Salas hotrodded blue DCB1 build - Page 292 - diyAudio
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Old 10th March 2013, 03:49 PM   #2911
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^ Yup, what he said!
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Old 11th March 2013, 08:17 AM   #2912
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cheers,

thanks! I'll check primaries today in the evening, I though that only secondaries should be phased.
Just to mention that if there is no load, trafo does not produce any audible hum.
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Old 11th March 2013, 09:48 AM   #2913
AndrewT is offline AndrewT  Scotland
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Use a bulb tester !
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Old 12th March 2013, 08:26 AM   #2914
stajo is offline stajo  Sweden
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Quote:
Originally Posted by buzzforb View Post
RESISTORS Precision (through hole) 3ppm/C wirewound squaristor GR102 / GG102 series
I dont think the exact numbers are a big deal. 250 should be fine, but ask Salas to make sure. I am by no means saying it will make a profound change, but at least they measure really well.
Has anybody used those for this purpouse? 200 or 250 ohms?

Staffan
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Old 12th March 2013, 08:46 AM   #2915
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Originally Posted by stajo View Post
Are you sure that you have connected primarys right?

First make sure you know which ends belongs to the same windings.

Then you need to connect the windings in series and they need to be in phase, meaning the "start" on winding number 2 connects to the "end" of winding number 1. If you connect the second winding the other way then the the first they work against each other and the trafo hums and gets warm very quick.

Staffan
the windings are in phase, just as you said and is described here.
So I tried with only one trafo and got similar hum, then I put it out of the metal box and vuala, it has disappeared. Seems the problem is in my rather small case. However if I place the trafo a bit higher (2-2.5cm) the nasty hum vanishes. I think I'll give it few tries more with a closed lid and see if the issue still persists. In case yes, need to go for some decent toroids then. Bad thing is that I'm too restricted in space.

Just to mention that it's an old pic and I know that trafos shouldn't be placed so close to each other

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Use a bulb tester !
Andrew, I need to buy a bulb first
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Last edited by dtses; 12th March 2013 at 08:51 AM.
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Old 12th March 2013, 09:04 AM   #2916
stajo is offline stajo  Sweden
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Originally Posted by dtses View Post
I know that trafos shouldn't be placed so close to each other
And definately not that close to the signal circuit eother, needless to say maybe

I think you have 2 choices: either put the trafo in a separate box, outside this, or find a small enough trafo that fits your box and your needs, place it to the right as far away from the buffer circuit as possible. Preferably with some grounded iron wall between.

Btw all inductors, spools, trafos etc are in some way affected to metal, magnetic material close by and changes their behaviour. Those should be made for mounting on metal but now they are also interacting. Or just bad trafos for the conditions.

GL
Staffan

Last edited by stajo; 12th March 2013 at 09:08 AM.
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Old 12th March 2013, 09:28 AM   #2917
Salas is online now Salas  Greece
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Connectors and cables to the Mosfets and the gate stoppers still on board than on gate pins and this build still looks stable for rail voltage on a scope?
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Old 12th March 2013, 09:33 AM   #2918
Salas is online now Salas  Greece
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If by lifting them up some interaction with their core and the metal case stops to getting them humming plus there is no hum and buzz in the audio you are done for practical purposes. If its perfect or not it takes hi bit FFT to see. Many good pc soundcards will suffice.
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Old 13th March 2013, 08:34 AM   #2919
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thanks, Staffan, I see what I can do. I have a 30VA toroid that does not produce any hum at all, perhaps that would be a good start then.

Anyway, I'm a bit disappointed, I thought it would be a nice compact oven including decent step attenuator and good components, but ended up eventually most likely with a need changing chassis as I do not accept separate box for PS and dreamed about >1A current

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Originally Posted by Salas View Post
Connectors and cables to the Mosfets and the gate stoppers still on board than on gate pins and this build still looks stable for rail voltage on a scope?
haven't attached the scope yet. The output voltage is stable and equal till 0.00 on both channels.
Resistors will be relocated as you already advised earlier few month ago to some other member here
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Old 13th March 2013, 12:53 PM   #2920
mantha3 is offline mantha3  United States
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would running the wire leads from the DBC1 to the 2SK170 under the power transformer make for some issues? Hum etc?
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