akai gx 625 voltage problem

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bertiesme

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This is my first post and I'm hoping for some help- I've aquired a Akai Gx 625 (USA model) which only has a 120 volt 60 Hz mains input- I want to run it in the UK- but so far all the step down transformers I've looked at, convert our 230 volt 50 Hz down to 120 volt 50 Hz. I gather that the capstan motor will run fine but the reel motors are 60 Hz- What I don't understand is that Akai produced other variants of this machine which were mains input adjustable, simply by moving a selector at the rear -but trying to find a stepdown amp that converts the cycle rating is like looking for the Holy Grail- Can someone help?
 
Does it matter if the reels are running at 50hz instead of 60? If it's like the Revox design, they'll be running a lot faster than tape speed anyway to maintain tension.
 
In the Akai user manual it states that with the models where the voltage is adjustable -Quote "CYCLE-
As the unit is equipped with CPG; AC Servo Motor, cycle change for capstan drive motor is not necessary; The following instructions are just for readjusting reel motors torques according to cycles"
It then instructs you to remove the rear cover and states " Cycle Change Switch is located on the System Control PC Board-Set to 50 Hz or 60 Hz position according to area power source"- As my deck is USA only it doesn't have this switch- On reading about cycle problems I gather that these motors will run at the wrong speed and more worryingly they may run hotter
 
In the manual it says "AC servo capstan motor".. JP, does it work the same as a DC servo motor, meaning it doesn't have to rely on the wall outlet to provide speed control? If yes, then speed won't be an issue... I also see pitch control on this deck which would indicate some sort of internal speed control, which is a good sign. Normally, in typical AC capstan motor units (TEAC 80-8 for example), it was a problem - its speed was totally mains controlled and it ran at the wrong speed. With DC servo it's not a problem and I'm wondering if AC servo serves the same purpose. One quick way to tell, is to purchase a step down transformer (at least 2x or ideally 3x the total watts used) so I think your model is 150W (check the back of the recorder) and you'll need about 450W, just as a safety factor. Make sure the store has a good return policy.
 
If it's got a pitch knob, the capstan is going to controlled independently from the mains. I'm not concerned about that since even if they did lock the frequency generator to the mains for its default timebase, you could still compensate with the varispeed. It's probably just an oscillator, though.

The big question is whether his reel motors (which seem to be AC induction motors) will care about running at the wrong mains frequency. He reckons they'll run hotter - I honestly have no idea.
 
Thanks for the response- I agree that the capstan motor is not the problem and I think I'll bite the bullet and get a 500 watt stepdown and see what happens-I still can't make out how Akai can incorporate cycle change in some of their decks as a matter of course- (and other manufacturers have this facility as well)- Yet step down transformer manufacturers seem to have ignored it-
 
Not sure about the reel motors but the internal power supply will get 20% hotter due to the 60 vs 50Hz thing but I think that every recorder of this nature (and they were built well back then), can tolerate such variances without issue, IMHO. Let us know how the step down trans works out for ya. I'd be very interested to know.
 
After a lot of investigation, I've been told that the 50 Hz- 60 Hz problem arises because of the way that power stations generate their electricity- Apparently, the easiest way out for me is to buy a 12 volt DC input to 110/120 volt output 60 Hz transformer ( of suitable wattage) made for the American market- The sort of unit that's used to power appliances in trailers etc- so that's what I'll try- I've been told that the reel motors definitely need to be supplied with the correct (Hz) frequency to govern the correct speed and that's why Akai had switch-able frequency in some of their models that were made for worldwide use-Of course if anybody out there knows different I'm all ears !!
 
So what exactly were you told to buy and how will it work? How will this setup provide the 60Hz in a 50Hz country? I'm having a hard time understanding. I'd appreciate some details.
 
Well, going from 12v DC to 110v AC will require an inverter. The inverter will synthesize the mains frequency, so all you need is an inverter that generates 60Hz instead of 50Hz as the local ones will. Means you'll have to have an extra stage to go from 240v at 50Hz down to 12v DC - finding a PSU which will do that with enough current to run the tape deck might potentially be a problem, though.
 
I see, thanks JP.... I'm not sure then if it's worth the hassle or expense. If it were me, I'd find a local store, get at least a 300W step down and try it out. Worse case scenario, I return it but I think it'll work, be cheaper and less hassle. What does your gut say JP?

I mean, those reel motors, if I'm not mistaken, all they do is generate opposing forces (in play/rec) for the capstan motor (which may be internally speed governed) to control speed. The reels also rewind and forward but that's not critical as far as our issue here. I think what's critical is that the capstan be confirmed to be controlled internally (like DC) and that heat (as a result of Hz difference) is not an issue (which I don't think it will be). This can be tested with an inexpensive step down (2 - 3 times total wattage). That's what I think, at least.
 
I know about enough to be dangerous, so I couldn't really make a sensible guess. My feeling would be that it should work, but I don't know if it would cause tension issues or possibly shorten the reel motors lives.
However, I do know that you'd need a decent inverter, which generates a good enough approximation to a sinewave to run an AC motor. One that generates squarewaves or a sinewave with too much stepping is liable to upset things more than the wrong mains frequency would.

EDIT: This might be handy:
http://www.donrowe.com/inverters/inverter_faq.html#modified
 
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Thanks guys for your thoughts on this problem. Like most people I originally thought only about stepping down the voltage without realising that there could be a potential overheating/speed control problem with the reel motors- What makes it worse is that I also have an Akai GX 630 but this one is voltage/cycle adjustable and the instruction book warns against running the machine at the wrong cycle- That's what's worrying me the most- Like Tape Wolf says, It's first of all going back down to 12volts DC then back up to 112volts A/C 60 Hz- The thing that gets me is, that if I'd bought the correct version of the 625 in the first place, I wouldn't have these problems, as Akai had it all sussed out years ago-Come back Akai !!-Regards. PS -I'll try that link
 
Akai GX 625

Thanks for that- but that is the problem- because this is a North American version, it hasn't got that switch- all it has printed on the cover is AC 120V 60 Hz 150 Watts-Since my last post, I have just got a 230V to 120 V stepdown transformer and connected it up and all the reels turn fine, all the logic controls work properly but-there is no sound or deflection of VU needles on play or record-Also the logic switches do not illuminate- On reading about this on other sites, I gather that there is a problem with faulty transistors on the pre amp board on this model, so I'm going to see about fixing those. Until that's done I can't tell if the 60/50 Hz cycle supply is a problem. The deck is in very nice condition so I'll keep going as long as it doesn't start to cost too much.
 
OK so there is no Hz switch on the PCB board inside, correct? That's still fine 'cause the manual pretty much confirms what was speculated that the Hz is a non issue with regards to the capstan speed (it's not controlled by a wall socket). It also looks like the reel motor torque might be a little off (due to the different Hz) and, as mentioned before, it might get a bit hotter on the power supply - all non issues in my opinion. That step down was a smart decision. The bigger issue is, as you mention, that the recorder is partly functional. I wonder if it was under-packed and damaged internally during shipping (likely, so check for cracks and hair line fractures on the PCB's). The other possibility is if the seller lied as to its condition.
 
I think you may be right about the Hz issue, at least all the mechanics seem to work properly-I've partially stripped the deck down since my last post and can see no damage to the pc boards etc., so I'm definitely going to replace the 2sc 2240 transistors on the pre amp board (which is what has been suggested is the problem) and hope that it gets the sound going - I bought the deck as untested and for a lot less than a good one sells for here in the UK, so I can't really complain- I've convinced myself that I can fix it-and if I can for less than £100, I'll be well pleased- I've a few old pc boards, so I'm sharpening my soldering skills up ready for the big event!! - I'll let you know how I get on- Regards
 
Just a quick update, I've near enough got all the parts that I think I'm going to need to fix the 625, then I'm browsing through Reel to reels on ebay and spot a UK spec 625 for a bargain price that's working-but needs some TLC- I just couldn't stop myself from hitting the "buy it now"!!-Luckily I have a decent sized workshop to hide it in-The problem with me is that once I've got this gear I can't part with it- I've got the feeling that I'm in sympathetic company here though- Regards, Bertie
 
bertiesme said:
The problem with me is that once I've got this gear I can't part with it- I've got the feeling that I'm in sympathetic company here though- Regards, Bertie
Click to expand...

Yup, same here, I just can't part with the gear... specifically with minty well built vintage tape machines (cassette and open reel). That's my weakness. You're in good company. :D
 
Well, I got around to replacing those defunct transistors and I now have sound and recording- My main worry about the reel motors running at the wrong speed has not materialised : which although I'm overjoyed about, I don't really understand why!-Only one problem left to fix- is the logic controls don't light up when pressed -only a minor annoyance but any ideas?-The other GX 625 I bought doesn't record so I'll replace all the transistors in that next- Regards
 
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