My Tascam 424 MKII Arrived -- Cracking It Open Already for Repairs

[DesertRatt]

My auction site 424 MKII arrived yesterday and I set it right up for a test recording. BUT, right off the bat the input trim pots are so worn they are shorting, snapping, and riddled with noise. Basically unusable. I more or less expected problems with a unit this old, so I was not surprised. The general condition was not bad, so I'm on to the repairs.

Cracking it open took about 20 minutes. I was quite impressed with the quality of construction and design. This was designed by very competent engineers! The top half of the case contains the circuit board with all the controls and switches, and the PCB in the bottom shell contains all the amps and circuits for the tape drive.

The (4) trim pots are quite easy to access, and so far it looks like they are available at DigiKey for less than a dollar each. I only need to confirm the value of the pots, which I will get done today when I break out the soldering gear. So, maybe a week to get the parts, and while waiting I can clean the rest of the unit. The plastic tape door has one broken hinge, so I will try to fashion a "splint" to get that working smoothly.

 

[sweetbeats]

Have you considered replacing the input coupling caps that feed those trim pots? Are you certain they need replaced? That’s not typical at all. Do you get any improvement in the performance fault if you exercise the pots?

 

[A Reel Person]

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I've found that if something in the input stage opamp/signal chain is blown, it will sound a literal mess, much as you described. Wacked out and sputtery. I can't ID the exact preamp component, but scratchy pots would also be highly indicated offenders in most gear of this age. I think the 424mkII is generally a good piece of gear. Best of luck.