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I'm having a similar issue to the initiator of this thread. In that I have Trident likely in need of repair though I'm not sure which component I'd have to swap out.
This the 1.2V Trident for the buff II. I may have a cooked transistor or opamp on my hands but I've done a few measurements to see if someone can suggest what this info might point to.
Current GND to OUT measures only .2V
Opamp pins:
1 -> 0V
2 -> .206V
3 -> 1.187V
4 -> 0V
5 -> 0.009V
6 -> 5.371V
7 -> 5.371V
8 -> .002V
R1 -> 3.442V
R2 -> 1.186V
R3 -> 0V
R5 -> 5.371V
R6 -> 3.467V
R7 -> 0V
Any thoughts on what this might point to?
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It is interesting to me that R4 is not in your list. Do you have it soldered in place?
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Hi Russ,
R4 is soldered in place and one side of it messures 5.471V the other 4.155V in reference to ground.
Best Regards,
Theo
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Its better to measure voltage across resistors, not from one to GND. What do you get when you do that?
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Thanks Russ,
I will give you the numbers across all the resistors later this evening. Can you provide the part number for QP1 QP2...I have a suspicion one of these is cooked and while I'm ordering a few parts from mouser I might as well order up a few of these in addition to some LMP77 opamps just in case.
-TJ
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QP1 1 FJPF1943RTU PNP Bipolar Power Transistor Fairchild FJPF1943RTU Mouser 512-FJPF1943RTU
QP2 1 BC560B PNP Bipolar Transistor Fairchild BC560BTA Mouser 512-BC560BTA
Hope this helps!
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These are for Tridents which use all SMD components I believe the parts you are referring to would be for the placid PS.
-TJ
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Russ,
Here are the values measured from one side of each resistor to the other:
R1 -> 1.514V
R2 -> 0.797V
R3 -> 1.195V
R4 -> 1.311V
R5 -> .024V
R6 -> 0.0V
R7 -> 0.0V
R8 -> .206V
R9 -> 0.0V
Is it perhaps likely I have some toasted resistors as well? Both LEDs do illuminate brightly.
-TJ
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Hmm that is very very strange.
What is the value of R4?
if you measurement is correct for R7 then the reg is shunting more current than is being sourced... That means there is likely a short.
Any chance you could take a good quality pic of the front and back?
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Hi Russ, Let me know if the resolution is sufficient. I did not have the unit powered on when I took the picture. Thanks very much for the continued support...hopefully I will soon have a working dual mono Buff II! The back of the board looks fine...nothing obvious at least. Best Regards, Theo Edited by user Wednesday, June 8, 2011 1:39:32 PM(UTC)
| Reason: Not specified tjencks attached the following image(s):  broken-trident.jpg (112kb) downloaded 257 time(s).You cannot view/download attachments. Try to login or register.
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The R4 resistor measures 10.8 ohms.
Best Regards,
Theo
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:EDIT: Never mind what I posted earlier, I was reading the wrong value. Edited by user Wednesday, June 8, 2011 2:54:47 PM(UTC)
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make sure you are testing the Trident on its own. Use something 47R dummy load.
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Ok what it looks like is a load side short. the reason being that the output of the opmap is high (trying to pinch off the shunt) and nothing is being shunted. that in turn means that all of the CCS current is going out the load or a short on the output net to ground. Testing the Trident in isolation will show which it is. Edited by user Wednesday, June 8, 2011 3:18:48 PM(UTC)
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Russ,
Can you give me a bit more detail on how I should test and hookup the Trident for test. I've got a external DC power supply.
Best Regards,
Theo
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All you really need to do is supply it with 5-5.5V. I would just set it at 5V for the test. You don't even really need a dummy load, just check the voltage at the output relative to GND. Edited by user Thursday, June 9, 2011 4:29:40 AM(UTC)
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Alright,
So I hooked up the Trident to my external DC PS. Set for 5.25V...I connected + to IN, GRD to GRD and - to out...
With this setup only LED1 glows but super faint and LED2 doesn't glow at all...R7 measured across the resistor is still 0.0V. I replaced the Opamp and QP1/2 with new parts and I still get the same effect so either I've got a short in the PCB or in one of the resistors or caps.
I will provide a more complete list of measurements today.
-TJ
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You should not have OUT connected to anything. Especially not "-"
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oops...ok my bad...let me retest.
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Alright now I believe I have things hooked up right..
The + of my DC supply is connected to "IN" on the Trident
The - and GRD are tied together and are connected to GRD on the Trident.
Now LED2 is brightly lit but LED1 is not at all.
IN -> GRD: 5.253V
IN -> OUT: 0.124V
OUT -> GRD: 5.127
R1: 2.131V
R2: 0.278V
R3: 1.805V
R4: 0.107V
R5: 0.024V
R6: 0.145V
R7: 0.0V
R8: 4.158V
R9: 0.968V
Thanks for all the help Russ...let me know what you think.
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