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<span style="font-family: helvetica; font-size: 12pt;">Reminds me of a project I worked on about 35 years ago. It was a memory controller board for a minicomputer system. My design was pretty straightforward, so I expected the controller to debug pretty quickly. Instead, the circuit was totally non-functional in weird ways. Being an engineer, I assumed I had made a horrible mistake in the design. A day of head-scratching and I still could not figure out what I did wrong.</span>
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<span style="font-family: helvetica; font-size: 12pt;">Fortunately, a co-worker who had spent many years as a tech had a brainstorm. He discovered that the capacitors which were supposed to bypass the Vcc distribution had been mis-installed at assembly in the factory. They were installed in vias between logic signal runs instead of between Vcc and ground. Capacitive-coupled TTL signals is no way to make a working system!</span>
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On 08/22/2022 9:34 AM Tim KC1RET <kc1ret.radio@gmail.com> wrote:
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</div>The saga of my 'dead' TS-2000 continues.
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<br>So after hours of deciphering schematics and finally performing a radio autopsy on my kitchen counter I was struck with this conundrum... How could the supply voltage read 13.8v at the connector, but only 5.2 where the wire connected to the main board?
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<br>At first I suspected the filter caps. They are soldered directly to the back of the connector inside the radio, dead-bug style. I cut they leads, one-by-one and they were all good & no change to the voltage reading. In a fit of desperation, I checked continuity between the board and the back of the PS; + was good, GND, not-so-much. Huh?? It was measuring 2.5k ohm! I disconnected the PS lead from the radio, 2.5k between the PS lead connector and PS terminal. Ah HA! (he says - well, I really said something else quite a bit more expressive but I'll leave the specifics to your imagination) I pulled the inline fuse out - Yup, it read not open, not short, but 2.5k. I replace the fuse and the rig fired right up!
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<br>So, when is a fuse not a fuse? When it is a resistor!
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<br>That is a new experience for me -- I'm def. NOT going to forget it.
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<br>73,
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<br>T.
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<p style="font-family: Verdana, Geneva, sans-serif; font-size: 10px; -webkit-margin-after: .5em; -webkit-margin-before: .5em;">Courageously sent from a non-Apple device that <em>includes</em> a headphone jack.</p>
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<td><h3>Tim Carter - KC1RET</h3></td>
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</table><p>"Computers are incredibly fast, accurate and stupid; humans are incredibly slow, inaccurate and brilliant; together they are powerful beyond imagination." -- <em>Albert Einstein</em></p><p style="font-family: Verdana, Geneva, sans-serif; font-size: 10px; -webkit-margin-after: .5em; -webkit-margin-before: .5em;">Warning: Spelling errors in this message are the product of a poor school system. Pay teachures more than athletes.<br>IMPORTANT: This email is intended for the use of the individual addressee(s) named above and may contain information that is confidential privileged or unsuitable for overly sensitive persons with low self-esteem, no sense of humor or irrational religious beliefs. If you are not the intended recipient, any dissemination, distribution or copying of this email is not authorized (either explicitly or implicitly) and constitutes an irritating social fauxpas. No animals were harmed in the transmission of this email, although the mutt next door is living on borrowed time, let me tell you.</p></td>
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