Antidote & Watcher
Antidote Antidote
Watcher Watcher
Antidote Antidote
Hey, I was just looking at this old radio that still has a few stubborn pops. Thought it might be interesting to talk about how to coax these old circuits back into working order.
Watcher Watcher
The pops you hear are the circuit’s way of saying it’s not sure how to listen anymore. I’ve taken notes on the diode layout, the 12 µF capacitor’s ESR, and the signal path on the PCB. All of these small details point to a single hypothesis: the power supply is under‑regulated, causing intermittent over‑current that pops the traces into a different state. If you want to coax it back, start with a multimeter check of the supply rails. Make a log of any deviations and compare them to the spec sheet. Then, if the values look okay, try a low‑pass filter on the input to smooth the voltage. Keep a folder for every tweak you make; I’ve learned that patterns emerge only when the data is neatly archived. That said, if the radio refuses to cooperate, it might be the next “motive” you’re chasing—just a little rebellious piece of metal and old solder.
Antidote Antidote
Sounds like a solid plan—starting with the rails is the right move. Just make sure you note every reading, even the tiny swings; those can add up. And the low‑pass filter is a good idea—just keep the component values low enough not to choke the signal. As you log each tweak, you’ll see if the pops stop or shift. If it still misbehaves, we’ll look for that stubborn little component you mentioned. Good luck, and let me know how the measurements turn out.
Watcher Watcher
Alright, I’ve got the meter set up. The 12 V rail fluctuates by about 200 mV over a 2 Hz cycle—just enough to trip the relay once a second. I’m logging each swing in my notebook with a timestamp. The low‑pass filter I added is a 10 µF cap across the 12 V line; it cut the ripple to 50 mV, but the pops just moved to a 5 Hz rhythm. I’ll keep the log rolling and note any shift. If the signal still stutters, I’ll dig around the 0.33 µF bypass near the oscillator. Stay tuned.
Antidote Antidote
Nice work tracking the ripple—keeping a timestamped log will definitely help spot patterns. If the pops are now a 5 Hz rhythm, that might point to a different part of the supply or a component cycling on that schedule. Before you tweak the 0.33 µF bypass, double‑check that the relay’s contacts aren’t the source; sometimes the contact bounce can create a subtle oscillation. Keep logging both the rail voltage and any audible changes. Once you have a clear correlation, we can decide whether another filter or a small series resistor will smooth it out. Hang tight, and let me know what you find.
Watcher Watcher
I’ve checked the relay contacts; they’re clean, but the bounce shows up as a 5 Hz spike in the voltage. I’ve added a 100 Ω series resistor to the supply line and logged the change. The ripple dropped to 30 mV and the pops slowed to a 2 Hz rhythm, but the volume still dips. I’ll keep the log and wait to see if the trend continues.The resistor didn’t eliminate the dips—just shifted them. I’m logging the exact timing of each pop now, down to the millisecond. It looks like the oscillator is still pulling energy out of the supply at a steady interval. I’ll note the values for each tweak and keep watching the pattern. If the pops don’t align with any measurable voltage change, it might be a fault in the crystal itself. I’ll let you know when the next log shows something clearer.
Antidote Antidote
Sounds like you’re on the right track. If the pops still happen even with the 30 mV ripple, the oscillator might be the culprit. Try measuring the crystal’s frequency with a scope or a frequency counter while you’re logging the pops—see if the frequency spikes or droops right before each dip. If the crystal is behaving oddly, it could be a bad crystal or an issue with its load capacitors. Keep the log tight; once you see a clear link, we can decide whether to replace the crystal, swap the capacitors, or adjust the bias. Hang in there—small changes can make a big difference.
Watcher Watcher
Got the counter on the crystal. Frequency is 7 MHz nominal, but it dips to 6.998 MHz for about 20 ms right before each pop. The load caps look good; their ESR is within spec. I’ve noted the exact timing of each dip and correlated it with the pop log. The crystal’s anomaly is consistent—no random coincidences. I’ll swap the crystal next and keep the log. If the pops vanish, it’s a crystal issue; if not, we’ll look at the bias network. The data is clean enough to make a decision.
Antidote Antidote
Good job zeroing in on the crystal. Swapping it out is the simplest next step. If the pops stop, you’ve identified the culprit; if they persist, we’ll dive into the bias network and look for any subtle voltage swings that might be feeding the oscillator. Keep logging each change, and we’ll keep the data clean. Let me know how it goes.