ATR-104 Troubleshooting

onlyaudio · Apr 23, 2012

I have an ATR-104 4-speed 4-Trk 1/2", 2-Trk 1/4" (w/CTTC head added to output on Ch-3) on which all four Rec/PB amps ceased to work. The machine (transport) powers up, along with the cooling fan on the rear, but none of the amps powers up. I've tensioned tape and the transport works fine, even in remote, using TimeLine Lynx II parallel control / KCU. We've checked main and +5V fuses on the main power supply and the two inside the power supply chassis, all fine. There are four cables (2 large, 2 small) running from the main transport housing up to the amp units. Each of the larger cables connects to a quasi D-Sub multi-pin connector, which leads me to believe they are audio. Each smaller cable contains two wires (therefore, power?) which connect to an automotive-style rectangular plastic connector. Checking those two connector (on the cable end from inside the main transport case) displays low voltage. Has anyone ever had experience with this or a similar situation?
Thank you.

RF
Burbank

Greg Norman · Apr 23, 2012

There should be +- 20 to 24 VDC getting to your I/Os via the main harness (attached to the PWA box). This comes directly from the power supply. You might have failed regulators in the power supply, or something wrong with the wake-up circuit.

onlyaudio · Apr 23, 2012

Thank you. We'll check those. I've also been reading that protection circuit(s) may have been triggered, or other power supply problems. It seems we've passed all the "simple" and "inexpensive" options.

pucho812 · Apr 23, 2012

If your positive it's the audio circuits, start like you would trouble shoot any piece of gear, with the PSU.

have you tried just passing audio without recording, you know the machine in input without rolling tape?

onlyaudio · Apr 25, 2012

As it turns out, after removing power supply, testing transistors, removing I/O modules and much other checking, I think we've narrowed it to the RC4194TK voltage regulator on one of the audio boards. Long journey to get across the street but we did evict some dust bunnies.
Thanks for your help.

onlyaudio · May 2, 2012

We believe the VR was bad, but I was able to find the entire back section of an audio card. John Austin at Sprague Magnetics in Sylmar, CA had the part, shipped it to us immediately and I was back to 4-speed 4-tracking in a couple of days. Sprague acquired a cache of parts from Ampex and is a good source.