Is it unwise to run 220V European TASCAM 238 on UK 240V voltage?

altruistica

Member
My mint condition European model 220V (47W, 50Hz) TASCAM 238 turned up today and cosmetically it's like it's just left the factory. I was just about to turn it on and then I thought I'd check the back to see if it was a 220V model or if it had a selectable voltage. Apparently there were 4 models produced .

USA /CANADA 120V 60Hz
UK / AUSTRALIA 240V 50Hz
GENERAL EXPORT 120 /220 /240V 50/60Hz
EUROPEAN 220V 50Hz

Mine is fixed at 220V, 50Hz. After reading many threads, apparently there was some kind of European harmonisation around 2009, when new products would be made to a spec of 230v with +10/-6% tolerance. But this unit was made well before that, 1991 perhaps?
I've read about a buck transformer or auto transformer which one I've found is around £85.


I measured the voltage coming out of my wall out of curiosity....it was 242V

Any opinions on what to do?
Cheers,
Al
 

rob aylestone

Well-known member
Ha! Years back, the UK was nominally 240V and the rest of Europe 220V. Then we harmonised and everything was tagged 230V. Absolutely nothing changed. They agreed a spec with a +/- of voltage swing so the French used 230V for calculations, but what came out the sockets was 220V. We carried on with our 240V and pretended it was 10V less - it never ever was. It's 243V here today.

In 40 years I have never lost any equipment taking ours to Europe or Europeans bringing there's here. 220-240V in perfectly happy. We have had this for 40 years nearly.

What IS different are cables. If I buy an amp from Germany it will usually have an IEC style connector with a UK plug, but some are supplied with continental connectors - two pins and a ground hole with two side strips. We throw these away and just connect a UK plug version. Switch mode power supplies are alsmot all 110-240V capable and it's on the label. A US product labelled 110-120V will probably go pop - hopefully a fuse but taking out power supplies with US imported 110-120V kit is pretty much the norm. Plugging EU/UK 220-240V kit into US outlets has never killed anything - bit lots of things just won't work.

We still use 50Hz supplies in Europe and the UK. Never 60Hz. What else is different? Some kit is fitted with a figure 8 shaped mains socket. It can go in either way and thios kind of equipment is double insulated and has a special symbol on it - denoting a ground is NOT required. Three conductor cables with a ground must NOT ever have the ground disconnected. with 240V, safety here is more serious - our mains voltage doesn't just sting - it can kill much easier than US 110-120V versions

There is no practical difference between 220 and 240V equipment.
 

jpmorris

Tape Wolf
By my calculations it'll mean the output of the transformer will be about 10% higher than usual, e.g. a 12V line will be about 13V. The voltage regulators can cope with that easily.
 

altruistica

Member
Thanks for the replies guys.......I ordered the transformer this morning (grrrrrr!).
Any thoughts on why Tascam made a 220V version and a 240V version (unless of course they are the same transformer?). Is it for legalities?
 

rob aylestone

Well-known member
Years ago, when we were into transformers, it was considered good engineering practice to simply add an extra tap and get optimum conversion. If you design wanted 12V, 8-10% over or under could be a designed in variance - but if you needed 12V and got 11, some designers would consider that imperfect.

I suppose the extra cost of the tap didn't upset the bean counters, so it was a good sensible feature. When I first qualified, we'd run kit from a bench variac - it was interesting to see at what voltage things started to not work. Sometimes you could go down a very long way!
 

altruistica

Member
Thanks Rob for the reply. As I've mentioned elsewhere, this Tascam 238 is in mint condition. It came with the original box and the seller (who deals in Studer and the like) said it had had the capstan PC board replaced (I'm not sure whether it was the whole assembly including motor or just the board). With that in mind, I guess I'm approaching running the unit like a 'health conscious fanatic'.......ie. what goes in determines how long something will last. If the windings on the primary transformer are expecting to see something around 220V, +/ - 5%, all well and good, but I don't want to be sending it 250V say, and it having to work harder just to keep things in check. It would probably work, but at what cost (if any), long term?
 

sweetbeats

Reel deep thoughts...
Al,

have you looked at the primaries on the main power transformer? Are there multiple taps like was suggested above?

The Service Manual indicates there *are* two primary taps on the “EUROPE” as well as the “U.K., AUSTRALIA” versions, one for 240V mains and one for 220V mains…see here…look at your power switch PCB and see if there are three wires connected…white for the 0V reference, and then two additional wires, red and violet…if this is the case I don’t know if there is a jumper or what, but the violet wire is for the 220V tap. With the red wire disconnected and the violet and white wires connected the device should be setup for 220V operation. It least that’s how it appears to me:

9F34E570-D19E-4747-8067-2831E1B98B47.jpeg

BB8B2722-5964-4E0D-B86C-E91BF4A3D0B8.jpeg

So if I’m correct, the same transformer is used for each version, you just have to couple the correct tap to match the mains voltage. Outside of that, if you DON’T have an option with your main transformer, the secondaries feed a pair of bridge rectifiers for the +/-12VDC power rails (which also chain to the +5VDC logic power rail) an unregulated -25VDC rail…I’d have to look further to see what that powers…and a low voltage AC rail. I can’t tell without looking further what the voltage is on the AC rail and what that powers. More to know there. As well as the -25VDC rail…that would be, in theory, operating at -27VDC on 240V nominal mains…not sure if that is too much. If I’d have to guess I’d say no because it is already unregulated, and so likely not critical…may be regulated locally in the device and as mentioned earlier very often rectifying and regulating components are over-spec’ed enough to be fine with even +/-20% primary power variance. The +5VDC rail input taps after the +/-12VDC rail bridges and filter caps, so if those components can handle it, that’s all the +5VDC rail cares about. So…*can* they handle it? You’ll have to do some sleuthing unfortunately. I don’t know if you can disconnect the main transformer secondaries from the power supply PCB, or if they are soldered in. If you can disconnect them then you can plug the device in and switch it on with the transformer secondaries unterminated and measure what the voltage is that feeds the +/-12VDC bridge rectifiers D1 and D2. Those taps should be a pair of red wires that power D1, and a pair of brown wires that feed D2. Just connect your AC meter across one of those pairs to see what the voltage is. Honestly I’d expect it to be less than 20VAC or something. The maximum reverse voltage of D1 and D2 is 100V. Not sure if that is peak or rms but regardless there’s a *lot* of margin there. The spec sheet says the bridges have average forward current capacity of 2 amps EACH. That’s a lot for something like the 238. So we’re good there. Then there are the main filter caps which are all 25V parts. So that’s where you’d want to consider if 240V runs you too close. I’d have to find it…there’s a way to calculate AC volts to rectified DC volts. With that you could estimate what, based on what you measure on the secondaries, the DC volts will be at the outputs of the bridges. If it’s less than 25V, then the filter caps are okay. If it’s really close or over 25V, well then buy a couple 4,700uF and three 3,300uF caps all at the next voltage spec (35V) and you’re fine there. Then you have the regulators U1~4. These are all standard 78xx and 79xx TO-220 packaged parts. Probably JRC. As far as I can see by the data sheets the maximum input voltage for the regulators is 35V. You’re golden there. Logic tells you the rectified voltage is not more than 25V (because the main filter caps were spec’ed at 25V). 10% over is 27.5V. That’s well below the 35V maximum of the regulators. And those are all the components you need to worry about with the +/-12VDC power supplies. This leaves still several questions to answer, but honestly I bet it would be fine as far as the +/-12VDC rails to operate on 240V. The bridges and regulators are well over-spec, and the caps…I’ve yet to encounter an 80s-90s vintage Tascam device that had power within 10% of any voltage tolerance of any electrolytic cap. And remember a 25V cap is designed to operate at that voltage for however many thousands of hours you find on the spec sheet, barring any other electronic or environmental stressors (heat, ripple, etc.), so it would be *fine* if the raw rectified voltage was 25V, but that’s just not how Teac did it. They left decent margins. Actually there is a cap I found in the 244 that is running close to tolerance on the power rail it sits on. And running caps OVER their voltage rating doesn’t mean they are going to burn to a crisp instantly, but it does mean their life will be shortened, how much depends on the sum of the stressors and over-spec conditions. If I was a betting man I’d say the raw rectified power is probably about 15 or 16VDC at 220V. So I bet it’s fine at 240V. The other questions that remain are the low voltage AC rail and what that powers, and the -25VDC unregulated rail.

Hope this helps.
 
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altruistica

Member
WOW...thanks Cory.

I haven't opened up the machine....it's like a new baby, I don't want to go operating on her unless I know she's broken (Hipporatic oath - 'first, do no harm').
It never occurred to me that there may be a service manual online. Anyway, I've found one although the scan isn't as good as the online 688 one.....but I also found this website that looks awesome:


I've already ordered the transformer I mentioned above, although at 50VA I don't think this is going to be powerful enough (unless I've misunderstood that the 50VA mentioned here in the specs, relates to 50VA being referenced to the 20V output (ie 50 / 20 = 2.5A (minus losses......2.5 x 0.6 = 1.5A). Maybe what I've typed here is all irrelevant because I'm not going to be using the transformer as a step-down 240V to 20V, but as a buck-transformer which just uses the phase reversed 20V output to decrease the 240V to 220V. In that respect, I would assume, rightly or wrongly that the 1.5A 'cancellation' current will be fine....I'll let you know if I electrocute myself (or if it's serious......my wife will). It does look much smaller physically than the Tascam transformer, but it's not being tasked as a transformer but rather as a modified power supply.

Whatever happens, I want to be certain that I'm not going to f**k it up when I turn her on.
I need to read a bit more methinks.

Have you seen the 238 stuff I linked above? It also mentions repairing the Dolby boards/
Al
 

rob aylestone

Well-known member
If you are cautious, and that's always sensible with precious kit, the 240V setting will ease your concerns. I mentioned this topic to a friend of mine who was an apprentice at Philips in the 70s. when he qualified one of his jobs was to take TV sets and experiment to make them cheaper - removing components and seeing how the specs changed. He tells me that one test was to see how 220V mains voltages (Holland) and UK 240V impacted on the TVs. They tried it both ways and came to the conclusion that the multi-tap transformer was a waste of money. There was no detectable reliability issue on 24/7 soak testing, and the production line was soon modified to use a new cheaper transformer with one single tap. He says they even had over voltage testing - where they powered the 240V kit from supplies 6% higher, as were occasionally found in some areas close to local transformer equipment.
 

altruistica

Member
Interesting Rob that conclusion by your friend at Philips. I guess I am being too cautious (which if you knew me....isn't like me at all.......must be old age creeping in). I wonder if I am at the start of a supply chain, as the sub-station that presumably serves our house, is located across the road, probably 50 yards away from our supply board.....I wonder if that's why the voltage when I measured it was 242V?
I just re-read your posting and was thinking of your friend's job. When you think about it, it is quite a strange job isn't it? A team of engineers have presumably designed a TV / product to fit a price and a market, and another team is tasked with presumably trying to make it cheaper? I bet they had some fun with it though, judging by the amount of You Tube videos of people blowing up capacitors and the likes.
 

altruistica

Member
A frustrating afternoon trying to make a buck transformer. The transformer I bought and linked above has no spec sheet with it, has no download for it and the support both online and telephone from RS Components is non-existent. I've tried working out what the outputs are, but what I've found out that this is impossible without understanding what theyr'e supposed to be from a fact-sheet. It seems to be one of those things that people buying this kind of stuff are expected to know it..........I hate that kind of thinking.
Rant over.
 

sweetbeats

Reel deep thoughts...
Goodness, Al…*please* just at least pop the cover and have a look at the power switch PCB and the connection with the main transformer primary…hopefully there are two of them. It should be in plain view. The 238 is roomy inside and nicely laid out, you’re not preserving anything by not opening it up…they already got into to replace the capstan servo assembly. Two screws on each side, one or two screws at the top of the lid on the backplane, slide the cover to the rear slightly so the front edge clears the front fascia, slightly splay the sides of the cover away from the chassis on each side and lift it off. You could solve your issue the same way Teac *designed* the issue to be addressed and swap two solder joints. Open it up, take a pic and post it and let me have a look.
 

altruistica

Member
Hi Cory,
Yeh you're right. I've had a bug these last four days so my thinking has been hit and miss. I should just take some time off and get myself right. I will do as you suggest and report back.
Cheers
Al
 

altruistica

Member
So I managed to open up the 238 today after feeling a little straighter in the head. I'd taken a look at the 238 service manual and went over what Cory had said and sure enough, it looks like Tascam have used a 'daughter-board' that hangs on the back of the push-button power switch, that is probably the same across all regions. On the UK/Europe/Australia units, the board has three wires, red, violet and white. On my 'Europe' designated model, the violet wire is wired as positive (is there is such a thing in AC terminology?) and white negative. The red wire is wired to the board but not connected to anything (other than another tap on the transformer). The board has room for the switching device mentioned on the 'General Export' model (some kind of rotary selector judging by the shape of the board). Anyhow, from the manual, it does seem as if it's just a case of swopping the violet wire with the red wire as Cory mentioned, so I've done that. As luck would have it, another 238 came up for sale in Scotland, so I've bagged it and it should be here early next week. I figured another machine would be useful as spares and also if I can pick up a TASCAM ATS-500 synchroniser, as a 14-track setup. I used one in the past and the sync is rock-solid. If anyone has one for sale please let me know.
When the machine arrives next week, I'll whip the cover off and just confirm the swopping of the leads is ok and I should be good to go.
I think I figured out the buck transformer as well, but that's another story.
Cheers for all the help guys.
Al
 

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altruistica

Member
So, the twists and turns this story has taken, it's almost like a Cory story.
The other 238 turned up today. I had to take some pics of it.
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Somehow.......I don't know how, the unit underneath all of this shredded up cardboard, was intact and looked undamaged. I plugged it in expecting it not to work, and it came to life. I put a cassette in that had some 8-track stuff on it from the 688 and amazingly it all seemed to work.

I then decided to take the hood off it to compare the transformer with the European model I had bought. It was then I noticed the '220V' tag on the rear of this unit. So THIS ONE was a European model also and I'd just happily plugged it into the 240V UK. Once the cover was removed, it was confirmed this was a European model with the violet wire from the transformer in the +ve position. I resoldered the red wire to the +ve as per the UK specs and tried the unit. Everything was fine, I hadn't blown the unit so I set about putting the unit in the rack and trying it with the Soundcraft Spirit desk. After making a new recording, I took the tape out and tried it in the unit I'd bought from The Netherlands. Strange....the unit is playing back at half speed. I then checked the manual to make sure there wasn't a setting that I'd forgot about. This unit has had the capston servo board replaced. I remeber reading that this board also served the 122 machine (which I think is a normal speed cassette machine) and there is a mark on the board to select 4.8cm/s or 9.6cm/s. You choose one of the settings by soldering between two semi-circle jumper positions (something I've never seen elsewhere). I took the unit out of the rack, but not before making a spoken recording to see if all other things being equal, the unit was performing as it should now I'd finally got it powered on. It was funny seeing the tape turn so slowly, but it did make a fine recording on all 8 tracks. I was half tempted to leave it as was, but then curiosity got the better of me, so I removed both units from the rack so I could compare boards.
I then used Cory's excellent instructions to get the board free from the Dutch machine and as I suspected, the solder was covering the wrong selector position. A quick desolder and careful resolder of the right position and the deed was done. I put the machine back together and found comparing it to the other machine, that the Dutch machine was running slightly quicker than the Glasgow machine. As neither machine has been set up correctly I may have to come up with a way of bringing them within spec of the 688 as well....as it is, the varispeed on the machines will enable me to do stuff. The manual mentions a TEST TAPE and a 3000Hz tone and a counter of kinds.

Any ideas how I might be able to calibrate between machines using a multimeter (a very good Bryson one) and a scope?
So, to recap, so much for me not wanting to open up the 'like new' machine. I end up doing a 'repair' on a new board because it had been setup incorrectly. I was thinking of reaching out to the Ebayer concerned, but it isn't like the unit was faulty or not as described. The hassle sending it all the way back to Europe when I knew what the problem was, just wasn't worth it.
 

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