Bruce Weiland
Well-known member
Hello again Adults and Adulteresses, :ROFL:
I hope I didn't offend anyone. :bowdown:
I recently bought a pair of VTL MB-225T's. They were originally manufactured in January of 1993, and update to 6350 phase splitters, and other updates in 2000, by VTL. (I bought a TL-5 from the same era, variable feedback adjustment - no manual).
These amps were designed with the EL34's. The circuit board has a label of MB 350. VTL never made any 350 models, to my knowlege. But Manley Labs did. However, as you may know, Manley Labs will not answer any VTL questions, even though their employees signatures are on the inside of my 1993 equipment. I am sure it has to do with legal consideration related to the split up.
I do have the owner's manual, but it is VERY rudimentary. I would like to better understand the tube layout.
Are the 8 output tubes paired front row to rear row, left to right in each group of four, or left bank of four to right bank of four, for push/pull?
One of my amps has a 2 amp, but the other has a 4 amp, B+ fuse. I am sure at least one is wrong.
My initial two emails to VTL had gone unanswered. I did call for at least some info on the B+ fuse. Unlike the AC fuse, which is a slow blow, according to Bea, it should be a fast blow. She said two, or three amps. She did not seem too confident when she said that.
The previous owner had all the bias pots turned all the way up. That would have been too much with the old tubes, but a dealer had put in new tubes without checking the bias.
That eventually took out a tube, and the fuse. I was lucky. All the tubes were biases over 500 mV. The recommendation is 275 to 300 mV. Boy those amps were running hot!
There does not seemed to be any info on the TL-5 line stage. I have ferreted out a bit. It is a two chassis, dual mono, tube pre, with tube regulation. It has four stereo inputs, switched by 8 silver contact toggles, a volume control, and a left and right trim knob that dials in or out negative feedback.
OK folks, any info, schematics, etc. for me.
I appreciate any response.
Bruce
I hope I didn't offend anyone. :bowdown:
I recently bought a pair of VTL MB-225T's. They were originally manufactured in January of 1993, and update to 6350 phase splitters, and other updates in 2000, by VTL. (I bought a TL-5 from the same era, variable feedback adjustment - no manual).
These amps were designed with the EL34's. The circuit board has a label of MB 350. VTL never made any 350 models, to my knowlege. But Manley Labs did. However, as you may know, Manley Labs will not answer any VTL questions, even though their employees signatures are on the inside of my 1993 equipment. I am sure it has to do with legal consideration related to the split up.
I do have the owner's manual, but it is VERY rudimentary. I would like to better understand the tube layout.
Are the 8 output tubes paired front row to rear row, left to right in each group of four, or left bank of four to right bank of four, for push/pull?
One of my amps has a 2 amp, but the other has a 4 amp, B+ fuse. I am sure at least one is wrong.
My initial two emails to VTL had gone unanswered. I did call for at least some info on the B+ fuse. Unlike the AC fuse, which is a slow blow, according to Bea, it should be a fast blow. She said two, or three amps. She did not seem too confident when she said that.
The previous owner had all the bias pots turned all the way up. That would have been too much with the old tubes, but a dealer had put in new tubes without checking the bias.
That eventually took out a tube, and the fuse. I was lucky. All the tubes were biases over 500 mV. The recommendation is 275 to 300 mV. Boy those amps were running hot!
There does not seemed to be any info on the TL-5 line stage. I have ferreted out a bit. It is a two chassis, dual mono, tube pre, with tube regulation. It has four stereo inputs, switched by 8 silver contact toggles, a volume control, and a left and right trim knob that dials in or out negative feedback.
OK folks, any info, schematics, etc. for me.
I appreciate any response.
Bruce
