Identifying my "new" Orange - 1972 OR120 Issues

[shai-hulud]

Hey folks! First I want to say how invaluable this forum has become for me learning new things about these most outrageous amplifiers. Anyways, the other day I finally managed to pay off my vintage Orange and I think the store has misidentified it. They said it was a 1972 OR120, but judging by the Orange Amp Field Guide I think it's a pics-only ORS100 - based on the blackened Orange logo on the top right on what I think is a plexi-glass face-plate. There is no serial number or model number on the back, but it doesn't appear as if they have been painted over or scratched off. On a repair receipt the tech gave the serial number of FA9225B11T2, which I'm assuming came from somewhere inside on one of the components. Here are some pictures I took, hopefully you guys can help me figure out what I just purchased! Also, are these Ruby EL-34's they installed really the best tubes for this head?? Thanks and Merry Christmas!
















edit: forgot to mention that I think the power input on the left on the back may be some sort of mod, maybe to plug into North America?

[Randy Bass]

I can't tell you for certain why the serial number is missing, but I think they were handwritten in ink at the time. It could have simply been cleaned-off by mistake (or deliberately!) at some point in the last four decades. It looks like the number the tech put on your receipt is just the model number of the cooling fan that was added inside the amp. It's a beautiful amp, whatever model it is (looks like a GRO to me).

[bclaire]

Almost looks like it never had a model or serial number written in...

The modern power cable connector looks like a nod to safety more than anything else to me...

[shai-hulud]

I'm getting some feedback that this is an OR120 and that Orange made some OR120s in the early 70's with the blackened logo (like the GROs seem to have). Would you guys be able to diagnose any mods and positively identify this puppy if I take some closer pictures of the insides? I'm pretty sure I can get at the circuit board and whatever else is needed, I just haven't found time to play with it since it came back from the shop.

Edit:
Also, Randy hahah good call on spotting the fan's serial number. You have eagle eyes.

[shai-hulud]

Unfortunately I seem to be having some problems with this head. First it was the fuses and the tubes going 40 mins after getting it back from the tech. Then when I got it back again, it just shut down after only 20 minutes of rock and roll. Pilot light just turned off and none of the tubes seem to be running anymore. I've been taking it to a tech from the store I bought it from since it's still under warranty, but this is the third or fourth time, and I have a feeling that when these guys are testing it out after repairs they aren't playing it very loud or for very long. Since this amp has only one volume knob, naturally I tend to play it pretty loud and a set could easily last for over an hour. I've been told that much of the wiring is original, but that there have been some mods done, not sure if this is what's causing the problem or if I just need to get super heavy duty tubes or what? I'm hoping one of you might be able to shed some light on this murky situation. For the precious minutes this amp has functioned for me, it sounded like the bees knees and pretty much exactly what I had been looking for.

[bclaire]

Super heavy duty tubes is probably the answer. Some cheap Chinese tubes will probably melt down in this head. The voltage on the back says 115 which is NOT what we see out of the wall typically. Therefore the plate voltages will be higher and you need sturdier tubes for sure... but that's only my first thought. With an older amp, it could be anything.

[a.hun]

+1 to that. These amps do need particularly strong power valves. They run them at unusually high voltages and many modern production valves just won't take that for long at all. (As in sometimes less than a couple of hours!) I'd suggest fitting JJ or SED 'Winged C' brand Svetlanas and getting your tech to bias them as cool as possible to prolong life. Or better still try and surce some decent old production valves - expensive but should last much better.

If your tech isn't familiar with old Oranges they may be treating the amp much as a Marshall. This can lead to problems. You could always refer them to this thread which is pretty much valid for all OR120s:
http://forum.orangeamps.com/viewtopic.php?f=2&t=42750" onclick="window.open(this.href);return false;

There is no way of knowing exactly what those Ruby valves were, Ruby Tubes being a supplier not a manufacturer...


Andy.