Mezmerize DCB1 Building Thread - Page 29 - diyAudio
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Old 17th March 2011, 01:46 AM   #281
palmito is online now palmito  United States
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Hi. I bought a board and because of my lack of experience building diy stuff, I have a few questions about the mesmerize board and the BOM:

1) Can I choose higher wattage audio resistors as long as the R is the same and the tolerance at least as good as the ones listed in the BOM?

2) The BOM lists two "1R 1/4w metal film 1%". I can't find them on the board... Could someone with better eyes than me show me their location on the board?

3) I want to build a hot-rodded version. I will use the 10R 4w 1% resistors instead of the 68R pair. The board location has three sets of holes, does it matter where the 10R goes? The middle set of holes or it doesn't matter?

4) I would like to take the board to 600ma. Ok for this board? If so, at this level I should use a cooling scheme like Tea-Bag's (http://www.diyaudio.com/forums/blogs/tea-bag/296-salas-dcb1-blue-edition.html)? Or on chip sinks are enough?

My ignorance of the subject matter is probably shining through with some of the questions... Thanks in advance for any help.
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Old 17th March 2011, 02:01 AM   #282
Tea-Bag is offline Tea-Bag  United States
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The 1R resistors are on the Hot-Rod Hypnotize board only.
The older BOM's are appropriate for the Mesmerize.

There is another blog entry for hypno/mesmerize - older but it has the right bom.
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Old 17th March 2011, 11:15 AM   #283
AndrewT is offline AndrewT  Scotland
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Quote:
Originally Posted by palmito View Post
2) The BOM lists two "1R 1/4w metal film 1%". I can't find them on the board... Could someone with better eyes than me show me their location on the board?

3) I want to build a hot-rodded version. I will use the 10R 4w 1% resistors instead of the 68R pair. The board location has three sets of holes, does it matter where the 10R goes? The middle set of holes or it doesn't matter?
higher wattage resistors generally come with higher tolerances.
you can use 250mW or 400mW or 500mW or 600mW. These all come in 1% E24 values. Check the resistor body length to ensure that when the legs are bent they fit the pad pitch.

The 68r in the standard DCB1 is not 68r.
It is 68//68r giving an effective 34r.
The third hole is left unused in this case.

If you need ~10r then you can use 20//20r (using the two outer holes) or 30//30//30r (using all the available holes). All give the same effective CCS resistance. You might be able to source 1W 30r 1% that fit the pad pitch.
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Old 17th March 2011, 11:47 PM   #284
palmito is online now palmito  United States
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So to get the equivalent of the 10R/5w I could use 3 27R/1w resistors per side? That would be 9R, what kind of mA would the board be at using 9R equivalent resistors? These three individual 1w resistors are equivalent to a single 5w one?

Thanks for the explanations, it's much appreciated.
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Old 18th March 2011, 12:05 AM   #285
Salas is online now Salas  Greece
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Circa 200mA, exact number depending on particular Mosfet's Vgs. 3W resistor total rating is enough for that. 5W size is reserved for running even more in the Hypno.
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Old 24th March 2011, 04:13 AM   #286
nezbleu is online now nezbleu  Canada
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Quote:
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Hi,
yes and no.
Use any cheap To92 that has sufficient Ic max. Speed, Vce0 and gain are unimportant in this slow switching application.
Thanks again for your help Andrew. I have been playing with this switching circuit for input selection, and I think I have it working. So far just using one input/output on a scrap of project board; tomorrow I will enable another input and make sure it works as intended.

Initially it did not work at all. I remembered that the data sheet for the flip-flop chip said it needed about 20ns set-up time between voltage being applied to the input pins and the clock pin low-high transition. So I added a small RC network on the clock pin (a small series resistor and a capacitor to ground) and suddenly it worked! Sort of... The transistor would switch off again after about 10 seconds, and it seemed very sensitive (eg., touching the clock pin with a dvm probe would cause the output to go low). Plus, at power-on it was a crap-shoot whether all outputs would be low or all high.

I added a decoupling cap on the power pin of the IC, and added another RC network on the ~CLR pin (to hold it low for a few ms while the chip powered up). I also realized that I hadn't provided a path to ground for the cap on the clock pin to discharge, so added another 10K resistor there. Now it seems to work properly, momentarily closing the switch on the input causes the output to go high, the transistor turns on, and the LED glows (haven't connected a relay yet), and it stays that way even when I poke around with my DVM probe. I'm calling it a qualified success so far! Now I just need to work up a layout for all 6 inputs.
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Old 24th March 2011, 01:34 PM   #287
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Default a reminder

Omron G6H-2 12VDC relays

I have added to the items I offer for the DCB1. These now include relays, matched strings of leds and a limited number of matched quads of 2SK170BL.

Post in that thread or pm me.
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Old 24th March 2011, 01:56 PM   #288
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Hi Ed,

You have a pm.
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Old 24th March 2011, 03:41 PM   #289
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Hi John,

I have responded to your pm.
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Old 4th April 2011, 08:05 AM   #290
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hi i had build the mesmerize but the first time i run out after 1 30 hour one of the capacitor 4700 and one rectifier mur120 (is that for the relay too) has burn out!!! the temprature on the capacitors both it was very high! and the power supply 50va 2x15v also it was very hot....what can be happen?
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