Tascam Porta 02 MkII - Mic/Line Inputs Work, but No Audio from Cassette Transport

[jacesjunk]

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!!!!!!!!!!!!!!

 

[Jack Saturn]

Are you using the original Tascam-supplied power adapter, or an aftermarket one? If it's the latter, take a photo of the specs label on the adapter and post it here.

Since you are able to get the machine to work by swapping in the top half from another machine, I don't suspect it's the power supply causing the problem, but I'd like to rule that out before providing further advice.

 

[jacesjunk]

Hey Jack Saturn,

Yes I am using the correct and original power supply for the Porta 02. And yes, when I used a bottom PCB and Mixer PCB from another unit, and bridged the leaf switch with a small metal screwdriver, I was able to get sound from the transport. So I don't believe there are any issues with the Mixer board since I get sound from a microphone, and able to get sound from the transport using a different bottom PCB.

My goal is to figure out what's wrong with the bottom PCB first before figuring out why the transport has to be manually bridged.. if you have any guesses LMK!

 

[Jack Saturn]

The reason I asked about the power supply was because if you *had* been using an incorrect supply which didn't provide enough amperage, there was a chance the circuit was starved. I've seen it before with client Tascam Porta02 and Tascam 414 machines — the tape mechanism would turn, but there would be no sound. Anyway, glad we can rule that out.

Please upload a photo of the leaf switch that you are jumpering in order to get audio to pass. Make sure the photo is wide enough that we'll be able to see where that switch resides in relation to the overall tape mechanism.

 

[jacesjunk]

Here are the photos. Yes there's a chance that the previous owner used and incorrect power supply but I believe there's a way to bring it back to working