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OK, so I did read some of the other posts here first. I have a Trident 1.2 V on a B-II that has just failed twice, that is I powered down for awhile, and on restart it worked again for an hour or so. LEDs lit, but ~0.4 V out. My pre reg puts out 5.36 V when cold and drops to 5.32-5.30 when warm, I have never seen an input voltage over 5.37 V, and seeing that this design drops V with warm up, I do not see how overvoltage could be the problem. I also power the entire DAC from an AC regenerator, which provides surge protection, and holds incoming voltage to 117 VAC, this is rock solid. I guess it could just be a boarderline opamp perhaps? I do not mind replacing the Trident, but as this failure DOES NOT seem possible to be caused by overvoltage, I am curious as to the cause?
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The problem the few times this has happened is that people don't realize that their voltage is too high right at start up. It will settle lower over time as stated in the manual. Though I cannot be certain what happened with yours, it could be any number of things. As always pictures and such might help spot a problem. You do definitely need adequate ventilation. Edited by user Thursday, September 29, 2011 8:28:21 PM(UTC)
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There is the possibility that your voltage measuring device may be under-reading and peak voltage on start-up may be exceeding the 5.5V max input voltage rating for the Tridents
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Voltmeter is a Fluke, and reads 3.3 V for output of other two Tridents, and any other regs checked read correctly, so it is not off. Pre reg voltage at cold start is 5.36-5.38 volts, and drops to around 5.30 with warm up. Chassis is well ventilated, and there is a lot of internal volume.
Replaced the opamp, and still have the problem (no lock, ~.05 VDC out instead of 1.2 VDC, both LEDs lit). Guess replacing QP1 & QP2 is next with TPA on vacation.
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Yeah it sounds like a dead transistor. Is it possible you shorted the CCS resistor?
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Russ White wrote:Yeah it sounds like a dead transistor. Is it possible you shorted the CCS resistor? Thanks Russ. This reg has been working for months and music just stopped one day. Anything is possible I guess, but do not have any idea how the CCS resistor could have been shorted. Is the Fairchild BC860AMTF the right part for QP1 and QP2?
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I have QP1 & 2 transistors coming today. Hopefully these will get my 1.2 VDC Trident back to life.
As it appears this Trident likely failed due to overheating, and I see in other threads that the 1.2 VDC Trident seems more prone to failure than the 3.3 VDC, I suspect that the increased voltage drop from 5.3 V to 1.2 V is pushing QP1 (or is it 2) a little in terms of heat management. Clearly better ventilation is advised in my installation, but I am also wondering if adding a tiny heat sink to the transistors might be advised for long term reliability? I have some copper foil, and could easily epoxy a tiny sink to the transistor bodies, of course being careful not to allow any shorting of other nearby components.
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Heat could have been in a factor, but there are other possible culprits as well.
Sure adding little glue on type heat sinks would not hurt at all. :)
The 1.2V reg definitely has the hardest job.
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Thanks Russ. Replaced QP1 and QP2, and am back in action with perfect 1.2 VDC.
I will go ahead and fashion some tiny heat sinks for QP1 and QP2 just for piece of mind.
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hello
got some 1,2v Trident replacements today and there were 3 different R values included: 10/15 and 20R
the old ones had 10R
which ones to use? why different values included?
best
Leif
Norway
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Tridents are also suitable for other uses. It just happens to be commonly used with the BII/BIII DACs.
Information on which resistor to use where can be found in the guide on the BII/BIII. 1.2V = 10 ohm/1%.
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sure I know but it was delivered as a replacement for a faulty one in a BII setup
that´s why I asked
I think the duty it´s supposed to do in the BII it´s a tad too much for it
maybe one should insert a 3,3 vreg in front, then the 1,2
just to ease the pain
best
Leif
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I think it's rather the variation in the measuring equipment that is causing problems. From 5.25V to 5.5V is only 5%. With a cheap meter it's very well possible the voltage you're measuring is not what is really there. And most people tend to run on the high side, thinking more voltage is better. All this combined with the 5.5V recommendation in the original BII manual is likely to explain quite a few of the failures.
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