A really nice example of an early Triangle Big Muff Pi repair. From googling, I guess it is late 60s, early 70s. It came in by post from London for a 24h turnaround repair on our express service.
The owner reported weak signal, loss of volume at times, and inconsistent behaviour when engaged and tone suck in bypass mode.
Initial Inspection
The PCB showed signs of age – several dry solder joints, probably factory. A few pads were damaged or lifting, most likely from previous repairs or stress over time. Three of the five electrolytic capacitors were leaking on test. All were replaced.
A quick check of the components also revealed a 150Ω carbon comp resistor had drifted way out of spec – measuring over 2kΩ! That would’ve had a big impact on the tone and gain structure of the pedal.
Work Carried Out
- All five electrolytic capacitors were replaced as a set. The originals were well past their best.
- The out-of-spec resistor was swapped for a fresh 150Ω part – we used a modern replacement, chosen for low noise and stable performance.
- Dry joints across the board were reflowed and cleaned up, and damaged PCB pads were carefully repaired to ensure good connectivity and long-term reliability.
- The battery clip and switch were both replaced. The old clip was missing a connection and held on with sellotape! The switch was intermittent.
- The owner asked for a true bypass mod, but didn’t want any drilling or visual changes – so no LED, and still battery-powered only. New 3PDT footswitch, but no drilling.
Testing
With everything reassembled, the pedal was powered up and tested thoroughly. Signal is now strong and stable, and the phat Muff tone is back. I tested it with some pumpkins style riffs (OK, OK I KNOW IT’S NOT AN OPAMP MUFF!!).
A really satisfying job on a classic circuit. No unnecessary mods, just careful repair and subtle upgrades to keep things running smoothly without spoiling the original vibe.
If you’ve got a vintage big muff pi in need of attention, we’re always happy to take a look.