View previous topic :: View next topic |
Author |
Message |
Nashou66
Joined: 12 Jan 2007 Posts: 16171 Location: West Seneca NY
|
Link Posted: Wed Aug 20, 2008 7:58 pm Post subject: |
|
|
the schematics for the decupoling caps dont show the orientation to each chip its just a general idea of where that rail goes to. on the actual schematics where the chips are, they do not have the decoupling caps, thats what the other set of schematics is for , those caps, and its just a general guide to how those caps are fed from the power supply rails.
yes use the continuity check as its the best way. I was only stateing that you should take care and check again and again from both the positive and negative and then also double check by crossing (neg to pos no beep, pos to neg no beep) if it beeps after a the cross check then make sure your testing from the correct feed CAP . After a while you'll get it, i suggest for now you change maybe two caps at a time and test the board in the PJ if it pops you only have to look for one or two caps, and it will help you learn.
Thats how I did it !
nashou
_________________ Don't blame your underwear for your crooked ass~ unknown Greek philosopher
"Republicans believe every day is the Fourth of July, but the Democrats believe every day is April 15." --- President Reagan
One Smart Dog!!!
Marquee High Performance Bellows now shipping!!
Marquee Modifications and Performance Enhancement
Marquee C-element and Bellow removal
|
|
Back to top |
|
|
Nashou66
Joined: 12 Jan 2007 Posts: 16171 Location: West Seneca NY
|
|
Back to top |
|
|
PaulB
Joined: 26 Oct 2007 Posts: 359 Location: Bonnie (but rainy) Scotland
|
Link Posted: Thu Aug 21, 2008 1:26 pm Post subject: |
|
|
I see what you are saying Athanasios, I'd picked up that the continuity check wasn't reliable but clearly it is - my mistake. I can only speak for myself obviously but your explanations above are actually making more sense to me know, something clicked and I GET IT, I ACTUALLY GET IT
Thank you for posting the CLM pics, I'm sorry that things didn't quite click before I asked you to take them but they are most useful as I will now cross-check my work against your own each time I do a few caps (once I get round to it - I'm holding off 'til the pj gets fully set up).
Again thanks for your excellent thread and assistance Athanasios, you're a hero mate, a flipping hero!
_________________ Paul
|
|
Back to top |
|
|
PaulB
Joined: 26 Oct 2007 Posts: 359 Location: Bonnie (but rainy) Scotland
|
Link Posted: Thu Aug 21, 2008 1:44 pm Post subject: |
|
|
Perfect
_________________ Paul
|
|
Back to top |
|
|
Nashou66
Joined: 12 Jan 2007 Posts: 16171 Location: West Seneca NY
|
|
Back to top |
|
|
PaulB
Joined: 26 Oct 2007 Posts: 359 Location: Bonnie (but rainy) Scotland
|
Link Posted: Fri Aug 22, 2008 4:46 pm Post subject: |
|
|
I'm certainly owe yourself and Andy a drink or two thats for sure!
Looks like I'm off to sunny Spain for a few weeks in October so now very unlikely I can make it. I must admit I'd sort of mentally pencilled it in as flights to London from my neck of the woods are realtively cheap but looks like a no-go for me I'm afraid.
Next time hopefully, and I'll treat you to some haggis and neeps! Lovely stuff
_________________ Paul
|
|
Back to top |
|
|
Nashou66
Joined: 12 Jan 2007 Posts: 16171 Location: West Seneca NY
|
|
Back to top |
|
|
antorsae
Joined: 16 Jul 2006 Posts: 297
|
Link Posted: Fri Aug 22, 2008 8:27 pm Post subject: |
|
|
I am on the beach
Not in Barcelona, though....
|
|
Back to top |
|
|
Arno P
Joined: 01 Jan 2007 Posts: 282 Location: The Netherlands
|
|
Back to top |
|
|
Nashou66
Joined: 12 Jan 2007 Posts: 16171 Location: West Seneca NY
|
|
Back to top |
|
|
PaulB
Joined: 26 Oct 2007 Posts: 359 Location: Bonnie (but rainy) Scotland
|
Link Posted: Sat Sep 06, 2008 6:46 pm Post subject: |
|
|
Well done Arno, welcome to the wonderful world of marquee modding!
This is probably more for Athanasios, I see you have caps across some of the chips in there - did I miss these somewhere, can't recall seeing them in the mod thread - worthwhile mod and if so, what are they?
_________________ Paul
|
|
Back to top |
|
|
Nashou66
Joined: 12 Jan 2007 Posts: 16171 Location: West Seneca NY
|
Link Posted: Sat Sep 06, 2008 7:10 pm Post subject: |
|
|
hi Paul, McPherve mentions putting caps across the power supply pins on all the op amps in the marquee in the archives on AVS, he states "in case there doing something they not supose to" I have them on some and not on others(forgot) but i do not think they do much since the other decoupling caps have been doen on the supply rails, but you can use either 100nf(.1uf) or 100pf caps. i used the .1uf diped tants positive side to positive pin of chip, but i think film or ceramics might be better.
Athanasios
_________________ Don't blame your underwear for your crooked ass~ unknown Greek philosopher
"Republicans believe every day is the Fourth of July, but the Democrats believe every day is April 15." --- President Reagan
One Smart Dog!!!
Marquee High Performance Bellows now shipping!!
Marquee Modifications and Performance Enhancement
Marquee C-element and Bellow removal
|
|
Back to top |
|
|
Arno P
Joined: 01 Jan 2007 Posts: 282 Location: The Netherlands
|
Link Posted: Sat Sep 06, 2008 9:53 pm Post subject: |
|
|
PaulB wrote: | Well done Arno, welcome to the wonderful world of marquee modding!
This is probably more for Athanasios, I see you have caps across some of the chips in there - did I miss these somewhere, can't recall seeing them in the mod thread - worthwhile mod and if so, what are they? |
Paul, the decoupling of opamps is one of the most common things to do...(if any designer forgets them in a high bandwidth circuit...he should be kicked )....they are standard 100nF foil caps....just have to be fast enough for spikes/HF....and above all...as close as possible to the opamp supply pins (and on top of it is as close as it gets)....on the board adds tracks in the paths which are basically coils (approx. 1nH/mm) causing a degrade of the decoupling function of the capacitor..
_________________ "Obviously you're not a golfer"
|
|
Back to top |
|
|
Nashou66
Joined: 12 Jan 2007 Posts: 16171 Location: West Seneca NY
|
|
Back to top |
|
|
Arno P
Joined: 01 Jan 2007 Posts: 282 Location: The Netherlands
|
Link Posted: Sat Sep 06, 2008 10:03 pm Post subject: |
|
|
Nashou66 wrote: | Right you are Arno, So you think the 100pf are to small a value or are for too high a frequency.
Athanasios |
Yes, most circuitboards (digital) have 22..47 or 100nF
100pF reminds me more of taming feedbackloops of opamps (or matching phono-input capacitances)
100nF in parallel with an electrolyt capacitor....would make sense if the bigger C is no larger than 10x that value (so I recall from someone who measured this for use in loudspeaker filters).
_________________ "Obviously you're not a golfer"
|
|
Back to top |
|
|
Nashou66
Joined: 12 Jan 2007 Posts: 16171 Location: West Seneca NY
|
|
Back to top |
|
|
Arno P
Joined: 01 Jan 2007 Posts: 282 Location: The Netherlands
|
Link Posted: Sun Sep 07, 2008 6:18 am Post subject: |
|
|
Nashou66 wrote: | Right, McPherve actually used the large value cap,a 100nf cap and the 100pf on the supply rails. So this aproach mayb asl used on the pins too? or the 100nf would be enough and the rest is over kill since the rails have this already?
Nashou |
The rails should be ok, only the local IC decoupling is an improvement to compensate when the buffering (capacitors) that are further away from it see a too long path when a spike/glitch/edge occurs....that's when the small locals catch up..
Since the opamps got their power supply rejection ratio I wouldn't mind to much about what needs to be done on the rails...but...for the transistors "touching" the bare suplly voltage there could only be a problem when there's a differential mode disturbance on the voltage rail (one side) since the common mode disturbances (+85V and -85V suffer the same voltage dips etc) should be covered by the balanced design (and the relatively high voltage on which small surges will have less influence)
Looks more as a regular power-amp design (with all respect for the HF handling capabilities they had to take care of) and in such a design you will see very stable ps filtering in the front stages and basic stabilisation in the power section.
_________________ "Obviously you're not a golfer"
|
|
Back to top |
|
|
Arno P
Joined: 01 Jan 2007 Posts: 282 Location: The Netherlands
|
Link Posted: Sun Sep 07, 2008 6:22 am Post subject: |
|
|
By the way...be careful with adding series inductors in the power lines....if the value is small it will help the filtering since it is a second order now together with the C .
BUT...this approach although very nice for tube amplifiers and HF circuits..can have a secondary negative effect of oscillation between the C and the L....trigger such LC circuit it could start to bounc quite a time
_________________ "Obviously you're not a golfer"
|
|
Back to top |
|
|
Nashou66
Joined: 12 Jan 2007 Posts: 16171 Location: West Seneca NY
|
|
Back to top |
|
|
Arno P
Joined: 01 Jan 2007 Posts: 282 Location: The Netherlands
|
Link Posted: Sun Sep 07, 2008 11:40 am Post subject: |
|
|
Nashou66 wrote: | So as long as the inductor has a very very low DCR it should be ok?
Athanasios |
Nope...
If it would be an "ideal" inductor of zero ohms....the oscillation is best.....
In case it does have a DCR....there is another disadvantage of the voltage drop
If oscillation is no issue....calculate the f3 of the filtering (L/C) and base the selection of the inductor on that
And another nice thing that could happen.....EM-signal injection (of any HF source around) on a coil in an antenna function
(My choice....leave the inductors out of it and keep the original design)
F = 1/(2*PI()*SQRT(L*C))
http://circuitcalculator.com/lcfilter.htm
http://wiki.4hv.org/index.php/LC_Oscillator
_________________ "Obviously you're not a golfer"
|
|
Back to top |
|
|
|
|