Hello all,
A few months back I asked the fine folks here about good amplifier candidates for a restoration project and got a lot of good suggestions. I finally settled on the Adcom GFA-545, specifically the first version as I didn't want to deal with the version II's bias servo sub-circuit just yet.
Despite my initial aim to repair a "for parts or not working" unit, I have chosen to buy a working one and received my exemplar today. The plan is to live with it for a while and get a feel for its sound unmodified, with the caveat that electrolytics capacitors in there are not in their prime. Then perform restoration bit by bit - I'm in no hurry on this.
Tomorrow I'll be opening up the case, do a general inspection, check fuses, blow dust with low-pressure compressed air, then take documentation pictures before I fire up the thing. I'll first power it while hooked to a "dim-bulb" limiter and ramping on variac from 1/2 mains voltage to nominal, while connected to inexpensive speakers and old iPod as source. I downloaded the service manual from hi-fi engine.
Now I'd like to know if there are other checks or recommended steps specific to this model that I should do beforehand. I'll try to make as many voltage measurements as I can and compare vs schematic annotations. I seem to remember reading it's a good precaution to replace thermal paste on the TDS-C201 thermistor compensators related to the output stage bias spreader. Any warning signs I should pay attention to when powering up?
Also if anyone has suggestions on the upgrade path I'm all ears. I only did caps replacement once on vintage gear and I generally went from the parts most exposed to ripple, large to small, going towards low level signal ones - e.g. PS filtering for output stage, then input stage, and finally signal/bias. Should I use the same approach? Note that I will consider the nice offerings from Hoppe's brain down the road.
I'm excited about this project as this amp looks like a serious piece of kit and I'm told it has great potential.
Thanks in advance for any insights.
- Joe
A few months back I asked the fine folks here about good amplifier candidates for a restoration project and got a lot of good suggestions. I finally settled on the Adcom GFA-545, specifically the first version as I didn't want to deal with the version II's bias servo sub-circuit just yet.
Despite my initial aim to repair a "for parts or not working" unit, I have chosen to buy a working one and received my exemplar today. The plan is to live with it for a while and get a feel for its sound unmodified, with the caveat that electrolytics capacitors in there are not in their prime. Then perform restoration bit by bit - I'm in no hurry on this.
Tomorrow I'll be opening up the case, do a general inspection, check fuses, blow dust with low-pressure compressed air, then take documentation pictures before I fire up the thing. I'll first power it while hooked to a "dim-bulb" limiter and ramping on variac from 1/2 mains voltage to nominal, while connected to inexpensive speakers and old iPod as source. I downloaded the service manual from hi-fi engine.
Now I'd like to know if there are other checks or recommended steps specific to this model that I should do beforehand. I'll try to make as many voltage measurements as I can and compare vs schematic annotations. I seem to remember reading it's a good precaution to replace thermal paste on the TDS-C201 thermistor compensators related to the output stage bias spreader. Any warning signs I should pay attention to when powering up?
Also if anyone has suggestions on the upgrade path I'm all ears. I only did caps replacement once on vintage gear and I generally went from the parts most exposed to ripple, large to small, going towards low level signal ones - e.g. PS filtering for output stage, then input stage, and finally signal/bias. Should I use the same approach? Note that I will consider the nice offerings from Hoppe's brain down the road.
I'm excited about this project as this amp looks like a serious piece of kit and I'm told it has great potential.
Thanks in advance for any insights.
- Joe
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