SH-101 tuning.

[monolith]

Hi , can anyone help me out?
I just got an sh-101, but it seems that tuning wise, it's too sharp. Even with the tuning knob all the way down it's about half a semitone too sharp.
It seems to very stable, just a little higher than it should be. Is it easy to open it up and tune it? or is it best left to a professional?
For the record, i have no experience with opening up synths.
thanks!

[justinvm]

The mc 202 has a little white calibration potentiometer on it, which can actually be accessed from the outside of the unit using a screwdriver (you use a screwdriver to rotate the potentiometer and adjust the tune).

I'd assume the 101 has the same thing. Look near the output sockets on the back.

If not the 101 will have a master tune potentiometer inside the unit. Service manual notes will be available to locate this.

- J

[Solderman]

The SH101 is easy to open and perform adjustments. Just remove the screws from the metal-bottom case, and the main PCB with little blue phillips head type trimpots for tuning will be facing you.
Adjustment Procedure
It really is best to do the D/A adjustments before anything else, but if you are sure it's performing properly aside from the VCO Tune, start with step 2B on the second F key(F3), with range at 8' and the transpose switch set low. Then test the F5 key at 16' and 4' ranges for equal tuning and start back at 2A if they aren't in tune.

[Maschinengeist]

I use to recommend to those who have never been under the hood of a synth (or who have no experience of electronics) to leave it to the professionals. But it can be perceived that I'm preaching for my tesm.

Have a look at the procedure and if you feel ok with it, go on but be careful. I've got a part of my repairshop who's filled with attempt (not necessarly tuning) that turned bad.

[ramos]

J - Pete's musicians market knows a guy who repairs vintage electronics. Take it in to him, they fixed my tb-303 and did an awesome job.

[crufty]

Hey all,

I've got a sh101 with no arp and no sequencer--nor an lfo, apparently. I'm wondering if I need to do the DA tuning procedure mentioned here.

I've got one of those crafstman multimeter--can I use that? I assume I'd set it to DC. Where would I stick the red lead and where would I stick the black?

Thanks for any help.

--Crufty

[Solderman]

I've got a sh101 with no arp and no sequencer--nor an lfo, apparently. I'm wondering if I need to do the DA tuning procedure mentioned here.

D/A calibration is for oscillator tuning from the 101's keyboard scans.

Is the LFO light blinking? Does Mod work when you switch to noise? The LFO actually goes to the CPU's T1 input, which is used to clock the arpeggio and sequencer. The external clock input is a switched jack that will override the LFO.

If you do not have experience troubleshooting these kinds of things, it's best to take it to a local tech.

[Steve Jones]

J - Pete's musicians market knows a guy who repairs vintage electronics. Take it in to him, they fixed my tb-303 and did an awesome job.

That was probably me.... Monolith, if you get stuck give me a call and I can talk you through it. My number is on my website.

[crufty]

D/A calibration is for oscillator tuning from the 101's keyboard scans.

Is the LFO light blinking? Does Mod work when you switch to noise? The LFO actually goes to the CPU's T1 input, which is used to clock the arpeggio and sequencer. The external clock input is a switched jack that will override the LFO.

If you do not have experience troubleshooting these kinds of things, it's best to take it to a local tech.

LFO Light does not blink. Mod doesn't do anything. I have no experience with sh 101's but have had basic elementary circuitry experience--many moons ago.

Before I take it to the tech, I really just want to try the DA tuning procedure. I took the sh101 apart, dusted it, and visually, the board looks fine. I put it back together and things are the same. But, I'm not sure where the black / red leads should go to get a good reading.

[Synthaholic]

Is the pitch bender working properly?

Sometimes tuning issues can be caused by a stuck or broken pitch bender.

[madtheory]

crufty- looks like you're wasting your time doing the D/A cal, your problem is with the LFO. Take it to a tech...

The black lead always goes to ground, the red to whatever point you're measuring.

[Steve Jones]

Strangely enough, the power switch, which is grossly over complicated on SH101's, is often a source of tuning drift as well. On pretty much any '101, while it is on, if you press gently on the power button you will hear the pitch go all over the shop.

[crufty]

Thanks Casio CZ, that's what I was afraid of. I had the black lead attached to a the screw near the pitch bend and the red on any of the three CV out leads. Spinning D/A R2 had zero effect on the voltage, which seemed to be locked in at -6.5 mV.

The pitch is fine for me. but the arp, sequencer and lfo don't work. It was an ebay purchase, one of those 'everything seems to work dealies" but the reality, once I sat down to use the sequencer/arp, was different.

I figured, well, maybe the D/A is having problems with the sequencing and perhaps thats related to lfo not working either. The tune up procedure seems do-able, but spinning R2 wasn't registering any changes so I figured I had forgotten how to do it right.

Anybody care to guess what the issue might be?

[Solderman]

On the D/A voltage check, place the multimeter red lead at the CV Out plug's tip, and the multimeter's black lead to the battery negative terminal. If you do not get a change when adjusting VR-2, then you either do not have a solid connection, or the CV Out jack has an open.

As has been mentioned multiple times, there is no relation between the LFO and the D/A functions. The 101's LFO is nearly all discrete components, save for a dual op-amp. If the LED is not blinking, my first guess is that either C9, TR4 or IC3 have failed. It might be a good idea to check continuity between the ribbon cable joints that connect the main board to the control board first. The "RATE" slider is on the control board, and is part of the LFO circuit. There are also several resistors in this circuit you could ohms check, and two diodes, D9 and D10, that you can check.

Take a look at the schematic at left center.

[madtheory]

Thanks Casio CZ

Who you callin' Casio CZ?!?