Orange/MatAmp OR120 output transformer info needed

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RB
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Orange/MatAmp OR120 output transformer info needed

Post by RB »

A good friend of mine recently purchased a 1970-72 OR120. It arrived DOA and I am helping him sort it out. I cant believe what was done to the amp over it's lifespan. I have rewired/changed/ fixed every shoddy/kluged up mess and have it working. I cant believe how loud the amp is.

There is one remaining issue. It does not have the original OT in it. It currently has a UL OT with no markings and the owner purchased an OT that was removed from a MatAmp to replace the UL OT.

I need to know how to wire this OT into the amp. It came without documentation and I have hours on various forums trying to get a clue on what wire is what with no luck. The markings/labels on the OT are worn/smeared and I cant decipher anything that was printed on the labels.

On what appears to be the primary are 2 pair of wires. 1 pair red & black 1 pair orange & black.

On what appears to be the secondary there are 4 pair of wires. 2 pair green & blue and 2 pair brown & yellow.

Thanks in advance for the help I know that will come from the what I consider the best and most mature amp forum on the web.

Regards
Randy
Stevem
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Re: Orange/MatAmp OR120 output transformer info needed

Post by Stevem »

First off if that OT that's in there now can produce more than 100 watts RMS ,then why not leave it in there and just drop off the two UL winding connections and put a screen supply back in place like stock since you have to do that anyway?

2) it does not sound like to me that the Ot you want to install has the needed 4, 8 and 16 ohm secondary taps from what you have discribed by the color codes to me!
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!😊

Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
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didit
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Re: Orange/MatAmp OR120 output transformer info needed

Post by didit »

Blue, Red & Brown just one pattern of common colours for the primary -- with black, green, yellow, orange for secondary. Other patterns are out there however. One might carefully work it out with multimeter. But Matamp has customer contact at their website, hopefully providing the definitive information upon request by end-of-day.

Best .. Ian
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Phil_S
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Re: Orange/MatAmp OR120 output transformer info needed

Post by Phil_S »

Odd description of that OT. Sometimes an output transformer is wired with more that one independent secondary windings...when there are 2 of them it is called bifilar wound...not sure what 4 make :o
More commonly, the secondary is one long coil that is tapped part way for 4-8-16 ohm secondary impedance, with, usually, a black for the "0" wire. You can easily test for continuity with your meter set to Ohms. I'm curious if any of them are connected internally.
Stevem
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Re: Orange/MatAmp OR120 output transformer info needed

Post by Stevem »

With the doubling of the colors it sounds like it's a Partridge brand OT.
Does it have steel bells on each side?
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!😊

Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
RB
Posts: 126
Joined: Thu Apr 06, 2006 11:36 pm
Location: San Diego CA

Re: Orange/MatAmp OR120 output transformer info needed

Post by RB »

Sorry for the slow reply but I have been hammered working on a restoration of a Webster model 80 wire recorder. Thanks to all that have taken the time to reply. I will attempt to respond to all remarks in this post.

Stevem
If I owned the amp I would NOT change the current transformer or convert it to non-UL. It sounds amazing as is. The owner wants a 4 ohm output which the current transformer does not have. He plans to use it as a bass amp on occasion and all his bass cabs are 4 ohm.

We cant think about this transformer in terms of what we are used to seeing. The primary has 2 windings and 4 wires which suggest that 1 wire from each winding would be connected together to create the CT for the HT/HV/B+. The secondary windings are reminiscent of the Hammond Audio/Hi-Fi transformers that used multiple secondary windings and you selected a combination of wires to get the correct turns ration/impedance.

It does have steel bells on both sides of the transformer with all the leads exiting through rubber grommets. If I could read the printing on the paper tags I think there would be a manufacturer’s code or some other info that would make finding info on the web easier.

didit, Phil_S,
Like I stated above we cant think about this in terms of what we believe are standard color or wiring configurations. Thanks for the recommendation of Orange UK. Haven’t received a reply at this time.

I had measured the resistance of all the windings and checked for the existence of any internal connection/shorts/short to frame before I made the initial post. I should have included that info at that time.

The Orange/Black primary winding is 14.7 ohms (I believe this to be the outer most winding of the 2).
The Red/Black primary winding is 11.9 ohms.

The Blue/Green secondary windings are both 1.5 ohms.
The Yellow/Brown secondary windings are both 1.3ohms.

Regards
Randy
Stevem
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Re: Orange/MatAmp OR120 output transformer info needed

Post by Stevem »

Well if you have a veriac and you think you know what the outers of the primary are power it up and measure the voltages on the big secondary wires.

With those resitances you posted on the secondary side you do not have a direct 8 ohm or 4 ohm tap unless some of those wires get hooked in parallel.
A 4 ohm tap will read .5 ohms, a 8 ohm .71 and a 16 ohm 1 to 1.3 ohms.
Note that you can only hold one meter lead with your fingers to make these very low ohm measurements, you must use one clip lead otherwise your reading will be off if you make the wires test connections with both your hands.
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!😊

Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
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didit
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Re: Orange/MatAmp OR120 output transformer info needed

Post by didit »

Suggestion was contacting http://www.matamp.co.uk/ as they seem to actually know what side is up vs just selling antique multi-coloured smoke.

Steve has excellent suggestion to test. However, a 6.3/5V heater winding will also work in a pinch. Do be careful as dangerous or at least startling voltages can be present and unpleasant.

Best .. Ian
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