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Old 14th November 2013, 08:01 AM   #1071
ThomasJ is offline ThomasJ  Norway
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Hi!

This is my first post here, but Ive been following for quite some time.
Me and a friend have been building a Mez each, and we both have the same fault.

One of the led groups wont light up. See photos for closer detail, and voltages.
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File Type: jpg bilde 4.jpg (886.1 KB, 229 views)
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Old 14th November 2013, 10:43 AM   #1072
AndrewT is offline AndrewT  Scotland
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Carefully measure the voltage across each unlit LED.
If one is back to front it will show a much higher voltage drop. LEDs are not good blocking diodes and may be damaged by reversing them. Better to replace rather than trying to carefully remove it for re-use.

If all the LEDs are reversed, then power Down and use the Diode function on a DMM (sometimes the 2000mVdc scale can do this job) to determine the rough Vf of each diode. Each should read open circuit when you swap the probes. If all are OK then swap them around. This time they should not be damaged by the reverse voltage, since they all help each other.
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Old 14th November 2013, 05:53 PM   #1073
ThomasJ is offline ThomasJ  Norway
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Hi, AndrewT. And thenk you for you response!

All the leds are mounted correctly, and the all work. Tested!
However this group does not light up. New today is that they light up very shortly when powering on (I use a switch on the tranny), but then fade out and die.

I also get DC go all legs on the power gets when measuring from the centre points on the board, across to the mid leg go both the 240s and the 9240s.

I am a newbee, and at a loss :-)

Thomas
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Old 14th November 2013, 08:07 PM   #1074
Salas is offline Salas  Greece
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See if all Mosfets correspond to their right positions VS their part# on their cases..
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Old 14th November 2013, 08:42 PM   #1075
ThomasJ is offline ThomasJ  Norway
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Do you mean that should check whether I mounted them on their correct place on the pcb?

-Thomas
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Old 14th November 2013, 08:43 PM   #1076
Salas is offline Salas  Greece
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Yes, check that each one has the right type print on its body VS its correct position on the board.
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Old 14th November 2013, 09:07 PM   #1077
ThomasJ is offline ThomasJ  Norway
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They seem to be correctly placed, with the metal side pointing outward, transistors standing above the pcb.

The markings on the transistors are irfp240 y27k aq and irfp9240 y25w am

-Thomas
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Old 14th November 2013, 09:16 PM   #1078
Salas is offline Salas  Greece
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OK. Also check there is no BC transistor in a K170s place by mistake, so we are sure about all the parts placing first.
After that put the DVM probes across the BE pins of the BC transistor on the dark LEDS side, it must have about 0.6V. If not, replace.
Then on the G,S pins of the MOSFET next to the dark LEDS. The one over the print "shunt reg". You must see 3-4V. If not, replace it.
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Old 14th November 2013, 09:26 PM   #1079
Salas is offline Salas  Greece
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Also with the power turned down and with the DMM in Ohm mode measure each K170 of the dark side across its outer pins. Must show 30-50R normally.
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Old 19th November 2013, 12:16 PM   #1080
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I thought I was finished project but I made ​​a mistake and I need your help to fix it.

Some of the key data:
All LED light.

ACC 16.27V 16.28V
DC + 10.82V - 10.09 V
Offset R 1.1 mV L - 0.54 mV (
How can I get it if relays do not work)

Hotrodded. I use 8.2 ohm resistors. Voltage across the resistor are:

+ 1.793 V - 1.685 V


And the problem. I used the NEC 12V relays that have the same pin configuration like Omron. I hear the relays to switch but there are not
electrical connection. What can I do.

I also used the 15, 0, 15, 150VA transformer, because I thought to give in the same enclosure the phono stage. I will change transformer for smaller. How VA would be optimal in the context of my other data.


Thanks Matjaž
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Last edited by submat50; 19th November 2013 at 12:22 PM.
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