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Just finished BuffII with IVYIII and having problems. This is my 3d Buffalo and first time I have had problems. I am re-using the PLACID BiPolar and LCDPS and MUX I used on previous Buff32S. The PlACID is set for 15.5v for both + and – for the IVY and both sides of the LCDPS is set for 5.5v for the mux and BuffII.
I get lock light but sound is very low volume and mixed with white noise. The Volumite does adjust the volume. I can switch inputs with the mux and get the same thing. Attached are photos
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I have photos but can never remember how to post them pelliott123 attached the following image(s):  1a.jpg (158kb) downloaded 317 time(s). 2a.jpg (155kb) downloaded 315 time(s). 3b.jpg (147kb) downloaded 315 time(s). 4b.jpg (155kb) downloaded 315 time(s).You cannot view/download attachments. Try to login or register.
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One other possible problem I can set the LCDPS for 5.5 Vdc for the buff un loaded but when I hook up the Buff I get 4.43 vdc and cannot adjust it up.
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It looks to me like you have melted 4 of your red Wima caps with the soldering iron.....?
*
Unrelated, but why are you using such ridiculously fat power wires?
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I think they Wima caps should be just fine. I would closely check for solder bridges. If you can't find any then test the opamps.
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The fact the the LCDPS can't hold its voltage strongly suggests a short or damaged VREG. Also 15.5V is a bit high for the analog rails. 15V is the maximum. Edited by user Sunday, August 1, 2010 8:27:18 AM(UTC)
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Also make sure that the LCDPS is not running out of headroom. What kind of transformer are you using?
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Wow thanks for the quick responses Beefy:I have the PS in a separate box that sits on the floor with all my other PS's for my system I lowered the voltage to the IVY to 15v my fault I set it wrong. no change just low volume lots of withe noise Russ:Transformers are from TPA and what was suggested in the manuals How would I check if LCDPS is not running out of head room. One side of LCDPS is running the Buff and the other is running the Mux Russ: which/what Vreg should I look at Edited by user Sunday, August 1, 2010 11:47:16 AM(UTC)
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You are probably running into current limiting because of the 10r power resistors on the lcdps. Try bypassing them by jumping there pins under the board and I think all your troubles will disappear.
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I think Brian is right. Likely the Rs in the LCDPS are limiting the voltage into the regs, I would short them as he suggests as it will not hurt anything at all. The other option is to use a slightly higher voltage transformer. The first option is simpler, so I would do that first. This stock filter R values on the LCDPS will work for a lot of applications, but for some the Rs need to be reduced, or simply replaced with jumper. There is no one R value that is optimal for every case.
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Thanks Russ and Brian
I will give this a try this evening when I get home from my day job
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I baypassed the resistors and got full voltage to the BuffII I now have both LED on the AVCC shunt reg module lit which was not the case before. But still have the same problem low volume with white noise. Volumite is functioning as well as the Mux.
I suppose next is to try to isolate the problem between the Ivy or the Buff, but I have know idea how to do that.
perplexed
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Try using SPDIF directly into the BUFII. How does that work?
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Ok I will try that
since I have a scope (only 50mhz) I thought I would try to separate the buff from the IVY and play a 1khz tone and look at the wave directly at the outputs of the buff to see it where the problem is.
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Well I feel like an idiot. And Thanks all for the help.
Russ pointed me it the right direction. Since I was using the mux I should have changed the default position of the SPDIF swith on the Buff Board. So a flick of the swtich and its playing in all its glory as I write this.
One question though, on the Placid PS I have the voltage accross R17 and R18 at .25 volts. It that right for the new IVY?
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250ma is fine, a little more than you need, but certainly OK.
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