How to bring up new old amp with Variac and DBT

Hi all, I just got a Bedini 150/150 MkII amp and Bedini 66 MkII preamp.

They have sat idle for 10 years so I want to bring them up slowly with my Variac and DBT.

I can't find any tables about what voltage increments I should step to and for how long I should keep it there.

Any help is much appreciated.

Of course I'll clean the huts of fist and do a visual inspection before I fire it up.

I assume I don't have to bring up the preamp with the variac....do i?
 
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I found a few things I don't understand and one issue.

on the preamp, this cap in the first pic is not bulging but the wrapper is off. is this a problem? Do I have to clip one end to test the cap?

Everything looks OK in the amp but I see there is fuses in the amp and next to those are 4 little threaded things. What are those and why fuses in side the amp. on the back of the amp there is the same fuse for each speaker connection.
 

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The internal amplifier fuses are likely power supply rail fuses.
Use your ohm meter to verify they are good.

Make sure your Variac is fused at its rated current (or less) to protect it.
A Variac can be instantly destroyed by excessive wiper current due to a heavy load.
Bring the voltage up slowly, over the course of an hour or more.
For example, raise it by 10% every 10 minutes.
Check the DC voltage at the amplifier output. It should remain under 0.1VDC.

Be careful to verify the AC voltage that you are applying to the amplifier.
Don't go over 120VAC. Some Variacs can easily go to 135VAC.
Using a dummy load is ok but not required, but don't use a speaker.

The unwrapped preamp capacitor is probably still ok.
Do also bring the preamp up slowly with the Variac, same as the power amplifier.
You could do both at the same time, if impatient.
 
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Ok, it all checked out meaning no smoke and no shorts. However I read in one of the links that DC measured on the outputs should never go over 0.1vdc so I measured both sides. The two sides are very different with the left side at -0.0958 vdc and the right side at 0.0103vdc. So one shows negative and the other shows positive.

Is that right?
 
Probably this is typical of that unit, and anything under 0.1VDC is no problem for the speakers.
The polarity of the offsets is random and not at all important.

Things should continue to improve (sound, offset, etc.) with burn-in for some time, even up to a month
or more of regular use. There's no need to leave either component powered on continuously,
and that could be a risk as well.

As you use the components other problems may be found, so watch for anything abnormal.
 
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John Bedini -quote- " Reset bias to 35ma across emitter resistor Positive Side" .


Several owners had offset problems some were due to the differential input pair ,while that amount of DC offset is not massive its best to get them near zero and equal .


Large amounts of DC offset move the voice coil of the speaker out of position.
 
I would wait on that for a week or two, and see if anything else shows up first.
It's not at all urgent, and possible to cause problems during the process.
In the meantime you can look for schematics.
 
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I agree Rayma. I have the Bedini model 66 pre amp on the variac while I set up these speakers I got in the deal. This is the first preamp I've ever seen that plugs into the wall but has no on-off switch.

There is no receptical on the power amp either for the pre to plug into.
 
thank you guys for walking me through this process. I got the amp, preamp, and a pair of Shahinian Diapason Ensemble speakers from an old lady who was moving back to Massachusetts from here (Albuquerque) and didn't want to haul them. all for $495.

I explained that the speakers were worth many thousands of dollars and she pulled out all the receipts and she told me she knew what it was all worth but wanted it all gone.

Played music of all sorts for 5 hours last night and I am very impressed with it all.

All 4 passive radiators are rotted out so I didn't crank it.
 

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yes they were. there was a lot of "does not, does too" about them as with the dispersion of the the 14 drivers in the pyramid tops the sound was not strictly conventional.

The rosewood is beautiful and the design is cool looking to the point I could just have them for the looks.

I have two issues with the set up. with no music playing I get a low level buzz and when I turn the amp off I get a huge thump. any ideas what I should do?