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First Power-up in 55 Years - Need Advice

Kasanay - Curious how you're doing with these amps. I'm familiar with them and would not advise powering up without a Variac at a very low setting. Power supply capacitors are electrolytic and after this much time it's almost guaranteed that they need to be replaced. Diodes may also be shot. If you start with a very low setting on the Variac and ramp up slowly over a few hours there's always a chance of reforming the dielectric in the caps if they haven't dried out completely. But, at the first sign of something frying shut it down fast. You could power up the power supplies by themselves first and check voltages once you've finished ramping up. If you get to the point of powering up the output section there's a small meter and a test point in the panel below the tubes. When you push the button below the meter it shows the DC offset in the output and should be set to zero. But, first check the voltage in the test point and use the Bias pot to set the bias to -20v. Then push the button to check the offset. Most likely it will pin the meter. If so, don't hold the button down, make a small adjustment with the Balance pot, push again and repeat until the meter stays in range. If you can't get the meter in range do not connect speakers as DC will be flowing through them. btw - the power supply transformer is 1:1 and supplies 120v with quite a lot of current. Be careful!
 
Matthew Polk said:
Kasanay - Curious how you're doing with these amps.
Click to expand...
Matthew,
I do not yet have the amps. I have made different travel plans and will not have these until the first week in June. This just works out better with my work schedule, the weather and travel plans.
Matthew Polk said:
When you push the button below the meter it shows the DC offset in the output and should be set to zero. But, first check the voltage in the test point and use the Bias pot to set the bias to -20v. Then push the button to check the offset. Most likely it will pin the meter. If so, don't hold the button down, make a small adjustment with the Balance pot, push again and repeat until the meter stays in range. If you can't get the meter in range do not connect speakers as DC will be flowing through them
Click to expand...
That's some great advice on setting the Bias and adjusting the balance - thanks. I was a little worried about making these adjustments. It sure helps to know the target values as there is no owner's manual for these things.
Matthew Polk said:
I'm familiar with them
Click to expand...
How did you learn of these amps? What is your experience with them? These are very rare and very few people know anything about the amps or the company that made them. I would appreciate any information you can offer.

Thanks
,
 
Well, I did it.
I drove about 2300 miles over Memorial Day weekend and picked up the OTL amps. After analyzing every option I had to transport these, it came down to simply driving out east, picking up the amps and driving back home. I left Milwaukee early Saturday morning and arrived in New Hampsire on Sunday afternoon. I did my deal Monday morning and headed back home right after. I was home by 9:00 am Tuesday. After a shower and a nap, I started going over the amps. With the help of my brother, a veriac and a DMM, we were able to get one power supply warmed up and checked out. All the voltages seemed to be reasonable so we connected it to one of the power supplies.
After some time we had the tubes glowing. All the voltages were spot on or very close to spec.
The bias is dialed in at -20 (like it should be), but I can not get the offset adjusted right. Oh well, tomorrow is another day.
 

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Those look like winter time amps. What are the performance specs on those beast and what where they designed for?
The transformer in the power supply makes my back hurt just looking at it.

BillWojo
 
Have you replaced the bad and missing tubes, as seen in the first picture? I see at least one 12B4 that has "gone to air" (the one with the white film in the top).

Without all the sockets filled with good tubes, you may not be able to zero out the offset. In fact- even if they're all ostensibly working- if any of the output tubes are out of spec enough, it may interfere with the zeroing.

Regards,
Gordon.
 
Getting 8 tubes working in PP is quite a task. Getting 8 tubes working in OTL is quite a bravery. Getting 30 Tubes working together is a nightmare and madness only found in Dr. Who? I am thinking about jumping to OTL from SET but there's a hellalot of things to mess with there and something could always go wrong.

The cool factor on these amps is off the chart! But getting them work would requires a dedications. But you have already proven that by driving almost half the country to get them. So, I wish you best of luck getting them work and enjoy them.

If it's Matthew Polk from Polk Audio hall of fame, then, I am sure he knows what he is talking about.

Nonetheless, Welcome to AK, Matt!
 
I reckon many of us would be interested in viewing the schematics.

It is often beneficial to review the protection and noise capabilities of old amps - advances in noise measurement make it easier to appreciate and improve levels, and better parts such as fuses could keep the amp alive for decades to come.
 
BillWojo said:
Those look like winter time amps. What are the performance specs on those beast and what where they designed for?
The transformer in the power supply makes my back hurt just looking at it.

BillWojo
Click to expand...
I have only had this on for a few minutes but heat doesn't seem to be to much different than a typical tube amp.
I have very little technical information on these. I think they are 35 watts and are intented drive 32 ohm speakers. These were built for a home listening room.
If you had unlimited funds back in 1960, and wanted the best sound system money could buy, you would contact Mirko Paneko and ask him to build and install a system. These amps would likely have been part of that system.
 
GordonW said:
Have you replaced the bad and missing tubes, as seen in the first picture? I see at least one 12B4 that has "gone to air" (the one with the white film in the top).

Without all the sockets filled with good tubes, you may not be able to zero out the offset. In fact- even if they're all ostensibly working- if any of the output tubes are out of spec enough, it may interfere with the zeroing.

Regards,
Gordon.
Click to expand...
Yes, I have replaced The obviously bad tubes. I have not done any testing of tubes, yet.
Thanks,
Joe Y
 
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Damn, those suckers look like they're going to blow the power grid and put us all into darkness. Would love to hear them!
 
megasat16 said:
Getting 8 tubes working in PP is quite a task. Getting 8 tubes working in OTL is quite a bravery. Getting 30 Tubes working together is a nightmare and madness only found in Dr. Who? I am thinking about jumping to OTL from SET but there's a hellalot of things to mess with there and something could always go wrong.

The cool factor on these amps is off the chart! But getting them work would requires a dedications. But you have already proven that by driving almost half the country to get them. So, I wish you best of luck getting them work and enjoy them.

If it's Matthew Polk from Polk Audio hall of fame, then, I am sure he knows what he is talking about.

Nonetheless, Welcome to AK, Matt!
Click to expand...
NYListens said:
Damn, those suckers look like they're going to blow the power grid and put us all into darkness. Would love to hear them!
Click to expand...
They may LOOK like that, but they don't seem to draw much. I would love to hear them, too!
Thanks,
Joe Y
 
trobbins said:
I reckon many of us would be interested in viewing the schematics.

It is often beneficial to review the protection and noise capabilities of old amps - advances in noise measurement make it easier to appreciate and improve levels, and better parts such as fuses could keep the amp alive for decades to come.
Click to expand...
I sure hope to keep these alive for decades. I think I'll post the schematics in the near future.

Thanks,
Joe Y
 
megasat16 said:
Getting 8 tubes working in PP is quite a task. Getting 8 tubes working in OTL is quite a bravery. Getting 30 Tubes working together is a nightmare and madness only found in Dr. Who? I am thinking about jumping to OTL from SET but there's a hellalot of things to mess with there and something could always go wrong.

The cool factor on these amps is off the chart! But getting them work would requires a dedications. But you have already proven that by driving almost half the country to get them. So, I wish you best of luck getting them work and enjoy them.

If it's Matthew Polk from Polk Audio hall of fame, then, I am sure he knows what he is talking about.

Nonetheless, Welcome to AK, Matt!
Click to expand...

I plan to go through a process of balancing out the tubes (however long that takes) and get them up and running. Then, I'll be diving into more details.
I did receive a message from Matthew Polk (yes, THAT Matthew Polk) about these amps. Apparently he also owns a pair of these amps

Thanks,
Joe Y
 
Great score! And judging by the size of those transformers,if you don't like them as amps you could always convert them to welding machines.Bet the car rode real smooth with those in the trunk:)
 
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