~1972 Orange OR-80

Maybe someone can help you date your Orange Amplifier?

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thedudear
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Joined: Fri Jul 06, 2018 11:29 pm

~1972 Orange OR-80

Post by thedudear » Sun Nov 11, 2018 12:32 am

Hey all, just got my OR-80 that I purchased over the summer back from my tech.

A myriad of issues with it (mostly) sorted out, I'm looking to get some input on dating this thing. It was sold as a 72' OR-80. Looking at the Orange Field Guide, that seems to match up except that the FAC "squiggle" starts at the bottom, as opposed to the top like some have suggested for the 70's amps.

I'm still not quite sure it's working correctly... it's super "farty" when you're not absolutely diming it, and if you do dime the amp, it squeals, even if the guitar volume is rolled down all the way.

S/N is 80035, but I read that serial numbers don't mean much. I was hoping it meant it was the 35th unit of the OR80 series >_>

The knobs are not original, i'm working on a fix for that. Ordered some new ones from Orange directly but theyre the wrong spindle size.

The OT is replaced with a Toneclone, any opinions on these?

There was a bunch of issues with the amp, a severed trace in the feedback loop, a bad bias mod (was running the tubes lean), some incorrect resistor values were all contributing to an amplifier that was totally unplayable. All sold as a "fine, working condition amp" :shock:

Link to the OR80 photos: https://imgur.com/a/8D8yYXp

Cheers guys and gals

Nick

LD50
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Re: ~1972 Orange OR-80

Post by LD50 » Sun Nov 11, 2018 4:08 pm

The external shots I can see are not particularly helpful re working issues!

The squeal is parasitic oscillation (poor wire routing - or more commonly a missing internal shield from the inputs.

We cannot be sure what your tech did. It should be pretty clean and crisp up to half volume even with humbuckers.

thedudear
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Joined: Fri Jul 06, 2018 11:29 pm

Re: ~1972 Orange OR-80

Post by thedudear » Mon Nov 12, 2018 3:14 am

Hey LD50, Ill get some internal shots soon enough. I also suspected parasitic oscillation, but my tech was unable to reproduce this. Is this a problem that could react differently with a resistive dummy load? It's puzzling since its such an obvious problem, turn the volume up, the amp output clicks and dies (at least in the audible frequency range). ???

I might take it into my own hands and tool up here for some diagnostics. I have a history of working with high voltages and electronics, but I have faint knowledge on how tube amps work. It will take some studying.

Cheers,

Nick

LD50
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Posts: 62
Joined: Thu May 19, 2016 8:35 pm

Re: ~1972 Orange OR-80

Post by LD50 » Mon Nov 12, 2018 2:03 pm

thedudear wrote:
Mon Nov 12, 2018 3:14 am

Is this a problem that could react differently with a resistive dummy load? It's puzzling since its such an obvious problem, turn the volume up, the amp output clicks and dies (at least in the audible frequency range). ???
Cheers,

Nick
Yes, classical PO
Is the shield present inside (a lot turn up with them missing!)?
Some amps use an aluminium shield to cover the bottom of the amp creating a 'Faraday' cage.
Some amps only do this when the amp is out of the head cab and the guts are exposed!
Decent hi res pics (global and close ups of the inputs) will probably be helpful.

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