Repair of a Rogers A100 Integrated Amplifier
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- Опубликовано: 4 июл 2022
- This old Rogers amplifier had a problem with the power amp section on one channel. Transistors had been replaced previously but issues remained.
The power amp module is so well laid out it was easy to reverse engineer and simulate. Back to the circuit and after some hunting around we find an instability issue that meant high currents were being drawn. With this understood all is looking well until we look at the distortion measurement. Something was amiss and I suspect the transistors that were previously fitted may not have been the real deal. Replacing the transistors with some modern equivalents got things sorted out.
These old amps are so time consuming and normally wouldn't make economic sense to repair. The Rogers name intrigued me however since the first loudspeakers I bought were the Rogers LS6. I still use these in my workroom today.
Future work - Possibly...
1. Change the op-amp for something quieter and look at the stability of the circuit.
2. Upgrade the volume control.
3, Reduce the gain - with a signal from a modern source the volume control is barely off zero. 
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Thanks for explaining the Zobel network effect. You learn something new everyday.
Great video, keep it up bro.
Excellent video. Could you put the spice files on line for the amp please? You do have some envious test equipment. what was your distortion analyser? Have you any idea where I may find a full circuit diagram? I have a problem on the preamp and I cannot find a schematic on the internet anywhere. Thanks Peter Thomas
drop me an email for the spice file
I remember this amplifier well. I don't recall it being over noisy but I do recall it having a really nice clean sound. Never sold well at all. Not the most attractive looking amplifier, customers did not like the look of it and never even asked to hear it. Looks nice and almost new in side. Fake transistors?? surely not! very hard to believe.
I quite like the look of it
what is the simulation software microcap.
what do you mean by you can't show schematics why not.
a really nice amp it worth replacing the op-amps? what you suggest. what is the volume pot is it log or linear?
what's a good replacement attenuator with surface mount carbon resistors.