tag:blogger.com,1999:blog-45406493714811361752024-03-21T19:59:24.154-07:00RetronicsOld and new combined.electronWranglerhttp://www.blogger.com/profile/15728575540450101135noreply@blogger.comBlogger6125tag:blogger.com,1999:blog-4540649371481136175.post-78836668353950789402015-07-29T08:40:00.000-07:002015-07-29T08:40:04.939-07:00Bluetooth boombox projectGood day, worthies.<br />
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Ok, here's the promised followup. <br />
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Pardon my messy workbench!<br />
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Here we see my test setup for a bluetooth boombox I've been considering for the last couple of months. I had originally planned to roll my own amplifier board based on the TDA2050, but ran into technical problems while etching the board. (My photoresist developer solution wiped the entire design off the copper sheet. What a letdown.) So, in a fit of despair, I ordered a <a href="http://www.amazon.com/Nobsound%C2%AE-TPA3116-Bluetooth-Receiver-amplifier" target="_blank">Nobsound GFB646</a> amplifier board from Amazon. This board uses a TI TPA3116 Class-D amplifier to provide 2x50W. It also includes a Bluetooth receiver and integrated volume/treble/bass controls. I will probably write up another post containing my thoughts and findings on this little board in the coming days/weeks.<br />
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The amplifier board is powered by a single supply from 12-25VDC. Anecdotal reports on the TPA3116 claim it is happiest between 19-21VDC. I just so happened to have a half-dozen AC wall-warts that are rated at 15VAC, 15W. Rectified, that is right at 21.5VDC. Hmm. In parallel, 6 of them should be able to handle ~ 90W continuous, which is probably overkill for a garage blaster. So, with this in mind, I constructed a simple non-regulated DC power supply using a bridge rectifier and a bunch of capacitance (~20000 uF) with various snubbers and discharge resistors thrown in for good measure.<br />
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The picture above shows the completed power supply being fed by 3 of the transformers in parallel. Care must be taken to match phases on the transformers as they were wired with no regard to phase at the manufacturer. Reversing a phase on one of the transformers leads to a short circuit condition, which can quickly destroy the secondary windings. Be careful!<br />
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I'll post updates on this project as I am able.<br />
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Happy building!<br />
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~ eWelectronWranglerhttp://www.blogger.com/profile/15728575540450101135noreply@blogger.com0tag:blogger.com,1999:blog-4540649371481136175.post-62567258094382684302015-07-23T09:39:00.000-07:002015-07-29T08:41:42.252-07:00Busy!Wow. Life can sure get busy in a hurry. I have been working on several projects in my extremely limited spare time and I will try to post something about them soon. Honest.<br />
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In the meantime, have you ever designed your own DC power supply? I have designed and built a couple of switchers, mainly to take 12V DC and push it up to 170V DC for Nixie tubes. These are low-current designs. I'm currently contemplating constructing a junkbox power supply that will supply 20V DC @ 5A. This is a little different beast and will be implemented using a transformer, bridge rectifier and a bunch of smoothing capacitance. I haven't decided yet whether I want to add any regulation to it or not.<br />
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Feel free to chime in with your thoughts.electronWranglerhttp://www.blogger.com/profile/15728575540450101135noreply@blogger.com0tag:blogger.com,1999:blog-4540649371481136175.post-60666864997970420442013-06-08T16:36:00.001-07:002013-06-08T16:36:37.985-07:00EICO Model 377 RevisitedRecently, as I was working on an audio amplifier project, the time came to test it with a frequency-controlled input signal in order to determine if it handled tone control properly. This was just the job for my recently-restored EICO Model 377 Sine and Square Wave Generator. Unfortunately... <br />
<a name='more'></a>... when the unit was powered up and allowed to warm sufficiently, I was unable to get any signal out of it at all. Zero. Zilch. Nada. Flatline on my oscilloscope.<br /><br />
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Once I got to a good stopping point with my amplifier, I took the time to examine the Signal Generator a little more closely.<br />
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After taking the case off and probing (carefully! remember the 'one hand rule'!) various points within with my meter and my scope, I was able to determine that there was no signal being sent to the output tube. (For reference, the schematic can be found <a href="http://www.nostalgickitscentral.com/eico/schematics/eico_schematic_377.pdf" target="_blank">here</a>.) The input to V-4 had nothing but some very low-amplitude noise on it.<br />
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Hmm.<br />
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Well, I backed up a little and looked at the first tube in the oscillator circuit, V-1. Specifically, I looked at the cathode, pin 5. The voltage there was 14 VDC, about 11 Volts higher than the schematic indicated. Odd. This pin connects to a small light bulb which doesn't light up, but provides the negative resistance used to form the sine wave. I wondered if perhaps the filament in the light bulb had broken, so I turned off power to the unit and gave it a minute to discharge the caps. Then I started to remove the bulb to check its continuity out of the circuit. As soon as I touched it, it nearly fell out of the socket. Aha! I screwed the bulb back down in the socket firmly and reapplied power to the unit.<br />
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Everything works again. Success!<br />
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Regards,<br />
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~ eWelectronWranglerhttp://www.blogger.com/profile/15728575540450101135noreply@blogger.com0tag:blogger.com,1999:blog-4540649371481136175.post-12764481913086002392013-04-29T21:30:00.001-07:002013-04-29T21:31:27.005-07:00Reviving old equipmentEvery now and then, I am handed the opportunity to breathe new life into old gear. So far this year, I have revived a Heathkit IT-28 Capacitor Checker and more recently, an EICO Model 377 Audio Signal Generator. Both are tube-based and built to last. Unfortunately, both had problems when they came into my hands.<br />
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More after the jump.<br />
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Once I got the EICO 377 opened up, it became immediately obvious that the capacitors need to be replaced. This piece of gear dates from the 1950s and the electrolytic and tubular paper capacitors of that era tend to dry out over time. This greatly reduces their capacitance and can also lead to (dramatic) failure if energized. As you can see, the large capacitor in the center of the chassis has sprung quite a leak of waxy electrolyte.<br />
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I am happy to say that a little bit of surgery with a soldering iron and some modern era capacitors of the appropriate voltage rating brought this guy back to life. I also took the liberty of replacing the power cord (non-polarized, 2 prong) with a polarized, 3-prong cord. The EICO chassis previously was floating, which strikes me as a Bad Idea. The chassis is now properly grounded. Sorry to say that I forgot to take a picture post-surgery!<br />
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The Heathkit IT-28 Capacitor checker also needed a new set of capacitors. None of them had leaked like the EICO's, but they were still in need of replacement. The Heathkit also had a couple of resistors that had swelled and cracked. Once the caps and damaged resistors were swapped out, I had another useful tool for my workshop. As a bonus, it has a cool green 'magic eye' display tube indicator! (that's the tube at the top of the chassis)<br />
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The next item on my list is a 5 MHz single-channel Heathkit Oscilloscope (Model 10-4541) that was given to me recently. If that one proves to be 'interesting', I'll do a post on it as well. ;)<br />
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Happy restoring!<br />
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~ eW <br />
<br />electronWranglerhttp://www.blogger.com/profile/15728575540450101135noreply@blogger.com0tag:blogger.com,1999:blog-4540649371481136175.post-52457513188932574642013-04-29T13:17:00.003-07:002013-04-29T13:17:43.820-07:00Compiling...Just a quick note to let you know that I'm still here. I'm busy with several projects, so I haven't had to time to post anything of note. Never fear! I plan to post <i>something </i>soon. Honest.<br />
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~ eWelectronWranglerhttp://www.blogger.com/profile/15728575540450101135noreply@blogger.com0tag:blogger.com,1999:blog-4540649371481136175.post-68022434358046859752013-03-15T10:54:00.003-07:002013-03-15T10:58:33.741-07:00Hello, World!Welcome to Retronics, my blog about... wait for it... Retro Electronics.<br />
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Ok, well, maybe that's not ALL it's about. I enjoy lots of modern-era stuff, too.<br />
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What I *really* enjoy is the interesting things you can make if you combine old-era electronics with modern stuff. We're not just talking Nixie-tube clocks driven with Atmel microcontrollers running C (though those are awesome). I'm talking about breathing new life into old stuff that has been written off as junk. Combining vacuum tubes with solid state electronics. Putting old equipment back to work. Up-cycling. Whatever. The sky's the limit! (unless we're talking about rocketry or balloon cams ;)<br />
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I intend for this blog to be a home for some modest build logs of my own. I don't have much free time these days, so updates will probably be slow in coming. I'll post some images of projects that I've done in the recent past, and also try to post some things about my current interests.<br />
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Questions/comments are always welcome. I'm always looking for a better/cheaper/faster way to do things and if somebody learns something along the way, all the better!<br />
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~ eWelectronWranglerhttp://www.blogger.com/profile/15728575540450101135noreply@blogger.com0