Xfmrless Tube amp, can it be made safe?

[443]

Someone brought this into my shop, and I did a little researching, I saw where a lot of people had these things and while I saw lots about how it could electrocute the user, I never found one story about someone being electrocuted by one of these things.

Question is. Can it be made safe? Other than converting it to use a real plate transformer, etc, could something be done such as simply a 1:1 isolation transformer on the input line with a good grounded cord and possibly a GFI? I question whether the amplifier is worth the expense of any of that, as it probably performs poorly, however, monetary issues aside, can it be made safe with those things or some other method?

Pics:

 

[paws264]

Someone brought this into my shop, and I did a little researching, I saw where a lot of people had these things and while I saw lots about how it could electrocute the user, I never found one story about someone being electrocuted by one of these things.

Question is. Can it be made safe? Other than converting it to use a real plate transformer, etc, could something be done such as simply a 1:1 isolation transformer on the input line with a good grounded cord and possibly a GFI? I question whether the amplifier is worth the expense of any of that, as it probably performs poorly, however, monetary issues aside, can it be made safe with those things or some other method?

Pics:

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That thing uses a "Voltage Quadrupler" on the line voltage to get the B+ therefore, make sure you use the highest rated "Power On" switch since all the current runs through there.

Look for the "Point of diminishing returns", I would get that thing out the door with as little investment of time and money as possible.

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[prowler]

That toms old amp you got there? He had 1 like that.

 

[Wire Weasel]

Hecho en Mexico

 

[Shockwave]

Since the DC ground on this B+ supply is not isolated from the AC line, the DC supply is not grounded to the chassis. The DC ground is floating while it gets it's RF ground trough the ceramic coupling caps. Not knowing this makes it dangerous once the cover is off. Make sure the ground plug has not been defeated and there is literally no chance of being shocked from the outside of this amp.

 

[office888]

That is probably the lightest looking tube amp I've ever seen.

 

[unit_399]

Question is. Can it be made safe? ...could something be done such as simply a 1:1 isolation transformer on the input line with a good grounded cord and possibly a GFI?

443 -
Actually this is a good solution as it would isolate the line from the dc supply. The transformer could be added externally, and the dc supply ground could be connected to the chassis to eliminate shock hazard. Isolation transformers are pretty easy to come by too. GFI ??? Why not. There is no such thing as too much safety.

- 399

 

[Captain Kilowatt]

That is probably the lightest looking tube amp I've ever seen.

That's because half of it is missing.

 

[443]

Poast! Bringing up old shiz. Wazzup?

 

[kc8adu]

i remember those things.had a guy down the road 20 years or so back that had one.he would get drunk,lock down the mic,and start playing guitar and bellering.
it would go about 2 hours of that and kabluey!.
i rebuilt it several times.and its plate caps were soldered like the one above.
as cheap as they came.3 36kd6's later and some other stuff it was ready for the next round.he had 3 amps and one night he blew up all 3!

 

[443]

i remember those things.had a guy down the road 20 years or so back that had one.he would get drunk,lock down the mic,and start playing guitar and bellering.
it would go about 2 hours of that and kabluey!.
i rebuilt it several times.and its plate caps were soldered like the one above.
as cheap as they came.3 36kd6's later and some other stuff it was ready for the next round.he had 3 amps and one night he blew up all 3!

That's an old friend of mine's amp in the pics, I never did do anything with it, just gave it back to him the other day, it was chilling in storage along with the rest of my radio gear, even my ham gear... Took it down last spring to make room in my shop for more regular work and was so busy all year that I just now got around to setting the station back up. I set it up where it won't ever have to be moved or taken down again to make room for anything else, so it should be up for good now, slowing piecing it back together and looking forward to using it this year, the DX seems to be rolling very well, already made tons of 10M contacts in my mobile, and it's only 200Watts on a mag mount wilson so conditions must be getting good. Was total crap this time last year, no conditions...