boss sd-1 repair

Barcode80 · November 12, 2006, 11:56:37 PM

i have an sd-1, and some traces came loose from the pcb. after further inspection i realized a diode had blown, probably from solder overheat. anyway, i installed 2 1n4001 diodes and a red LED for the assymetrical clipping arrangment. IT SOUNDS CREAMY AND AMAZING.... except if i turn the drive up above about 2. if i do that, it starts oscillating (i assume that is what it is called). it kind of turns into a tone generator?!?!?! it emits a tone that gets lower in pitch as i turn up the drive pot. any ideas? i really want to get this working because this clipping diode arrangement sounds sweet in this circuit. but i want to be able to turn up the drive knob.

interestingly enough, it is already pretty distorted with the drive at 2, so i am guessing that may be related...

Barcode80 · November 13, 2006, 04:45:27 PM

okay, since the dc jack isn't working, and i've seen some posts about power supplies and squealing, i'm guessing the two are somehow connected. HELP!!!

anyone know a good debugging choice for this particular prob?

Barcode80 · November 16, 2006, 08:26:01 AM

bumpety-bump-bump-bump

Barcode80 · November 18, 2006, 11:25:04 PM

seriously, need some help here....

Barcode80 · November 20, 2006, 01:56:05 AM

c'mon guys, DEAD PEDAL HERE!!!

MartyMart · November 20, 2006, 04:40:56 AM

Mate, people are avoiding this 'cos it's a pain in the ass to fix this sort of damaged pedal
.... so there's no easy answer at all.
I mean - DC jack bust ... traces lifted etc .. ??
With some more time and experience you could trace the problem and fix it, but it's a bit like
asking someone to service your car - by instructing YOU over the telephone !!

Best idea, borrow a known GOOD SD-1 and take readings with a DMM & eyeball the sections
that seem damaged ... that will get you on the right track, also a couple of good photo's
may help us to help you ?

MM.

Dirk_Hendrik · November 20, 2006, 07:03:36 AM

I'm with Marty on this one.

The described power problem, loose traces and a burnt diode suggest that the thing has been connected to a reversed polarity power supply.

MartyMart · November 20, 2006, 07:07:19 AM

Quote from: Dirk_Hendrik on November 20, 2006, 07:03:36 AM
I'm with Marty on this one.
The described power problem, loose traces and a burnt diode suggest that the thing has been connected to a reversed polarity power supply.

This sounds the same as your other post about the Boss BD-2 !
Watch those PSU's geezer

Barcode80 · November 20, 2006, 12:11:07 PM

ah, thank you! i was just looking for a reasonable starting point. i wasn't necessarily looking for someone to walk me through the whole mess, i was just looking for ideas on where to start. okay, i'll see if i can track down someone with a working sd-1. I'll check back in with questions...

oh, and btw, this one was having this issue before i ever connected to a power supply

i am starting to question the integrity of the regulated wall wart i use to test my pedals now though... what is weird is that the bd-2 from the other thread has been run on the power supply numerous times for much longer than the 2 or 3 minutes it was on it when it died. odd... but i will try both these pedals on my signalflex multi-pedal supply and see if i get different results.

Barcode80 · November 21, 2006, 12:31:59 AM

okay, i've now noticed that the sd-1 had a capacitor missing?!?!?! i assume the previous owner removed it. i'm not sure if this is related to a mod or what, but i replaced it with the stock value of .01uF. i don't think this has anything to do with the jack not working, but do you guys think that might be the cause of the loud squeal??

i can't check tonight as it is too late to be cranking up amps, but i was curious.

Barcode80 · November 21, 2006, 12:40:48 AM

another thing i noticed: when the pedal is powered up, the LED used as one of the clipping diodes lights up.should there be enough voltage running through the clipping diode for it to remain on all the time?

Barcode80 · November 27, 2006, 03:58:28 AM

OKAY, i replaced all the trannies, the IC, and etched a new pcb by scanning the old one and filling in the traces that had lifted. i wired it all up, and PRESTO! it works! I assume it is probably the IC or one of the trannies that went the way of the dodo. i replaced the obscure trannies all with 5089's and replaced the fets with J201s. the clipping is a little less pronounced than i would like, so it is time to start switching out diodes, but i'm so excited to have it working!

on a side note, i wouldn't recommend the scanning, etching, and replacing the entire pcb method other than for a learning experience. you can buy a new sd-1 for 40 bucks. i just valued the experience, and since i paid only 40 bucks for both the sd-1 and the bd-2 i have (up next for repair), i feel like the functioning pedal and the experience and education i've gained from fixing it are worth it all.

i was wondering about diodes. i know everyone is on about that germanium diode series and such for clipping, but i have no germ diodes. right now i have 2 4001;s and a red LED for clipping. I was wondering about the LED, because it is one of the clear housing LEDs. does this make a tonal difference? should i put in a solid red?

MartyMart · November 27, 2006, 04:59:17 AM

WAY TO GO !! HEY fantastic work, that's a great result

The Ultra bright LED's have a different forward current, could be clipping sooner or later ( data sheet )
I usually just use "ordinary" red 3mm LED's - the one that used to be the boss indicator will do !
What I like in SD-1's is 2 x 4148's and a single 4001, that should give you a nice crunch without too
much compression ( D5/D6/D7 if I remember right ! )
Check for the other SD-1 mods also ..... SEARCH

MM.

Barcode80 · November 27, 2006, 11:11:43 AM

oh yeah, i searched alright

that's why i built in the big fat yellow mod when i built the new board

I'll try that combo of the 2 4148's and the 4001, i'll let you know if i like it.

i might do the same scan and trace for my bd-2. it was kind of fun! and it lets me create a resource for those in the same boat who don't wnat to buy a whole new pedal when a half hour of etching and soldering will revive their pedal.

Barcode80 · December 04, 2006, 03:59:26 PM

well, i tried that diode combo, and gave it a week or so of playing to tune my ears to it, and i think it is just way soft. problem is, i don't know any way to get more defined clipping outside of 4148's. any ideas?

also, it seems that i might have to undo the fat yellow mod, as it seems a little too warm for me. maybe this diode combo without the fat mod?

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boss sd-1 repair