Teardown: Instek SFG-1003 (Function Generator)

[olsenn]

Here are some photos of the insides of a Goodwill Instek SFG-1003 3MHz DDS function generator:





Doesn't look like there's much to this guy!

[gamozo]

i can see there's another pcb on the bottom in the last pic. can you check whats that for?

I'm pretty sure that that is metal and it's just a reflection of the PCB. As you can see, the solder spots match up, and on picture one, it clearly has a metal shield under it.

Impressive 'illusion' that picture gives

[alm]

Looks like what you would expect. My guess is that the TSSOP IC near the crystal is a DDS generator IC (eg. AD98xx), the other IC's on that board are auxiliary stuff like amplifiers or analog switches. MCU is on display board. Not sure what the stuff on the bottom left of the pictures is?

[Bored@Work]

Not sure what the stuff on the bottom left of the pictures is?

My guess is this is the power output amplifier.

[saturation]

Nice, thanks for making this available.  I have this unit, but mea culpa, have not had the time to take it apart.

Alas the photos don't have the best detail to make a more informed critique, its best if we can read the labels on the smallest components.  If you can't get better photos I'll tear mine down and add to this thread when I can 

Construction appears very good.  I did not expect the power switch to be relayed by that plastic extender all the way to the rear, but that keeps AC line interference away from the board, a nice subtle touch rather than save money and move that switch up front.

The power amp on the lower left get obviously warm during operation, so it seems to work at a high quiescent temp even with outputted dialed very low.  I like that the makers not only took time to insure the power resistor spacing has the proper clearance to cool them down, but they added insulators to their extended leads.

The ground planes on the main PCB are very generous so is the shielding you see below it.

Is there a mark on who the actual manufacturer is of the unit?

I like this unit, I use it a lot, it works very well and output is very stable.  The 2 drawbacks I find is the DDS low pass output filter increases the rise time and rolls off the edges of the square waves, as expected.  However you can get a clean fast square wave rise time from the unfiltered sync port, and the duty cycle adjusts this too.  There is no cancel button so if you type in wrong values you can't clear your input and start over until it times out, or you overwrite it.  A well spent $153 from tequipment.net, delivered.

[Salas]

Having this unit too and being happy with its price to performance ratio I have just seen the new AFG series being announced. Any early hands on experience with those new models anyone? The 2005 5MHZ model with ARB but not modulation or sweep is attractively priced I think. One thing that bothers me a bit with the 1013 model with voltage display I got is I must flip the display, its not there together with the frequency display. Its also correct only for 50 Ohm termination. The AFG series has no attenuator, it would be fortunate if that means a less noisy signal in mV range that I use a lot. Although the published characteristics don't hint to a higher signal quality class than the 1000 series. I might be guessing wrong though.

http://www.gwinstek.com/en/product/productdetail.aspx?pid=5&mid=305&id=1313
http://www.testequipmentdepot.com/instek/signalgenerators/afg2005.htm

[saturation]

Very nice units from design and performance, but also a much higher price point.  Perusing these models, I also note the old SFG-1003 is now $170, up $17 from when it was new [ tequipment.net prices].

[Mars]

Is it possible to easily modify this unit from a 120V version to a 240V version? The datasheet says "AC 100V/120V/220V/240V±10%, 50/60Hz", but it came hardwired to 120V from an US based seller. The fuse would have to be replaced, and the jumper/resistor close to the transformer would have to be moved to the 240V footprint (you can barely see them in the OPs picture below the xfmr). But the two big black squares directly to the left of the transformer are 120V relays (OUAZ-SS-105L) which sort of stopped me in my tracks, because I bought this thing to assist me in a project and not to have the FG as a project in itself.

Am I out of luck here?


SFG-1003 spec: http://www.gwinstek.com.tw/en/product/productdetail.aspx?pid=5&mid=72&id=94
Relay: http://www.te.com/catalog/pn/en/8-1419130-6#features

[saturation]

The simplest thing is get a 220V->110V step down transformer and no modding or concerns about it needed.  You also don't have to change or get a plug converter for 220V.




http://www.voltage-converter-transformers.com/step-down-transformer.html

[david77]

....transformer are 120V relays (OUAZ-SS-105L) which sort of stopped....

Whatever gave you that idea? They're 5V relays.

[alm]

The contacts are rated for 120 VAC (and 24 VDC). Given the location, I consider it unlikely that they're switching mains. They appear to be located on the secondary side of the transformer. So I don't see any issue running this unit from 240 V if you change the tap wiring and fuse.

[giacomo]

Hi, do you still have the photos ? I was considering to buy this on element14

it seems to be still the best buy for the price point