Moog Music Forum

I have order some Op Amps ..

I did some checks with a scope and found there is no Waveform at all at R1, R22 @ R23 but there is as R53 , R73 and R89 same as R111 ,R130 & R145..

if I jump from R53 to R1 I get a waveform.. ? so could it be the Resistors or something before R1 not sure what happens before I can get .06 43k at maplin but they look much smaller I guess .06 is ok to use

grayedout wrote:I have order some Op Amps ..

I did some checks with a scope and found there is no Waveform at all at R1, R22 @ R23 but there is as R53 , R73 and R89 same as R111 ,R130 & R145..

if I jump from R53 to R1 I get a waveform.. ? so could it be the Resistors or something before R1 not sure what happens before I can get .06 43k at maplin but they look much smaller I guess .06 is ok to use

just check with the OSC board removed and the R1 etc reads the same as the other ..

Waaaaaaait a minute.

Didn't you start this thread by saying that OSC 1 was "super high" in pitch, and now you're saying that there is no rectangular and triangle waveforms for OSC 1 ?????????

The only thing you should be concerned about, for now, is to make sure you have a sawtooth waveform with the scope connected at the collector leg of Q15 (Edit: rather Q3). According to your first statement, it should be of high frequency (super high pitch). The other waveforms are derived from this sawtooth.

The pitch control (by control voltage) and waveform generation are two separate sections of the oscillators.

Begin by trying to fix the super high pitch problem first, in the pitch control section. One thing at a time.

I am trying to fix the super high OCS 1 , which stay super high and does not track keyboard or pitch wheel or master tune.

I was tracing the OSC board with a tech frend , and we found there is now waveform shouldn't at R1 etc. which are part of OSC 1 sound source so it looks like my problem is before the IC etc

Thanks all I am saying .. Not new falt

Cheers again , for anyone that is taking time to help

Best

Andy

Ok Thanks

I have a sawtooth at Q15 (which is OSC 2) but nothing at Q3 (OSC 1)

thealien666 wrote:Waaaaaaait a minute.

Didn't you start this thread by saying that OSC 1 was "super high" in pitch, and now you're saying that there is no rectangular and triangle waveforms for OSC 1 ?????????

The only thing you should be concerned about, for now, is to make sure you have a sawtooth waveform with the scope connected at the collector leg of Q15. According to your first statement, it should be of high frequency (super high pitch). The other waveforms are derived from this sawtooth.

The pitch control (by control voltage) and waveform generation are two separate sections of the oscillators.

Begin by trying to fix the super high pitch problem first, in the pitch control section. One thing at a time.

not sure what the High Pitched OSC 1 problem was but not there is no sound at all from OSC 1

Dead OSC 1.

Strong suggestion: send your oscillator board to a tech for repair.

Good luck.

point taken, My friend is staying in a week a full time Tech he will look at it , but I will need part in stock so he can fix it while he is down..


If anyone know were the OSC source starts so I can track on the board that would really help ..

Just to recap :
there is no waveform at Q11 or R1

Just a note not to immediately assume it's a component.
It could also be a bad PCB connection, loose connection or any number of possible other problem(s.)

Proper troubleshooting is analyzing the schematic and theory behind operation.
Replacing parts based on a hunch is not troubleshooting.It's educated guesswork.

The difference is between paying a "tech" 2-4 hours guessing and paying someone that has enough experience to solve the problem in 30-60 minutes.
It's cheaper to pay an experienced tech $75/hr than it is to pay less to someone that might take hours locating the problem.

Kevin Lightner wrote:Just a note not to immediately assume it's a component.
It could also be a bad PCB connection, loose connection or any number of possible other problem(s.)

Proper troubleshooting is analyzing the schematic and theory behind operation.
Replacing parts based on a hunch is not troubleshooting.It's educated guesswork.

The difference is between paying a "tech" 2-4 hours guessing and paying someone that has enough experience to solve the problem in 30-60 minutes.
It's cheaper to pay an experienced tech $75/hr than it is to pay less to someone that might take hours locating the problem.

you are 100% right on this, in my case it has very little to do with money and more to do with being a hands on person. be it Oak Door's and Windows the odd synth , to date a JP8 and ARp2600.. my new thing is a MiniMoog.. and I love it. but my oldest friend is a tech so I alway have him to call and fall back on..


This Forum is new to me and I have found it a great place... I just hope I can give something back soon..

Andy

Hi all, just an update to close this , my old friend Simon Flinn came to stay last weekend (a great tech vintage gear or not). Anyway there was not part failure he cleaned the connection from Osc card to socket with a rubber and re soldered some dry joints .. That was it


Thanks again for all your help!!

Very best

Andy

Great! Exactly what Kevin had suspected.
Thanks for the update, and have fun with your Minimoog, Andy!

Alain.

thealien666 wrote:Great! Exactly what Kevin had suspected.
Thanks for the update, and have fun with your Minimoog, Andy!

Alain.

It was exactly not what I didn't expect?

Glad you're making progress!

Kevin