Cleaning out (upgrading perhaps?) a Soundcraftsmen Pro Power 4

philbobilbo

New Member
Since I've just recently acquired a sweet sounding Pioneer SX-1010, I thought I'd open up the guts of my old Soundcraftsmen Pro Power 4 and have a look on the inside (pictures below). The thing has performed like a true champ ever since I bought it used in the early 90s, but thought I'd have a look. Besides from all the dust (and even cobwebs in one corner!) the unit appears ok, with no "burnt" looking items. My questions are this:

1. I am assuming it would be safe to use compressed air to blow all the dirt out of this great unit. True?

2. Should I buy a can of Deoxit and use it on any of the electrical items?

3. Thought I'd read somewhere that you can use Swiffer sheets as filters on the intake to keep dirt from being sucked it (obviously taped). Is that true?

4. Are there any upgrades or special mods that would be worth attempting on this unit? I'm guessing no...


Gotta tell ya, I told friends years ago that I'd put this amp with just my Bose 301s up against anyone's surround sound for the sheer "theater" effect, and ones that have heard a good movie on it are stunned, especially when there are lots of explosions!!! (ha, ha!). The 1010s power is great, but the Four is rated at 250/ch, so the 1010 is no match power-wise.

I'm thinking of opening my NAD 1600 to see if it could use mods as well. If anyone knows about it, I'd be glad to read your thoughts.

Here's the links to the pics:

http://i22.photobucket.com/albums/b344/ohilpneal/DSCF0099.jpg

http://i22.photobucket.com/albums/b344/ohilpneal/DSCF0097.jpg
 
Compressed air should be OK if it's from a can. Air from a compressor is normally saturated with water, so unless you've got a drier on the compressor's outlet, you're likely to squirt water under pressure into lots of places it shouldn't go.

I'm not familiar with your amp, although I'm guessing it's a power amp? Deoxit might be a good idea on the RCA sockets and the speaker binding post contact surfaces.

A Swiffer sheet would certainly filter dust out, BUT (and it's a big BUT) it will restrict airflow into your amp to a degree when clean, and when dirty it may reduce airflow enough to cause severe thermal stress to some of the components. My gut instinct would be to forget the idea, and just put up with occasional housekeeping.

If it's of a fair vintage, replacing the electrolytic capacitors is a good place to start. Their effective capacitance decreases over time, and their ESR usually goes up. Degeneration in big filter caps on the PSU will cause increased ripple voltage on the supply rails with a detrimental effect on the speed and dynamics of the amp. Some decent quality low ESR types are what you want. I would also replace all of the electrolytics in the audio circuits. For the audio caps, I'd recommend trying Sanyo OS-CONs, Elna Cerafines or Silmics, or even Rubycon Black Gates.

Check for DC offset on the speaker outputs - there's a really good thread on here about it. It can reveal failing trannies, and bias problems.

Replacing the driver and power trannies with something faster with lower noise can bring significant sonic improvements, but it all depends on how far you want to go.
 
As I can see from your pic's, your Soundcraftsmen is a MOS-FET amp. Using the famous Hitachi 2SK135/2SJ50 Power Mosfets, they came in style in the early eighties. The Hitachi Mosfet was very reliable and almost indestructable as it did not suffer from the 'second breakdown effect' that kills normal bipolar transistors when overheating.
Don't worry if your amp runs hot, the Mosfets like it hot even when idling - and will limit themselves when it should get too hot.
But I would not use a filter on the fan, rather clean out the dust once in a year, as the other electronic parts may get too hot, should the filter reduce the airflow too much

Helmut
 
I recommend that if you blow it out with compressed air you either do it outside or use a shop vac at the same time to vacuum up the dust and crap you will blow around. You don't want to put that stuff back into your living environment, or inhale it.
 
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