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Old 27th October 2007, 04:36 AM   #281
Pars is offline Pars  United States
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Hi Chris,

Quick response!

As for the board, I probably can drill the pin circle out more towards where it should be. Givn the voltages, I didn't know whether I would be inviting arcing by decreasing the diameter (i.e. smaller sockets). Plus it is a really nice Azuma ceramic/gold socket in there now (I replaced all of them).

If I were to send you the file, could you take a look at it to see what you would do for resitance values with the 47u/100u caps?

Thanks and regards,

Chris
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Old 27th October 2007, 04:44 AM   #282
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Hi Chris,
Sure, I'll have a look. Please send me all the info you have as it has been a while. It will help me focus.

If you have a print of the schematic and values you used, I'll plug them into PSUDII and have a look. I really should get to know how to use a sim package.

-Chris
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Old 27th October 2007, 04:55 PM   #283
Pars is offline Pars  United States
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Hi Chris,

BTW, I managed to cut the noise I was having at least in half (even showed up in RMAA as a lower noise floor. The culprit? The large Cerafine caps I was using in the HV reg section... they were too close to the pot.

Click the image to open in full size.

Changing it to something more like Marc Legare's:

Click the image to open in full size.

lowered the noise considerably. I just received the (3) BG VK 150u/350V caps so I'm going to put those in. For coupling caps, it was recommended to me that the ClarityCap SAs are quite good (several cap shootout recommendations on them as well, such as http://www.humblehomemadehifi.com/Cap.html), and they are rather cheap ($4.40 for a 1uf 630V).

Chris
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Old 27th October 2007, 06:47 PM   #284
anatech is offline anatech  Canada
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Hi Chris,
You just illustrated what I've tried to tell people often. Parts well over the original size will cause you trouble.
Quote:
and they are rather cheap ($4.40 for a 1uf 630V).
I don't know if I would say they are cheap, but they are not silly expensive at least. Please try to stay with similar capacitance values as originally installed.

Anyway, you are on a good path there. It should be sounding really good these days.

-Chris
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Old 18th May 2008, 07:35 PM   #285
Pars is offline Pars  United States
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Default Coupling caps (again)

Still haven't changed these yet but had a question or two regarding sizing. I've decided to go with Dynamicaps and am going to do the line stage only at this time. The heat shields on the PCB allow caps up to 18mm or so (maybe 20mm) if I retain them (which Anatek recommended I do). This means 1-2uf caps max if I stay with that.

Click the image to open in full size.

The C8 / R17 combination concerns me a bit as 8uf Dynamicaps are 1.28" (33mm) in diameter. If I use a 1uf cap, R17 at 100K brings the -3db point to 1.6Hz. All other resistors for the high pass filters throughout the preamp are 1M (R20 in the line and all phono stage). I was told that I could increase R17 (1M is the datasheet max) to perhaps ~500K or so? So, it seems my options are:
  • 1 Use 1uf and leave R17 alone... it will be fine at 1.6Hz
  • 2 Use 8uf and leave R17 alone, you don't need the cap shields (or another value? 4uf? other?
  • 3 Use 1uf and change R17 to ~500K (or another value)?

Thanks,

Chris
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Old 19th February 2011, 06:13 PM   #286
Pars is offline Pars  United States
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Just an update on this. I found the noise (hum) problem I was having, thanks to some prodding from Alan (VivaVee): the heater supply. It had ~50mV of ripple on it. After being strongly prodded, I took a look at the layout and found some sub-optimal connections. Moved them and added a cap from the LM350K datasheet. No ripple that my scope will trigger on (looks flat), and no hum.

I borrowed a pic from max29 earlier in the thread. This is an earlier board than mine (SA5, not SA5.1?)

On the left side, towards the center, there is a + and - connection. This is the heater input DC voltage from the bridge. Notice "C" and "5". These are the output to the regulator and the - output of the heater to the main board. Notice C75. This is the first filter cap for the heaters. Taking the input to the regulator and the circuit output after filtering might be a good idea

The resistor (R72) from the adjust terminal (BD) to the output (trace that "5" is on) is also tied in prior to the cap.

Thanks Alan! (and Chris)

One thing that always disturbs me is when someone fixes something in a thread like this, and never reports back what the final solution was. So, I am.
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Last edited by Pars; 19th February 2011 at 06:27 PM.
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Old 17th May 2011, 11:11 AM   #287
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Default Help me identifying the capacitors

Hi all this is my first post, so glad to be here.

I recently get an SA-5.1 pre for my hifi system. Previous owners had it upgraded at line stage and phono stage (standard and premium respectively) to Mike Elliott. Now I want an upgrade at power section. I don't want to send the item to US, so I want to do it here in Turkey. I'm novice about diy so have it done a technician but I need help to identify and choose replacement parts. This picture is power section inside the main chassis:

Click the image to open in full size.

I can see:

10uf 400Vdc
110uf 100Vdc
1uf 210 Vdc
0,47uf 210Vdc


And this one is the from the power supply unit:

Click the image to open in full size.

5v 4700 (uf ?)
16v 2200uf
I can't see a proper name on the 4 big ones. Just 500 "Vdc"

I looked in to the Percy Audio catalog but couldn't see the parts. 210Vdc value seems to be rare. So please show me the way, I need help
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Old 17th May 2011, 08:21 PM   #288
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Is the power supply schematic availabe for this or the 3.1?
They seem to go first.
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Old 18th May 2011, 02:19 AM   #289
Pars is offline Pars  United States
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Read the thread. HV reg section is in post 214. PSU itself is in post 220. My schematic, but more accurate than the official one. Any schematics you find may not be accurate, so compare to what is in there. Published schematics are likely the plain SA3/SA5 rather than the .1 versions.

Firochromis: someone has already recapped that PSU as stock they have 2 large caps (both 100uf/500V), not 4 as yours has. Yes, they need to be 500Vdc. The first cap (C77 IIRC, right one as you look at it from the front) should really be <50uf according to the tube datasheet for the rectifier. I would use something like a Panasonic TSUP if you can find them. 105șC would be a bonus.

If you are looking for boutique, I have a 100uf/500Vdc Elna Cerafine that I used for awhile in mine (had a pair of them). I replaced one with a 47uf. Not the easiest to fit as they are big. Mine is in the FS section. Otherwise, not much available for boutique in HV these days.

EDIT: also look at this thread
Counterpoint SA5 Preamp Problem

I would pay attention to whatever Chris (anatek) or Alan (VivaVee) recommend, as they have tons of experience with these and know what they are talking about. I would listen to this regardless of what you have read ANYWHERE else.

EDIT 2: These are what I used in the HV reg section of mine: 150uf / 350v, VK Series BlackGate. Still available at partsconnexion, maybe elsewhere. You'll need 3 of them. Read post 43 in the link above re. caps.

Last edited by Pars; 18th May 2011 at 02:41 AM.
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Old 18th May 2011, 06:47 AM   #290
tmblack is offline tmblack  United Kingdom
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How do I bias the preamp tubes?
And how is the bias voltage derived, a secondary winding and diode,cap,resistor combination?
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