Ensoniq DP/4+ REPAIR (cap leakage, corrosion)

[eling]

I have changed all caps, VRs, and trim pots throughout the unit and the majority of ICs on the analog board. Absolutely no change in behaviour.

Next step... Transistors?

 

[blatboy]

Man do I appreciate this thread. Thank you so much. My board fortunately doesn't seem to have very much corrosion but it's noisyAF. Replacing all the caps now. So far, so good.

 

[58Glammer]

Man do I appreciate this thread. Thank you so much. My board fortunately doesn't seem to have very much corrosion but it's noisyAF. Replacing all the caps now. So far, so good.

What kind of noise? I had noise after recapping, but it was more kind of distortion... I solved this by adjusting the blue dc offset trimpots.. (can be done for each channel by bypassing the effects) There is a sweatspot for each channel, where the distortion noise is gone.

 

[blatboy]

Combination of static, distortion, and audio not sounding like it's coming through clearly... sometimes not even sounding at all. Once I finish with the caps (there's definitely corrosion and all my testing has shown dead caps ) I'll try to tweak those trimpots. Thanks for the hot tip.

 

[58Glammer]

Hi Everybody

I have another DP4+ on my table from a friend. It´s cap´s time came as in them most of these units from the 90ties ... It was already vissible.

So this unit had the DC Offset error displayed when turned on.

I thought, ok, I start with a complete recap of the unit and hopefully the DC Offset error disapears...

Channel 1-2 worked great, even before recapping. But on channel 3-4 ... nothing...

After recapping.... the DC Offset error still was present. I followed the audiosignal with the osci ... and ended up on one of the OP AMPS (U101) for channel 3-4 on the input path... I measured 15V on the in and outputs of the OP Amp... My guess is that this op amp is dead...

I´m not good in knowing Op Amps and my question is, what could I order to replace it?
On the OP Amp is written: 4565 and 5G28B

In the schematics it´s U101 (NJM4565) I found a model by Nisshinbo at Mousers .. Now after comparing the different models they offer, I ended with the 4565M version that has 5mm in width and 5mm in length .. they all have the same specs but different sizes..

If the error still remains after exchanging the OP Amp, where could I look for a fault?

Some of the spots on the analog board looked already contaminated by the fluid from the caps... I reflowed all parts on the input section.

Also a question is, if the fluid causes trouble underneath the parts? (resistors, caps, diodes) And maybe they should all be removed , cleaned underneath and resoldered again.. ?

All other areas look good so far. The contaminated area had bad looking solderjoints .... and some of the leads looked corroded.. but still leading...

Next and last question... what is the best way/fluid to clean the contaminated areas?

Thanks for tips

 

[Whoops]

Hi Everybody

I have another DP4+ on my table from a friend. It´s cap´s time came as in them most of these units from the 90ties ... It was already vissible.

Oh gosh, I'm worried, I don't use my Ensoniq DP4+ for 3 years now, it's in storage.
I have to open it up to check it's inside condition, but I'm totally afraid of doing that knowing that what I find could be an horror film

 

[Script]

Three years ? No more procrastinating. Tiago, open it now! Swap the caps, turn the trimmers (if needed), then go grab the €1k5 or more from evol

 

[Whoops]

Three years ? No more procrastinating. Tiago, open it now! Swap the caps, turn the trimmers (if needed), then go grab the €1k5 or more from evol

It's more Fear than procrastinating, I think.
But for sure I really have to do that, I was thinking in selling it to be honest, after I got Altiverb I can't seem to need any other reverb processor.
I liked the Ensoniq DP4+ a lot, but I also like to mix on the beach during the summer (this is true) using just my laptop, and I feel that gives me more Vibe to mix (better mixes) than staying closed down in studio with my outboard in a Sunny/Hot day.

But praise for the DP/4+ and for all of you that are bringing the units back to life

 

[Script]

what is the best way/fluid to clean the contaminated areas?

In general, I use a combination of:
- gentle scraping first for lumps of dried up dirt

...and what's described in this thread on 'PCB Cleaning'
https://groupdiy.com/threads/pcb-cleaning.79612/post-1021244
[You might be able to buy isopropanol/propyl for very cheap in a pharmacy if you ask nicely and can explain what you will use it for.]

Also I use just solder flux (Chinese 'Amtech handsoldering flux' over here) which has very good dirt-dissolving/lifting properties.

 

[58Glammer]

Thanks a lot for the tips!
I will report, when I got the op amp.. and if it solved the problem

 

[Script]

Hey, 58Glammer, so you managed to get the first unit (your own) that you worked on back up and running ?

 

[58Glammer]

Hey, 58Glammer, so you managed to get the first unit (your own) that you worked on back up and running ?

Yes, I did! See side 4.Thanks again! Actually my unit was ok. I decided to recap it after I recapped a lot of units in my studio while the pandemic. Started with my mixing board, then some of the synths and drummachines and then the fx units like an old Dynacord Tam 19.. Some of my samplers as well (A S950 after a recap sounds awesome! Highly recommended!)
Knowing from the 90ties Gamegear these SMD elcos had a problem I decided to swap them in the DP4+ as well. I also had the feeling, it did not sound that good anymore. Now after recapping and calibration it sounds great!
After the DP4+ I also recapped my DP Pro units.. and I wished I had done this before the DP4+ .. With this practice I had done a much better job on the DP4+ ..
This unit I got now had a lot of visibility leaking caps.. Underneath of some of them it looked pretty nasty. Cleaned it up and installed the new ones .. Attached some pics. But still this dc offset on Ch 1-2

So hopefully exchanging the op amp will sort this out.

I‘m thinking of removing the parts in the audio entry area to clean whats underneath (I think it’s fluid from the leaking elcos) to avoid more damage over time..

 

[Script]

Ah, I clearly see the damage.

Ch 3&4 are good ? Seems worse over there. So if it looks like that, it's not hopeless yet. Knocking on wood.

 

[58Glammer]

Ah, I clearly see the damage.

Ch 3&4 are good ? Seems worse over there. So if it looks like that, it's not hopeless yet. Knocking on wood.

Yes, the damage is visible but the traces work fine..
Ch 1-2 works great.. Ch 3-4 DC offset.. I also checked for shorts on the parts in the ch 3-4 area , but nothing.. U101 had 15 V on all in- and outputs.. So I removed it and ordered a new one (they are available from the same brand as the ones in the DP4+ )
I will report when I got the op amp.

Any tips what else could produce the DC offset beside the op amp (I don‘t even know if the op amp produces the offset) ?
I checked all the diodes in the entry but they seem to work fine.. everything led to U101

 

[Script]

Any tips what else could produce the DC offset beside the op amp (I don‘t even know if the op amp produces the offset) ?

15V on all dual op amp INs and OUTs is sure wrong.

At some point I suspected the protection diodes (they hang between +/-15VDC, others hang between +/-5VDC), which revealed at least two faulty trace connection (holes/stitches?) from top to bottom side of PCB. The diodes themselves looked fine, just didn't connect to voltage source. Injects 5 or 15 into the audio path from the complementary diode.

The DC trimmers are further down the line.

Other than that maybe what musgrave described above in #98. "The horror. The horror" (The Boards of Darkness by Joseph Conrad :/ ).

 

[58Glammer]

15V on all dual op amp INs and OUTs is sure wrong.

At some point I suspected the protection diodes (they hang between +/-15VDC, others hang between +/-5VDC), which revealed at least two faulty trace connection (holes/stitches?) from top to bottom side of PCB. The diodes themselves looked fine, just didn't connect to voltage source. Injects 5 or 15 into the audio path from the complementary diode.

The DC trimmers are further down the line.

Other than that maybe what musgrave described above in #98. "The horror. The horror" (The Boards of Darkness by Joseph Conrad :/ ).

Thanks a lot for the tip with the diodes .. Just made notes from the schematics and the diodes numbers I should check, but from musgrave‘s post #98 (eyes opening) I just have to follow the bad looking traces.. starting with cr 31 that lays on -15v
From what I found under this diode(See pic) I decided to take off all diodes .. clean and reinstall them... maybe with all parts in the entry section.. even ch1-2 to get sure.. As musgrave wrote, the fluid doesn‘t stop to react..

 

[58Glammer]

Not the most perfect solder job, but I removed all diodes, caps and resistors from input ch 1-4..
It looked good underneath ch 1-2 (they worked perfect when tested) but underneath the parts from ch 3-4 .. it was nasty ..
I cleaned all parts, cleaned the areas and resoldered all parts.
I did not take off the chips as I‘m not sure if I won‘t do more damage than repair to them.. So I left it for now..

As soon I got the new op amp, I will continue and will report here.. if it was a success..
Thanks again


Look at C425

 

[Script]

Argh! And the fun continues

 

[58Glammer]

Finally I took off the rest of the parts as well and cleaned everything up..
Some of the pads from the chips looked contaminated and as expected the chips in the ch 3-4 section looked worse than ch 1-2..
Also took off the last resistors and caps on the left side of the chips.. they looked like they should.. as they were not contaminated like the others, they were clean underneath... Most of the other parts I took off from the input channel area looked pretty dirty.. I cleaned them up with a PCB cleaner that has a brush on top.
Now I will resolder all the parts.

 

[Script]

Electrolyte accumulated under and between the pins of some logic ICs too might explain faulty channel switching, I assume. Did you have that ? If so might try measuring between traces as musgrave suggested.