Delta 1010 Clock Mod
Someone did a clock mod on my Delta 1010 PCI card by replacing the clock with his own improved design that uses a PI filter. The improved clock is on a small board that is attached with wires to the original card:
It uses a United Chemi-Con MVH series 2200uF 16V 125 deg.C aluminum electrolytic surface mount capacitor (see the big cap in the picture) which has been retrofitted with leads in order to attach to the board. My question is, why was a 125 dec.C cap used? Does it really get that hot in that area of the board? If not, what could have been the specific reason for this choice of cap when there are many other 2200uF 16V caps with lower impedance and higher ripple current rating that might be better. For example:
Nichicon HN - 8 mOhms impedance @ 20 deg.C / 100KHz; 3370 mA rated ripple
Rubycon ZLG - 12 mOhms impedance @ 20 deg.C / 100KHz; 2900 mA rated ripple
Panasonic FM - 15 mOhms impedance @ 20 deg.C / 100KHz; 3190 mA rated ripple
The MVH cap, in comparison, has 100 mOhms ESR @ 20 deg.C / 100 KHz; and only 1200 mA rated ripple.
I am very particular about this part of the soundcard as it has a huge effect on performance. Will I be able to improve it by replacing the MVH cap with a Nichicon HN, for example? What other caps would you recommend as replacement?
I think you might want to take a look at the way this thing has been installed instead - you'll likely net a bigger improvement by installing it with the shortest possible lead lengths, particularly the oscillator output and ground leads.
In the case of the capacitor there could be all sorts of reasons why that capacitor was chosen, none having anything to do with the temperature rating. ESR does not tell the whole story particularly in high frequency applications, ESL plays a large role, and the cap ESR may play a role in regulator stability not to mention damping high q resonances in the capacitor itself. I doubt ripple rating is an issue in this application - it does not appear to be a filter capacitor following a rectifier.
It may or may not have been randomly chosen with no thought to the issues mentioned above.
Best advice would be to try some of the alternatives mentioned after looking at supply noise with a good scope and see if you can improve it. Keep the original in case no improvement is found or it in fact performs worse.
Thank you so much for your advice! :)
How many volts is the supply to a PCI card? Isn't it only 5 volts? If so, I can use an even smaller cap that's rated for 10 volts and it would be fine, right?
Hi man, glad to hear your 1010 is in working condition again. I totally agree with kevinkr. Low ESR is not per se improving things. Put the clock card as close as possible to the PCI card, that´s all what I would do. In the current state the wiring forms nice antennas picking up HF dirt.
For further improvements read this; it will not be thoroughly related to your PC but there are a lots of worthwile suggestions: http://imageevent.com/cics/v03theart...gcomputertrnsp
You could also try something like my cookie tin shield:
Well, my 1010 isn't totally fixed yet, but at least, damage to additional channels has stopped. I think it was a bad cable that was the culprit. I will need to replace SMD caps and resistors to fix it completely. Do you happen to know the type (tantalum, ceramic, etc.) and value of those cream-colored SMD caps in the 1010? They all look the same. I hope they're all identical.
Thank you so much for that article you referred me to! There's lots of useful info and good tips in there. My hands will be full trying them out.
That cookie tin shield you made looks awesome. How were you able to attach it securely to the card? It scares me to attempt doing something like that and risk the possibility of shorting something. I imagine, that metal needs to connect to ground somewhere. Where do you have its ground connection?
Time to go for reasonable LCR meter ... ;)
In reading direction from underneath the PSU caps:
C25 0.44 µF
C20 0.90 µF
C6* 1.15µF (* unreadable)
The cap values repeat in order to equal DAC and opamp structures. You may also do some reading in this: http://www.asahi-kasei.co.jp/akm/en/...93/ak4393.html
You will find that the 1010´s layout is quite close to what AK suggests.
For SMD resistor marking read this: http://www.talkingelectronics.com/pr...eMount-P1.html
Before you desolder those litte bastards you should compare your readings with mine. All the SMD parts are also fixed with kinda superglue and it´s a pain in the *** to get them off. Also the solder pads are not very stable on the PCB, they peel off easily when getting too much heat and then you are f****d.
I put some plastic sheet around my PCI card for insulation, so there is no possible shorting to the cookie tin sheet. That sheet is contacted to the PC chassis with a soldered litz and a screw.
Awesome! Thank you very much, you're so very helpful! I'm so glad to find help on this project that I'm about to lose hope on. ;)
Now if I could only desolder those little buggers. Why did the manufacturer put glue on them? It's an extra step in the mfg process, and what for? I hope not all 1010's are like that. BTW, do you know if those caps are ceramic or tantalum or what else?
Thanks again! :)
Sorry, I forgot: All the caps are tantalum. The glue is for fixing them before soldering.
I wonder how you made sure that the caps are defective ...
I'm not really sure if the SMD caps are defective. I just want to try a "shotgun approach", i.e., replace all of them without regard to whether some of them are still good or not. I have already replaced all the large caps and still the problem persists. I want to try replacing the SMD components next. BTW, in this circuit, which component is more likely to fail -- SMD cap or SMD resistor?
just a word of warning - boards like this are very delicate. I've been doing mods to soundcards for some time, and I can tell you they don't take well to fussing - and break very easily, and are quite difficult to fix. There is a pretty high risk/benefit ratio, and you have to be willing to lose the board. I have already lost one. I really suggest you repeat work someone else has done and who can spell out exactly what you need to do...
|All times are GMT. The time now is 04:43 AM.|
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2015 DragonByte Technologies Ltd.
Copyright ©1999-2015 diyAudio