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new TRT 100 findings [message #8083]

Mon, 22 January 2007 07:27

stevem
Messages: 4733
Registered: June 2004
Location: NY

Senior Member

Over the weekend I lent my 2001 TRT 100 all tube Kustom to afriend to gig with while I repaired his amp, and when I got it back on sunday I had time to really run it thru its paces and address some things about it I wanted to improve.I picked this head up when the muscians friend folks where blowing them out for 400 bucks, down form their original price of over 700 bucks, and now I know why!
The amp is made ok, or as you would expect for something made in china, but it does have some strong points.
It has nice semi torodal power and output transfromers, a full size reverb pan, and in their USA done design Kustom kept all the potential A/C preamp hum causing wiring on the back wall of the amp with all the preamp section on the front wall.they also have a nice vented steel cover on the back to protect the phase inverter and the 4 output tubes and its these 6l6gc output tubes that where part of the mystery I came across.
Since I got the amp I have only used it 4 times for rehearsal, and I never liked the lead channel as for me I needed more highs then it could give, and also the amp did not sound like it was putting out 100 watts rms thru its 4-12 cabinet, and as it turned out I was right.
In testing it out on sunday I found it to be out putting only 62 watts RMS, a far cry from 100.So I did some more test at different impeadance loads to see if the output trnasformers secondary wires where hook up right, as I have come across this problem with many tube amps before, but they where right.Then I checked out the schematic and noticed that the output tube sockets where wire with pins 1 and 8 being common and I also noticed a location by the output tube bias adj pot where a resistor was left out and that really made me wonder and pull my beard.
So I grabed my marshall and yanked out its four EL34 output tubes, stuff them in the Kustom and reset the bias and fired it up.Sure enough the amp then put out 84 watts RMS. The only thing that may be a problem with this change is that the EL34s unlike the original 6L6GC tubes need more heater current as the voltage with the 6l6s was 6.1 and it dropped to 5.8 volts with the el34s so I need to run a long test a see just how hot the power transformer may get do to the extra load. If worse comes to worse I can install a seperate filiment transformer just for the output tubes.
I do not know what the story may be with the TRT100s litle brother the TRT50, maybe they got the output transformer right in that model for its 6L6GC output tubes, it would be interesting to find out, but know I know one of the resons why they never sold that well and had to blow them out at that 400 price, you`ve got a amp advertised as being 100 watts rms wimpin out a 60 watts rms due to its mismatched output tubes and output transformer!