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Old 15th April 2013, 10:28 AM   #441
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My experience with the RTP3D.

In January the RTP3 was ready for take off, i adjust everything that could be adjusted.
Some hours ago i checked all voltages and currents.
Same check the next two weeks, everything is stable and fine.
Nice preamp.
But last week the music was very quiet on one canal.
Short look inside, one tube doesen`t glow as bright as the other once.
Now i measured the voltage drop on the heater.It was to low.So the current of the heater ccs was to low.
Now checked all other heater voltage drop, most of the Tubes were in thair limits but not in the range i adjust them 3 months ago.
Readjust all heater ccs everything is fine an the RTP3 works.

I use a precision trimmer (25 times turnable) to adjust the current flow.
Doese anybody of you have an idea whats happened??
Is it some kind of tubeheater burn in that causes the variance??

I use the Electro Harmonix 6922(heater current is 365 mA and not as the historical 6922 with its 300mA).

Maybe some of you have made the same experience like me.
Have a look at your RTP3 maybe somthing is going wrong.


@Klaus (VTR)
Which caps in the superreg do you changed to Foilcaps??


Roland
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Old 15th April 2013, 07:25 PM   #442
mishak is offline mishak  United States
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Quote:
Originally Posted by vtr View Post
make a elevated voltage, not to stress the heater cathode isolation and to block the micro diode between heater and cathode, 30-40V is fine with a voltage divider from filtered B+ and some capacitance.
Hi Klaus,

I will try it also later

Quote:
the differences you see is due to different constuction and tolerances of tubes
klaus
Absolutely, agree.
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Old 15th April 2013, 07:37 PM   #443
mishak is offline mishak  United States
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Quote:
Originally Posted by Salas View Post
Congratulations. So the original PCB configuration for heaters reference was the cause?
I don't think so. PCB is perfect in my opinion. Heaters conductors (+, ground, + for the second group of tubes) are made on the upper side of the board, straight and wide, when other connectors are located on the bottom side.

The problem was that regulated heater DC came from the independent totally isolated regulator, when other 6 regulators (4 for each tube HV, one for +15 and one for -24) had a common ground. Heater totally "floated" in the air. When I connected two grounds with 0.22 capacitor hum was dramatically reduced.

I hope it could be reduce even more by elevating heater voltage as VTR suggested by 40V, I'll try it later. It is pretty good right now.
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Old 15th April 2013, 07:54 PM   #444
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I am massively surprised that you are seeing any benefit from DC heaters.
AC is absolutely silent on my non-balanced FVP5.

Shoog
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Old 16th April 2013, 11:02 AM   #445
vtr is offline vtr  Switzerland
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Default superreg and current heater

i changed thy main electrolyt to 10uf Foilcap, but be aware it can start oszillating.....

and yes heater burn in and some readjustment is usual when tubes are changed-allen recommended the pcc88 because this is designed for heater current.




Quote:
Originally Posted by dcd3500rg View Post
My experience with the RTP3D.

In January the RTP3 was ready for take off, i adjust everything that could be adjusted.
Some hours ago i checked all voltages and currents.
Same check the next two weeks, everything is stable and fine.
Nice preamp.
But last week the music was very quiet on one canal.
Short look inside, one tube doesen`t glow as bright as the other once.
Now i measured the voltage drop on the heater.It was to low.So the current of the heater ccs was to low.
Now checked all other heater voltage drop, most of the Tubes were in thair limits but not in the range i adjust them 3 months ago.
Readjust all heater ccs everything is fine an the RTP3 works.

I use a precision trimmer (25 times turnable) to adjust the current flow.
Doese anybody of you have an idea whats happened??
Is it some kind of tubeheater burn in that causes the variance??

I use the Electro Harmonix 6922(heater current is 365 mA and not as the historical 6922 with its 300mA).

Maybe some of you have made the same experience like me.
Have a look at your RTP3 maybe somthing is going wrong.


@Klaus (VTR)
Which caps in the superreg do you changed to Foilcaps??


Roland
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Old 19th April 2013, 09:08 AM   #446
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Join Date: Feb 2012
Default Group buy hint

Hello,

just to let you know. A group buy for ceramic parts has been started. Just let me know if you need something.

cheers, tom
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Old 17th July 2013, 09:38 PM   #447
cdwait is offline cdwait  United States
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You do have the heater supply referenced to a tap/voltage divider on the B+, correct?
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Old 18th July 2013, 06:46 PM   #448
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Yes thats correct.
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Old 27th July 2013, 12:19 AM   #449
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Anybody know how much current Allen ran through the SSM2210s? (I.e. how much current for the current source in the phono section) Same as the JFETs?
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Old 27th July 2013, 06:59 AM   #450
Alex M is offline Alex M  United Kingdom
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Quote:
Originally Posted by relder View Post
Anybody know how much current Allen ran through the SSM2210s? (I.e. how much current for the current source in the phono section) Same as the JFETs?
9.5mA through each transistor - a total of 19mA through the CCS.

Click the image to open in full size.

Alex
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