Weak/No output on Tascam 48-OB

  • Thread starter Thread starter lo.fi.love
  • Start date Start date
15 years later...

I'm looking to buy a Tascam 48 OB and found one that seems great, except the XLR outs do not work due to bad relays. I'm not sure about all the factors that relate to this issue, but found this thread while researching how to fix this. If I understand this thread, the OP's issue was with the RCA outs and fixed them by replacing the relays for those -4 outputs. The problem with the unit I'd like to buy is with the +10 XLR outs. Not sure if I have the right.
The Tascam relay for the XLR outs is part K001 or K002 (essentially the same part)? Anyone happen to know if Hamlin makes a replacement for these XLR relays? Thanks!!
 
Are you certain the relays are faulty, or are the relays fine but the drive circuitry has failed? Those little dip relays do fail with age, but i could be something else?
 
Yeah I would not be starting with the relays. And regardless K1 and K2 are not the relays I’d be looking at…those relays have to do with controlling signal during recording and sync vs repro output. K3 and K4 pass signal to the outputs…they are muting relays which mitigate thump in the outputs…but they both get their power from the same place and function at the same time, and the -10dBv unbalanced and +4dBu balanced outputs source their signal from the same place, so if the +4dBu balanced outputs are not working globally, but the -10dBv outputs ARE working, +1 to wkrbee’s suggestion…I’d start by checking the power rails that power the balance amp…+/-20V bipolar supply.
 
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I don't actualy have the deck yet. Seriously considering buying it, but - even after reading quite a bit of info - don't know enough about these to feel like I can make an informed decision.
Wondering if an experienced tech would be willing to consult with me? Happy to pay a fee for your time/expertese.
 
"
  • Often times newer opamps draw more current. Not a big deal if you are doing one here and one there on a smaller system, but can become a real consideration if you are going through and doing a whole mixer...might be too much for the PSU.
  • Newer "faster" chips have the propensity to go into oscillation and it is a common practice to put a film "bypass" cap between the + and - input pins on the chip to prevent this from happening. How deep does the rabbit hole go..."
Abso-bloody-looootly! ^ The current pull issue is especially moot when swapping the TL0X types for bipolar input ics such as the NE5532. People will bang on about sonic differences but I am not aware of any peer reviewed A/B testing? If a circuit is well designed IMHO just fit better than a 741 and you will be fine!

Yes, the LM4562 IS a superb op amp. Better noise and distortion figures than the already excellent NE5532 (which is WELL MORE than good enough in a tape deck!) but. The LM is in fact noisier than the NE5534 in certain circuits such as an RIAA pre amp so sweeping generalizations about op amps are bull squirt. The noise produced by ANY active device depends on the input impedance and varies for different chips.

Lastly, don't want to be rude but the "scatter gun" approach I have read here to tracking down a loss of level would have gotten me a severe bllking from my boss! You need a scope and probe and go down the PCBs systematically to see where the signal is being lost. I actually used to use a Levell mV meter (analogue scale) with the AUX out feeding a scope above it on a shelf. A powerful combination since you get the (true as it happens) rms voltages but also can see if they are "clean".

Oh yes! "Tiny" relays have long been a PITA. They would fail in the audio circuits of Hitachi VHS recorders and in fact caused audible instability. A quick fix in the field was to snap off the plastic cap and give them a blast of Electrolube.

Dave.
 
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