Trident 65

Twenty five years have passed since Trident Recording Studios made the decision to build their own Multitrack Recording Console.

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Trident 65

Postby brianroth » Fri Jan 04, 2008 3:47 am

I had an email asking about a replacement PSU for one of those desks.

What rails, and at what current rating are required?


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Postby Bo Hansén » Thu Jan 10, 2008 8:13 pm

Hi Bri,

Yes, the series-65 and 75 psu are a problem, (as some other UK made console psu)

The first editions of series 65 and 75 in the middle of the 1980´s, they use the Trimix and series-70 psu, and that was a very good design.
The regulators was 78 and 79HGK, a TO3 4 terminal 5 amp adjustable type for the +/- 18 volt audio rails and uA78P05SC TO3 2 terminals 10 amp for the 5 volt "logic" rail, and a LM317HVK TO3 for the 48V phantom rail.

But then they build a cheap psu especially for the S-65/75 with less current delivery on each voltage rail.
In this units thye use a usual 78T18-CT (3amp) and 7918-CKC (1,5amp) for the +/- 18 volts audio rails.
Later om they add a extra pass transistor on the 7918 regulator, so also this was capable for 3 amp as the 78T18-CT. (because there are not any 79T18 manufactured)
Then they use a 78T05-CT (3A) for the 5 volt rail and a TL-783_C for the phantom rail.

This psu (I think it is the psu you talk about) is very weak and can only feed a smaal S-65 consol with ok result.
The psu have also a very bad 0 volt/ground design and generate a lot of rippel products in the ground system.

I have rebuild some of them, but the box is verry small, so it not so easy to add bigger mains transformer, filter caps, bridge and more pass transistors.
It is better to buy or build a new psu.

I will guess that a 24 input, 8 group, 16 monitor console will draw total 1,5 amp on each audio rail and 2-3 amps on the "logic" rail for all LED´s, VU-lamps and logic circuits.
So around the dual current for each rail shall you have as target for this size of console.

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Postby JSLyson » Sat Jan 12, 2008 10:54 pm

Hi Bo,
So what about the Trident series 80B supplys.... Mine Is original and has worked all these years just fine. But you hear alot of people say ALL Trident PSU are bad? My original 80 series looks like it is built very well. The only problem I see is a lack of saftey feature if somthing fails in the supply? And two of the transistors get direct fan and the other two on the outside do not. Any thoughts and input? Also about the +/- 20V? I dropped mine down to +/-17V changing a zener diode after uping the mains selection. Seems fine but i get a spike when amp powers up? Thank You, John
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Postby Bo Hansén » Sun Jan 13, 2008 4:29 pm

Hi John,

Yes, the Series-80 PSU have work fine around the years.
It have a 5 transistor discrete regulation design, and two of transistors are TO3 power "pass transistors" connected in series.
One is a "pre-regulator" and act as a coarse regulator, and the second as fine regulation with the finaly voltage amount include the adjustment and protection.

On aprox. 30 consoles that was sold to the Swedish LRAB broadcast corp. we use a modifyed psu system, there the psu unit delivery +/- 24 volt insted for +/-18 (20) volt and then we have a lot af regulator cards onboard in the console that take down the 24 volt to 17 volt.
There was regulator cards for different module sections, so if ther was some module fault, there was still other in and output module sections that was ok and ready to work.

Also the Trimix/series-70 psu have run ok around the years, but the first issue of the TSM consoles have a hybride Trident/OEM brand psu, that run very hot, and have a lot of problem. (later on they use same design as S-80 psu)

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Re: Trident 65

Postby John Frings » Tue Dec 18, 2012 9:01 pm

Fortunately you have several options. You could do what I did with my 65. I purchased two new Power ones, I believe they are 7amp, They supply the main rails and the original supplies everything else such as the meter lamps, 48V and leds on the console. It worked out fine. I would probably opt for even more amperage if I were doing it again. There is also someone listing a variety of new power supplies for The tridents including the 65 on ebay. Go to musical instruments, then on the left menu select pro audio and then , live and studio mixers, then type in trident. They have had these listed for many months. Not cheap but they look to be well built. Either way you can figure on spending about a $1K whether you go the Power One route or buy one of those listed on ebay. You will notice some sonic improvement with better supplies. I did. Jim Williams was a big help on this so you could talk to him as well.
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