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Roender'S FC-100 - Group Buy

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W

wineds

Member
Joined 2006
pinnocchio said:
Guys, I need some help please...

As per my previous posts, one of my FC-100 module died some time ago. It kept burning PSU fuses so I checked it but couldn't find the issue. After chacking some more, I realized that most output devices had been destroyed. So I went ahead and ordered a bunch of N and P and matched them, soldered them to the PCB and changed the 15034-35 drivers.

Checked all voltages from shunt and PSU before, checked fuses and powered on. Amp powered properly and I started the calibration process, that is bias. I turned it all the way to 38mV (reading across output resistors) and then after a minute or two, D2 went very dim and bias dropped to 0mV... Heatsink got a little colder and then D2 came back fully lit and bias went back to normal. On next power up, D2 kept very dim but I also realized that it was also D7 that was dim and bias stays at 0mV.

I'm guessing something is wrong with the input stage, probably got damaged when the output stage got destroyed. I can check voltage reading but I don't know what to look for really... Could the pre-drivers be damaged as well? If it is the case, Q19, Q20 are obsolete and because of this, finding a match set is not going to be an easy task... I don't mind paying but I want to be sure it is the problem.

Thanks
Do
Click to expand...

Hi Do. Sorry to hear about your trouble. I still have some 2sa1360/2sc3423. Closest match I have is hfe 158/183 which is not bad as there was about hfe 20 difference between all of them in my build. Let me know if I can help.

Cheers, Paul
 
anatech

anatech

Administrator
Joined 2004
Paid Member
Hi Do,
Cover the shipping and I'll do my best to help you out. If parts are needed, you can supply them. Or ship it with parts and I'll make sure you get the unused ones back. Do me a favour and ship with the heat sink you are using.

I'll PM you my details, and if you are okay with the arrangement just let me know when you have shipped so I can watch for it.

Best, Chris
 
pinnocchio

pinnocchio

Member
Joined 2010
quebecdiy.forumactif.com/
wineds said:
Hi Do. Sorry to hear about your trouble. I still have some 2sa1360/2sc3423. Closest match I have is hfe 158/183 which is not bad as there was about hfe 20 difference between all of them in my build. Let me know if I can help.

Cheers, Paul
Click to expand...

Hi Paul,
Hold on to them for about a week or two, I'm traveling these days and will not have time for anything.
Thanks!

anatech said:
Hi Do,
Cover the shipping and I'll do my best to help you out. If parts are needed, you can supply them. Or ship it with parts and I'll make sure you get the unused ones back. Do me a favour and ship with the heat sink you are using.

I'll PM you my details, and if you are okay with the arrangement just let me know when you have shipped so I can watch for it.

Best, Chris
Click to expand...

Hi Chris,
That's really a great offer. As per above, I will have to wait a little since I'm traveling for work these coming days. I will prep stuff when I'm back.

Thanks for everything
Do
 
L

lordoff

Member
Joined 2006
Merry Christmas to everyone,
and Happy New Year!

Best wishes and healthy, full of time for diy projects!

I feel little obsession from FC-100 design and project.
My primary interest in diy audio was tube differential amplifiers, but...
my everyday amplifier are Luxman L-530 and I love this sound.
Those luxmans are very, very similar in idea to Roender's FC-100.
Expecting FC-100 to be more, more refined in sound, thankfully excellent power supply and contemporary design.

So guys, any PCB board available somewhere? Or gerber files...
I will try to read again all long themes, to understand very well evolution of design and parts in times....

:)strangely or not, don't asking about sound :)
because, yes, I know very well how can sound good designed folded cascode!

Best Regards,
Kiril
 
Rudi_Ratlos

Rudi_Ratlos

Member
Joined 2009
In case that you are using Fischer SK104 heatsinks: the heatsinks have pads that connect to the GND plane of the PCB.

You need therefore to isolate the MJE - transistors (back and screw), the collectors of which are connected to +/- output voltage.

The BD transistors need not to be isolated since they are made of plastic.

Regards - Rudi
 
bk856er

bk856er

Member
Joined 2011
Thanks as always, Rudi. My BD devices are plastic cased, but have exposed metal on the backside. Will probe them when I open the antistat packing. Probably safest to isolate with a sil-pad, but the srew/nut at least won't need a nylon shoulder washer like the MJE.


BK
 
A

archidea1

Member
Joined 2014
Hi All,
I wonder if somebody has experienced the same issues during first power on.
I strictly followed Rudi's build guide, checked all part prior to soldering.
The circuit seems to work fine, at least all diodes are lit initially.

attachment.php


However it is only when the voltage drop measured is 0.0mV.
When I try to increase the drop with potentiometer R22 it raises very rapidly to about 70mV. I tried to power on with one or two diodes shorted, similar result (with two diodes shorted I can keep it at 0.0mV, with one shorted the drop goes quickly to 70mV).

Do you think there is a fault somewhere or is it a matter of bypassing the NJE diodes?
I would mention that my transformers when idle give me 26v (not 25V), -/+37V after rectification, should this be a problem?.

I uploaded videos showing the power on.
20180226_220559.mp4 - Google Drive
20180226_221052.mp4 - Google Drive
20180226_220805.mp4 - Google Drive

Regards,
Greg
 

Attachments

  • 20180226_221948_HDR.jpg
    20180226_221948_HDR.jpg
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Rudi_Ratlos

Rudi_Ratlos

Member
Joined 2009
Greg:

at first glance your build Looks quite o.k.
Did you solder (manually) the two wires on the solderside of the PCB to:

1) connect Frontend-GND to Backend-GND
2) connect the Negative Feedback

Please remove the wire to short the second thermal track diode and try to do the adjustment again.

I wish you success - Rudi
 
A

archidea1

Member
Joined 2014
Hi Rudi,

I did solder the two wires as per your build guide (the red and purple line).
I will try again with only one thermal track diode shorted.
My concern is that the bulb lights not only when initially charging the caps but after several seconds it lights up again (70mV drop).

I assumed the pot R22 is to adjust the drop starting from 0mV going up to 38mV.
I can no way get this reading on my voltmeter. Its either 0mV or 70mV.
I don't want to accidently destroy the components, I guess it would be a real pain to get a new set of matched triplets!

Thanks.

Regards,
Greg
 
Rudi_Ratlos

Rudi_Ratlos

Member
Joined 2009
Greg, I remember that there is a problem, when you run both the frontend- and the backend-PSU from behind a bulb tester that is connected to your mains.

Since you know that your frontend will not produce a short, run your frontend-PSU from your mains directly (without bulb-tester) and test again.

Regards - Rudi
 
bk856er

bk856er

Member
Joined 2011
Wrapping up my SPO. The round PCB fuse holder (Littlefuse 576-56000001009) is too small and doesn't fit the board. Looks like I need ~8mm lead spacing and 10mm silkscreen outline. Anyone know the pn for this holder or even the fuse type? I'm not having any luck searching for "similar" items on Mouser.


Board pic here, since evidently there were some variations within the GB: http://www.diyaudio.com/forums/group-buys/293550-roenders-fc-100-buy-23.html#post5073614

BK
 
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