Pearl - CE-22 Chorus Ensemble  [schematic]

All about modern commercial stompbox circuits from Electro Harmonix over MXR, Boss and Ibanez into the nineties.
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rfx
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Post by rfx »

Cant find much about this one. so here are guts.
if there are questions please post
print
print
DSC01402.JPG (146.03 KiB) Viewed 5447 times
top
top
DSC01398.JPG (633.5 KiB) Viewed 5447 times
outside
outside
DSC01401.JPG (43.38 KiB) Viewed 5447 times
Rfx

Moderator: pedal pictures were added.
Attachments
Pearl Chorus Ensemble CE-22.jpg
Pearl Chorus Ensemble CE-22_back.jpg

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Nocentelli
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Post by Nocentelli »

Great looking pedal - I had a PH-44 for a while, the ramp switch was cool: What does the second switch do?

Also, that input knob is was a pain on the phaser: It seemed to affect the dry sound in bypass in a weird way - What's it like on this unit?
modman wrote: Let's hope it's not a hit, because soldering up the same pedal everyday, is a sad life. It's that same ole devilish double bind again...

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Post by rfx »

The pedal is not working the battery snaps are broken (i hope that is the only problem)
I got it for free because it is not working. The second switch seems to be a vibrato

Rfx

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drbob1
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Post by drbob1 »

Pearl built effects that were take-offs of the other japanese effects of the day, but often with "more". In this case, I believe it's a two channel chorus. One side has just the speed knob. The other appears to be a combination of a chorus (speed only) with a Vibrato (delay, rate, depth), so probably a pair of BBD chips in there. Not sure how a really slow chorus with the vibrato kicked in would sound, maybe like some kind of weird tap thing with wow and flutter?

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Post by Nocentelli »

rfx wrote:I got it for free because it is not working. The second switch seems to be a vibrato.
Bargain! My PH-44 just stopped working one day. I send it to Berarduur, who obviously traced it and posted it here at fsb (I didn't know about this place and had little interest in DIY stompboxes back then). He stated that the problem was a duff 12v regulator, so that might be worth checking out if the battery snaps turn out not to be the only problem. I'm guessing it's 18volt dc like the PH-44?
modman wrote: Let's hope it's not a hit, because soldering up the same pedal everyday, is a sad life. It's that same ole devilish double bind again...

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rfx
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Post by rfx »

yep 18 volt.
Replaced the battery snaps today and channel 1 is working (it is a nice chorus).
the switch of channel 2 is acting up. sometimes it works, sometimes it doesn't.
Channel 2 (chorus, vibrato, and delay vibrato) can go from leslie type sounds to total unusable detuned vibrato.

bdd's: mn3007 and mn3009

I need to build a 18 volt supply for this one, it eats battery's.

Rfx

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lolbou
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Post by lolbou »

rfx wrote:he switch of channel 2 is acting up. sometimes it works, sometimes it doesn't.
i would replace both with new ones. These fail with time and are cheap and easily available. :wink:
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Post by rfx »

Ok the switches are working now. which brings the next problems:

chorus 1 works but distorts like the input is to high, even with the input volume set on 3 (this is way before the peak light starts blinking.)

chorus 2 does not work but also distorts.
vibrato depth works
vibrato speed works
vibrato delay (this it a pot with built in switch): when switched on i get clean(ish) sound the vibrato is gone and no delay.

All trimmers inside are in the original position with the paint seal from the factory still on.

I have no idea where to start looking.

I hope someone can help.

Thanks in advance

Rfx

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Bernardduur
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Post by Bernardduur »

I've traced the unit :)
Audio.JPG
CH2.JPG
CH1.JPG
'No more....... loud music.......'
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Post by Bernardduur »

Switch.JPG
PSU.JPG
'No more....... loud music.......'
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Post by Bernardduur »

A most awesome chorus that has 2 chorus settings, a vibrato setting and a time set vibrato over the chorus.......

Awesome!
'No more....... loud music.......'
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Post by sadrew »

Hi there, I've just got one of these for very cheap. It has been sold as non working, but came out that was just a battery clip broken connection :twisted: :applause:

The switches seem to be in need of replacement, as they are acting weird.

Please can anybody point me to a part number for those switches? Never used them before..

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Post by lolbou »

sadrew wrote:Please can anybody point me to a part number for those switches? Never used them before..
(got your PM :wink: ) These are quite standard momentary pushbutton actually. I do remember salvaging some from old VCRs. But you may consider buying new ones since these are likely to fail (I think).

Banzai has some : http://www.banzaimusic.com/SPST-MO-9-Switch.html . I bet many others do.

But even my local electronics shop does, so you may get some for cheap in Italy... :secret:
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Post by sadrew »

Hi there, I've managed to get this chorus working.

Sound is really good, better than expected.

However, it still has some problems.

If output 2 is used, chorus 1 doesn't chorus (but chorus 2 does). Just pass dry signal.
Output 1 works for both, and output 1+2 works just for chorus 2.

Then, on both channels there is a loss in volume during the decay.
It's kinda like a gate/expanding effect, when the signal gets below a certain level, there is a drop in volume.
It's more noticeable on high strings than on low strings.

I've recorded an audio sample to show you.

Maybe I should try re-adjusting internal trimmers, but I'd prefer have your opinions before.
Attachments
CE-22 sample.mp3
(331.97 KiB) Downloaded 82 times

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Post by GorillaHuman »

Thanks for tracing the schematic Bernardduur, very helpful!! Got a defective unit on the bench: voltage regulator fried and leaking capacitors (10uF were all gone, rest looked OK, interesting detail.. bad batch?). After fixing these issues, the sound remains dry, and the switch for "Effect on/off" does not trigger the LED or audiopath. I can hear some time-shift going on at the BBD's so, I am suspecting logic switching on this unit is at fault. Now, I could just blindly replace the MC14069UB, MC14013B, MC14007UB (2x), HD14016BCP to (hopefully :-)) fix the issue... but where's the educational experience in that?
I have been trying to find methods to troubleshoot these chips in a standardized way, but I cannot find anything helpful. Does anyone know what's the best way to attack this? Where to start, how to isolate the chips, what if some gate remains open/closed, how does that influence my measurements? Links or insights are appreciated!


P.s. Sorry for necromancing this, but I guess future visitors might want this information in this same thread.

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Post by The G »

Wow, that's a lot going on in this pedal!

The first things I'd check would be voltage on the clock inputs of the 4013 (pins 3 and 11) and outputs (Q - pins 1 and 13, Q - pins 2 and 12) in both bypass and effect-on states.

I tried to understand the schematic and, while I didn't grok it yet, here are the bits I got (hopefully right):
  • the MC14069UB is used in a latch configuration like the one in the "CMOS Cookbook" by Don Lancaster, at page 257, figure 4-2c, only using a SPST switch instead of a SPDT and adding some debouncing. I did not get why its output goes to one of the MC14007UB multiplexers, but then I couldn't find where said multiplexer is connected also (S3 connection from pins 1, 5, 12 of MC14007UB on Switch.JPG).
  • the MC14007UB are used in the analog multiplexer configuration from the datasheet (see also this Analog Devices wiki).
  • an envelope (E1) is taken from the MN3007 filtered output and used to command (F1 and F2 connections) the SK30A JFETs, thus altering the low-pass filters around R38 (CH1.JPG) and R21 (CH2.JPG) such as the higher the signal the less filtering it gets. Kinda like a noise filter. Don't quote me on that, though.
  • I wish all ICs were numbered on the schematic... actually I wish ALL parts of the schematic were numbered :lol:.
Attachments
"CMOS Cookbook" by Don Lancaster, page 257, figure 4-2c
"CMOS Cookbook" by Don Lancaster, page 257, figure 4-2c
IMG_20210206-163747.png (17.68 KiB) Viewed 3985 times
4007 as an analog multiplexer
4007 as an analog multiplexer
4013 pins
4013 pins
IMG_20210206-144952.png (17.41 KiB) Viewed 3985 times

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Post by GorillaHuman »

Excellent reply; thanks G! I've read up on the links carefully. I believe the circuit is this complicated due to the remote pedal function which allows to toggle between speed and effect on/off via an external footswitch.
I measured a couple of voltages:

4013:
1: 12 (I-II/Vib LED on) // 0 (LED off)
2: 0 // 12
3: 0
4: 0
5: 0 // 12
6: 12 // 0
7: 0
8: 0
9: 12
10: 0
11: 12
12: 12
13: 0
14: 12

4069:
1: 0
2: 12
3: 12
4: 0
5: 0
6: 12
7: 0
8: 12
9: 0
10: 0
11: 12
12: 0
13: 12
14: 12

4007:
1: 0
2: 0
3: 0
4: 0
5: 0
6: 0
7: 0
8: 12
9: 0
10: 12
11: 0
12: 0
13: 12
14: 12

Also, I desoldered the D5 and D6 from the remote speed and remote on/off to ensure this part did not affect my measurements. No difference in voltages.
I pressed the buttons, kept them pressed down while measuring; no difference. Diode D3 and D4 go to 12v when pressed down; and back to 0 when released, so these work...
Based on these measurements I am suspecting either 4069 and/or 4013 are at fault?

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Post by GorillaHuman »

Yes. 4069 was defective: Replaced and its sounding great again! :shred:

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