Good evening,
I have a Brenell MK5 tape deck that has 240V/50hz synchronous motors on it. I'm running it stateside here and am wondering if there is a way to adjust the motor speed outside of DC-AC inversion or someting along those lines?
Surely this must have been done at one point or another to play tapes recorded "across the pond?" The motors are 3W 1275RPM. Any help is appreciated.
I have a Brenell MK5 tape deck that has 240V/50hz synchronous motors on it. I'm running it stateside here and am wondering if there is a way to adjust the motor speed outside of DC-AC inversion or someting along those lines?
Surely this must have been done at one point or another to play tapes recorded "across the pond?" The motors are 3W 1275RPM. Any help is appreciated.
Inquire about a new 60 Hz pulley and at the same time ask if the motor can be set to 120V. Otherwise the transformer will be needed.
The rewind and take up motors are both synchronous and not pulley driven. The capstan motor drives a rubber idler wheel which turns another flywheel and finally the capstan. The only pulley is for the counter which I don't care to bother with at this time.
I am thinking a variable frequency drive or generator/alternator setup might be the only practical ways to go about it. The frequency converters available commercially are rather expensive. This was more a curiosity than a necessity.
I am thinking a variable frequency drive or generator/alternator setup might be the only practical ways to go about it. The frequency converters available commercially are rather expensive. This was more a curiosity than a necessity.
Depending on your level of skill you could build a 50Hz source to power the deck. I designed one with crystal control which is here:
http://www.diyaudio.com/forums/anal...rator-induction-motor-powered-turntables.html
This would work equally well with a tape deck if scaled up.. The version I am using will provide 120V/240V at 50 or 60Hz with ppm frequency precision at up to 50VA load.
All tapes are recorded at standard speeds so should play fine on any deck supporting those speeds and the required EQ. (NAB or IEC)
http://www.diyaudio.com/forums/anal...rator-induction-motor-powered-turntables.html
This would work equally well with a tape deck if scaled up.. The version I am using will provide 120V/240V at 50 or 60Hz with ppm frequency precision at up to 50VA load.
All tapes are recorded at standard speeds so should play fine on any deck supporting those speeds and the required EQ. (NAB or IEC)
Thank you very much for this link Kevin. I am very much appreciative. I am going to take some time tonight to review this thread.
I have my doubts reel motors are synchronous. I'm more inclined to thing they are torque motors which can be stalled or run at a slower than usual speed without problems. As I understand, synchronous motors don't like to run at a higher torque load then designed for. Are you sure about your descriptions of the motors? Obviously I can't see the labels.
AS a follow up, a chart found on the web has motor information. There is one statement about the earlier machines that used shaded pole motors, and the a later machine that used a Papst synchronous motor for the capstan.
GB 59 Stereo recorder Three Star Stereo tape recorder
GB 63 Mark 5 series 3A ECC83
GB 56 Tape recorder TR Mk II Z729 3 speed (15 ips, 7.5 ips, 3.75 ips) open reel tape recorder with 3 shaded pole AC motors. ...
GB 70 ST Stereo ST200 Two track model. The ST400 is similar but four track. 3 tape speeds. First Brenell a...
GB 61 Tape Rcorder EF86 3 tape speeds: 15 / 7.5 / 3.75 ips. Three motors (Pabst motor for capstan). Transportable,...
GB 63 Type M Mark 5 Series 3 ECC81 "Portable" two track three head reel tape recorder. 4,75/9,5/19/38cm/sec., flutter 0,05%. ...
GB 61 Record/Playback Amplifier Mark 5 Series 3 EF86 Record/Playback Amplifier designed for use with Brenell tape recorders, needs optional pow...
GB 60 Mixer Unit AF mixer with 3 inputs and one output, hammer gray finish.
GB 60 Hi-Fi Tape Link ECC81 Record-/playback amplifier for three head tape recorder, seperate power unit, DC heated va...
GB 65 STB-2 Four speed, mono-stereo half track (record/playback) or quarter track /playback only) open...
I'm not sure where these details fit for your problem,
GB 59 Stereo recorder Three Star Stereo tape recorder
GB 63 Mark 5 series 3A ECC83
GB 56 Tape recorder TR Mk II Z729 3 speed (15 ips, 7.5 ips, 3.75 ips) open reel tape recorder with 3 shaded pole AC motors. ...
GB 70 ST Stereo ST200 Two track model. The ST400 is similar but four track. 3 tape speeds. First Brenell a...
GB 61 Tape Rcorder EF86 3 tape speeds: 15 / 7.5 / 3.75 ips. Three motors (Pabst motor for capstan). Transportable,...
GB 63 Type M Mark 5 Series 3 ECC81 "Portable" two track three head reel tape recorder. 4,75/9,5/19/38cm/sec., flutter 0,05%. ...
GB 61 Record/Playback Amplifier Mark 5 Series 3 EF86 Record/Playback Amplifier designed for use with Brenell tape recorders, needs optional pow...
GB 60 Mixer Unit AF mixer with 3 inputs and one output, hammer gray finish.
GB 60 Hi-Fi Tape Link ECC81 Record-/playback amplifier for three head tape recorder, seperate power unit, DC heated va...
GB 65 STB-2 Four speed, mono-stereo half track (record/playback) or quarter track /playback only) open...
I'm not sure where these details fit for your problem,
Thanks for the reply. I believe you could may be right, but I am no expert by any means.
The power supply has taps for 240, 210 and 110v. I have it set to 210V right now, giving me 6.3V-on the dot- for filament voltage. I think that the deck power supply was standardised and either 50Hz or 60Hz motors were provided dependent on the market. I definately have the 240V/50Hz model for the motors. The two series wirewound resistors are for keeping heat down on high speed setting.
The markings etched on the take up (right) and capstan motor:
3W RPM 1275 CCPE 0 40320
And the rewind (left):
5W RPM 1275 CPE D 40886
The power supply has taps for 240, 210 and 110v. I have it set to 210V right now, giving me 6.3V-on the dot- for filament voltage. I think that the deck power supply was standardised and either 50Hz or 60Hz motors were provided dependent on the market. I definately have the 240V/50Hz model for the motors. The two series wirewound resistors are for keeping heat down on high speed setting.
The markings etched on the take up (right) and capstan motor:
3W RPM 1275 CCPE 0 40320
And the rewind (left):
5W RPM 1275 CPE D 40886
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Sorry, I can't decode anything else for you. There were plenty of hits typing in the Brenell Mk 5 tape deck as a web search. It's a good place to start looking.
Thanks, I do believe these are in fact synchronous. I am going to explore kine frequency conversion further. Much obliged for your help.
Hello Ggizzy,
None of those motors are synchronous. They are induction motors. The quoted speed of 1275rpm is the clue. synchronous speed would be 1300rpm @50Hz.
Induction motors always lag synchronous speed by a few rpm.
Sincerely,
Ralf
the 50Hz line freq gives 3000cycles per minute.
Your synchronous motor must run at 3000/n rpm.
a 2pole will run @ 1500rpm (not 1300rpm)
4 pole @ 750rpm
8pole @ 375rpm
16pole @ 187.5rpm
They do not run slow, they are locked to the driving frequency.
An induction motor, when developing no torque, would also try to run at those same speeds.
But friction requires some torque and so the induction motor even with no external load will run slower than the driving frequency.
The more torque you apply the slower the induction motor will turn.
Your synchronous motor must run at 3000/n rpm.
a 2pole will run @ 1500rpm (not 1300rpm)
4 pole @ 750rpm
8pole @ 375rpm
16pole @ 187.5rpm
They do not run slow, they are locked to the driving frequency.
An induction motor, when developing no torque, would also try to run at those same speeds.
But friction requires some torque and so the induction motor even with no external load will run slower than the driving frequency.
The more torque you apply the slower the induction motor will turn.
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Thanks. So they'll run about 20% faster when used on 60hz? I was under the impresion synchronous or induction motors were used in these older tape recorders because of their longevity. Did early pro tape decks use DC motors in order to more easily vary the speed? How did thy play tapes from other areas of the world with different line frequency? Rectify-inverter with non-pure sine output?
After reading more it looks to me that a variable frequency drive of some sort would be the only real solution outside of changing the motors out, which I'm not willing to do. This is the first tape recorder I've restored and is only for personal use, so I can stand to live with only being able to playback on this deck. Tape tension and snapping might be another issue with the motors running faster though.
After reading more it looks to me that a variable frequency drive of some sort would be the only real solution outside of changing the motors out, which I'm not willing to do. This is the first tape recorder I've restored and is only for personal use, so I can stand to live with only being able to playback on this deck. Tape tension and snapping might be another issue with the motors running faster though.
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There must be a slip mechanism.
That allows the reel to run at correct, but variable, rpm to suit the tape speed/s.
It's the tape speed that must be accurate to allow replay on different machines
That allows the reel to run at correct, but variable, rpm to suit the tape speed/s.
It's the tape speed that must be accurate to allow replay on different machines
I'm not sure about a slip mechanism. You mean a mechnical means of adjusting for the freuency difference? The unit has a three-position rotary switch which can select tape speeds. They made two different capstan sleeves which changed these available speeds. I have the 1/2" sleeve allowing for 1 7/8, 3 3/4 and 7 1/2 IPS. The 1" sleeve makes these speeds 3 3/4, 7 1/2 and 15 IPS.
Incoming mains is taken to all three motors. My guess is that should someone have ordered a unit for the States they fitted 110/115V motors to the unit and had yet another variant of the capstan sleeve or idler wheel fitted? This is conjecture obviously, but it might explain why the PT primaries are switchable between 240, 220 and 110VAC.
Incoming mains is taken to all three motors. My guess is that should someone have ordered a unit for the States they fitted 110/115V motors to the unit and had yet another variant of the capstan sleeve or idler wheel fitted? This is conjecture obviously, but it might explain why the PT primaries are switchable between 240, 220 and 110VAC.
Hello Ggizzy,
Please tell me what that sentence means. Are all three motors directly connected to the line voltage?
Also, do the reel motors drive the reels directly, or do they drive the reels via friction clutches. Older professional three motor tape machines drive their reel platforms directly with AC induction Torque motors, while the capstan motor always is a Hysteresis Synchronous AC motor driving the tape directly with the motor shaft.
Sincerely,
Ralf
All the motors are driven from line frequency. The two reel motors are direct as far as I know. There is a brake drum and the reel is tightened by a top screw-type knob.
I attached an image I found advertising the unit after the unit I have. I believe they may use similar motors. (It says synchronous hysteresis for capstan motor)
I attached an image I found advertising the unit after the unit I have. I believe they may use similar motors. (It says synchronous hysteresis for capstan motor)
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Brennan MK5 Tape recorder
Hello Ggizzy,
If the reel motors indeed drive the reel platforms directly, the line frequency becomes immaterial in my opinion. In a typical machine like yours, in playback or record mode, the supply and take-up reel motors have approximately 35VAC supplied to them, while the supply reel motor is wired to run in a CW direction and the take-up reel motor is wired to run in a CCW direction. Being wired to run in opposite directions, causes the reel motors to hold the tape tension at approximately 6 ozs. ( for 1/4" tape) As the capstan motor transports the tape, the supply reel motor is being forced to turn in a direction opposite to the way it is wired. The rpm of the take-up reel motor is limited to whatever amount of tape the capstan delivers to it. During FF the take-up motor receives approximately 70VAC, while the supply motor remains unchanged. In REW mode, the voltages are reversed. So in my opinion, line frequency cannot be that important.
The voltages quoted, pertain to a Scully model 280 tape recorder and are meant to illustrate the principle involved only.
Before you invest in a power supply to obtain 220V/50Hz, I would just try a step up transformer.
You mentioned 1/2" and 1" sleeves. Can you show a picture of them? Any skilled machinist should be able to make a new set where the diameters reflect the difference between the line frequencies.
Sincerely,
Ralf
Hello Ggizzy,
If the reel motors indeed drive the reel platforms directly, the line frequency becomes immaterial in my opinion. In a typical machine like yours, in playback or record mode, the supply and take-up reel motors have approximately 35VAC supplied to them, while the supply reel motor is wired to run in a CW direction and the take-up reel motor is wired to run in a CCW direction. Being wired to run in opposite directions, causes the reel motors to hold the tape tension at approximately 6 ozs. ( for 1/4" tape) As the capstan motor transports the tape, the supply reel motor is being forced to turn in a direction opposite to the way it is wired. The rpm of the take-up reel motor is limited to whatever amount of tape the capstan delivers to it. During FF the take-up motor receives approximately 70VAC, while the supply motor remains unchanged. In REW mode, the voltages are reversed. So in my opinion, line frequency cannot be that important.
The voltages quoted, pertain to a Scully model 280 tape recorder and are meant to illustrate the principle involved only.
Before you invest in a power supply to obtain 220V/50Hz, I would just try a step up transformer.
You mentioned 1/2" and 1" sleeves. Can you show a picture of them? Any skilled machinist should be able to make a new set where the diameters reflect the difference between the line frequencies.
Sincerely,
Ralf
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