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U14-3 Measurement

PostPosted: Fri May 22, 2015 9:38 pm
by gtilford
I am to the point of checking the Si570 by measuring the output or U14-3. With my scope I have the prettiest 56 MHz, 530mv sine wave you ever did see (see attachment). I'm using a 200 MHz scope, so I don't think that the waveform is being distorted. According to the build notes I should be seeing a 56 MHz, 3.3 V p2p square wave. Suggestions?

Thanks in advance,
Greg

Re: U14-3 Measurement

PostPosted: Sat May 23, 2015 1:20 am
by mrwizardly
By this time you certainly should have some experience in soldering the surface mount resisters/capacitors...etc.
As is common through all the troubleshooting threads- check the solder points. Verify all the parts are in their proper places.
Take careful notes (check off the parts on their supplied page) when parts are installed.
Recheck the regulators:
(page 8)
U1, U2 and U15 tab should have their respective voltages.
Be sure there is 3.3V on U9 (2, 6) Be extremely cautious in probing- a slip can cause damage.

Up to this point there are no RF parts, just logic. Please don't continue until this issue has been resolved.
Check to make sure there is no solder where it shouldn't be as indicated when installing Si570 (U9) page 10.

Some suggestions that have made soldering very reliable for me: I use a 35 watt .5mm tip and my iron is plugged into a motor controller which is turned down to about 18-25 watts (not very calibrated vernier).
Overheating solder can cause voids and is the source of many cold joints.
Paste flux/rosin is a must. I have .010in, hair-thin solder that has a rosin core- but I depend on the flux/rosin paste more.
By the time the flux gets out of the solder you are using there may be voids in the joint already and the joint may not be very well cleaned.

Hope this helps.
Mark
W7EAZ

Re: U14-3 Measurement

PostPosted: Sat May 23, 2015 5:28 pm
by gtilford
All of the voltages are good. The LED is flashing "PCM3060," which is right. I have good connections (pins 10,11) from U11. I couldn't find any solder bridges. I removed the Si570 and there was good solder contact on all of the pads. I think I may have a bad device. Does this sound right?

DigiKey doesn't have any in stock. I found this one at the KM5H store. Is this the right component for replacement?

http://km5h.softrockradio.org/index.php ... duct_id=49

It says, "Start-up frequency 56.32 MHz" which is right and "I2C Address 55 Hex" which I'm not sure about.

Thanks,
Greg, KM5GT

Re: U14-3 Measurement

PostPosted: Sat May 23, 2015 10:50 pm
by mrwizardly
Were the voltages still correct with the Si570 removed?
I know we are grasping at straws- but dividing the steps up is sometimes overlooked.
What I do know if you click on "ExtIO" on the right side of the Tune Frequency you can check the address it is reading over the bus.
Click the TAB "Si570" and it says the I2C address.
Click the TAB "Calibrate" you can see the 'Factory start-up frequency'. All of those seem to match what you have.

I will not comment on the part- as I do not know if there are different versions. I'll leave that up to the creator.
73,
Mark
W7EAZ

PS: I'm having issues with the transmit side. Shelving it for a while until I understand the components a bit better and their interactions.
Going back and reading some of the forums to help where I have enough knowledge how...

Re: U14-3 Measurement

PostPosted: Sat May 23, 2015 11:47 pm
by W4MMP
gtilford wrote:All of the voltages are good. The LED is flashing "PCM3060," which is right. I have good connections (pins 10,11) from U11. I couldn't find any solder bridges. I removed the Si570 and there was good solder contact on all of the pads. I think I may have a bad device. Does this sound right?

DigiKey doesn't have any in stock. I found this one at the KM5H store. Is this the right component for replacement?

http://km5h.softrockradio.org/index.php ... duct_id=49

It says, "Start-up frequency 56.32 MHz" which is right and "I2C Address 55 Hex" which I'm not sure about.

Thanks,
Greg, KM5GT


Hi Greg,
Yes, that is the correct part. It was once a very common part at Digikey and Mouser. Perhaps the 50ppm versions are falling out of favor.
If I may suggest, before you order one of the most expensive parts of the Peaberry, lift U14 and see what the voltages are then. Much better to find that U14 is bad and loading down the Si570. It appears you have the tools to lift the ICs since you wore able to lift the Si570 which is one of the most difficult ICs to remove. In the mean time I will break out my loaner scope and take a look at the output of the Si570.

Edit: What is the output of U14 QSE_Q (9) and QSE_I(12)? The levels should be about 6V P-P at the LO frequency.

Re: U14-3 Measurement

PostPosted: Sun May 24, 2015 4:10 am
by gtilford
First, thank you all for your help! I am at the stage of the build where U14 isn't installed yet. The main players are U11, the PSoC and U9, the Si570. I checked the regulator voltages without the Si570 installed per Mark's suggestion. They are the same with and without the Si570. I re-installed the Si570 again and the same results .... Ron, looking forward to hearing what you see with your scope. I have attached a snapshot of my output.
U14-3.PNG
U14-3.PNG (21.16 KiB) Viewed 4126 times

Thanks,
Greg, KM5GT

Re: U14-3 Measurement

PostPosted: Mon May 25, 2015 6:11 pm
by W4MMP
Hi Greg,

I measured the output of the Si570 at Pin 4. It is a perfectly clean sine wave at ~56MHz. Everything I have read indicates the output should be a square wave, but on the other hand every graphical output I have seen shows a sine wave, go figure. As for the specific Si570 output level: A 1.75V P-P signal is riding on DC level of .55V which means the signal goes between .55V and 2.5V (my scope may not be producing the most accurate voltage levels, but its in the ball park). I must ask are you sure of your measurement. It appears your scope probe is set for 10X but you are reading the scope as if the probe is 1X. Sorry, that is what it looks like to me.

I really think is a "move along, nothing to see here" moment ;)

Re: U14-3 Measurement

PostPosted: Tue May 26, 2015 2:06 pm
by gtilford
Hi Ron,
I appreciate you digging out the scope and looking at your Si570. The trace I posted was using AC coupling on my scope. When I checked it with DC coupling my signal biased up to around 1.5 (maybe 1.6 VDC, I just eyeballed it) with the 500mV signal riding at that bias. My scope settings look okay, but maybe some setting is wrong .... At this point I think it is either a short between the operator's headsets or a bad Si570. So I can get on with my build I ordered a replacement along with a case for my finished project (optimism). An expensive way to test, but if the Si570 is indeed good I've always wanted to build a basic signal generator; I now have the main part for a future project....

I'll post my results when the new part comes in.

73, Greg

Re: U14-3 Measurement

PostPosted: Thu May 28, 2015 7:46 pm
by gtilford
Well, I don't know what to think. I installed the new chip. The measurements look the same. I checked the calibration on my scope. Everything looks okay. I tried both channels on the scope, with 2 different probes. Same result. This is what my waveform looks like with DC coupling.

73, Greg, KM5GT

Re: U14-3 Measurement

PostPosted: Thu May 28, 2015 8:34 pm
by W4MMP
Hi Greg,
I'm not sure either. Your scope output is identical to mine except for the relative voltage levels. If it were not for knowing your voltage levels , I would not have been able to determine a difference.

However looking at the schematic, I believe it is safe to install U14 and examine the output of U14. U14 is not dependent on any other device (other than U9) and I believe C54 should have already been installed. The output of U14 will be a real square wave at TTL levels (QSE_Q/I an QSD_Q/I).


Sorry , but I have no other suggestions.