Mezmerize DCB1 Building Thread

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komigenie

komigenie

Member
Joined 2006
hifiholic.com
pwalker said:
I am looking for a Mezmerize DCB1 Board as well. If you have one that you would be willing to sell, please PM me.

Regards,
Paul
Click to expand...

Nah, i am gonna keep it ... I have all relays soldered, and i got me all PRP resitors in hands, caps too .. just need matched transistors to complete that one ...

Sorry ...

I just finish my DC-B1, and for a moment i was about to get rid of Mezmerize, but i change my mind
 
O

orpheus

Member
Joined 2004
Try as I might, I can't get the Mezmerize I built to output the correct voltage. On the positive leg, I get about 9, and on the negative, around 7. The 2nd set of LED's on the negative leg are usually not lit, but they do occasionally light up. I have also had it with the positive leg at around 10 and the negative around 9, but that doesn't last very long before it fades back to around 9+ and 7-. I have changed the 5 LED string, and tested and resoldered all the connections, checked the board traces against an empty board, and checked and quintuple checked all the part orientations and resistor values.

The part that really disturbs me is that it will very occasionally work correctly, and this always coincides with the neg leg 5 LED's lighting up. I have changed out the LED strings on the negative side, and I have swapped the 2sk170's on the negative side (since I have a bunch of those on hand). Neither had an effect.

I am using a 12 volt transformer.

Here are some voltages:

output from Diodes: 11+, 9.9-
Across R1: .7+, 1.2-
Across first LED set: 5.57+, 5.57-
Output from first LED set: 5.4+, 4.4-
Input 2nd LED set: 9.1+, 7.15-
Across 2nd LED set: 9.67+, 7.8-
Output 2nd LED set: 0.3-, 0.3-

I did match the LED's to get around 1.8 volts from each one. When I switched the LED"s in the negative leg, I grouped them to measure as close to 9 and 5.4 volts as I could. All 5 of the vref LED's together were measuring around 9.1 with a 2SK170 used to power them through a battery.

If I could take any more measurements, please let me know. I have been trying to fix this for hours now, and I haven't been able to figure out what is wrong. If anyone has any ideas or suggestions, I would very much appreciate help.

Thank you for your time.
Aaron.
 
Salas

Salas

diyAudio Chief Moderator
Joined 2002
Paid Member
There are 10 or 1 Ohm resistors under each K170 that feeds the strings of 5. Is there enough voltage drop across those resistors? That indicates the currents. Should be near 70% IDSS of the JFETS you used. Is it so? If yes, although I haven't heard of such a bug in the course of the threads before so to answer from experience, I would check the BC transistors and Mosfets also. Is there Vbe and VGS proper on all? You report small drops across R1, maybe the CCS MOSFETS are not OK?
 
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orpheus

Member
Joined 2004
Salas said:
There are 10 or 1 Ohm resistors under each K170 that feeds the strings of 5. Is there enough voltage drop across those resistors? That indicates the currents. Should be near 70% IDSS of the JFETS you used. Is it so? If yes, although I haven't heard of such a bug in the course of the threads before so to answer from experience, I would check the BC transistors and Mosfets also. Is there Vbe and VGS proper on all? You report small drops across R1, maybe the CCS MOSFETS are not OK?
Click to expand...

Over the 10 ohm resistors, I get .042 volts on the positive leg, and 0 volts on the negative leg. I used 2SK170BL's, but I didn't measure the idss of them before installing them for the power supply. Both the 2SK170's in the power supply for the 5 led string were exchanged, so there have been two sets in there with the same problem.

Should I pull the mosfets and transistors and then measure them, or could I measure them in circuit to test them? What measurements would you like me to post?

Thank you so much for your help.
 
Salas

Salas

diyAudio Chief Moderator
Joined 2002
Paid Member
The 0 reading on the negative leg 10R is tell tale there is no current for its leds. The positive leg indicates 4.2mA which can be coming from a 6mA fet or less (low end for BL), when tested for idss with a 9V battery. Where you got those K170BL? Pull the negative leg K170 and test for idss first. If its OK put it back. Having no current there with a good K170 means the negative side CCS will not give it any, or something draws all of it elsewhere. Do you get a cold negative side to the touch for both Mosfets? With complete circuit running, measure voltage between gate and source of each negative side mosfet, and between base and emitter of the BC transistor. Should be 3.5 to 4V and 0.6 to 0.65V.
 
A

AndrewT

R.I.P.
Joined 2004
orpheus said:
...........I am using a 12 volt transformer.

Here are some voltages:

output from Diodes: 11+, 9.9-
Click to expand...
What does that mean or indicate?

for ~10V output from the Salas type regs, the DC input voltage when mains power is at lowest end of tolerance should be >=16Vdc.
When mains is at normal tolerance expect 17to 18Vdc.
When mains is at highest tolerance, you would expect the regulator to survive with upto 19 to 20Vdc at the input.

If you are only getting 11Vdc and 9.9Vdc at the inputs to the two Salas type regulators then your transformer is either broken or you have wired it up incorrectly.

The DCB1 works well with a 30Vac centre tapped transformer, i.e. 15,0,15Vac
 
Frosteh

Frosteh

Member
Joined 2011
Does anyone know the price of the matched JFET's? I'm also looking for a PCB, but that seems to vary more since I'll have to find one that someone didn't want since I missed the last GB.

EDIT: Never mind. Found these on ebay. Will these work? I only need 2 matched pairs, not 4 matched, right?
 
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Frosteh

Frosteh

Member
Joined 2011
Salas said:
You need 2 matched pairs in the 7-8ma region. Each pair can be a bit different, you don't need 4 in same IDSS. The bags look Toshiba to me in that link. Also Andrew has very well matched LSK170s (excellent American clones).
Click to expand...

Is there something wrong with the Toshibas? $3.10 for 4 is quite cheap. Any advantage to using the LSK170's (other than supporting a fellow DIYer and faster shipping from the UK than Israel)?
 
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Tea-Bag

Tea-Bag

Member
Joined 2006
Paid Member
you can't guarantee what matching level this guy provides, but you could ask.

Ed Lafontaine and Blues are two other guys who might be able to sell you this stuff stateside, and then you get matched quads. Dont forget you need 6 additional ones to complete the power supply section. They do not need to be matched.
 
Frosteh

Frosteh

Member
Joined 2011
Tea-Bag said:
you can't guarantee what matching level this guy provides, but you could ask.

Ed Lafontaine and Blues are two other guys who might be able to sell you this stuff stateside, and then you get matched quads. Dont forget you need 6 additional ones to complete the power supply section. They do not need to be matched.
Click to expand...

This is what he quotes: "I declare +/-2% to be on a safe side but really I select no more than +/- 1% (Vgs = 10V)." What exactly does this mean? I'll pm Ed and Blues to see what they'd want for a couple matched ones.
 
Ed LaFontaine

Ed LaFontaine

Member
Joined 2004
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