• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Skyline SK-10 Amplifier info?

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I just picked up this cute little 4 tube stereo amplifier. A Skyline SK-10.
Weird little circuit, 1 12AX7, 2 35C5's, and 1 35W4.
Appears to be set up with serial filamants and dual 2500ohm output trannies kicking into 8 ohm speakers.

All the tubes are old Matsuhita branded.

Anyway, It powers up, Apears to work fine, BUT,
If I try plugging in My Real McTube preamp, Soon as i plug it in, Out goes the circuit breaker on the wall outlett. NOT GOOD~!!!

Trout:smash: Good thing I wasnt touching both units or it would have been a friday fish fry!!!

Anyway, The MCTUBE has a 3 wire cord,All common grounded.
The SK-10 Has a 2 wire cord.

When I Use the McTube on my regular guitar amp, It Functions perfectly, So Im Guessing Its an issue with the SK10.

Any Ideas?

I Have The McTube schematic, But after about 2 hrs on google, I cant come up with anything on the Skyline SK-10.
Trout :xeye:
 
The 35W4 only contains a single diode, so half-wave rectification has been done. I have never heard of this make of amplifier before, but in the past, many AC/DC sets were made with the heaters straight across the power supply (sometimes with a barretter in series) and a single thermionic diode providing HT. The idea being that it could be line operated, and of course it does away with the power transformer and the added safey it provides. Putting the power cord in the wrong way brings the chassis to a dangerous potential and results in what you have experienced.

Check Tim Williams (Sch3mat1c's) site line operated 50C5 amp. It even uses the same rectifier, and he has had a similar nasty surprise when connecting to other equipment, in this case burning up a patch cable while trying to connect it to his computer! I would suspect the Skyline has a similar circuit.

:att'n: For anyone else reading this, please don't build line operated equipment... they are freaking dangeous!
 
SK-10 Amp

I would say that it has no power transformer and one side of the AC line is grounded. This was very common years ago as a cost cutting measure. As you can never be sure how your AC outlets are wired, it is possible that your chassis could be floating at 115 volts (US) or 240 volts (UK, Aus etc) with respect to earth. You were lucky not to do serious damage to external equipment not to mention yourself.
If you want to persist with it, get a isolation transformer but it will probably cost you more than the amp is worth.
Be careful.
Cheers
Rob
 
audiousername said:
The 35W4 only contains a single diode, so half-wave rectification has been done. I have never heard of this make of amplifier before, but in the past, many AC/DC sets were made with the heaters straight across the power supply (sometimes with a barretter in series) and a single thermionic diode providing HT. The idea being that it could be line operated, and of course it does away with the power transformer and the added safey it provides. Putting the power cord in the wrong way brings the chassis to a dangerous potential and results in what you have experienced.

Check Tim Williams (Sch3mat1c's) site line operated 50C5 amp. It even uses the same rectifier, and he has had a similar nasty surprise when connecting to other equipment, in this case burning up a patch cable while trying to connect it to his computer! I would suspect the Skyline has a similar circuit.

:att'n: For anyone else reading this, please don't build line operated equipment... they are freaking dangeous!

Yep,, Its clearly a death trap!! No power tranny,, 117V Line operated. I'll post a picture of it tomorrow. I got it for $3.00US at an estate auction, At least the 12AX7 is worth that.
Maybe I'll shoehorn in a Transformer and rewire it into something safer.
Trout
PS
Sad to,, At Full power, Not even a hint of hum or noise!!
 
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