i had the day off, so i took my dad's broken radio apart to try and fix it. thought anons might appreciate it, since this thing is literally older than me. anyway the station doesn't change at all when the knob is turned (even though the frequency indicator on the front side moves normally). the pulley string seems to be intact, but i'm clueless to why the station remains unchanged. can some radio guru point me in the right heading.
>>2976481without sounding like an asshole.you are in over your head.
>>2976481Watch a hundred episodes of Mr. CARLSON'S LAB
Mercury level is low
>>2976481watch shango066bandersentvradiotvphononut
abort abort
>>2976504fair. well i managed to confirm few things in the process:> the pulley thread works ok> the variable capacitor rotates with the knob> frequency does change while rotating the knob (opposite to what i thought earlier)> audio is faint on one station - non audible on all others - almost normal on the strongest station> non stop crackle for as long as radio is on> plugged external headphones, same crackle, same faint audio> most if not all caps are not leaking or bulging>>2976522>>2976509yeah but unless you do contribute something, my guess is you don't know any better neither
>>2976481Half the old radios that have your symptoms it's just corrosion on the coil and/or dirt making bad connections on the board. Use contact cleaner and work the knobs back and forth after vacuuming the whole thing and cleaning up any obvious debris on the board, 2/3s of the time that will do it. If there are any corroded connections resolder them and it should be fine.
>>2976531this >>2976504and this is me >>2976522 careful skippy >non audible on all others - almost normal on the strongest stationattach antenna>non stop crackle for as long as radio is oncrackle or static? static is normal in old radios.if crackle clean pots with deoxit.>most if not all caps are not leaking or bulgingmeaningless on old radios they have to be tested with an actual old timey capacitor tester.you do have one right? no? well you will need one. I suggest a heathkit vintage capacitor tester.
>>2976537>coili brushed and vacuumed the board. the coil has no contact points. it has multiple winding wires branching from it and soldered to the board. with a varying capacitor attached to the knob to cycle frequencies. at the top left is a mode select knob for switching between am/fm bands. touching it can affect the crackle coming out.>>2976554>attach antennait's attached. moving it or extending it did not change symptoms>crackle or staticit's constant crackle that won't let for as long as radio is on. increasing volume to max slightly increases crackle. >you do have one righti have a multimeter but will obv need to de-solder each cap to test its capacitance. >this >>2976504>and this is me >>2976522sorry. i just wanted to fix it for my dad. it's simpler buying him a radio that isn't 40 years old (literally) but it's not the same. anyway thanks for the tips.
>>2976568>touching it can affect the crackle coming out.clean inside switch with deoxit. check for cold solder joints.>i have a multimeternot the same. capacitors can indicate good but are still bad. you need an actual capacitor tester.
>>2976568>anyway the station doesn't change at all when the knob is turned (even though the frequency indicator on the front side moves normally). the pulley string seems to be intact, but i'm clueless to why the station remains unchanged.Be sure the white nylon wheel rotates when you move turn the knob to change stations.Be sure the silver shaft is fitted inside the white nylon wheel and the shaft turns with the wheel.The part on the other side of the board connected to the shaft is what selects the station.
>>2977359I know nothing about radios but this topic is super interesting.>>2976554Keep helping OP if you can.
>>2977597i didn't have deoxit, and not sure if 70% ethanol is appropriate, but will attempt to clean the mode select, volume and tone knobs, (they do crackle when touched so there's probably bad contact). maybe even inside the variable cap.what i found so far are leaky caps. one when tested in circuit produced a continuous beep but not sure if the cap is shorted or some other parallel component is responsible. i ordered me some soldering tools which will arrive on tuesday.
>>2977359yes the wheel, pulleys, and variable capacitor all connect and rotate ok. that was first thing i checked when my dad told me it only runs one station. but the stations do change, it's just that the audio is too faint, with constant (frying pan) crackle and overall just terrible. the stations that still runs is probably the strongest signal.
>>2976537This sounds likely. Autistically clean every connection with a small wire brush using all your spare time for two months.
>>2977696Those caps are not leaking. That's just some glue they used for some reason. I've seen it before in very old electronics
>>2976537>>2977725i did clean:> mode select contacts> volume potentiometer > tone potentiometer > inside the variable capi found this resistor that should be at 82k but instead it's reading around 120 ohms on the multimeter. could be something. it's situated right by the connector for the front volume needle.>>2977732ok that's good to know. but the shorted capacitor is definitely shorted right?
>>2977761Do you have a schematic of the circuit? I would advise against measuring things in circuit. Besides, a resistor is unlikely to fail and I would expect it to burn up if it did short. Electrolytic caps are the most likely to fail and cause issues, and they will even keep showing their rated capacitance to a DMM, except they now have a somewhat low internal parallel resistance. My last repair was due to such a fault: a cap allowed DC to pass and drop, and it pulled the power rail slightly down enough to cause problems, but not enough to be obvious. The fucker blew on the bottom too instead of the top, and I found out only when I had no other option but to desolder every cap to measure it individually to find the obvious but otherwise hidden failure. Transistors are close second to be the ones that release the magic smoke, but something must have likely gone wrong somewhere else for it to happen, so they might be more of a symptom than a cause.
>>2977793>Do you have a schematic of the circuit?no and i've looked. my first image of the pcb is the closest thing to it. but all resistors measured in board were as close to their color coded values as possible, except for that one >>2977761it's a toshiba rt360rhttps://www.youtube.com/watch?v=P8IzBZ8hEH4
last clean up yielded results. I get stations now! Hopefully it won't fade out again. I still want to tinker with it. try to replace the cap and resistor as soldering practice. will come back after i break it again.
>>2977761>but the shorted capacitor is definitely shorted rightI can't see from the picture if it is shorted or not. Maybe it is in parallel with the center terminal of the potentiometer. Try rotating the potentiometer to the opposite position and check if the capacitor still beeps continuosly
>>2977832>solid stateThey actually insisted on stating that it was not made with vacuum tubes
>>2977869>I get stations now!>>2977869>I still want to tinker with it.If you have it working, STOP.Tinker with something else.
