From Kenny Balys Sent Thu, Apr 19th 2018, 14:05
From Kenny Balys Sent Thu, Apr 19th 2018, 14:05
Hi Dave, Thanks for the advice. The variable inductor is still micro Henry'ing but is no longer variable. The twisty thingy inside has failed. The Hohner master oscillator inductor is a small vertical box that is sealed in a can so I cannot get in there without destroying it. So what I have now is a stable top octave source oscillator that is stuck out of range of the secondary fine tuning pot. I have decided to get a full set of silver mica 200pf to 300pf capacitors, trying different combos until I get a stable master clock frequency that I can tune in with the fine tune. The fine tune on the Hohner String Performer ranges +/- 1 quarter tone. This should be plenty. I think/hope this is a valid repair. On 19.04.18 03:33 , Dave wrote: > Hi Kenny, > > Tunable LC oscillators are very common, especially in older radio > frequency circuit. The LC combination forms a resonant circuit when > combined with a feedback amplifier creates an oscillator. > > I wouldn't expect an inductor like this to just die. They can be > mechanically damaged if something hits them, or if you attempt to change > the tuning. > > You can test the inductor with an ohmmeter. It should have a fairly low > resistance - it's just a long wire at DC. > > I'd be more likely to check any active components first (usually a > transistor), and then the cap, before suspecting the inductor. > > -Dave > > > > On April 18, 2018 7:42:51 AM PDT, Kenny Balys <xxxxx@xxxxxxxx.xxx> wrote: > > > My Hohner String Performer lost tuning right at the beginning of a > recording session yesterday :( > > I opened it up and the suspect part is a variable inductor: > > Hohner part L1= BV Nr 005837 > > I have tracked this part down to a company called Amidon in Germany. It > has the following specifications: > > Amidon BV Nr 005837, colour code Black, Green, Brown, 5 MHz response, L > = 19.6 uH, Q=120 at 1MHz, Anschluß an Stift A:5 E:4, 27 Euros price > > Neato. I don't understand any of this. > > If I want to get going now, can I not just bang together a 2MHz > oscillator with CMOS gates? > > If anyone understands these things, why would a master oscillator be > inductor based? What benefit is it? > > This thing feeds the 50240 Top Octave divider. > > I checked my Crumar and it's master oscillator also sports an inductor. > > The old PAIA stuff seems to mostly use CMOS gate based master > oscillators so at least there is > > So where is the question? > > Ok.... has anyone replaced an inductor based master oscillator with a > CMOS gate based one on a top octave divider based synth. I am shortly to > do just that (as a band aid)... is this nuts? >