Orange OR120

Guitar Adjuster · Post by **Guitar Adjuster** » Sat Sep 29, 2007 2:49 pm

Any one know who made the PT and OT for these amps? It's a 70's model OR120.

Post by **Brian Wallace** » Sat Sep 29, 2007 3:07 pm

It depends as there was Partridge and Parmeko transformers being used.

Guitar Adjuster · Post by **Guitar Adjuster** » Sat Sep 29, 2007 3:50 pm

Brian,

If I post a picture can you tell? Also can you duplicate them?

Allen

Post by **Brian Wallace** » Sat Sep 29, 2007 8:10 pm

Yes and I am doing a teardown on a Parmeko OT as we speak.

Wicksy · Post by **Wicksy** » Sun Sep 30, 2007 6:12 am

That'll be from an old pix only or120. They used laydowns in those days with the transition about '73 to the Parmeko standups. Very well made iron. Theres a place called PRL in Hudderfield, UK that made the iron for Matamp. I got a replacement OT for a GT-120 i'm restoring. Pretty much the same specs.

Post by **Brian Wallace** » Sun Sep 30, 2007 10:07 am

This one is from a 72 120.

Guitar Adjuster · Post by **Guitar Adjuster** » Sun Sep 30, 2007 11:14 am

Ok, here are some photo's--I was tole it was a 70's something but I have no way to verify. I am trying to clone these trannies or at least get close to them "tone" wise.

Wicksy · Post by **Wicksy** » Mon Oct 01, 2007 9:06 am

Whats the serial number? That'll tell us an date. Based on the pictures, i'd say your amp is anything from '73 to about '76 ish when the Overdrive series came in with the cruddy MV.

The tranny that Brian posted was from the pix only head with the plexi panelled front from about '72 - '73

Guitar Adjuster · Post by **Guitar Adjuster** » Mon Oct 01, 2007 2:18 pm

Brian---do these look like original iron?

Post by **Brian Wallace** » Mon Oct 01, 2007 5:06 pm

I don't know about the MPT-100. What do you think Wicksy?

How about some inside shots so I can see the solder joints?

Guitar Adjuster · Post by **Guitar Adjuster** » Mon Oct 01, 2007 8:05 pm

Brian Wallace wrote:I don't know about the MPT-100. What do you think Wicksy?

How about some inside shots so I can see the solder joints?

It's a 1974 version, it's had the original circuit board pulled out and another type of amp installed (Not an Orange any longer). From what I gather it has the original PT but the OT was replaced back in 94 with who knows what? Do you know the B+ for this PT?

Here are some scarry ass gut shots!!!

http://s43.photobucket.com/albums/e397/ ... 2/?start=0

Wicksy · Post by **Wicksy** » Tue Oct 02, 2007 2:22 pm

For a '74 amp (are you sure its a '74? Serial number should be 11xxx ish).

The PT is definitly changed...likely a MM version. Should be delivering ~500V B+ without tubes installed.

The best way to tell if the OT is legit is if the secondary tap wires are twisted ie each tap has two wires together. It looks ok. As for your circuit board, do you know if it is even a correct Orange circuit in there? Or did the tech remake the PCB? I had to do this with a Matamp GT-120 board. The old 70's PCBs are well known for trace lifting.

Heres the board i made for the Matamp:

Wicksy · Post by **Wicksy** » Tue Oct 02, 2007 2:30 pm

I had a look at your pics...good news is thats the right OT, bad news is i dont think its an Orange anymore

Looks like the FAC isnt working (or exists for that mater) The FAC should be a six way switch with various caps attached to it. Its a variable high pass filter essentially.

I'd advise having it rebuilt. Theres a guy call Rubb over at the Plexi Palace who might be able to help with a PCB template for etching. Then its a matter of populating the board and re-assembling the amp. I can post up some pics of what it should look like inside if you want.