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I need to order capacitors to do Bobwire's mods on the 709. Bobwire doesn't have specific capacitor recommendations. Others have recommended Panasonic HFQ series caps from Digikey. Any other thoughts? For the 0.1uF bypass caps should I use something different?I've got the iron hot and the wick ready. Wish me luck, friends.
Alan
I plan to tear into my Samsung this weekend, even though the service manual is still on backorder. I bought an assortment of Panasonic FA caps from Digikey for the power supplies. They have the lowest impedence of any easily available electrolytic that I'm aware of, but that may change if Pacific starts stocking Rubicon ZA/ZL series. I also have a few Black Gate electrolytics which I think are the best choice for coupling caps.The larger sized and capacitance FA's have lower impedence (look at the Digikey's catalog page 325, but in some locations height is limited above the transport and width by neighboring components. You also have to decide if you want a nice, clean, less vibration sensitive, and probably more reliable board with low impedence caps flush to the board surface and optionally silicone calked, OR big, yet lower impedence caps dangling every which way.
I lean toward the tidy and reliable side unless the location is critical for performance. Also, right now I don't have the time to critically listen for the optimal part for each location, so I'm just going to blast through with what's worked well in the past for me.
Some of the caps bobwire has listed can be 6.3v instead of 10v if it matters to you. HFQ's come in 6.3, but not FA's. I just went with 10v parts for the simplicity.
I probably won't add any bypasses to most of the FA's and none of the Black Gates. FA's have very low impedence, even up to 300khz so unless you have a bridge to measure high-frequency impedence, the bypass you use will not make any contribution whatsoever, and no matter what, its still a huge improvement over what was there. I do bypass analog supplies to DACs. That I can hear and is very worth trying different bypasses for best sound quality. Most people seem to think Black Gates as coupling caps sound excellent, if not best without bypasses. One other factor on the Samsung is that power supply cap mounting locations are not always as close to the load chip as is optimal. The consequence of a mass-produced single layer board where trace routing often requires compromise. If you still want to bypass, a few locations looked good for tacking down a surface mount ceramic from power to ground traces right next to the power pin on the IC.
Oh, and I'm going to try LM6172 opamps. I got some surface mount ones from Abbot (see national's site). They are the only ones who would sell small quantities and National will only sample 2 at a time (I'm doing a 909 and need 4-5 for that along with more for other projects). SO-8's are ok for replacing. Cut all the legs, remove the body, then unsolder the leads. Least damaging to the traces.
Mark
PS
Before you mod, you may want to get the latest version of EPROM software. Mine came with 3.23 and according to www.709online.com, 3.27 or so is more current. I'm picking my machine up from the shop tomorrow with the new (covered by warrantee) EPROM.
I used the Panasonic HFS series. They are low impedence caps. For all the caps I replaced and some additional, I used Panasonic P series .1uf / 50v polyprops. The Panasonic Electrolitics are considerably larger than what you are replacing. The large board has the caps facing down toward the transport. You will have to put the new caps in at an angle to clear the transport. Don't expect the mods to make this machine into a world beater. Also, improvements can be made with dampening to the chassis, transport, transport tray, etc. I also, took both boards out and put them through a 24 hour dry ice cryo process which smoothed things out sound wise. A final note. Most of the caps you will be replacing are rated at 16 volt. Also, One cap is a 35 volt(PE39). Get a couple of extra 25 volt ones as well.
That cryo sounds pretty nifty. Maybe I could just offer my Toshiba a cold beer :)
Everything I have tried this on has benefited. Pouring a beer on a Toshiba sounds good to me. Please give it a try and report back on the sonic effect.
I've used the HFQ's to good effect, but wiser souls have said the Panasonic FA series is even better if you have the headroom (I think they are tall and narrow). For the 0.1uf, I used ceramic for the digital supplies (I used X7R series ceramics). For analog you can use your favorite film and foil.Good luck, and have fun!
--daryl
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