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Simplistic Mosfet HV Shunt Regs
Simplistic Mosfet HV Shunt Regs
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Old 16th February 2020, 12:30 PM   #6071
indaco is offline indaco
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Quote:
Originally Posted by artosalo View Post
Do you refer to this circuit?
Yes this one
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Old 16th February 2020, 05:09 PM   #6072
artosalo is offline artosalo  Finland
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That PNP transistor must be power type such as MJE2955 etc.
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Old 16th February 2020, 08:47 PM   #6073
indaco is offline indaco
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Ok, thanks...I asked because the 2N5401 of the schematic is low-power PNP.
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Old 22nd March 2020, 02:13 PM   #6074
Avellano is offline Avellano
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Hi Salas,
I don't know if the topic has already been posted in the long 3d, if so, I'd appreciate a link to the post number.
I'm using two indipendent hvshunt reg on an amplifier which uses an input stage (6j5 srpp) dc coupled with a 300B output stage.
Everything works but the two regs reach the desired working voltages really slowly (about 40 minute ).
In this time the 300B' s circulating current never becomes dangerous but its desired working point is reached with great delay.
What can be done to make sure the regs reach the desired voltage in the shortest time possible.


Thanks


Luigi
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Old 22nd March 2020, 04:36 PM   #6075
Salas is offline Salas  Greece
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Simplistic Mosfet HV Shunt Regs
Hi

How many Volt it climbs in about 40min after the initial Vout? Looks like positive thermal drift? In that case, its the JFET heating up giving out more current to the Vref resistors as its ambient temperature changes enough. That can be few Volt only if the system is correctly set and not overheated.
Try distance the regs from the main heat sources, if the tubes are near to them, and/or use bigger sinks when those are the worst radiators to the JFET area if they are saturated with MOSFET dissipation.
So you could watch when setting an initial Vout if and how closer the final Vout results. If it remains as before it could be something else than thermal drift. Maybe not enough CCS setting.
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Old 26th March 2020, 04:14 PM   #6076
merlin el mago is offline merlin el mago  Europe
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Salas have you seen this: PCB Tube Anode Adjustable PSU Regulator Salas V2 from stereo24 on Tindie
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Old 26th March 2020, 08:29 PM   #6077
Salas is offline Salas  Greece
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Simplistic Mosfet HV Shunt Regs
No, first time I see that one. Close style copy. Says out of stock, not hiding original source, has link to the thread here too. In general, IMHO, better to choose supporting official GB boards in all diy projects from all authors when available.
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Old 26th March 2020, 09:44 PM   #6078
merlin el mago is offline merlin el mago  Europe
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I only bought from GB.
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Old 27th March 2020, 11:15 PM   #6079
morpheous is offline morpheous  Italy
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Hi

I bought a pcb to make a tube preamplifier based on ls26 cat-sl1
The high voltage is 260 V 80 mA. I purchased two shunt regulators because the PCB has two B + and a 260 V earth.

I have some questions:

First: is a shunt regulator sufficient?
Second: how can I set the current and V output from the shunt controller?
Third: what is the value of the resistor for the checks before connecting it to the pcb?
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Old 28th March 2020, 01:04 AM   #6080
Salas is offline Salas  Greece
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Simplistic Mosfet HV Shunt Regs
80mA for one 12AU7 section, two 12AX7 sections, one 6DJ8 section, per channel? That's 20W B+ power draw per channel at 260V. Sounds like way too much. 10mA per channel is far more likely.

SSHV2 can go at least up to 100mA CCS each. Post#1 has link to the SSHV2 circuit description. There is a PDF manual attached under the description also. In the manual its explained how to set it. Its actually very easy because it has trimmers both for CCS mA and Vout.

For test load resistor use 27k 5W. Start with setting 30mA CCS per channel. Read 300mV at TP for that. Then take it to 260V output.

If the preamp uses much much more than 10mA per channel, unlikely, the rail voltage will drop significantly lower than 260V when you will connect it. Then up the CCS slowly until it gets to 260V on the preamp. Add another 20mA CCS and leave it at that.
 

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