Sansui BA-3000 power amplifier overhaul

Hi Fi Delirium · December 1, 2024

Had the awesome opportunity to overhaul this powerhouse Sansui BA-3000 from late 70s. It was very tired with evidence of moisture corrosion and running too hot. Typical of many of the imported Japanese ones I’ve seen that succumb to the humid climate. When buying from Japan it’s wise to factor in the work to bring them back to top working condition, often a lot of work. As long as you’re prepared for this or have the skill to do it yourself, it won’t come as such a shock. A lot are sold as ‘junk’ items with no guarantee of functionality so it’s a bit of a lottery as to what you’ll end up with.

All boards had a proper going over - Driver boards, Filter board, Meter boards, protector board, Power Supply Board. All 12 main output transistors were replaced too as they’d lost most of their gain through heat damage. These were replaced with more robust On Semi MJ21193G / MJ21194G. Electrolytic caps were replaced with mostly Nichicon brand, lower values replaced with Wima polypropylene.

Quite a few diodes were replaced, mostly heat stressed ones and the notorious double ones that are known to fizz out without warning.

Most transistors were replaced as many were heat stressed and there are a quite a few that deteriorate with age.

Relay contacts were cleaned with Deoxit. They were carbonised and a little pitted so something to consider replacing later on.

Centre voltage and bias trimmers replaced with Bourns type.

Ceramic caps in signal path replaced with C0G type as they are a real improvement.

The power supply board was pretty baked as it cops the most heat stress, so I upgraded the electrolytics from 85 degree to 105 degree temp rated and replaced all the semiconductors and a couple of diodes that are prone to failure. The Uniwatt transistors were replaced with more robust ones with higher max ratings.

Apart from these highlights, all boards were re-soldered and de-fluxed. Centre voltage was re-adjusted to an astoundingly good 1mV on each channel, which has benefits in reduced distortion. Taking time to match transistors can really pay off. Bias current was re-set and the amp tested at length and with great joy. This thing has power in spades and just breathes life into my usually hard to drive Dynaudio speakers.

After thorough testing which was a joyful experience, the amp is back with its owner and I’ve taken the gamble and bought one for myself. Will be interesting to see what sort of condition it’s in when it shows up.