cz-5000 CZ-5000 Stereo Chorus slider extremely loud and unexpected distortion issue?

[coolsen]

Hello people, 

Ive had my CZ 5000 for a good few years now and am trying to work out what is going wrong with the stereo chorus slider. Whenever i adjust the level with the fader, I get a really horrible, loud distortion, which overpowers the entire signal and pumps the overal volume ridicoulsly loud. It is also very crackly when moving the slider and is compltely unusable. I have to find a spot on the the fader, and that could be anywhere (random) to have the distortion sound turn off. 

I have noticed also (using headphones) that the signal is slightly panned to the right, is this normal? perhaps this is related to the stereo chorus issue?

Has anyone experienced this before with the cz-5000? any help would be much appreciated!
 

[Chas]

The big CZs use an analogue BBD stereo chorus chip that is known to deteriorate with age and become noisy. I forget the name of the chip, but some people have replaced they with new chips and successfully eradicated the noise. 

 

It could also be that your chorus slider has become dirty/ oxidized and needs cleaning. The same likely applies to the volume slider. 

 

Another possible cause of output noise/ volume issues is the output relay. Sometimes these just need cleaning, sometimes they need replacing. 

 

All the above are typical age related CZ issues, and if you are lucky a simple clean of the affected components and/ or a light service should have your CZ back in good shape again. 

[coolsen]

Many thanks, Chas! 

[coolsen]

So I managed to open it up and and give it a good clean, the boards didnt look terrible but there was some slight corrosion here and there at some solder points. I also managed to get to the relay output and give it a clean. Turned to the bad boy back on and still the same issue. I didnt manage to get to the sliders so it may be worth going back in a giving them a clean.

The volume isnt bad really, just a tad noisy. The real culprit I suspect is the stereo chorus chip which is hella distorting and also panning the signal slightly to the right.

Would you happen to know the name of the BBD Chorus chip at all? Im looking through the service manual and cant seem to find the name, im not even sure where it sit on the board! 

Any help would be much appreciated.

[pianokeyjoe]

Look up Burr Brown BBD ic chips. I learned of such chips when I was a teen back in 1992 and they are called Bucket Brigade Device ICs. Used for Chorus, Delay, and Flanger Effects back in the 80s and 90s.

[Chas]

I've uploaded the CZ5000 Service Manual and Parts List to the forum Files section, @coolsen. You can download it at the link below.

On Page 3 of the manual (Page 7 of the PDF reader), you can see the stereo chorus circuit. 

 

Interestingly, the CZ5000 uses 3 x chorus chips, and they are all specifically MN3209 (shown as BBD1, BBD2 and BBD3 in the schematics).  The MN3209 looks to be an update on the classic MN3207 BBD chorus chip as used in many vintage chorus and delay based effects pedals/ units. 

 

Hope this helps!
 

 

Edited December 22, 2022 by Chas

[coolsen]

Thanks a bunch for that, Chas, thats super helpful. Would you happen to know any reputable sites that sell cz 5000 replacement parts? Ive has a look around around and cant seem to find anyone who stocks, specificly, replacement chorus sliders, which is a pain as the slider by this point is fully disfunctional!

[CYBERYOGI =CO=Windler]

Dismantle the slider and patch the broken carbon track with a soft pencil streak (works but not very robust).

 

You may also try conductive carbon paint (I even used silver paint). It needs to dry fully to stabilize its resistance. The layer needs to be thin enough (but not too thin) to get roughly correct value. I removed some of the paint again with a cotton swab and isopropanol to revive Bontempi/Farfisa slide pots, but that's all try and error.

[TedFu]

Hi,

 

I'm also having the same problem as the OP and I've replaced the BBD chips already but that hasn't resolved the issue.  When the chorus is turned up and I'm not hitting any notes, I can hear a pulsating white noise so, suspecting it's the signal relay, I popped the top off and applied some deoxidizer to it.  Sadly that hasn't helped either, so I am now looking at replacing it.  However, the part (an Omron V2G-2-DC5V) is no longer manufactured.  Omron do currently sell a V5G-2-DC5V but I don't know if it is a good drop-in replacement since I can't find the datasheet for the original V2G-2 anywhere.  If anyone here has that datasheet, could they kindly please share it or just confirm that the new V5G-2 works?  Thanks in advance!