First 2022 post small gremlin in Euro sequencer

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Pav
Wiggling with Experience
Posts: 366
Joined: Sat Mar 19, 2016 3:21 pm
Location: UK Hampshire

First 2022 post small gremlin in Euro sequencer

Post by Pav »

Hi Tony,

Wishing you and fellow wigglers a successful new year.

Just wanted to Check if I'm diagnosing 2 minor gremlins in Euro Seq. Correctly.
First use this month..
I appear to have lost any gate on step1. The led step 1 now only lights on reset. All positions of A or B switch. No gate also means no sound when cv from A or B plugged into an Osc. All other steps fine. Question is Possible dry joint on the switch...anything else I should check?

The second issue is in Row B step 4 when all row B pots are full clockwise. Step 4 is one tone higher than the rest of the pots. No Quantizer involved. I'm told by mate that it's just unfortunate 1 of 16 pots is less close to the 50K spec than the others and being analog should expect differences.
Do u agree and is there a possible fix other than to replace the pot, or live with it?
rgds Pav
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Synthbuilder
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Re: First 2022 post small gremlin in Euro sequencer

Post by Synthbuilder »

Pav wrote: Sun Jan 30, 2022 10:00 amI appear to have lost any gate on step1. The led step 1 now only lights on reset.
When you say it only lights up on reset, does it not light up when the sequence is cycling as well? Like as if the skip step is selected?

When the LED 1 lights up do both the step pots control their respective CV outputs? In particular channel B.

If it's just the gate output that is missing then the most likely problem is that the step switch's middle pin isn't soldered properly or that D5 and D6 are around the wrong way. If the B channel CV output is not working at step 1 as well as the gate output, then this would suggest pin 4 on U1 is not soldered properly.
Step 4 is one tone higher than the rest of the pots.
It is expected that there is some variation between steps as there is a small difference in resistance value between the resistors in the resistor networks. There is also a variation between the maximum voltages at each output of the pot driver chips. I measured no more than +/-5 cents on x4 range. That you have nearly 50 cents off indicates more variation than is expected. It's almost certainly not the pot, as you would probably have a lower output, and not higher, if it were just the pot. I'm guessing the problem is the resistor network RN3 on the pot board. Although it would be wise to check the output of U2 first. Compare pin 2 and pin 4. Both should be very close to 5V. If pin 2 is significantly higher, by about 80mV or so, then that would be your problem and U2 should be replaced.
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Pav
Wiggling with Experience
Posts: 366
Joined: Sat Mar 19, 2016 3:21 pm
Location: UK Hampshire

Re: First 2022 post small gremlin in Euro sequencer

Post by Pav »

Hi thanks for this. I tested again this morning.
I physically wiggled both the step1 skip switch and the gate A switch and both LED and Gate came back to life on step 1, so im now pretty sure this a just switch pin joint issue a reflow can solve.

To answer the questions - CV -A and B channels were not sounding on step1 but were on 2-8.
Either I was not seeing the skip switch position correctly , or as i think it might be an intermittent joint on the skip switch pin.
I can physically stop the Gate A working now on demand by movement by loosening and tightening the nut on the switch...so something to fix there.

This morning after and hour of running, sods law applied itself and the Step 4 tone higher issue seems to have resolved itself mostly. I tried different
sound sources to make sure it was not external voltage variation. In one case it dropped a few cents (testing by ear not meter), but not higher.
So gremlins only - but you have given me the info to diagnose should it reoccur after i type this.
rgds Pav
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