fixing a broken Pearl delay pedal - where to start?

Everyone needs a stompbox.
User avatar
oid
PAT. # 2.972.923
PAT. # 2.972.923
Posts: 834
Joined: Sat Feb 10, 2018 8:19 pm

Re: fixing a broken Pearl delay pedal - where to start?

Post by oid » Thu Aug 09, 2018 10:20 am

s_mcsleazy wrote:
Thu Aug 09, 2018 7:04 am
any gut shots of the thing? might be the easiest way to figure it out. the big hope with bbd pedals from this era is hoping the chips still work and the regulators aint died
It uses the MN3007 so replacements are available if dead, why would the regulator matter? I can not recall seeing a single pedal that uses anything but discrete or lm3xx series regulators, been made for ever and if you feel the need you can easily scrape up vintage and save a a few pennies.

I have never encountered someone worrying about the regulators, perhaps this is a paranoia caused by the modern surface mount pedals with regulators which are to small to effectively dissipate the heat and a pain to replace?
Logic gates based on billiard-ball computer designs have also been made to operate using live soldier crabs of the species Mictyris guinotae in place of the billiard balls.

User avatar
Pacafeliz
PAT. # 2.972.923
PAT. # 2.972.923
Posts: 18518
Joined: Sun Jul 29, 2007 6:34 pm
Location: Cococologne, Germany

Re: fixing a broken Pearl delay pedal - where to start?

Post by Pacafeliz » Thu Aug 09, 2018 10:33 am

HOLY SPAGHETTI BATMAN!!! :bored:
(i have no idea what i'm doing - but then again, so i am at most things in life... and/or life itself...) :derp:

Image

Image

Image

Image

Image

what i CAN see is that nothing is loose or so...
i love delay SO much ...that i procrastinate all the time.

User avatar
oid
PAT. # 2.972.923
PAT. # 2.972.923
Posts: 834
Joined: Sat Feb 10, 2018 8:19 pm

Re: fixing a broken Pearl delay pedal - where to start?

Post by oid » Thu Aug 09, 2018 10:55 am

That looks to be quite a different circuit than the schematic you sent me, will try and hunt down a proper schematic for it. Not a big deal if one can not be found, you took good pictures and they will do the job. Used the 3005 instead of the 3007 and 9 volt power instead of 12, probably less than 9 after regulation.

Nothing jumps out as obviously fried from a quick scan but my phone's screen is a tad small to give a good look. likely a good number of those electrolytics could use replacing, one of them is also the possible culprit, the blue cylindrical things, but we will give it a full check up and make sure we find all the problems. Old single sided PCB which is nice, no plated holes and easy for desoldering parts.

I will send you some info regarded needed measurements after work.
Logic gates based on billiard-ball computer designs have also been made to operate using live soldier crabs of the species Mictyris guinotae in place of the billiard balls.

User avatar
Pacafeliz
PAT. # 2.972.923
PAT. # 2.972.923
Posts: 18518
Joined: Sun Jul 29, 2007 6:34 pm
Location: Cococologne, Germany

Re: fixing a broken Pearl delay pedal - where to start?

Post by Pacafeliz » Fri Aug 24, 2018 8:39 am

sorry this took so long... i think i might have time to look into this this weekend.

i do have a soldering iron and the ULTRA BASIC skills... :blush: :ph34r:
i love delay SO much ...that i procrastinate all the time.

User avatar
oid
PAT. # 2.972.923
PAT. # 2.972.923
Posts: 834
Joined: Sat Feb 10, 2018 8:19 pm

Re: fixing a broken Pearl delay pedal - where to start?

Post by oid » Fri Aug 24, 2018 11:29 am

Not a problem, your first step will be to check the power supply voltage at each of the ICs, those black flat things, you have a 4558 dual opamp, three 1458 dual opamps, a MN3005 BBD (buck brigade device, it makes the delay) and a 4013 dual D-type flip flop. In this unit we have negative power, so the pin we normally connect to ground is connected to -V and the pin we connect to +V is connected to ground (0V), 0 being greater than any negative number makes it all the same, we just need the +V pin to be a higher than the -V pin.

First things first, orientation to integrated circuits. Look at the component side of the circuit board we see a 4558 on the top right corner, it has 8 pins and they are numbered from the top left corner to the top right corner, so pins 1, 2, 3, and 4 are on the left from top to bottom and 5, 6, 7, and 8 from bottom to top on the right, The top of the IC is always (almost) marked by a U shaped notch, sometimes this goes all the way through like on the MN3005, sometimes it is just a notch like the MCI4013 next to it, pin 1 is generally marked with a dimple but if you look at the MN3005 the dimple is on the opposite side from where I said pin 1 is, not everything follows the standards! Pin 1 is still top left, they just put the dimple in an odd spot, it is always wise to check data sheets and not make assumptions! the MN3005 also has another oddity, it looks like the MCI4013 next to it with 14 pins, but if you look close it just has eight, 4 on top and 4 on bottom, this is an 8 pin IC and is counted the same as any other, the top two left pins are 1 and 2, the bottom two left pins are 3 and 4, 5 and 6 are the bottom right leaving 7 and 8 for the top right.

So to check the voltages, your meter needs to be set to VDC (voltage direct current) and if it has a manual range function you need to put it to at least 20 Volts, if it is auto ranging you just set it to VDC, your meters manual will help you here if that make no sense. The black meter probe goes to any convenient ground, I generally pick one off one of the audio jacks, they are easy to find and big enough to stick a probe on with ease, the red probe will go to what is to be measured. First measurement are your batteries, make sure they are both close to 9V and then plug them into their clips, if the pedal is the sort that does not turn on without an audio cable plugged into one of its jacks, plug one in and then check these pins:
MN3005 - pin 1
4558 and 1458s - pin 4
MCI4013 - pin 7

Remember, if you are looking at the underside (trace side, copper side) of the PCB pin number is reversed from the component side! If you are looking at the component side you count counter clockwise from the top left, if you are look at the copper side you count clockwise from the top right.

And make sure your board is not resting on anything conductive while powered, hold it from the edges or set it on some heavy paper or card stock, do not want to short anything out and make more work for ones self.
Logic gates based on billiard-ball computer designs have also been made to operate using live soldier crabs of the species Mictyris guinotae in place of the billiard balls.

User avatar
timtam
PAT. # 2.972.923
PAT. # 2.972.923
Posts: 2729
Joined: Sun Oct 22, 2017 2:42 am
Location: Melbourne

Re: fixing a broken Pearl delay pedal - where to start?

Post by timtam » Fri Aug 24, 2018 6:20 pm

Pacafeliz wrote:
Fri Aug 03, 2018 6:59 am
no sound, no reaction from the on/off switch,
So you get a power ON light but NO guitar sound in either position of the Normal / Effect switch ?

I would test the foot switch and input and output jacks first (ie the points of most mechanical stress).
"I just knew I wanted to make a sound that was the complete opposite of a Les Paul, and that’s pretty much a Jaguar." Rowland S. Howard.

User avatar
oid
PAT. # 2.972.923
PAT. # 2.972.923
Posts: 834
Joined: Sat Feb 10, 2018 8:19 pm

Re: fixing a broken Pearl delay pedal - where to start?

Post by oid » Fri Aug 24, 2018 7:28 pm

timtam wrote:
Fri Aug 24, 2018 6:20 pm
Pacafeliz wrote:
Fri Aug 03, 2018 6:59 am
no sound, no reaction from the on/off switch,
So you get a power ON light but NO guitar sound in either position of the Normal / Effect switch ?

I would test the foot switch and input and output jacks first (ie the points of most mechanical stress).
Check his first post, battery check light comes on, strongly suggests power supply. I suppose if it uses a switched jack to turn on the power when audio is plugged it could cause such a problem if the jack is corroded.
Logic gates based on billiard-ball computer designs have also been made to operate using live soldier crabs of the species Mictyris guinotae in place of the billiard balls.

User avatar
timtam
PAT. # 2.972.923
PAT. # 2.972.923
Posts: 2729
Joined: Sun Oct 22, 2017 2:42 am
Location: Melbourne

Re: fixing a broken Pearl delay pedal - where to start?

Post by timtam » Fri Aug 24, 2018 7:46 pm

oid wrote:
Fri Aug 24, 2018 7:28 pm
Check his first post, battery check light comes on, strongly suggests power supply. I suppose if it uses a switched jack to turn on the power when audio is plugged it could cause such a problem if the jack is corroded.
You're right, 'battery check' light seems to be something different to a 'power ON' light (which this unit doesn't have ?). However this vid suggests battery check light comes on as you plug guitar in (but does not stay on) on a functioning unit ...
https://www.youtube.com/watch?v=rbQXQ0Bux8Q

So I guess the question is does the battery check light stay on ?

@Pacafeliz have you located any instructions ? I've seen a few 'dead' pedals (esp more complex ones) that were actually working fine .. once we figured out how they were supposed to work. ;) I guess the few YT vids would be a suitable substitute.
"I just knew I wanted to make a sound that was the complete opposite of a Les Paul, and that’s pretty much a Jaguar." Rowland S. Howard.

User avatar
oid
PAT. # 2.972.923
PAT. # 2.972.923
Posts: 834
Joined: Sat Feb 10, 2018 8:19 pm

Re: fixing a broken Pearl delay pedal - where to start?

Post by oid » Fri Aug 24, 2018 8:48 pm

timtam wrote:
Fri Aug 24, 2018 7:46 pm
You're right, 'battery check' light seems to be something different to a 'power ON' light (which this unit doesn't have ?). However this vid suggests battery check light comes on as you plug guitar in (but does not stay on) on a functioning unit ...
https://www.youtube.com/watch?v=rbQXQ0Bux8Q
It sort of looks as if you insert the plug part way to get it to check the battery, insert it all the way to get audio, that makes a fair case for bad or corroded input jack. Could still be a power supply issue, but I think that tips it in favour of the jack.

Wish I could find a schematic of the delay with the battery check, getting curious about it, suspect it is not much more than the switches on the jack and the led, tricky and elegant, led does not suck power all the time, just when you want to check the battery status. Not the most useful feature, but well concieved.
Logic gates based on billiard-ball computer designs have also been made to operate using live soldier crabs of the species Mictyris guinotae in place of the billiard balls.

User avatar
timtam
PAT. # 2.972.923
PAT. # 2.972.923
Posts: 2729
Joined: Sun Oct 22, 2017 2:42 am
Location: Melbourne

Re: fixing a broken Pearl delay pedal - where to start?

Post by timtam » Fri Aug 24, 2018 9:30 pm

The only schematic I've come across is over at freestompboxes (quick join to see) ...
http://www.freestompboxes.org/viewtopic ... 60#p236485

I see the thing requires TWO 9v batteries (or ext DC from 12-18v, -ve tip; switching jack switches battery in/out).

Some more info here ...
http://mirosol.kapsi.fi/2013/10/pearl-f ... log-delay/
Suggests at least 15v best, despite 12v DC label.

http://www.dirk-hendrik.com/pearl.html
"I just knew I wanted to make a sound that was the complete opposite of a Les Paul, and that’s pretty much a Jaguar." Rowland S. Howard.

User avatar
oid
PAT. # 2.972.923
PAT. # 2.972.923
Posts: 834
Joined: Sat Feb 10, 2018 8:19 pm

Re: fixing a broken Pearl delay pedal - where to start?

Post by oid » Sat Aug 25, 2018 2:12 am

Looking at the input jack in the first picture it is quite the jack, something in the stereo switched jack family. The battery check circuit can be seen, just a pair of resistors and the LED hooked up to the jacks switches. Fairly simple, should be able to just bypass the battery check to test the pedal.

Pacafeliz, ignore my previous post about checking voltages for the time being, I will work out what that input jack is doing tomorrow and let you know how to bypass it, this might turn out to be an easy easy fix. Also, if you tested with a stereo cable that would likely cause it to stay in battery check mode, this needs a mono cable on the input to work, so if you did use a stereo cable , try again with a mono, it may solve your issues!
timtam wrote:
Fri Aug 24, 2018 9:30 pm
The only schematic I've come across is over at freestompboxes (quick join to see) ...
That is also the only schematic I have found, at the input jack he notes that plugging in the cable turns the unit on but as drawn it has no effect on the power, he just left it off for some reason most likely, perhaps he was unsure about that fancy jack with all of its connections.
timtam wrote:
Fri Aug 24, 2018 9:30 pm
Suggests at least 15v best, despite 12v DC label.
He also states it has no regulator, which it does. The regulator does not take effect until about 15.5 volts so neither 12 nor 15 will kick it in, they just burn off a half volt or so as heat, likely the supply they sold for it had internal regulation and the regulator is just there for the batteries. The only effect I can see the higher voltage having is on headroom, but that input stage is versatile enough to make that a non-issue, you would also be able to achieve a slightly better signal to noise ratio but that would be hard to realize on a pedal board. I like that input stage, I may have to steel it someday.
Logic gates based on billiard-ball computer designs have also been made to operate using live soldier crabs of the species Mictyris guinotae in place of the billiard balls.

Post Reply