I have tracked down most of the QRV07 parts in the USA.
But what about the power supply? How to specify this? Two technical specialists at electronics supply companies said there was not enough detail to select a wall wart. What specs do I need for a USA power supply?
INPUT: 110-120V 60Hz (but how many watts?)
OUTPUT: ???V ???mA
Other???
Doug
If you'll check the BOM the specification is Transformer 230V prim 12V sec 2,3VA
The secondary voltage should be 12 VAC and 2 VA at least.
I finally finished collecting parts and got the board populated.
(http://www1.picturepush.com/photo/a/4430864/220/4430864.jpg) (http://picturepush.com/public/4430864)
But I am still confused about the power supply. (I am a music guy, not an electronics wizard.) These are 230 V transformers designed for European power sources. In the USA we have 110-115 V on the wall. Will the transformers convert automatically? This is the transformer I bought:
http://search.digikey.com/scripts/DkSearch/dksus.dll?lang=en&site=US&WT.z_homepage_link=hp_go_button&KeyWords=567-1036-5-ND&x=0&y=0
If this does not convert to 230 V automatically, what is the best solution?
1) Replace the 230 V transformers with 110/115 V transformers. Would this require any special wiring or changes to the board? Any new specifications for the transformers?
or
2) Buy an external converter? There is a 40W unit available at Radio Shack.
or
3) Other solution?
Regards,
Doug
I wasn't so clear in my answer. Since we have 230 VAC I have used a transformer with 230 volts primary voltage. If you have 115-120 volts you must choose such transformer. Some people have used 230/24 at 115 V but in your you will only get 6 VAC. You must change the transformers.
Pulse P/N:030-7330.0
115V and output 12V/192mA
http://productfinder.pulseeng.com/product/030-7330-0
Digikey didn't stock them :cry:
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Sorry, a short question. I'm not pro in electric.
If 230V output 24V/1A and I connect to 115V, I'll got 12V/1A or 12V0.5A?
You will get somewhat lower VA rating but I can't tell how much, more than 50% though. In your case more than 1 A.
The Pulse 030-7330-0 that palchiu suggests is exactly what I ended up buying (from Mouser). I had the same professional PCB assembly firm remove the 230V transformers and mount the new Pulse units. But they don't do voltage tests.
Back home, a technically adept friend who owns a good multimeter applied 120V power and tested the transformers. 120V in, exactly right on both. But TR1 produces 6.65V and TR2 = 18.09V. (???) TR1 gets hot, while TR2 remains fairly cool.
This makes no sense to us. Is a transformer defective, or is there a short downstream? Or other???
Putting the probes on various points on the regulators and on the outputs yielded even more puzzling readings. Exactly which points are the test points on regulators and the output?
I should add that I ended up substituting two OPA1641AIDs for the AD8610s on the recommendation of a local headphone and amp expert who likes the OPA better than the 8610. I assume this will not alter the essential functioning of the amplifier?
The opamp choice is free. Many different types will fit.
If the transformer gets hot, have you checked any polarity og caps? LM317/337 in their right positions?
I do not see any capacitors placed backwards, as far as I am able to judge. The LM regulators can only be placed in one position, it appears. Correct? The chips Br1/Br2 are placed with + and - as on your online photo of the populated board. The six large cylindrical capacitors appear correct. See my photo above -- I can resend in higher resolution if necessary.
I don't know if all soldering joints are perfect, but I did not do the soldering myself because I'm a beginner at this. I took the PCB to a professional assembly firm which populates PCBs for Silicon Valley manufacturers.
The LM317/337 and D44/45 are all mounted with insulation?
I don't recall seeing any instructions about insulation. What does that mean in this case? The data sheets for the National Semiconductor LM.... regulators (purchased from Newark) don't mention insulation.
Which parts are DA44/45? I don't see this designation in the BOM or on the board.
... sorry, I was thinking of something else, JSR06. You have only LM317/337 soldered directly on the pcb of course.
Per-Anders, I may have discovered an assembly mistake. Please compare C14/C7 with R22/R10 on this photo. I see how they are arranged on your online photo of the populated board, and I don't think mine is correct. If R22 is supposed to be a resistor and C14 a capacitor, then the two chips may be reversed.
If this is true, could full voltage -- applied for a couple minutes for testing -- harm some elements of the system?
(http://www1.picturepush.com/photo/a/4627449/640/4627449.jpg) (http://picturepush.com/public/4627449)
If the transformers are of the same type I'll guess the load is different. Do you get +- 12 V DC with one faulty transformer?
Your reply above posted just before I posted the response above it (I was working on it for quite a while).
No, the transformers output different voltage (see above), and neither is 12V.
To have 10 ohms in the place of C7 will create a huge current but 100 nF in place of R10 isn't harmfull at all.
The 10 ohms me be broken but otherwise it would work if you'll change position of those parts.
Douglas, your questions:
12.7 Volt out is fine.
The input is where it's written input in the schematics, terminal X1
In the pcb it says INPUT in the print and the connections are L GND CHASSIS GND R (= Left input, signal ground, chassis connection, signal ground, Right input)
If you have only three wires in, just omit the second ground connection. It's for RCA plugs.
The output is at X2 and you can see OUTPUT both in the schematics and at the pcb. The headphone is connected via three wires, L, GND, R.
3.5 and 1/4" plug/jacket
http://en.wikipedia.org/wiki/Phone_plug
About pot connection. The pot has CW, WIPER , CCW
CW = input
Wiper = output
CCW = Common ground
The pot you are using:
Seen from behind, lugs down.
From left: CW, W, CCW
http://sound.westhost.com/pots.htm
http://www.allaboutcircuits.com/vol_6/chpt_3/6.html
http://en.wikipedia.org/wiki/Potentiometer
Wire size: More than 0.2 sgmm, AWG24 is sufficient but I would have chosen shielded wire