Okay! Updates on diagnostic process...
On Mooly's recommendation, I got some freeze spray. I found that if I put a few drops on top of the oscillator, it immediately interrupts lock and then recovers. If there is still some of the liquid on top, it might drop lock once more before I have to put some more on. After 3-4 times dropping lock, it no longer does so even after additional application of the spray.
Other things...
1. I checked the S/PDIF input and it appears to match the coax input schematic rredline posted above. The 75 ohm resistor turned out to be 76 (I guess it's a 5% part). I might replace it.
2. Checked the supply voltage everywhere I could think of, just in case. Everything appeared to be OK as far as I could tell.
3. Checked over the board for dry/cold solder joints. Reflowed a few things just in case. Everything looks OK.
On Mooly's recommendation, I got some freeze spray. I found that if I put a few drops on top of the oscillator, it immediately interrupts lock and then recovers. If there is still some of the liquid on top, it might drop lock once more before I have to put some more on. After 3-4 times dropping lock, it no longer does so even after additional application of the spray.
Other things...
1. I checked the S/PDIF input and it appears to match the coax input schematic rredline posted above. The 75 ohm resistor turned out to be 76 (I guess it's a 5% part). I might replace it.
2. Checked the supply voltage everywhere I could think of, just in case. Everything appeared to be OK as far as I could tell.
3. Checked over the board for dry/cold solder joints. Reflowed a few things just in case. Everything looks OK.
Update 2: It seems that, after doing the freeze spray test, I now rather consistently get 3 unlock events instead of 2 (that is, without doing anything to the board/XO/etc.), the first of which occurring earlier (~20 sec) than previously, and the other two occurring somewhat later than before.
Well... don't get your hopes up to much but that does need investigating. Replacing the osc would be the only way to do that. 75/76 ohm. Your meter leads will probably have around 0.3 ohms resistance that add to the value... there is no problem there even if a 68 or 82 ohm were fitted. Its not that critical.
The use of freeze spray shows that the PLL works. If the oscillator changes the frequency with temperature, the DPLL had to readjust. After and also during the readjust of the PLL, there may be also a reset of the internal FIFO. The frequency drift causes the drops.
If you use a normal oscillator, the frequency changes +/-50ppm or more over the working temperature.
I'm waiting about one minute to warm up the XO and have no lockout after this time.
If you use a normal oscillator, the frequency changes +/-50ppm or more over the working temperature.
I'm waiting about one minute to warm up the XO and have no lockout after this time.
Sorry for the late response. More work than usual this week 🙁
I feel very silly for forgetting about the resistance of the meter leads. Anyhow...do you have any recommendations regarding how to remove the oscillator? It's the SMD 4-pin type, as noted previously. I think it's 5x7mm or thereabouts in terms of footprint.
Also, I apparently at some point bought a CCHD-575 100MHz. I just found it in a small box of parts; I don't remember when I got it. I haven't checked if it fits but I think it's for roughly this form factor.
This all sounds right. I think in this case, however, the degree of instability is new (it wasn't doing this before). Also, it is even less stable than before following the freeze spray test. I didn't cool it down much with the spray (it didn't get cold or even "cool"). The slightest temperature variance appeared to be enough to disrupt lock, although after a few times it was resistant to at least the rather moderate testing I did. I'm thinking it's worth at least trying a replacement of the oscillator.
I feel very silly for forgetting about the resistance of the meter leads. Anyhow...do you have any recommendations regarding how to remove the oscillator? It's the SMD 4-pin type, as noted previously. I think it's 5x7mm or thereabouts in terms of footprint.
Also, I apparently at some point bought a CCHD-575 100MHz. I just found it in a small box of parts; I don't remember when I got it. I haven't checked if it fits but I think it's for roughly this form factor.
This all sounds right. I think in this case, however, the degree of instability is new (it wasn't doing this before). Also, it is even less stable than before following the freeze spray test. I didn't cool it down much with the spray (it didn't get cold or even "cool"). The slightest temperature variance appeared to be enough to disrupt lock, although after a few times it was resistant to at least the rather moderate testing I did. I'm thinking it's worth at least trying a replacement of the oscillator.
there are only small pads like 1x1mm so scalpel type knife should work, I used this one for surgery of my xo, take it horizontaly underneath and you should be good to go 😉
Hmmm... without a dedicated rework station something along the lines kukynas suggests could be your only option. Just try and be very careful not to damage the print.
if you plan cahnging your original xo 7x5mm to crystek with 14.3x8.7mm than you should make sure your traces are ready for such diameter and of course be carefull with surgery
Hmm...running into some difficulty with surgery. The pins are recessed into the package on the currently-installed oscillator. I'm having trouble cutting them 🙁
kukynas - I can't find 14.3x8.7mm in the specs. From the datasheet, it looks to me like the CCHD-575 is 5x7.5mm package - very slightly larger than the other oscillator. Its pins are spaced the same as a typical 5x7mm device, though. I don't have it in front of me at the moment, but this matches what I recall it looking like. Am I missing something?
kukynas - I can't find 14.3x8.7mm in the specs. From the datasheet, it looks to me like the CCHD-575 is 5x7.5mm package - very slightly larger than the other oscillator. Its pins are spaced the same as a typical 5x7mm device, though. I don't have it in front of me at the moment, but this matches what I recall it looking like. Am I missing something?
my bad, I overlooked you talking about 575 insted of 957 so you are correct...
well, you have to count with fact you might damage the old one so if you proceed be ready for it...
well, you have to count with fact you might damage the old one so if you proceed be ready for it...
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Well, I figured the old one is toast with this method of surgery. I'm wondering if maybe I should try ChipQuik to remove this, though. That is, try to make a solder bridge of ChipQuick across the terminals on each side and attempt to push the oscillator off the pads, then use wick thereafter to detach it. Wish ChipQuik were cheaper though 🙁
I didn't plan to re-use the old one so my decision was easier 🙂 I'm bit afraid that even overheat can damage it so whatever you decide to do you should be carefull with soldering xo 😉
Update: Oscillator installation was successful. However, so far, I'm still getting an unlock event around 25 seconds after power-on. Haven't had time to test yet whether it will do repeated unlocks. Although, I did try 192KHz Fs and it locks, but loses lock frequently. So, it seems to be unhappy there (and 100MHz is plenty high for 192 support). So, I'm guessing there is an additional problem somewhere. Though there is a caveat - when I was trying to install the CCHD-575, I got some solder on the metal shield that covers the small PCB to which the oscillator is attached (this device isn't like a standard package where it's all one piece). I'm not sure if, by getting solder on the shield (and thus heating it up), I inadvertently damaged the part either at that point, or when wicking the solder back off. I tried to space out contact with the soldering iron so as to avoid heating the part up too much, but maybe I didn't do enough.
Also, I never managed to figure out who made the original oscillator. I'm wondering if anyone can identify it. I've attached a picture of it.
Also, I never managed to figure out who made the original oscillator. I'm wondering if anyone can identify it. I've attached a picture of it.
Attachments
You wont have damaged anything with the bit of solder and heati, they are a lot tougher than that.
So you still have a lock problem. spiri mentions a minute or so before his is OK, which to me suggests something in the basic design could be marginal.
You really need to put this problem to the company that produce these I think.
So you still have a lock problem. spiri mentions a minute or so before his is OK, which to me suggests something in the basic design could be marginal.
You really need to put this problem to the company that produce these I think.
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