Rigol oscilloscope prices have sky-rocketed!

2 problems I have had with modified sine wave inverters on electronic equipment

1. - They won't run my Dewalt cordless drill charger (comes on but wont put a noticeable charge into the battery), I think that they use a series capacitor type power supply (transformerless).
2. - Blew the mains fuse in my ERSA temperature controlled iron (has

50hz transformer).

I see no reason that a pure sine wave unit wouldnt work fine though.

Modified sine wave should work ok with 240v soldering irons (240v element, no transformer) or switchmode power supplies. I would however test these thoroughly before taking into the field.

:

ff,

re.

in...

om DC to any sort of

a waste of money.

I blew up a $100 notebook power supply using a modified sine inverter. Data centers use true sine. Generally, data centers use a double conversion UPS. That is, convert AC to DC, surge surpress the crap out of the DC (which is far easier than AC), then create a low THD sine wave.

In any event, I can't have the RF hash generated by the modified sine in the test environment.

Pretty much. eBay is a profit-oriented corporation and doesn't have to allow any particular person to be a customer. They will concentrate on satisfying the big sellers who bring them big money, and the big IP owners (and the government) who can cause them big problems. Telling some troublesome small seller to go away is a low-cost way of avoiding problems.

There is no specific eBay restriction on radio scanners that I can see. I'm not sure the prohibition has ever been applied to private importation for personal use. Here's the relevant law-- they slipped it into the back (Sec 403) of a bill mostly aimed at regulating the

1-900 bandits.

It's been years since I've even seen an analog phone anyway, so it's kind of a non-issue these days.

Hmmm...

Exemption:

1. Three or fewer radio receivers, computers, or other unintentional radiators as defined in Part 15 of the FCC Rules, are being imported for an individual?s personal use and are not intended for sale.

So it doesn't look like there is any prohibition on importing a few for private use, provided you fill out the proper paperwork (not that you'd likely be asked if USPS handled it) and you are what the US Feds call the _importer of record_.

BTW, Disney regularly complained and had auctions terminated of items made from legitimate licenced Disney fabric. They seem to have backed off recently, but only because the sellers spent the money and time to take Disney to court directly.

Here we are talking about grey-market goods. Since the mfg company generally owns the trademark, it has a say over what eBay allows-- even if the sales are legally allowed. Mfrs like to have the freedom to maintain separate distribution networks- for example, a product sold in the US may be cheaper than one sold through a distributor in Canada. And it may be cheaper again in China, but perhaps no warranty is provided (and maybe quality control isn't as good or accessories are not as complete). If they don't limit grey market sales, local disties won't have enough margin to survive and service (and their brand name) will suffer. It's a legitimate concern, but also in restraint of trade (seems to be allowable in the US, judging by car dealers). In the US this is sort of an IP issue, and it could be a contractual issue with offshore distributors (eg. no sales allowed outside of your geographic area or we cut you off). Pretty hard to enforce in some cases:

Best regards, Spehro Pefhany

--
"it's the network..."                          "The Journey is the reward"
speff@interlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com

On a sunny day (Sat, 2 Jan 2010 21:39:14 -0800 (PST)) it happened " snipped-for-privacy@sushi.com" wrote in :

Very long time ago I had a video recorder that had a synchronous 220V capstan motor. So to drive it I used a power amplifier (2 x MJE3055 IIRC) feeding into a main transformer used in reverse driving the low voltage winding), and a 50 Hz sine wave oscillator. Efficiency was low, but, since I already had that amp and transformer, cost was low too. It worked, but never became a permanent setup... No RFI at all :-)

motor.

transformer

oscillator.

low too.

Maybe a bit from the rectifiers in the power supply.

Best regards, Spehro Pefhany

--
"it's the network..."                          "The Journey is the reward"
speff@interlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com

Just use a 1:1 transformer between the inverter and device that has issues. You'll get a clean enough wave form on the other side to correct for the issue.

Also, to a couple of friends of mine having problems trying to run their auger on the wood stove via an inverter, in case power went out. I had them use a transformer, because it would trip the inverter every time the initial start on the motor would take place. This was with a inverter well capable of driving the little AC motor. Also, putting an incandescent lamp across the load helps with reactive type load devices to reduce the effects on the inverter.

I don't think the cost of a 1:1 transformer for the troubled unit would cost as much or more as a sine wave inverter, as long as the device is lightly loaded. But then again, I you had a lot of devices that has problems with this, then maybe a sine wave unit is practical, price wise.

I also had something similar. I was unable to see a product listed on ebay a guy sent me a link to with my original IP address (located in Bulgaria); had to hide behind some proxy to be able to see it (the guy just wanted me to comment on the thing, was some sort of power supply).

To believe all the "just market forces" cliche we are bombarded with every day (anything else being branded "conspiracy theory") is just naive nowadays. It is more like "just Darwinian forces", which is not the same.

Dimiter

------------------------------------------------------ Dimiter Popoff Transgalactic Instruments

motor.

transformer

oscillator.

was low too.

Trying to vision the setup using bipolar on a 220v motor ?

I can only assume it was operating at a much lower voltage and maybe in quasi bridge state?

On a sunny day (Sun, 03 Jan 2010 11:21:45 -0500) it happened Jamie wrote in :

motor.

main transformer

oscillator.

was low too.

Oscillator -> amplifier -> 220V-12V transformer in reverse -> motor. No it was no bridge, just an audio power amp 50W RMS or so. I think you can do this with a 12V car audio amp from a car battery too.

motor.

main transformer

oscillator.

was low too.

Well, that explains it!..

2 3055's doing a class B or AB ..

Did stuff like that when making linears years ago via sweep tubes for the chicken and 10 meter band for use in the car.

Used a couple of Radio shafts 6 volt CT xformers and some bipolars to form a electronic multivibrator circuit. Voltage multiplier for the plate voltage on the other side.. Connected 2 sweep tubes in series for the heaters, hence the use of the 12 volt systems. Pie tank, plate choke etc....

The rest is history!..

I pay zero dollars for my American Express card(s). No _direct_ fees, at least, annual or otherwise. I'm sure businesses I buy from make certain they make a profit, though. So I'm probably paying for it when I buy anything at all from a sales outlet that so much as accepts the card. I'm probably paying for other cards, too, whether or not I care to use them. It all comes out in the wash. (Speaking of which, what is the German equivalent for that last idiom?)

Jon

Mostly they use a slang expression: "Es ist Pott wie Deckel". Pretty much not-translateable :-)

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.

But a 1:1 transformer will probably cost more than the modified square wave inverter. (Modified sine wave is a misnomer)

MrT.

My AmEx is a "Clear" card (really dumb idea, it can't be read). There is no annual fee for it, either.

Yes, it does. Either you take the kickback or you don't.

What do you know about them? Legit? A scam? What about shipping? The site seems to indicate $1.00 for shipping 5 kg or less, but I wonder if I'm misunderstanding. I say "seems to" because I clicked on shipping method. The $1.00 might be a charge that is in addition to whatever the actual shipping charge is. Shipping cost simply can't be just one dollar, but I suppose it's possible the company doesn't charge the customer the actual shipping cost.

Anyway, it all seems too good to be true, so it makes me wonder.

Ed

. t

capstan motor.

o a main transformer

e oscillator.

cost was low too.

.

to

The true sine UPS are switchers of some sort. Maybe class D amp?

ge

t

ve

Surplus isolation transformers are pretty cheap. I have a 1:1 and considered using it with a stock modified rather than true sine. But I figured just screw i. The UPS runs enough gear that it is worth doing things right. Also, do you really want to put square waves in a transformer? Won't that heat it up?

I came across a used isolation transformer at Excess Solutions about two weeks ago. I think it was $20, and it would break your back if you bought it. When RA Surplus went out of business, a got two big ass

120V to 100V Mitutoyo transformers for operating Japanese gear. So big I really should have said no. However, the price was stupid cheap. Anyway, back to back, this wold make an high power isolation transformer.

Why should 'dumping prices' be a problem ?

geoff

Undercutting the "sole agent" could be a problem for the sole agent.