Just updating that the problem was solved mainly by cleaning the key contacts. So basically it did happen as a result of dirty keyboard contacts I believe. --- In vintagesynthrepair@yahoogroups.com, "narfman96" <narfman96@...> wrote: > > Hi Gil, > > CV pitch is one volt per octave in the Minimoog. It doesn't take much of a resistive connection to throw the scale off. > > --- In vintagesynthrepair@yahoogroups.com, "Gil" <gilwe@> wrote: > > > > Cleaning the keyboard contact with alcohol cleaner, I could play for a couple of hours without seeing the problem. How likely that this was caused by bad key contacts ? how does this (resistance) affect the pitch ? > > > > > > > > --- In vintagesynthrepair@yahoogroups.com, "lhammond" <lhammond@> wrote: > > > > > > I use felt pipecleaners as you can bend them around contacts and they > > > absorb cleaning liquids. But the best is to pullthe rodd and buff it on > > > the sort of machine a jeweller will have. And rotate it if worn. > > > > > > lorne > > > > > > > The pitch changes as a key go down indicates a resistive connection > > > > between the contact and bus rod. Often they are worn, sometimes damage > > > > through bad maintenance. There are many ways to correct, some very > > > > imaginative to stupid. The bus and contact have a thin gold plating, > > > > once worn off, problem area. > > > > > > > > > > > > I remove the bus rod to allow better access to the keys side contact. A > > > > good desoldering skill set is required as the plastic can be damaged by > > > > too much heat . Sometime I just rotate it 90 degrees to give a new gold > > > > area to contact. One guy told me he used unwaxedd, so dental floss wet > > > > with contact cleaner and sawed it back and forth. Main thing, as the > > > > contact strikes, you do not want changes, as voltage equals pitch. > > > > > > > > Drill a hole in the pot with a small drill to allow pot spray to be shot > > > > in. Insert the drill into the chuck so only an 1/8 inch sticks out, cut > > > > off or grind off if to long. This prevent the drill from going to far > > > > into the pot and doing damage. The metal is hard, so patience. > > > > > > > > R > > > > > > > > > > > > > > > > > > > >>________________________________ > > > >> From: Gil <gilwe@> > > > >>To: vintagesynthrepair@yahoogroups.com > > > >>Sent: Monday, July 9, 2012 8:40 AM > > > >>Subject: [vintagesynthrepair] Re: Minimoog D pitch drifting > > > >> > > > >> > > > >> > > > >>Hi all ! > > > >> > > > >>So I received it a week ago and did the following - > > > >>1. I took all PCB's out and cleaned the connectors > > > >>2. I rewires a few bad solder joints going to the pitch and modulation > > > >> wheels > > > >>3. I cleaned the PCB sockets and checked for tight connectivity between > > > >> the PCB's and flags > > > >>4. Replaced the 1458 ICs in the generic tuning circuit (where the Tune > > > >> pot goes) > > > >> > > > >>I see the tuning problem less then before but it still happens from time > > > >> to time. I *think* it happens more when playing certain keys in the > > > >> middle of the keyboard (although I don't see why it will only happen when > > > >> playing this specific area). sometimes, the pitch will raise and fall as > > > >> I push some keys down (like when using after-touch) - can bad kayboard > > > >> PCB cause this ? > > > >> > > > >>Also, in the specific machine, the master Tune potentiometer doesn't > > > >> reflect the tune. The "default" tunning is a down that what it should be. > > > >> The Tune pot shows correct resistance values when rotating it, and the > > > >> soldering and connection to the sockets (and then PCB) looks ok... Which > > > >> is weird. Also, tapping on the pot, it doesn't seem to reflect the tuning > > > >> at all, as if it is dead... but it is not :/ > > > >> > > > >>--- In vintagesynthrepair@yahoogroups.com, "Paulo Palmieri" > > > >> <paulopalmieri@> wrote: > > > >>> > > > >>> That´s right. To affect the 3 oscillators maybe the countour generator > > > >>> could be the problem or the PCB conectors already commented here. > > > >>> This is the late version more stable than the first generation. > > > >>> > > > >>> Good luck and be in touch! > > > >>> > > > >>> Paulo Palmieri > > > >>> > > > >>> > > > >>> ----- Original Message ----- > > > >>> From: Quazimodo > > > >>> To: vintagesynthrepair@yahoogroups.com > > > >>> Sent: Friday, June 29, 2012 4:51 PM > > > >>> Subject: [vintagesynthrepair] Re: Minimoog D pitch drifting > > > >>> > > > >>> > > > >>> > > > >>> So it's a late, *stable* one... OK, then it will probably be much > > > >>> like I said in the first place. > > > >>> > > > >>> Check those flags...! > > > >>> > > > >>> --- In vintagesynthrepair@yahoogroups.com, "Gil" <gilwe@> wrote: > > > >>> > > > > >>> > > > > >>> > Thanks. Serial is 12044. Supposed to get it in a few days so I'll > > > >>> be able to tell what it exactly uses (or do you know be the serial > > > >>> number?) > > > >>> > > > > >>> > > > > >>> > --- In vintagesynthrepair@yahoogroups.com, "Paulo Palmieri" > > > >>> <paulopalmieri@> wrote: > > > >>> > > > > > >>> > > Hi Gil, > > > >>> > > > > > >>> > > Probably there is a variation in the cv voltage that controls the > > > >>> oscillators. > > > >>> > > I experienced similar issues on the osc 1 of a RA Moog model (the > > > >>> first earlier version) and the only thing that solved the problem > > > >>> was replacing the 2n4058 transistors. > > > >>> > > Please, provide more info such like serial number and if your > > > >>> oscillator board has only transistors or 2 ICS SG3821 or > > > >>> CA/LM3046 or 3 UA726 ICs. > > > >>> > > > > > >>> > > Regards, > > > >>> > > > > > >>> > > Paulo Palmieri > > > >>> > > > > > >>> > > > > > >>> > > ----- Original Message ----- > > > >>> > > From: Gil > > > >>> > > To: vintagesynthrepair@yahoogroups.com > > > >>> > > Sent: Thursday, June 28, 2012 9:55 AM > > > >>> > > Subject: [vintagesynthrepair] Minimoog D pitch drifting > > > >>> > > > > > >>> > > > > > >>> > > > > > >>> > > I'm handling a friend's mini, which acts strangely. The overall > > > >>> pitch (of the entire machine) will change suddenly, up and down, > > > >>> not to far from the correct pitch but a few semitones... It > > > >>> affects all oscillators at the same time. Is this a known issue > > > >>> in old minimoogs? I would usually suspect either power supply > > > >>> main voltage instability, bad caps or transistors, but being it > > > >>> affecting all 3 oscillators, I tend to think it is not oscillator > > > >>> circuit related ? :/ I'm new to minimoogs so any help would be > > > >>> appreciated... Thanks ! > > > >>> > > > > > >>> > > > > >>> > > > >> > > > >> > > > >> > > > >> > > > >> > > > > > >
Message
Re: Minimoog D pitch drifting
2012-10-02 by Gil