RMI-FC100, a single stage audio power amplifier

Excellent, Daniel!
I'm glad that you finish amplifier! Good choice you make!

I am running 200 mA bias per output transistor.

DC offset is 1 or 2 mV cold and 0.5 mV warm.

Credit to Mihai Ruata's design work and credit to Neb (ZDR) for the compact board design.

Did you try with 170mA bias like original design?
I think, Mihai post somewhere in theme, respectful explanation for this...
 
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For perspective RC-100 builders,

I have 2 packages of the GB offerred by Rudi Ratlos in 2016. I received them in 2017 and only opened up to see what was sent. One set is with the shunt regulation pcbs and the other is with the LT3062, as I thought I would like both. I also purchased an extra set of RC-100 and shunt boards from Rudy in 2019, as he wanted to get rid of them.

All of these will be going on the Swap Meet page in a while. If you are interested at present, I can guarantee that you will not pay more than what I paid in 2016-17.` Let me know if any interest or check out the swap meet in a short while.

Myles
 
I blew a channel. It looks like one of the outputs wasn't screwed down tight enough and over heated and blew, it's clearly blown. It's an NJL0281 and I will probably have to check the drivers Q19 (2sc3423) and Q3 (mje15035) as well as the other outputs. Does anyone have a matched set of NJL0281 transistors to sell? Would it be a problem if I just dropped one in or should I buy a few and match them?
 
Hi Luke

I have two NJL0281's left over from my RMI-FC100 project. Don't know if you are aware of it, but there was a problem with the thermal sensing diodes in the early production of these devices. In production, wrong diodes were installed in the devices making it difficult to set the bias. The irritating part is that these devices were not withdrawn from sale and were being delivered many months after the defect was discovered. I suspect the devices I have are in this category.

I live in the Mitcham area of Adelaide. Feel free to PM me if interested.

Keith
 
I have built two channels of the FC100 amp using ZDR's PCB's. When I powerup the front-end PS, all Leds are on but the voltage over de Diode string is not highe than -1.40 VDC. This is not enough to set the bias current.

I have double checked everything but found no errors. Both cahnnels act in exactly the same way. I have also checked voltages and currents according schematic on page 136 of this thread, measured values are all very close to what is stated here.

722983d1545163176-rmi-fc100-single-stage-audio-power-amplifier-rmi-fc100v1-voltages-amp-2-jpg


Enybody any ideas or advice on what else to try to get voltage over de diode string on target (1,5 VDC)