I have a Pioneer A443 Stereo Amplifer (1989) that's been in good dry storage for 30 years!

I've read that the capacitors from that era rarely give problems, but are there any precautions or checks I should make before connecting it to the power?

Thanks

 

Check the input AC voltage setting is correct. I usually change the AC line operational fuse with a smaller value (1/2 A) close to the expected idle current on a first power-up.

Get your camera ready and power it up.

 

I am not the "replace the capacitors" type of person.

I say turn it on with no speakers connected, volume set to 0. Check for smoke or flash.
If all is well, test with cheap speakers at low volume.

If you are so inclined and you have the necessary components and test meter, instead of speakers use dummy load resistors 10-100Ω across the output connections. Volume level set to 0. Measure the voltage across the resistors. Expected reading is 0V. (You should confirm that the meter is working properly by checking with a 1.5V battery.)

If the voltage is zero then it would be safe to connect speakers and test at low volume levels.

If all is well, leave it on for a day and then check that all is well.

Good Luck!

 

Old power transformers can have problems after sitting for many years. I had one smoke on me after sitting for ~40 years a couple of years back. I've been advised to use a Variac and slowly ramp it up to operating voltage for old mothballed equipment. FWIW

 

I would suggest opening the case and looking at everything carefully, in case somehow conductive items have entered. Small change is incredibly destructive, so are pins and paper clips. And you can blow out any dust that may have entered.
I would have cheap speakers connected so that you can tell if suddenly sounds start happening, and do a fast switch off. One trick is to try it with a 100 watt light bulb in series with the mains power. It will not play right but if the bulb lights at full brilliance then you have saved something.
Download and save that PDF of the service manual, it could be vital to have it if not all is perfect.

 

Thank you for all your replies and the service manual. I will take your advice and try it out soon. Must find some cheap speakers to avoid damaging the good ones. The Amp has been stored well, and had hardly been used from new, so it could be a great find, fingers crossed!

 

Must find some cheap speakers to avoid damaging the good ones.

Or you could protect your speaker with something like this

 

Actually, you could provide reasonable speaker protection with an eight ohm one watt series resistor and connecting to the 8 Ohm terminals. The resistor would fail before the speaker was damaged, and presently resistors are cheaper than fuses.
I suggest verifying that the fuses are no higher ratings than the specified value as a smart check prior to applying power. Simple and safe!

 

The internal fuse in the amp is 2.5a slow burn, the amp requires a max of 240v/550w. Just trying to decide what fuse to put in the plug for maximum protection?

When I run the amp it will be cover off watching for smoke and I've found some old speakers.

 

Actually, you could provide reasonable speaker protection with an eight ohm one watt series resistor and connecting to the 8 Ohm terminals. The resistor would fail before the speaker was damaged, and presently resistors are cheaper than fuses.
I suggest verifying that the fuses are no higher ratings than the specified value as a smart check prior to applying power. Simple and safe!

If I put fuses in series with each speaker, to leave permanently if the amp goes bad in the future, what value would you recommend? The amp and speakers are maximum 8ohm and 60watt, so ohms law suggests 2.75amp, is this a good way to go? Thanks for your feedback.

 

I would put a 12V 50W halogen light bulb in series, something like this:



It protects your speaker from overload but does not blow like a fuse.

 

Are the speakers also 30 years old? If they are I would check the surrounds before operating them. (after checking the HI-FI of course)

 

Please let us know how it turns out. I have a Knight Kit 12 watt amplifier that I assembled back in about 1964 that has not been used for a long time. Probably not since 1970. So it may also need a few precautions. But the tubes are barely used, only the capacitors will be suffering from old age.

 

I have ordered an ESR capacitor tester so I can test the capacitors without removing them before plugging in the Amp. I read that electrolytic caps start to deteriorate if you don't use them at least every 2 years, and the Amp has been stored for 30! so thought this would be a wise precaution. Its also a nice piece of kit for my toolbox I'll let you know how it goes.

 

Please let us know how it turns out. I have a Knight Kit 12 watt amplifier that I assembled back in about 1964 that has not been used for a long time. Probably not since 1970. So it may also need a few precautions. But the tubes are barely used, only the capacitors will be suffering from old age.

My dad was born in 1964! Sounds like you have been playing with electronics for a long time haha he can barely work the tv remote control.

 

There is a speaker protection circuit relay, that will detect any voltage on the outputs, .

Here is a snapshot of the output.