Ensoniq DP/4+ (cap leakage, corrosion)

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Script

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Spent a brief hour to look over a friend's Ensoniq DP/4+ today to assess whether a repair is worth the effort.

The unit is from 1995. It had been in heavy use until it stopped working in 2015. Problems back then -- owner says -- were "DC error" warning message, followed by input failure on one channel and complete blackout very soon after. Owner said that back then some of the traces looked 'burned' and that he thinks I should check tantalum caps on the 5V rails. (Hmm, I found that same info here on this forum.) Anyway, for the last couple of years the unit has been stored in a dry closet.

Well, after opening the unit and removing dust with a small brush, three SMD electrolytics simply came off -- ugly leakage underneath and in vicinity (see picture). Several other SMD electrolytics all over the board are also wiggly when touching. They'd all best be replaced.

Picture shows the 'problem' part of the board. Several corroded traces and the blue circle shows heavily corroded pads after superficially scratching off the leaked electrolytic skunk. One fully corroded trace (left on picture) lies bare but still conducts. Question is how well and, more importantly, for how long.

Anyway, a repair would be looking at:
- some 50 electrolytics, mostly 22uf 16V 5mm, but a few other values too. Best to swap them all out -- something that should have been done a long time ago directly after DC error message and most likely even before that after a total of maybe 2,000 working hours ---- traces look 'burned' -- what ?
- fuses (I'd guess)
- regulators (possibly)
- new battery (for sure)
- possibly tantalum caps on power rails (possibly maybe)

However, the biggest investment here, if any at all, is time. And even more so after ugly cap leakage. So advice highly welcome before I commit to this:

- Anyone here with experience in Ensoniq DP repair who could give hints on what else is highly prone to failure in these units ? (I will measure everything anyway, once committed, but still).

- Anyone who can give advice on what to do with those corroded traces ? I haven't come across such wreckage before and am not fully sure how to clean/restore, if possible at all. I did some brief and random connectivity checks and corroded solder joints and traces seem to work fine so far -- but might wire-jump if only a few.

- Pads. In that condition, whould solder connect to them at all ? How to clean/restore, if possible at all (isopropyl, acetone, anything else) ? Or would need to wire-jump the caps over the affected pads 😵 ?

Thanks in advance.

P.S.: To all DP owners. Better check your caps sooner than too late ;)
 

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JohnRoberts

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that looks pretty ugly but perhaps not terminal... first step is to use a solvent like alcohol and a brush to clean the smutz off the board , that will better reveal the condition of the PCB traces and pads.

JR
 

Script

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I hate SMD -- makes my neck hurt Cleaning shmutz with some alcohol will be much easier once all those caps are off the board. Even a toothbrush is too big.

Meanwhile I quickly tried to verify pad and trace integrity by very gently scratching off the dirt with the tip of a scalpel. It's solid underneath -- so not hopeless and therefore quick and dirty tinning test. Pads seem not copper and look fine after tinning. Not so happy with the two traces I tried though. On pic it looks dirtier than before for all the flux still there.

Still assessing.
 

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Script

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Fully disassembled the unit today. All on wire connectors -- a 15-minute breeze.

Apparently some cap leakage to PCB underside.
Some solder is missing on side-to-side trace connections (called stitches?)
Some more corroded traces.
Leaked electrolytic cap near +5V regulator.
Tiny patch of green rust on one regulator lead.
Clear heat marks on -5V and +15V regs on PCB underside.
More SMD caps with dull solder joints on the front board
Two 3.3uf SMD caps on PSU -- right next to two chunky heatsinks -- uh!
Two blows fuses (5V rails).

In medical terms that would be callled multi-organ failure (or perhaps already signs of post-mortem decay).

Well, it more and more looks like a project for a hole series of rainy days. Big unknown is the integrity of the firmware. If that is gone, the patient is braindead -- yet still smiling...
 

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JohnRoberts

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Sometimes those intentional solder bridge/jumpers are programming jumpers to support alternate configurations.

I see at least one maybe(?) solder bridge (lower right of first image).

Good luck

JR
 

Script

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Ah, thanks -- good to know. Will keep in mind should I decide to start on this. Good thing is that above wreckage from electrolytics in signal path is in one of four identical inputs.

Overall what bothers me is not a total of 51 electrolytic caps plus 12 tants (plus some other bits) that also probably better be replaced. The time killer here is the extent of corrosion on top of that....
 

Script

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And wrong I was. Wreckage is worse than expected.

Images:
1) Those other caps in that area look somewhat fine, don't they ? Almost innocent.
2 ) And here without the 1990s SMD electrolytic tombstones -- Surprise !
3) With a bit of patience :: overall less daunting, but not fully happy either.

Checking traces for connectivity would be next but I need a break.
 

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Script

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All electrolytic caps on all boards (audio, digital, PSU, metre) are now removed. A total of 62 SMDs, they are ALL dead -- not measuring anything meaningful. The winner is 50uf for one of the few 100uf. The rest : nada. Also the 3.3uf's are basically all gone.

Cleaned all pads and restaurated traces (tinned and additional wire, if necessary). Three pads are bad ([partially] lifted). Glued back on but new cap might need additional wire-jumping to make it stable.

Some side-to-side holes (stitches? / eyes?) also look affected. Found at least two that no longer connect. Those come next. Need something like a dentist scraper now.

--some images later--

ASIDE
To all DP/4+ owners. If your unit is still running and has never been recapped, you might want to plan for it or at least check for cap leakage. Traces turned black is a sure sign of leakage somewhere -- even if caps seem fine on visual inspection.
 

Script

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And here some images of restauration work all over the audio and digital board.

- Some traces just needed scratching off of dirt and corosion and then tinning (will all be sealed later).
- Other traces in very bad shape are tinned and connect via a wire soldered onto the trace.
- All pads (and in three cases what remained of them) were thoroughly cleaned, checked for solidity and are now fully flush with the board. Although on the images some pads don't seem to be, but that is due to shades, copper shinning through, and solder flux. Accidents tell me those pads take on solder very easily and very quickly ;)

P.S.: The unit has been officially declared dead... ... so I can do with it what I want. I take it as a training ground ito fill some spare time.
 

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Whoops

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I was reading this thread and got really scared, I have an Ensoniq DP4+ unit that I love, but I don't use it for some years now because I changed my mixing setup to "In the box". After seeing your photos I'm afraid my unit might be having the same issues.

I don't think I've ever seen a pcb in such bad shape and I really admire you and support you in trying to repair it, I hope you succeed as these are great sounding units.
 

Script

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Sorry, it was never my intention to scare anyone.

The unit here had been in really heavy use for years, including touring, I'd assume. Anyway, I am not emotionally attached to it in any way and with its boards in such condition, there really is not much I could possibly destroy. I have had some experience with SMD -- enough to avoid it wherever I could.

But as JR said above, SMD had come to stay, and the early-generation components are true oldtimers by now. Right now the world is moving on to programming, I think). So, yeah, after the unit has been abandoned, I decided to take up on it as a pastime and use it fior learning purposes -- nothing to loose for me.

@Whoops, as for your unit, easy enough to just open it and take a very close look with magnifying glass. Could also run the internal diagnostics program. user manual and schematics are around on the net, while maintenance and in-depth test procedures including measuring point (for the DP4, not 4+, but similar I assume) are all described in the Service Manual, which is available as a pdf download from musicparts dot com.

This latter manual is quite funny (and maybe typical,). It's a step-by-step maintenance guide that requires the unit to be powered up for meaasuring. Good. However, in the case of the slightest problem, this guide always gives the same answer: "Replace main board", "Replace digital board", "Replacee PSU" "Replace front panel assembly". Not a single word of 'repair' in it. -- Welcome to SMD in the early 1990s 🏌️‍♂️
 

Whoops

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However, in the case of the slightest problem, this guide always gives the same answer: "Replace main board", "Replace digital board", "Replacee PSU" "Replace front panel assembly". Not a single word of 'repair' in it. -- Welcome to SMD in the early 1990s 🏌️‍♂️

😂 😂 😂 😂 😂
 

JohnRoberts

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This latter manual is quite funny (and maybe typical,). It's a step-by-step maintenance guide that requires the unit to be powered up for meaasuring. Good. However, in the case of the slightest problem, this guide always gives the same answer: "Replace main board", "Replace digital board", "Replacee PSU" "Replace front panel assembly". Not a single word of 'repair' in it. -- Welcome to SMD in the early 1990s 🏌️‍♂️
I recall back in the 60s when a major TV manufacturer advertised to great fanfare their "works in a drawer". They used plug in PCBs that could be replaced in the field for rapid servicing. This was clearly a premium brand since cheap TVs wouldn't use relatively expensive PCB connectors.

JR
 

Script

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Time for some udpate. Progress has been slow, cos other things are way more important. This is a spare-time project.

STATUS: traces and pads all restored as best as possible. Almost all SMD electrolytics soldered into place. Pictures will follow, but in parts, together with some observations. So here are:


FRONT AASSEMBLY BOARD
- three dead electrolytics replaced,little to no cap leakage though)

1627027329265.jpeg

All it needs, if anything at all, is sealing the bit of trace to the right cap. Am using green nailpolish for this. Doesn't necessarily look nice, but this ain't a beauty contest.

_____________________________________

PSU
- Had to remove 3000uf and 4700uf caps to have access to SMD electrolytic. While at it, swapped out those big caps too. The SMD electrolytic sits between those big caps and a regulator with a massive heatsink on it. This 3.3uf cap had slightly leaked.
- Notice the tiny spots of nail polish covering areas affected by leaked electrolyte.
- Among all caps this is the one that I feel most uncomfortable about putting back in cos this is a heat area !! There's plenty of space elsewhere on the PSU board for an SMD cap to sit. -- In hindsight one might even say it's a scene of design crime ; )

1627027987249.jpeg

1627028008308.jpeg


(More to come)
 

Script

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DIGITAL BOARD

The digital board is three layers -- that's why the board looks darker. Middle layer is 'only' power. Only 3.3uf caps here. Most didn't measure anything after removal -- which makes me think that the majority of caps on all boards probably have leaked over time after exitus of unit. Note to self: never let that happen !

Overall less damage to pads and traces here (superficial), but still time-consuming. Connectivity of affected traces all OK. All traces sealed with nail polish -- which indeed doesn't look very nice, does it ? I'm aware that there is professional sealant for this, but I just couldn't care less ; )

1627031652881.jpeg


Illustrating the destructive power of leaked electrolyte =8 /
1627031571356.jpeg


Electrolyte flooding. The trickiest part of the digital board. Still might want flux paste to be cleaned up a bit.
1627032260485.jpeg
 

Script

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ENSONIQ DP/4+ BATTERY

it took some time to find a replacement. Some places sell them advertising theirs as the 'one and only' ever to use in this unit, but they are all somewhat costly (for a frickin' battery) and mostly don't disclose themselves as what they are.

Original battery must have had prongs soldered onto it (says so in the manual, I think). Battery in this unit though was a different type -- with soldered prongs but likely wrong size of prongs, so they sat forced into the holes and therefore were difficult to get out. Even most careful removal eventually damaged a hole and trace.

Image of battery installed with wire-fixed trace visible underneath. Shot the battery very cheap and used a common, good-quality holder. This could easily have been the most expensive replacement part.

1627033387162.jpeg

[start aside]
Personally I don't think there really is a need for batteries with soldered prongs, as long as the holder is of good quality and strong. Why ? Well, for one, on professional tours there should be a fully programmed back-up unit anyway just in case (somewhat out of the question for this oldtimer piece of gear). And, second, flightcases have stickers with 'Fragile' or 'Handle with care' or the like written on them -- so should some stagehand think they absolutely have to kich'n'throw such cases, they deserve to get fired (just an opinion). Reliable stagehands are important.

Anyways, this unit -- should it ever open its eyes again to see the day of light -- would not get moved much. Also, albeit Japan, earthquakes over here are usually not strong enough to jolt batteries out of holders ; )
[/end aside]

Still a long way.
 

Script

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Problematic trimmer area looked like this. Still needed 'eyes' to be cleaned and redone. Note that there is a retinned trace under the cap. This raised the component a little bit off the board, so the soldering pad needed a bit more solder to make the cap sit firmly.

An alternative would have been to wire-jump components / traces around the cap. Trimmer ready for reinsertion and needs one two firm connection on top side, two on underside.
 

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