Burns Orbit Three

[welsh_chris]

One thing that I would advise anyone using or repairing one of these to look out for. On the one that I serviced last year, the taps on the mains transformer were brought out to a tag strip on the outside of the chassis. If anyone reached inside the cabinet and stuck their fingers into the gap between the chassis and the front of the cabinet, it is possible to touch these live (mains voltage!) terminals. Presumably the idea was to make changing from 240 volt to 120 volt operation relatively easy without the expense of a voltage selector switch. I permanently spliced the wires together with heat shrink sleeving over the joints, thus eliminating the potentially lethal exposed terminals.

[Ted]

I have to tell you that it may just be the vilest sounding amplifier I've ever heard. Slightly improved by modern speakers (the original Burns-branded Elacs last about 25 seconds at full power). Anyone who doesn't get a headache from one of these is probably under 21.

[J M Fahey]

GOSH !!!
GAWK !!!!
A nightmare come true !!!
Although .... it should have "the best sound in the World" , it has all Wima capacitors, plus "Mustard" caps and ...... suspense ..... carbon composition resistors, all 1963 vintage !!!!!!!!!
And transistors are "sweet sounding Germaniums"
Eat crow, "parts-are-the-sound" crowd !!!

[Ted]

Willie

Here are some pics from inside of one that hadn't been too badly messed with.

All three of the ones I've done conformed pretty closely to the schematic I posted earlier.

[willy barden]

I took on a rebuild of an Orbit 3 some years ago without knowing that it had been considerably modified inside. Reverse engineering is proving tricky - has anyone got good photos of the internal layout as it should be? Incidentally, this one has (inaccurate) schematics/ circuit diagrams stapled to the inside of the box - they are as much use as a chocolate fireguard but not as tasty!

[imaradiostar]

I guess it's collectible but whenever I find amps like that I want to gut them and build a little tube combo out of them- especially if they look cool and have half decent speakers!

jt

[J M Fahey]

Fascinating. A contemporary of the famous Vox T60, about the same technology.
Must have terrible crossover dostortion, impossible to correct.
A couple pictures (including the guts) might be interesting.
Thanks for posting.

[welsh_chris]

It's working now. The smoke that the customer noticed when first switching on after years (decades?) of storage was dust burning off a power resistor at the back of the chassis. Cleaned the volume controls etc. and it plays well enough. Can't turn the tremolo off, needs a new foot switch. Biggest concern is the exposed mains terminals where you can change the transformer taps for 120 volt or 240 volt. Certainly wouldn't pass a PAT test today! I'll permanently splice these wires and insulate with shrink tube if the customer wants it. Other wise leave it as it is a suggest it's just a museum piece to look at but not use.

[Ted]

I've done a few of them now. The transistors in the power regulator darlington have been dead on all of them. This causes the supply to rise to the unregulated 50V level. (Should be 36V or so).
I've replaced the regulators either with discrete silicon or a silicon TO3 Darlington. For the germanium O/P trannys I use ASZ15s which are still just about available and a tenner a pair. I don't have any qualms about changing the pre-amp transistors for silicon, with a bit of bias tweaking. These amps sounded terrible in the first place, so there's no point trying too hard to make them sound good.

[welsh_chris]

Here's a greyscale image - more readable than the black and white.

Hi Ted, thanks for posting this. I've just been asked to repair an Orbit 2, the customer says that he's also got an Orbit 3 in need of service. Not sure whether it'll be economic to repair either at this stage, Ge transistors are quite rare today and expensive if you do find any!

[Ted]

Here's a greyscale image - more readable than the black and white.

[Ted]

Here it is - I've cleaned it up a little

[teemuk]

Can you post the schematic here for reference for rest of us who might someday come looking for one, please?

[Ted]

Two channel w 2 inputs each and seperate treb-bass-vol, a multiple position rotary voicing selector switch, switchable 120/240volt mains, Footswitchable Vibrato/Reverb, 3x10" Speakers, a Serial Number in the mid 300s...VERY COOL!!!

When it was new, it would have cost more than an AC30. They sold them in Harrods ( a very posh London shop). Even when they're working well they don't sound very lovely - early transistor sound and cheapo 10" speakers give me a headache. Those early germanium power transistors deteriorate with use and age to make things worse.

The best details - the red lacquered, hand made wooden pedal and the optional Studio/Normal switch which switches in a bigger capacitor to the emitter circuit of the output stage driver.

A toggle switch to select between 110 and 240V? For those of you who live in 110V countries this isn't a problem, I suppose. Like the stupid rotary selector on Twin reverbs...

[Ted]

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