chiguy
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Posts posted by chiguy
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Not sure if related but I once had a Time Machine backup that looked good and copesetic but Time Machine complained of it being a bad image (and therefore unusable) when it came time to restore. All the data was still there however so a third party program (sorry, don't remember which one and this was done for a friend whose hard disk died) was used to extract the files from the Time Machine image.
Is the data from your Time Machine backups still available? Time Machine might not be able to make sense of it (or throw errors like what you're seeing) but perhaps a different program can see the data and files.
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Really dumb question here. I got so more zeners for my power supply. What value am I testing / measuring for? I have a multimeter and a generic Chinese made transistor tester.
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Would 1.3W zeners be okay for the power supply?
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How does one reduce the current in this amp?
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Thanks everyone! I've ordered some zeners.
I didn't think having +/- 350VDC on the dot was terribly important, I wasn't expecting such a difference in range however. While testing last night, part of me was thinking "just plug the amp boards in, what's the worse that can happen?"
On that note, what would happen if I ran the amp boards with my power supplies as they are now?
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A side question, would there be any benefit in adding a GND binding post like what Stax does on their amps?
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Thanks for the advice!
It was pointed out to me that with 5% zeners, 350 x 1.05 = 367.5 and yup, I am using 5% zeners. I guess I got unlucky. =\
What I'm currently using:
I guess I can order some more zeners test for the best ones. I can't find anything that are better than 5% at 1.5W.
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So I finally received my transformers. I've built 2 KGST PSUs and all of the measured DC voltages seem to be within a few volts of what's expected. However, the -350V line is off on both PSUs. One PSU stabalizes at around -366.6VDC and the other PSU stabalizes at around -360.2VDC after about 10/15 minutes . The +350V lines are +353VDC and +356VDC. The transformers I have measure around 320VAC with no load on the HT lines.
Is this something to be concerned about? Anything I can do to bring it down a bit?
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I've mainly used Red Hat based distros and they have usually included a media check when you try to install. I'm not entirely sure what that does as I haven't looked into it. Does your distro have a built in media check?
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How do you check the md5 checksum on a DVD (in Mac OS X 10.8.5)? Disk utility doesn't seem to do it anymore.
I downloaded and burned a version of Ubuntu to a DVD and want to check and make sure it burned correctly before installing.
There's a guy running md5 checksums on DVDs here: http://forums.macrumors.com/showthread.php?t=834540
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I was tossing around the idea of mounting Stax jacks using threaded rods and nuts using blind holes on the back of the panel. My other thought was cap screws also with blind holes.
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Do you have another pair of headphones to try? If you rewire the channels so that the old right is the new left (and vice versa), does the problem swap to the other channel? I'm just thinking about ruling out the possibility of a bad pair of headphones. Do the headphones work fine in another amp?
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I'm going to be using a 135VA transformer with 117VAC. So 135/117 is 1.15A. I'm guessing a 1.5A (or 2A) slow blow fuse will be suitable?
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Which case is that by the way?
Also, what are the recommended fuses to use for this amp?
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Hmm okay. I'm going to be using larger transformers (110mm diameter x 75mm height) so I guess I'll see how that goes in a few weeks when I receive them.
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Aside from the transformer being larger than specified, are there any issues (or benefits) with using a larger transformer?
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I'm still waiting for a transformer but as of now, I've gotten the PCBs completed. What I'm wondering now is what are the proper power-on and setup procedures?
This is what I'm thinking. Some dumbness/ignorance here so feel free to correct me:
PSU
Connect transformer to 115/230v AC mains via input recepticle with fuses
Connect 280VAC and 30VCT to the PSU
Do I need a dummy load on the PSU before powering on? What can I use?
Power on, measure DC outputs, measure Bias voltage using the Bias test point.
Adjust trimpot as needed. What does the trimpot adjust?
All the GND connections go to chassis ground?
Amp
Leave the servo opamp out.
Connect the DC power inputs.
Connect the AC Heaters.
Insert tubes.
All the GND connections go to chassis ground?
Do I need to connect the outputs?
Do I need to connect the inputs?
Adjust the balance.
Adjust the offset.
Power off and insert the opamp.
Check heatsink temperatures.
Am I missing anything?
Thanks!
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I'm going to be using Par-Metal 12x12x4 cases with 7/16 inch standoffs.
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This thread reminds me I still haven't received boards. Has anyone in the US gotten boards yet?
Yes, weeks ago.
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I measured the holes when ordering screws and standoffs. I'm going to be using 1/4 inch hex 4-40 standoffs and screws for the amp boards and 5/16 inch hex 8-32 standoffs and scews for the PSU boards.
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I didn't measure the grid leakage current and the tubes are the default types the amp takes (sorry, I don't remember as this was a friend's amp). The caps I used are linked above.
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You're right, it doesn't matter which way they face. I'm just being OCD.
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It wasn't quite finished when I took this. The little 0.1 caps are missing.
Toroidy.
I put the trimpots as indicated on the silkscreening (both facing each other) but now that I think about it, I should have put them going the same way to make adjusting them easier.
Edit: To clarify, on the amp board silkscreen, the 1K trimpot has the adjusting screw on the right and the 2K trimpot has the adjusting screw on the left. I wasn't thinking when I put them in and just followed the silkscreen.
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Bought and received some Alpha pots and some other PCBs from Spritzer. Awesome process and PCBs. Thanks!
The ultimate DIY? A Stax SRM-T2!
in Do It Yourself
Posted
Mmmm, very tempting. Awesome work! This may be my next project after I finish my KGST.