Good day all.
I recently picked up an old oscilloscope that I thought would be a handy tool for trouble shooting my amp projects. It is a Telequipment Serviscope s51-a. It works like a charm and is in wonderful working condition. I have run a few tests with and such, but now it comes down to using it properly.
I'm working a power amp at the moment using an HH scott UL output transformer. The layout can be found on this schematic
http://pacifictv.ca/schematics/scott210c.jpg
I measured resistance between taps to double check what the schematic is indicating. As far as i could tell everything checked out.
Having an oscilloscope now, I thought there might be some better way of testing the transformer, or the amp in general to find out where the problem is. I have never used an oscilloscope before, and was hoping someone could give me a little run down on what magic can be done with this tool to give me some insight into if my OPT is wired wrong, or merely bunk.
Thanks in advance.
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Never mind. I got some sound coming out of the power amp now. Sadly it is very distorted and ugly and when I turn the volume all the way up, the sound cuts out completely. I think I may have something wrong in the initial gain stage before the PI. If anyone has any ideas, i'd love to hear them, but if not I'll pick away at it and see what I can figure out.
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I did some voltage checks and my idle voltages are as follows.
bias : -47.4
6l6 plates : 489
6l6 screens : 487
6sl7 PI plates : 485
6sl7 PI Cathodes : 8.1
12at7 driver plate : 229
12at7 plate cathode : 4.12
12at7 CF line out Plate : 417
12at7 CG line out cathode : 126.4
I haven't taught myself how to do load lines yet, but I think that is my next step. It seems to me like the cathode voltage on my driver is far too high.