Madisonears
Thanks for sharing that experience. I’m going to try another de-solder/rebuild with my last red board.
A few questions to anyone/everyone:
1. Can the LM3886 survive the heat required to remove it, or is it better to just plan to plug in a new one?
2. Are there other components on the board that are highly heat sensitive?
3. My removal method involves de-soldering braid coated with liquid flux then a heat gun for components with more than two pins. So how much heat can the PCB stand? I’m assuming no discoloration means no damage.
4. Are there any points along the construction path where one can do some “so far so good” tests/readings, or does everything have to be in place before applying power?
5. Should the input be shorted at first power-up? I have never done that but I see it mentioned on several build threads.
Uriah – Do you have any more matched resistor sets? If not I have three partial sets that cover all the needed values by mixing. Are those resistors matched within each set or just to a specific tolerance?
And finally, can anyone suggest why pin7 on the LM318 would be reading 6.8 and not 12 as it should?
Thanks for sharing that experience. I’m going to try another de-solder/rebuild with my last red board.
A few questions to anyone/everyone:
1. Can the LM3886 survive the heat required to remove it, or is it better to just plan to plug in a new one?
2. Are there other components on the board that are highly heat sensitive?
3. My removal method involves de-soldering braid coated with liquid flux then a heat gun for components with more than two pins. So how much heat can the PCB stand? I’m assuming no discoloration means no damage.
4. Are there any points along the construction path where one can do some “so far so good” tests/readings, or does everything have to be in place before applying power?
5. Should the input be shorted at first power-up? I have never done that but I see it mentioned on several build threads.
Uriah – Do you have any more matched resistor sets? If not I have three partial sets that cover all the needed values by mixing. Are those resistors matched within each set or just to a specific tolerance?
And finally, can anyone suggest why pin7 on the LM318 would be reading 6.8 and not 12 as it should?
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One thing I'm learning about this amp (and in my case combined with LDR attenuation) is that it is very responsive to program material variations. Some CDs sound thin and under-recorded and the next might require reduced volume. I take that as a positive element of the amp now, but I remember thinking differently before I understood what was happening. I think once the hum and any other problems are fixed, what the amp "reveals" about music recording equipment and A&R choices will be very interesting.
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Bob, thanks for your post. I see where you're coming from. 6.8v on 7 is not cool. 7 is ground and should be zero. I think you have a place to start now. Shoot, I posted before your response to madisonears posted. I meant pin 7 on 3886.
Presapian, you need to try my alligator clip suggestion. You have a grounding issue. However, that won't fix bass. What's the value of C13?
Uriah
Presapian, you need to try my alligator clip suggestion. You have a grounding issue. However, that won't fix bass. What's the value of C13?
Uriah
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Remove the LM318 and measure Vcc again - if it's +12v, the LM318 is most probably bad. If it's still 6.8V, the problem lies elsewhere - maybe the zener.
1. Yes, but it's a matter of luck. Plan to have a spare new one, at any rate.
2. Electrolytics, Wimas, LM318.
3. The large tracks can withstand the heat, but small isolated pads and tracks may delaminate.
4. You can safely leave the LM318 and LM3886 out, and apply power to measure the rail voltages.
5. Not required, there's a DC blocking cap installed at any rate.
Yes but No!
Siva, Pin 7 does read 12V without the chip and correctly reads 12V after replacing a NS with a TI.
Pin 4 reads 11.7v to 11.8V
I'll order a few more TI 318s and a couple 3886s to try before I jump into disassembly.
I really wish there were more points to measure but Mario is probablly the secret holder.
HEY MARIO !!!!
Uriah - I don't know what that (voltage division) is. Can you elaborate?
Siva, Pin 7 does read 12V without the chip and correctly reads 12V after replacing a NS with a TI.
Pin 4 reads 11.7v to 11.8V
I'll order a few more TI 318s and a couple 3886s to try before I jump into disassembly.
I really wish there were more points to measure but Mario is probablly the secret holder.
HEY MARIO !!!! Uriah - I don't know what that (voltage division) is. Can you elaborate?
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i can't find output impedance for my dac but the pre's silvaweld swc1000- Output impedance : 200 ohms. little chipamp sounds much more impressive through this setup whereas myref simply sounds underpowered. the buzzing is equal in both channels so i'm guessing it's an issue of the common component- the transformer? i will take it to a techie today to get it evaluated since i just don't feel confident enough to probe with lethal voltages.
also i talked about this a while back but mine came with bypass caps installed between the holes of c19,20, paralleling behind c7. do you think this could have damaged any of the chips?
visited two technicians today who both told me there was nothing wrong the transformer nor the way i was hooking it up. i bought a pair of 3886 for good measure and replaced one of them before wiring the transformer back in. strange and wonderful thing is, the amp was dead quiet the first time i fired it up. i couldn't believe it. i re fired it and once again, dead silence. whoopi! but after i played music through it once and unplugging everything, there is that hiss again, though much quieter than it was before.
i shake the amp, bend around the wires and the hiss is constant through out. it only seem to respond when i touch the heat sinks or the top of c9. too bad i couldn't find 318s. at this point.
only other tests i can think of are replacing the op-amps and stripping the amp from the chassis and heat sinks and try running it bare...
could anybody guess as to what's wrong? maybe i have fake smoothing caps. the noise i get is a hiss+low hum
component swapping still continues a midst the diagnosis.
c15 does affect the sound for me. compared to nichicon vr, nichicon muse 100v has more air and much bigger soundstage. but bass impact takes a step back even further. now the sound feels like i'm only listening to mid+tweet (3way) arg..
i shake the amp, bend around the wires and the hiss is constant through out. it only seem to respond when i touch the heat sinks or the top of c9. too bad i couldn't find 318s. at this point.
only other tests i can think of are replacing the op-amps and stripping the amp from the chassis and heat sinks and try running it bare...
could anybody guess as to what's wrong? maybe i have fake smoothing caps. the noise i get is a hiss+low hum
component swapping still continues a midst the diagnosis.
c15 does affect the sound for me. compared to nichicon vr, nichicon muse 100v has more air and much bigger soundstage. but bass impact takes a step back even further. now the sound feels like i'm only listening to mid+tweet (3way) arg..
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