Vintage repairs !! Takes me back to my days repairing, restoring and collecting 1980’s video games, very similar technology, what with the Z80 processors and 2114 Ram… This unit is actually a mates, a fellow Turntablist/Producer Jimmerman, you can check out his stuff here on Soundcloud and here on Youtube. This is the second unit ive done for him as i had the pleasure of working on his SP1200 too. This time though i thought i’d do a Blog on it. Images can be clicked on to view them full size !
All information contained on these pages are here for my reference only, i will not be held responsible for any damage or injury done to you or your equipment ! Some parts of electronic equipment can hold high voltages which can shock or burn, some electronic components are very susceptible to staticdischarge. Aging IC’s and pcb tracks can be easily damaged if due care is not used when working on them… You have been warned !
Tasks are as follows:
Replace display for a brighter, low voltage, modern one.
Remove the defunkt high voltage loom used by the old screen.
Replace all the radial electrolytic capacitors.
Clean all the button contacts and replace a faulty button.
Remove the old “and dead” pcb mount battery
Install a button cell battery holder and lithium 400mAh button cell.
! Before working on ANY electronic equipment i ALWAYS disconnect it from the mains electricity !
I started by removing the 3 x machine screws (arrowed) from the top rear edge of the unit, and placed them in a clip top plastic bag, so they wouldn’t get lost.
I then sat the unit on its end and removed the 5 x machine screws (arrowed) from the base, and put these in the plastic bag also, none of these screws were original, in fact they looked to be the type that hold the casings onto a PC.
I could then lift the lid forward and gain access to the inside.
I then removed loom connector CN5 from the main pcb, leaving the other end connected to the lid.
… and then by pressing out the levers on the ribbon connector CN1
…removed the ribbon connector so that the lid was completely free from the base.
with the lid out the way i could then remove the 8 x screws (arrowed) securing the pcb to the base.
Before touching the pcb or any components on it, i tied myself and the unit to ground, using a wrist strap and clip, so we were at the same potential, to avoid any static discharge.
I then began undoing the hex nuts from the 1/4 ” Jack sockets.
Once removed i put all the Hex nuts and washers in the bag with the casing screws.
I then used a pair of pliers to remove the nut from the ground binding post, and removed the 2 ground wires.
I then removed the nut and screw from Transistor VR4, lifting back the transistor and its insulating mica, being extra careful not to get heatsink paste on anything.
Now i could gently remove the main pcb from the base.
I decided to start with the battery removal first, so i cut and removed the plasic tie.
I then unsoldered both pins of the battery using my Metcal soldering station and solder sucker.
With the battery removed i then tidied up the solder pads using solder braid (or wick)
Until the holes were clear both sides.
I then took a button cell holder (always handy to keep in stock)
…and then offered it into place to work out how i was going to get it to fit, as the pins didn’t line up with the battery’s holes in the pcb.
I decided i would fit the positive (+) pin in the positive hole and then make an extended leg to attach to the negative (–) pin to reach the negative hole. So i took a small axial lead capacitor…
…and cut one of its legs off.
i then took some snub nosed pliers gripped the leg 3mm in from the end and bent it 90°
I then cut some Van Damme silicon tubing..
…and trimmed the length of the leg to 11mm, and bent out the negative (–) pin on the battery holder.
I got out my Hot glue gun and put a medium sized blob on the pcb right in the middle of where the battery used to sit. Then i quickly inserted the positive (+) pin into the hole (component side of the pcb), aligned the holder and then pressed firmly till the glue solidified.
I then turned the pcb over and soldered the back of the positive (+) pin. Turning the pcb over again, so it was component side up, I then tipped the negative (–) pin of the battery holder & the long end of the leg i made earlier with solder, slipped the silicon tube over the 11mm length, placed the 3mm end into the negative (–) hole on the pcb and then soldered the leg to the to the battery holders negative (–) pin. With this now firmly in place i could turn the pcb over and solder the negative (–) leg to the pcb.
As i needed both hands to do this mod, sadly there are no pictures, but heres what the finished mod looks like, nice and neat, but also practical. In future when the battery dies, it can be replaced without the need to remove the pcb and no need for any soldering.
To keep things tidy, i then sprayed my soldered joints with pcb/flux cleaner…
…which i rubbed in with a Q Tip until all the flux residue was gone.
Next i turned my attention to the radial electrolytic capacitors, which were the originals from 1984 ! So they probably werent filtering as good as they should be. I started by slicing through the glue between the capacitors with a scapel, being careful not to hit the pcb and damage any tracks.
I then turned the pcb over, unsoldered the pins and removed the caps.
Same as before i then used solder braid (wick) to clean up the holes front…
I then delved into my parts store and picked out…
… 2 x 470μf 63V & 1 x 4700μf 16v radial electrolytic capacitors all them 105º rated
I then soldered the 470μf to the pcb first.
…and again cleaned off the flux residue.
Then i removed the 4700μf and replaced that too..
With the new caps in place i then turned my attention to…
…replacing the heatsink compound and insulating mica on transistor VR4.
…and then refitted the nut and bolt making sure it was nipped up tight. I then installed a 3v 400mAh button cell battery into the holder.
I then removed the control pcb from the lid.
This switch here doesnt work and needs replacing.
At this point it was apparant that at some time in its history a drink had been spilled in the unit where pads 1 and 2 were located, as the cardboard was stained (arrowed) and there was a larger build up of damp dust around the buttons (arrowed)
I turned the pcb over and unsoldered the pins to the faulty switch.
Cleared the holes with braid (wick).
…and cleaned off any flux residue (do you see a pattern emurging here).
I then soldered a new button in place and then tested it with my multimeter, open line when not pressed.
…and an audible beep with the display .000 when pressed, to show continuity across the pins.
Even though that was the only button not working, most of the others were quite intermittant, requiring several presses sometimes before they would work, so i got out my plastic pry tool (came in a Iphone tool kit).
…and pry’d out the blue plastic cover of a button.
Then using ESD tweezers, removed the spring plate (a slightly convex piece of spung steel, that flattens when pressed, creating the circuit between the 2 contacts of the button).
I then got out my Isopropanol alcohol…
…and cleaned the underside of the spring plate using the alcohol and a Q tip.
Using ESD tweezers i removed any fluff from the inside of the button housing…
… blew out any remaining dust with an airline.
Then cleaned the inside of the housing with alcohol and a Q tip.
I then reomoved all the other button covers and spring plates.
This is the before pic, just after removing the fluff from each button, you can see how dull and tarnished the contact pins are, 32 years of oxidation ! The thin contact pin in the top right hand corner of each button were almost black in colour.
So i got out my needle file set and a small piece of Emery paper…
…and gently filed and sanded off all the oxidation, then blew out any dust with an airline and again finished off with alcohol and a Q tip. This is the after shot, you can now see the contact pins in the top right hand corner of each button. With the buttons re-assembled, i tested each one for continuity with my multimeter.
Most of the pcb was lagged with dust.
So i got out a ESD brush…
…and gave the pcb a good clean, with the worst brushed off i then gave it a good blow out with an airline.
Next job, remove the old display, so i undid the 4 bolts and nuts (arrowed) holding the display in place..
I could then lift the display out of its slot, but it was still attached buy the ribbon connector and HV power lead.
The middle section of the displays HV power lead was glued to the pcb, so i gently slit through this with a scalpel, being extra careful not to damage the pcb tracks.
I then turned the pcb over and located where the HV leads solder pads were.
I then used solder braid (wick) to remove the solder back…
Until the lead was free from the pcb. That just left the ribbon connector holding the display to the pcb. The new low voltage display has pins 1 to 14 reversed, so reusing this ribbon connector wouldnt work. To make removing this easier, i cut through the ribbon connector at the loop (arrowed) with some side cutters.
…until i was left with this.
I then got my scalpel and carefully slit between each of the metal tracks within the ribbon.
Which meant i could then grab each individual metal track one at a time with my ESD tweezers, heat the solder pad with my soldering iron and gently pull each one free.
Again removing any left over solder with braid (wick) and cleaning with flux remover, both back…
I then got out a strip of pin header and snapped off a section of 14 pins.
placed it into the freshly cleaned holes (solder side).
Turned the pcb over and soldered all the pins to the pcb.
Then cleaned off any flux residue.
I then cut some lengths of wire approx 6″ in length…
…and cut 14 short lengths of heatshrink tube.
I then put the new display in the croc clips on my helping hands, and tipped all the pins with solder.
I then started soldering the wires to the pins, heat shrinking each one as i went, i just made up the colour key, but made a note of what they were:
Black ⇔ Ground
Red ⇔ Positive 5vdc
Orange ⇔ Null
Green ⇔ Switch signal
Purple ⇔ Read Enable
Yellow ⇔ Write Enable
White ⇔ Data 1
Blue ⇔ Data 2
Grey ⇔ Data 3
Black ⇔ Data 4
Black ⇔ Data 5
Black ⇔ Data 6
Black ⇔ Data 7
Black ⇔ Data 8
(Can’t you tell i ran out of colours lol)
As the holes on the new display are in a different location to the original, I then got a plastic clamp and held the new display in place, making sure it was centered just how i wanted it.
I then marked the postion for the new holes with a Sharpie, and drilled them out using a 3mm drill bit.
I then got out a round needle file…
…and made the holes slightly larger.
I then picked out 4 x 12mm nylon standoffs, with nylon hex nuts.
Because the Noritake display is slightly thicker than the original, i reused the original displays nylon washers as spacers, which proved to fit just right.
I then bolted the display in place.
…and cut another 14 lengths of heat shrink tube.
Then i trimmed down each wire to create a smaller loop and started soldering them to the header strip i had installed earlier, but in reverse order to the display, heat shrinking each one as i went. Here you can see that the Ground and Positive 5vdc are at the opposite end to the display’s pinouts.
The finshed display loom, which i added a plastic tie to the middle.
I then reinstalled the control pcb back into the lid.
Refitted the cover and turned it on… Bingo nice bright display !
Here is the finished article ! All buttons and faders work as they should and it now also holds its memory.
Respect has to go out to all the Producers that used (and still use) the Emu SP12 for beat making, 5 seconds of sample time is not alot, making creativity quite challenging ! Props to Jimbo for keeping true to his roots and making “dem fat old skool Hip Hop beats” the way they were meant to be…
Sadly i forgot to take pics of a few bits, like cleaning the faders etc.. but fitting this work in over the course of a week, those little over sights do happen…