- Joined
- Oct 20, 2025
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- Gear owned
- Tascam Porta One
I am currently restoring a Tascam Porta 02 MkII (Blue model) and have run into a specific power/audio failure. The unit functions perfectly as a mixer and I can plug in a microphone and get clean audio through the master outs and headphones. However, there is absolutely no audio playback from the cassette transport, and the VU meters do not move when a tape is playing, despite the motor spinning and transport working correctly mechanically.
Through cross-testing with a known-working Porta 02 (Red model), I have confirmed that the Blue Mixer board and the Blue Transport both work perfectly when connected to the Red unit's bottom PCB. This isolates the fault to the Blue model's Bottom PCB. Specifically, I’ve discovered that the bottom board is sending improper power to the transport circuits. When I attempt to bridge the Leaf Switch (the "Master Kill Switch" that engages the audio/bias rails) with tweezers to troubleshoot the connection, I get visible sparks and an audible "pop," indicating a hard short to ground on that power rail.
I’ve checked for common issues like "death glue" and have performed basic resistance checks on the 500-series components, but the short persists. It seems the board is effectively "suffocating" the tape playback circuit while allowing the mic/line preamp section to function. Has anyone experienced this specific failure where the mixer works but the tape side is dead and sparking? I would appreciate any advice on which specific components on the MkII bottom board typically fail in a way that shorts the play-command rail.
I made this video on Youtube that shows and explains the issue better. If anyone has any ideas, LMK!!!!!!!!!!!!!!
Through cross-testing with a known-working Porta 02 (Red model), I have confirmed that the Blue Mixer board and the Blue Transport both work perfectly when connected to the Red unit's bottom PCB. This isolates the fault to the Blue model's Bottom PCB. Specifically, I’ve discovered that the bottom board is sending improper power to the transport circuits. When I attempt to bridge the Leaf Switch (the "Master Kill Switch" that engages the audio/bias rails) with tweezers to troubleshoot the connection, I get visible sparks and an audible "pop," indicating a hard short to ground on that power rail.
I’ve checked for common issues like "death glue" and have performed basic resistance checks on the 500-series components, but the short persists. It seems the board is effectively "suffocating" the tape playback circuit while allowing the mic/line preamp section to function. Has anyone experienced this specific failure where the mixer works but the tape side is dead and sparking? I would appreciate any advice on which specific components on the MkII bottom board typically fail in a way that shorts the play-command rail.
I made this video on Youtube that shows and explains the issue better. If anyone has any ideas, LMK!!!!!!!!!!!!!!
