Salas hotrodded blue DCB1 build - Page 120 - diyAudio
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Old 6th August 2011, 03:29 AM   #1191
cersepn is offline cersepn  United States
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Quote:
Originally Posted by Salas View Post
Its highly possible nothing happened to the DCB1 itself. If all offset sampling will measure OK after long in power, then its OK. Tell us more about your source and active speakers, also type and length of interconnects.
Source is motherboard onboard sound for now . 3.5mm -> 2 x rca to DCB1. Speakers are dynaudio bm5a. They accept only xlr, so i made a rca -> xlr cable using an existing balanced cable. I have no idea if they are AC coupled. I tried looking it up but i found no information regarding that...

I have a feeling i mucked up the wiring inside and one of the joints came loose, causing a short or something.

Also, i realized something strange. When i leave the dcb1 turned on at the workbench, all 4 heatsinks get warm and toasty. But when i'm using the dcb1 to play music, one of the 4 heatsinks is really abnormally cool. Not sure if it's the room fan being the cause of it... but the temperature seems too low to be true.
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Old 6th August 2011, 03:40 AM   #1192
Salas is offline Salas  Greece
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The signal part has nothing to do with the sinks part. That is the PSU. If its not some draft cooling it, its a very weird thing that I first time hear in the threads. Measure PSU voltage the cool sink's side when it does it, with volume down, and see if its OK still.

Can there be weird sounds erratically coming out of the computer audio card, due to CPU halts, drivers etc.? Remember DCB1 will pass down to 0 Hz.

Also how long are the connections from audio card to input and from DCB1 to the actives? It may be important.

But check all your connections are well done firstly.

P.S. I read in your speakers manual that pin 3 of its XLR input is normally expected grounded when unbalanced to balanced is used. Is it? Did you use the same wring when checked with your other pre and the sound was still low? Says it has several limiting circuits for overload. Are their power plate sinks just warm when its low volume with the other pre now?
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Old 6th August 2011, 06:03 AM   #1193
cersepn is offline cersepn  United States
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Cables are approximately 1.5m (max) for each connection.

Hmm i guess the pin 3 works that way? I have the rca->xlr wired in this way (#2):
Click the image to open in full size.

Yes the power sinks are the usual warmness when used with other pres. I'm just wondering what could have caused the overload. Could it be caused by any solder joints coming loose and touching each other in the rca->xlr cable? Then what damage could have been done?
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Old 6th August 2011, 06:52 AM   #1194
Salas is offline Salas  Greece
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I would have been worried if you had said something like 5m to the actives about it may had needed higher value interfacing resistors than 220R not to oscillate on cabling capacitance, but 1.5m is very near to what all people use with DCB1 in home systems.

Both 1 & 2 on the graph ground pin 3 fully. So you had it grounded as your speaker's manual usually expects.

I am suspicious of possible bad joints, the computer's output as a source and what it may give out erratically through a DC preamp as the operating system does stuff, possible peculiarities in the unknown Dynaudio active plate amp, its preamp, filters, on board protection and limiters. As for what it may had happened to it and is lower but still has voice...don't know, from a tripped and stack limiter to burned stuff in a Class D power circuit. Check it with a balanced source with XLR output and XLR ready made cables first.
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Old 6th August 2011, 10:41 AM   #1195
AndrewT is offline AndrewT  Scotland
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The DCB1 is six circuits tied together.
The common PSU for all power.
The negative shunt regulator.
The positive shunt regulator.
The left B1 buffer.
The right B1 buffer.
The regulated relay mute.

Once the shunt regulators are tested and proved to be working it becomes impossible to damage the PSU and the shunts by outside loading. Even shorting the shunt outputs cannot damage the shunts and the PSU.
The Shunts by design are short circuit proof.

No matter what loading you put on the B1s, you cannot damage the shunts.
No matter what loading you put on the relay, you cannot damage the PSU, there is a protected regulator in between.

If one of the shunt sinks operates at varying temperatures then that points to a shunt regulator build error.
Did you test the shunts for open circuit loading when mains is at highest voltage?
Did you test the shunts for short circuit loading at highest mains voltage?
Did you test the shunts on maximum "normal current" draw when mains is at lowest voltage?

Disconnect the B1s from the Shunts.
Test the shunts properly.
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Old 6th August 2011, 10:57 AM   #1196
cersepn is offline cersepn  United States
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Salas: My other preamp is balanced so i run xlr direct from it, so maybe it's the rca->xlr cables with the problem. I shall check and revert back

AndrewT: Thanks for the detailed, technical help. Your advice is flying past my head though - i'm too much of a newbie and i don't know how to do the tests you speak of. Any more specific help please? Thanks!
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Old 6th August 2011, 11:33 AM   #1197
AndrewT is offline AndrewT  Scotland
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You need a voltmeter that reads DC and AC.
start up the shunt regs.
Let them run for half an hour.
Measure:
the Mains AC voltage.
the secondary AC voltages.
the rectified voltages.
the regulated voltages.
the voltage drop across the CCS resistors.
the temperature of each heatsink.

Now short the regulator outputs to ground.

Repeat all those measurements.

The CCS mosFET will be very hot and even hotter when the mains voltage is at it's highest. The circuit should not be damaged by this test. If it does not recover and operate properly after removing the output short then you have built your HotRod wrong.
When the CCS FET is "hot" the output (shunt) FET is cold during the "shorted" test.
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Last edited by AndrewT; 6th August 2011 at 11:36 AM.
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Old 9th August 2011, 02:29 PM   #1198
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Default Hot Rod Question

Thinking about my hot rod operations on my wondrfully working DCB1:

Resistors: 4.5 Ohm 12 W Mills (I have two of these laying around)

Heatsinks:

http://www.newark.com/jsp/search/productdetail.jsp?SKU=10WX1023
http://www.newark.com/jsp/search/productdetail.jsp?SKU=02M0324

I'll use silpads (not sure if I need Arctic Silver adhesive) to attach the clips to the heatsink. It will not be bolted to the chassis.

Would this work?
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Old 9th August 2011, 02:56 PM   #1199
Tea-Bag is offline Tea-Bag  United States
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I dont think so. Maybe if you thermal epoxied two on top of each other at least for the first set of fets for CCS.
I hate artic silver, too conductive. Like their thermal epoxy for glueing hear sinks.
You would need to break off the pins too.
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Old 9th August 2011, 04:11 PM   #1200
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Do you mean the resistors won't work or the heatsink or both?

Quote:
Originally Posted by Tea-Bag View Post
I dont think so. Maybe if you thermal epoxied two on top of each other at least for the first set of fets for CCS.
I hate artic silver, too conductive. Like their thermal epoxy for glueing hear sinks.
You would need to break off the pins too.
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