I recently got a cheap ‘broken’ Hafler P3000 that I wanted to fix and use as a reference amp.
Lucky me, it turned out it was just a fuse problem!
As an 115V 60Hz US model, to use it here @230V 50Hz requires a bulky step down transformer.
The sound performance was nice but the amp made a lot of transformer mechanical noise, so called ‘humm’ or ‘buzz’: clearly a show stopper.
I rewired the two independent 115V primary windings of the original transformer into 230V but the humm persisted. The old amp required a PSU overhaul.
Hafler produced in the past replacement 230V transformers (used in the P3000CE model) but they are no longer available. Dynaco (Hafler owner nowadays) would not sell me the equivalent 115/230V bi-voltage transformer from the P3100 either.
The secondaries provide two times 50-0-50V for the output stages and two times 15-0-15V for the input stages. I could not find a single transformer with all these secondaries nor a user-defined toroid that would fit in a 2U Modushop chassis together with the amp modules.
Each input stage is equipped with +/-18 VDC regulators while each output requires separate unregulated 65-0-65 VDC.
I found a solution, probably not the best one: two small 2x15V superposed toroids and two beefy superposed 500W +/-65V SMPS. I also tried two smaller 240W SMPS but the amp (presumably the SMPS) would go into protection after a few minutes.
On the PCBs, I removed the big PSU electrolytics, the rectifier bridges from the output stages and did some rewiring to keep the same faston connectors now with DC.
The amp now works great and goes unnoticed between tracks.
Comments are welcome.
Lucky me, it turned out it was just a fuse problem!
As an 115V 60Hz US model, to use it here @230V 50Hz requires a bulky step down transformer.
The sound performance was nice but the amp made a lot of transformer mechanical noise, so called ‘humm’ or ‘buzz’: clearly a show stopper.
I rewired the two independent 115V primary windings of the original transformer into 230V but the humm persisted. The old amp required a PSU overhaul.
Hafler produced in the past replacement 230V transformers (used in the P3000CE model) but they are no longer available. Dynaco (Hafler owner nowadays) would not sell me the equivalent 115/230V bi-voltage transformer from the P3100 either.
The secondaries provide two times 50-0-50V for the output stages and two times 15-0-15V for the input stages. I could not find a single transformer with all these secondaries nor a user-defined toroid that would fit in a 2U Modushop chassis together with the amp modules.
Each input stage is equipped with +/-18 VDC regulators while each output requires separate unregulated 65-0-65 VDC.
I found a solution, probably not the best one: two small 2x15V superposed toroids and two beefy superposed 500W +/-65V SMPS. I also tried two smaller 240W SMPS but the amp (presumably the SMPS) would go into protection after a few minutes.
On the PCBs, I removed the big PSU electrolytics, the rectifier bridges from the output stages and did some rewiring to keep the same faston connectors now with DC.
The amp now works great and goes unnoticed between tracks.
Comments are welcome.
