I powered off the unit, disconnected the power line (VERY IMPORTANT) and checked the unit's main fuse with a multimeter eg F001 - it was fine. Was puzzled. Hence I reconnected everything and tried to use the DAC again. Still "dead in the water", I repeated the previous check and discovered F001 blew this time. F001 is supposed to be 250V 200mA but had been previously replaced with a 250V 500mA since the 200mA fuses are pretty hard to came by (where I am).
Next I proceeded to check all the fuses on the various PCB(s) with the multimeter; all the existing fuses were fine. Hence suspect a shorted transformer, most probably L001 again since it had been replaced long ago and another visitor on my previous post informing of the same issue. Since I had some spare 500mA fuses handy, I could replace F001 but this time, remove the power to L001 before performing the power-on test. Bingo! The unit could be power-up without L001.
First a recap. When L001 was replaced years ago I did not have access to the Marantz CDA-94 service manual (courtesy of HiFiEngine) and thus did not know how to proceed as there was no information on L001 as there were no markings on the bloody thing!! A retired repair techie from DIYAUDIO advised to use a lower spec transformer instead. Hence I purchased a 12V 133mA toroid with dual secondary(s) from Element14. In those days there were not many choices and you had to pay thru your nose for the part (since they charged for courier delivery if you did not meet the minimum purchase sum). Since the replacement transformer had dual secondary(s), the kind DIYAUDIO techie provided guidance on how to connect the new dual secondary transformer (the original transformer had 3-cables, the replacement came with 4-cables). I have since learnt that the replacement transformer with dual secondary(s) was connected using the center tap technique.
Fast forward to the present - was checking the internet for replacement recently ... boy has times changed! You would be overwhelmed by the available choices and surprised by how much prices has lowered!!!
Previously would have loved to install a Talema 7XXXX-series replacement but the cost was prohibitive then since the local agent had minimum purchase requirement(s) etc etc while eBay shipping from overseas was quite expensive. Nowadays it's possible to procure the OEM equivalent for a pretty decent price.
While trawling the net for information, came across a translated site informing all the transformers used in the CDA-94 were with 1A output.
Hence settled on the 15W version with 15Vx2 secondary(s) and 500mA output per secondary and the matching mounting PCB - see pix(s) below and additional information on the respective caption(s).
|L001 replaced with the blue OEM transformer|
|Replacement transformer on mounting PCB attached to chassis bracket using plastic screw with additional washer between PCB and the chassis mounting bracket|
|Close-up of the replacement transformer and cabling|
|"Center tap" technique hookup at terminator end; fuses after the termination point upgraded from 500mA to 750mA|
Please note the cabling used for the replacement transformer were salvaged from it's dead Noratel predecessor.
The CDA-94 back in business again ... now considering procurement of some heatsinks for the opamps, TDA1541A and the SAA7220 chips.