ESQ-m sounds garbled when first turned on

[cromdubh]

When first powered on there is a bit of a sweeping sound that goes up and down for a few seconds and then the sound of the patches is initially garbled sounding (like it’s being modulated by noise or something). After about 10-30 seconds it clears up and the thing behaves normally from that point on.

Any speculation on what this is? Is it a dying capacitor or something?

[crochambeau]

I would suspect failing capacitors as my first directive, yes.

Often caps will reform a little under use/DC charge (which could explain why you observe the issue clear up over time). If the garbled section is 30 seconds when turned on first thing and then that time shortens a bit if you turn it off and then back on after it has warmed up it could point at caps.

This sort of thing tends to degrade over time, so I would advise digging into it to head further issues off at the pass.

[cromdubh]

I would suspect failing capacitors as my first directive, yes.

Often caps will reform a little under use/DC charge (which could explain why you observe the issue clear up over time). If the garbled section is 30 seconds when turned on first thing and then that time shortens a bit if you turn it off and then back on after it has warmed up it could point at caps.

This sort of thing tends to degrade over time, so I would advise digging into it to head further issues off at the pass.

Thanks for your response. Yeah I just timed how long it takes to clear up and after being off for the night it took about a minute to sound normal (interestingly, this time I also noticed that the patch changed a couple times by itself during this period). After that it behaves completely normally. If I turn it off and back on again after a few seconds it sounds normal right away (no "heat up" time). If I leave it off for about a minute or two and then it turn it on, it sounds garbled for a few seconds and then normal. Seems there's definitely a proportional relationship between how long it's off and how long it takes to recover. So it sounds like this is almost certainly a cap issue? Hopefully I can get away with just doing the power supply ones, which I might attempt today (I have the caps, I'm just always nervous about desoldering things).

[cromdubh]

Well, all the large capacitors have been replaced now (I didn't do the 22uF or the 10uF caps yet). Problem still persists.

[crochambeau]

Do you have an oscilloscope?

Watching the rails upon power up (when it's doing the garbled thing) could guide you on this.

Changing out the bulk caps is good stewardship, so while it didn't fix the issue it might prevent others down the line.

I would continue to replace the smoothing caps on the power rails, and scrutinize the voltage regulators for dry solder joints. Could be a "connection through thermal expansion" issue.

Honestly, it could be a lot of things. I've been guided by plenty of red herrings in the past. Good luck on your hunt!

[cromdubh]

Do you have an oscilloscope?

Watching the rails upon power up (when it's doing the garbled thing) could guide you on this.

Changing out the bulk caps is good stewardship, so while it didn't fix the issue it might prevent others down the line.

I would continue to replace the smoothing caps on the power rails, and scrutinize the voltage regulators for dry solder joints. Could be a "connection through thermal expansion" issue.

Honestly, it could be a lot of things. I've been guided by plenty of red herrings in the past. Good luck on your hunt!

Forgive my ignorance, when you say "rails" you mean all the different voltage lines like the +5, -5, +12, -12 points?

I did just go through the service manual and tested all the points that they recommend testing (on pg 38). Everything looks normal *except* "digital supply" (should be 13.5 to 16.5 and mine is 19) and "analog supply" (should be 22.8 to 28 and mine is 29). I'm not sure if this is cause for concern or what would even make this happen. I also tested it unloaded and that didn't yield any different results.

[crochambeau]

Forgive my ignorance, when you say "rails" you mean all the different voltage lines like the +5, -5, +12, -12 points?

Yes, that exactly.

Unloaded supplies can often run higher than when they're working in circuit.

When you're measuring the higher than specified voltages, is that at the ICs being supplied, or hot off the power supply?

[cromdubh]

Forgive my ignorance, when you say "rails" you mean all the different voltage lines like the +5, -5, +12, -12 points?

Yes, that exactly.

Unloaded supplies can often run higher than when they're working in circuit.

When you're measuring the higher than specified voltages, is that at the ICs being supplied, or hot off the power supply?

That's the points that appear to come from the transformer, measured between points 1 and 3, and 4 and 6 respectively on that cable connector. Here are the results for all the points the service manual recommends testing, grouped by the three connectors on the power supply board:

Transformer
Digital Supply 19 VAC (should be 13.5 to 16.5)
Analog Supply 29 VAC (should be 22.5 to 28)
Display Filament 10.2 VAC

To Main Board
+5 Digital 4.9 VDC
V Reset 4.6 VDC
+12 Analog 12 VDC
Analog GND 0 VDC
-12 Analog -12.4 VDC

To Display Board
+5 Display 4.9 VDC
-V Display -26.8 VDC
Center Tap Offset -20.9 VDC
Filament 10.2 VAC
Filament to Center Tap 5.1 VAC

I do have an oscilloscope but I haven't yet monitored to see if I can see anything interesting while I power up. I need to find a better way of attaching the lead to whatever point I'm testing so I don't slip and accidentally brick my unit (I nearly did this with my EX-8000 once).

[crochambeau]

Took a peek at the ESQ-1/ESQ-M service data, this is the page you're referencing, yes?



Most of the numbers seem within acceptable ranges (except the display feed, which is all over the place). I do see a discrepancy with the unregulated +V to main board and what you label as V reset, did that one hold steady when you tried everything unloaded as well?

I see you typed AC at a couple of points, and I'm only seeing DC on that chart, typo?

If your regulators are being force fed higher voltages they're going to run hotter, is your wall voltage within spec?

I dunno, I don't feel like I have a solid idea to throw at this. I'd be watching the voltages at the ICs with a scope at this point (but I fully understand not wanting to slip).

[cromdubh]

Took a peek at the ESQ-1/ESQ-M service data, this is the page you're referencing, yes?



Most of the numbers seem within acceptable ranges (except the display feed, which is all over the place). I do see a discrepancy with the unregulated +V to main board and what you label as V reset, did that one hold steady when you tried everything unloaded as well?

I see you typed AC at a couple of points, and I'm only seeing DC on that chart, typo?

If your regulators are being force fed higher voltages they're going to run hotter, is your wall voltage within spec?

I dunno, I don't feel like I have a solid idea to throw at this. I'd be watching the voltages at the ICs with a scope at this point (but I fully understand not wanting to slip).

The service manual I have looks a bit different, but it's mostly a layout thing. Here's what I've got:

https://i.imgur.com/OUYMiwR.png

As you can see the transformer values are AC and so are the last two for the filament.

Wall voltage is basically right on target, about 117V.

Yeah, I'm going to have to either figure out some good way of testing the IC's or bring it to someone else who knows what they're doing. Of course the thing "works" now, but I feel like if I don't take care of this now it'll just get worse (in fact, it sort of already has, since I don't think it used to do the thing where it jumbles around the presets when I first start it up).

Thanks a lot for your input.

[crochambeau]

Jumbling patches.. what does the back-up battery read?

Anyway, good luck, they are cool synths and worth the effort to keep going.

[madtheory]

The service manual I have looks a bit different, but it's mostly a layout thing. Here's what I've got:

https://i.imgur.com/OUYMiwR.png

That's because there are three different versions of the PSU A B and C.

https://www.vintagesynthparts.com/wp-co ... manual.pdf

I guess it's important to check that your particular PSU conforms with one of those three!

[cromdubh]

The service manual I have looks a bit different, but it's mostly a layout thing. Here's what I've got:

https://i.imgur.com/OUYMiwR.png

That's because there are three different versions of the PSU A B and C.

https://www.vintagesynthparts.com/wp-co ... manual.pdf

I guess it's important to check that your particular PSU conforms with one of those three!

I'm not even sure how to tell, since it neither gives schematics nor part numbers for those boards in that manual (unless I missed it, and I've been over it a few times). It's different than the one that's in my ESQ-1.

At this point I think it's out of my league, since the problem has been getting much quickly worse. The last time I turned it on it took a couple minutes to go back to normal. I am going to have to either look into selling it for parts or see if someone experienced can charge me probably as much as the unit is worth to fix it. AT this point really regretting not returning it the instant I noticed something was a little fishy.

[madtheory]

I'm not even sure how to tell, since it neither gives schematics nor part numbers for those boards in that manual (unless I missed it, and I've been over it a few times).

You did miss it . It's on page 14. Tells you the numbers written on the transformer for each version.

These are a pain to fix, since the service manual does not go to board level. See here for handwritten schematics. You could also join the mailing list.

I gave up on mine as soon as the Arturia version came out, then I sold it for parts.

[cromdubh]

I'm not even sure how to tell, since it neither gives schematics nor part numbers for those boards in that manual (unless I missed it, and I've been over it a few times).

You did miss it . It's on page 14. Tells you the numbers written on the transformer for each version.

These are a pain to fix, since the service manual does not go to board level. See here for handwritten schematics. You could also join the mailing list.

I gave up on mine as soon as the Arturia version came out, then I sold it for parts.

Oh jeez, thanks for bringing that to my attention. Don't know how I missed that.

Funny thing is, mine doesn't exactly line up with *any* of those. The transformer does not have any ESQ labeling on it. The power supply board itself is 4001006601, which is pretty close to 4001005601 from the service manual. I can't imagine this is literally the wrong board entirely. Wrong transformer I could actually believe, and that might explain why some of my numbers coming from the transformer are wrong.