. Would a light dimmer work? It is only a matter of lowering voltage. Current is not much of an issue. I suppose I could use brush less DC motors but the type I need for the sake of the shaft are not available. Any simple speed controllers off the shelf would be nice.
 

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Old 09-08-14, 06:03 PM
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We don't post email addresses as it promotes spam.

The transformers you need are multitap type.... like used in the old Tandbergs and Revoxs.
Trying to think of where to check for them.
 
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Old 09-08-14, 06:03 PM
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Please provide me with links or a way of contacting these people as I am new here and do not know how to contact other members. Thanks.
 
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Old 09-08-14, 06:37 PM
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I saw SCR based motor speed controllers on EBAY in the $10 range. They are similar to the so called ROUTER controls which are for brush motors only. These are said to be for lights, small ac motors, although types were not described. fans, ect. Am I on the right track?
 
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Old 09-08-14, 07:11 PM
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Please provide me with links or a way of contacting these people as I am new here and do not know how to contact other members. Thanks.
That is what the forum is for. That is what forums are all about.
 
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Old 09-10-14, 05:49 PM
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For all intents and purposes the reel motors are in a stall condition. Both must sustain continuous duty that way without overheating and while constantly putting a gentle torque to keep the tape taut while a third motor powers the capstan that moves the tape at constant linear speed. All this without the need for constant manual tweaking of a speed control as one reel empties and the other fills up. (Some tape recorders use clutches so the reel can rotate at any speed depending on tape movement while the reel motor runs at a faster constant rotational speed and not in a stalled condition.)
 
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Old 09-10-14, 06:11 PM
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I ordered a transformer, again 110 in/50 out. Same as in the past. no infinite speed control, just halfing the voltage so one or both run at a constant slower speed. Full speed in PLAY mode would stretch the tape and break it.
 
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Old 09-11-14, 12:24 AM
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Allan is correct about the motors in a R-R tape unit.

The speed of an AC motor is determined by the frequency of the applied power. Voltage has very little, if any effect on the speed. Lower voltage WILL have an adverse effect upon motor torque and it WILL cause the motor to heat up.

Ever notice on a R-R recorder that when the tape comes off the reel that BOTH reels speed up considerably?
 
  #12  
Old 09-11-14, 01:24 PM
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With all due respect you are both correct and incorrect at the same time. You are correct in that when the tape comes of the reels the motors do speed up to wind speed, full voltage, full speed. This is because in PLAY mode both motors are rotating less than full rpm deliberately. This is to reduce stress on the tape. The roller/capstan contact moves the tape. When the tape falls of the reel all forces from the roller/capstan is removed and the motors are now free of torque and speed limitations. This does not happen because the limit switch opens removing power to the motors and capstan solenoid. How the motors run at full rpm and also at half rpm is unknown. I do know I can and have used transformers and VARIACs to lower volts and reduce rpm.

As for the value of the start/run cap if the value is too small the motor will not get off stall or rotate too slow. I had to change the cap of one of my main motors in order to wire it for the 2 speeds it had. One cap for coil 1, one cap for coil 2, for line 2, and line 1 for coil 1. Simply switched line 2 between the 2 caps, connected for the correct rotation which depends whether the roller sits below or behind the capstan.

That has been my experience over the years. For such small motors the only issue I have run into is that for motors on 7" decks have less built in torque than those for 10". A full 10" reel in wind mode driven by the less torque motor will stall near the end of the wind. Just some things for you to think about.
 
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