Boss DS-1 Pedal Repair (with video)
Here was the posting on eBay:
£27.35 BOSS DS-1 Distortion Pedal - Spares / Repairs - No Sound When Engaged.
Lights up on PSU, bypass works - no sound when engaged Good cosmetic condition Sold as seen
I thought, OK, I’ll have a go at this! After all, the DS-1 is a legendary pedal for acid/techno…
The pedal arrived, I eagerly dismantled it, and was faced with some very clear issues:
It was clear that, the diode D1 was blown, and capacitor C23 next to it had a little mohawk from where it had bulged out upwards.
From the serial number, it seems this is an early 2000s model. I consulted a schematic I found online, and it was clear that both of these were in the power circuit:
I spoke to my mate Jon and he suggested that maybe someone had plugged in the wrong power supply - this totally makes sense that the components would blow if that’s the case.
I desoldered the diode, which was fully broken in two, and pulled out the cap also:
I tested the cap, yep, ESR meter suggests it’s totally borked!
So, I soldered in some replacements I happily had in my parts bins:
It still didn’t work. Oh no! Back on the test bed!
I could see that there was what looked like capacitor leakage around C15. So, I pulled out that cap and the surrounding resistors:
They all read fine, but I replaced them anyway; the resistors looked a bit grubby. I cleaned the PCB with some isopropyl alcohol and it looked much better.
It STILL didn’t work! At this point, I did some voltage tracing by putting a probe on neutral and measuring voltages at certain points corresponding to the schematic. Voltages seemed OK although I’ve never done this before so I wasn’t confident.
Eventually, I built a simple audio probe:
I traced the signal point-by-point through the circuit. I got as far as the op-amp and suddenly it all dropped out!
At this point, I realised that the op amp must be blown. I managed to find a few articles and threads online suggesting that this is a common issue when people feed the DS-1 the wrong power.
The waiting game
I found some replacement op-amps on Mouser.co.uk. Little did I know, they’d be shipping from Texas!! No wonder they wanted £12 for Fedex delivery!
When it eventually arrived, I socketed the op-amp so I could swap it out if necessary. Apparently there are a number of op-amp mods for this pedal…
IT WORKED! I put it all back together and was stoked.
Closing thoughts
This is a greatly smoothed out version of what happened - there was a lot of flailing around! I probably spent about 8 hours in total on this project, including all the research I did, although that’s hard to quantify.
That said, I enjoyed fixing this pedal immensely. I found it so satisfying to trace the fault down and pursue it.
Whilst I spent a small fortune on components and shipping (I went down a few blind alleys with suspecting various caps I didn’t have in my drawers; components are reasonably cheap but you really get stung with the postage), so it cost more than buying a new one, it was the fun of the fight that I relished.
And next, to try it on synths!
Helpful articles
- https://www.diystompboxes.com/smfforum/index.php?topic=85893.0
- https://www.reddit.com/r/diypedals/comments/pc18ut/how_to_make_an_audio_probe_and_use_it_for/
- https://www.coda-effects.com/2015/07/troubleshooting-guide-for-guitar.html
- https://www.electrosmash.com/boss-ds1-analysis
- https://www.musicradar.com/how-to/the-fx-files-boss-ds-1
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