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Old 6th November 2012, 12:26 PM   #441
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Marjohn, I have a sufficiently big quantity of 2SK170BL at hand, all of which have an IDss of > 9mA!
My little test-rig (see attached image) confirms this.

If you like to have the EAGLE-files of this small test-rig, I will send them to you - no problem: "We are DIY."
I will also be able to offer you well matched pairs of 2SK170BL (...must have the same Vgs +/- 1mV at Id=6.25mA),
once I know how to adjust my LTSpice model.

Best regards - Rudi_Ratlos
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Old 6th November 2012, 12:38 PM   #442
AndrewT is offline AndrewT  Scotland
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Roender.
I have a problem.

I have added a separate regulated supply to the FC100.
The FC100 PCB in this GB uses a single bridge rectifier. That limits the Main Audio Ground to be connected to the Centre tap of a dual secondary transformer. That ground line runs right along the middle of the PCB and does the same on your original PCB.

I am working with the original PCBs at the moment.

I have a choice of where to connect the auxiliary PSU Zero Volts to the main PSU.
a.) At the Zero Volts on the wires from the centre tap
b.) at the Power input connector on the PCB.
c.) at the hole for the ON board Ground at the left end (next to spk out)
d.) at the hole for the ON board Ground at the right end (next to the NFB tapping solder point).

The "problem":-
If I connect the regulated output with a twisted triplet to the three points at the right hand end, I get an ~4V offset in the regulated output voltages. i.e. the regulated +-50Vdc becomes +46Vdc and -54Vdc. Even the 4 smoothing caps on the reg PCB have offset voltages. They change from +-58Vdc, to +54Vdc and -62Vdc.
If I connect instead the INPUT ground of the regulator to any of the first three listed above the offset becomes zero as near as I can measure. I see a very few millivolts of difference depending at what ends of the long Ground line I measure at.

I cannot see why connecting the OUTPUT from the reg to the right most ground creates this offset. I have puzzled for a few days repeating the experiment with different regulators and different transformers and different wiring and I cannot eliminate the offset.
It makes the cascode in the LTP sink run hotter. I will probably increase the size of the sink from 30C/W as I have done with the first of the Rudi PCBs.

I will hand draw what I have described and post a pic later today, or at the latest tomorrow.
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Last edited by AndrewT; 6th November 2012 at 12:52 PM.
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Old 6th November 2012, 12:51 PM   #443
AndrewT is offline AndrewT  Scotland
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Quote:
Originally Posted by roender View Post
I second that. It's not an easy job and took many hours to closely match jfets.
And that is why I respect the Euvl team in the way they matched the output mosFETs of the F5x.
They developed a machine curve tracer that automatically logged the results and then used some software to select the matches from those many thousands of results.

A similar system could be used to these jFETs, but having read their testing procedure I think the resources they brought to the table would probably exceed the cost of all the F5Xs that are being built (about 50 so far).
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Old 6th November 2012, 04:32 PM   #444
AndrewT is offline AndrewT  Scotland
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The grounding scheme with regulator for the front end Vcc/Vdd

There is no chassis and as a result no complications with extra connections to PE.
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Old 6th November 2012, 06:08 PM   #445
jprco is offline jprco  Canada
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If it's not one thing - it's another!
Any reason why the links to the Reichelt BOM's for the FC100 components don't work anymore???
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Old 6th November 2012, 07:53 PM   #446
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Jean, I had to rebuild the carts!

Here they are again:

FC-100_Speaker Protection (needed 2 times):
https://secure.reichelt.de/index.htm...07;PROVID=2084

FC-100_Soft-Power-On (needed 1 time):
https://secure.reichelt.de/index.htm...09;PROVID=2084

FC-100_Shunt-Regulator (needed 2 times):
https://secure.reichelt.de/index.htm...04;PROVID=2084

FC-100_Amplifier (needed 2 times):
https://secure.reichelt.de/index.htm...39;PROVID=2084

FC-100_Backend-PSU (needed 2 times):
https://secure.reichelt.de/index.htm...41;PROVID=2084

Best regards - Rudi_Ratlos
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Old 6th November 2012, 08:30 PM   #447
mj777 is offline mj777  Philippines
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Quote:
Originally Posted by Rudi_Ratlos View Post
Marjohn, I have a sufficiently big quantity of 2SK170BL at hand, all of which have an IDss of > 9mA!
My little test-rig (see attached image) confirms this.

If you like to have the EAGLE-files of this small test-rig, I will send them to you - no problem: "We are DIY."
I will also be able to offer you well matched pairs of 2SK170BL (...must have the same Vgs +/- 1mV at Id=6.25mA),
once I know how to adjust my LTSpice model.

Best regards - Rudi_Ratlos
Thanks for sharing the test rig Sir, yeah sure sir just pm me when you have already matched pairs of this transistors.

regards,
marjohn
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Old 7th November 2012, 05:16 AM   #448
roender is offline roender  Romania
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Quote:
Originally Posted by AndrewT View Post
The grounding scheme with regulator for the front end Vcc/Vdd

There is no chassis and as a result no complications with extra connections to PE.

Hi Andrew,

You should connect A with E. Your topology is not suitable for ground separation between front end and power stage because there is only one common AC central tape.

Kind regards,
Mihai

Last edited by roender; 7th November 2012 at 05:23 AM.
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Old 7th November 2012, 09:12 AM   #449
AndrewT is offline AndrewT  Scotland
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How do the Roender PCBs connect together with dual bridges instead of single bridges?

This will not apply to the Rudi PCBs because the amp PCB has on board single bridge.

But I will probably use a common transformer arrangement for all the Roender and Rudi PCBs.
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Old 7th November 2012, 09:15 AM   #450
roender is offline roender  Romania
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Quote:
Originally Posted by AndrewT View Post
How do the Roender PCBs connect together with dual bridges instead of single bridges?

This will not apply to the Rudi PCBs because the amp PCB has on board single bridge.

But I will probably use a common transformer arrangement for all the Roender and Rudi PCBs.
Do you mean dual bridge per channel? I had never use that configuration.
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