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Old 13th May 2013, 08:09 AM   #1
kaushik is offline kaushik  India
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Default SALAS hv with 150V

Hi i have got a transformer delivered with


150V and 6.3V secondaries

wanted to use the "salas HV with 3 led Nov09 circuit" , the input is rated as 350V

and output as 300V

can i work with 150V input and output of 135V approx with the trimmer adj.
or some other mods needed ??? The schematic is this one
Click the image to open in full size.
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Old 13th May 2013, 01:02 PM   #2
kaushik is offline kaushik  India
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Click the image to open in full size.

sorry for mini thumnail by mistake the circuit is this one

A) will it regulate 150V ?
B)can i make the filament supply with 4148 bridge rectifier out putting 6.3V?
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Old 13th May 2013, 01:37 PM   #3
TheGimp is offline TheGimp  United States
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If you rectify the 6.3V output you will get close to 8.9V at 0.707x the original current rating. You will have to regulate this down to get 6.3 for heaters. Why do you want to use DC on your heaters?

The Salas regulator can regulate 150V, however you will get close to 212V as the input of the regulator if you FWB rectify the 150V output. So you have to watch dissipation. How much current do you need?

You can change the regulation set-point by changing the value of R4.
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Old 13th May 2013, 01:55 PM   #4
AndrewT is offline AndrewT  Scotland
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The Gimp warns of the problem.
The 150Vac winding when rectified will give ~210Vdc +15% -10% depending on mains voltage and loading.
Assuming +15% on 210 gives ~240Vdc
If you regulate down to 135Vdc then the CCS has to drop 105V. It will get mighty hot !!!!!!!

At the other end if your rectified is low by 10% you have ~190Vdc. This leaves a CCS Vdrop of 55V when in worst case. This CCS will not drop out in worst case loading.
This is the clue that you have a transformer that at 150Vac is far too high for your 135Vdc requirement.
Check out a 120Vac transformer at worst case highest and lowest voltages.
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Last edited by AndrewT; 13th May 2013 at 02:00 PM.
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Old 13th May 2013, 02:39 PM   #5
kaushik is offline kaushik  India
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Thank you for the inputs .
@TheGimp i am new to the tubes
so i can guess Ac for filaments is fine .The transformer the sec windings are 6.3 -0 - 6.3 V planning to use 2 filaments of 12AX7 series .

>>> simple resistor dropping is fine ? or a CCS is recommended ? (how bad will it sound with filament unregulated )
@Andrew
There is no requirement to keep 135V i think 175V also is fine with 12AX7
i would use what ever the HV salas gives me as the tubes can also take 300V .

Planning to use in a SRPP configuration .

I have only 330Uf 200V cap for filtering , i hope it will not blast
>>>Please suggest a dummy load (220k resistor ?)to test the HV section , cant risk the tubes
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Last edited by kaushik; 13th May 2013 at 02:47 PM.
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Old 13th May 2013, 03:34 PM   #6
TheGimp is offline TheGimp  United States
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If you are building an SRPP stage, you need more than 150V. 200-300 would be good for SRPP.

You will need to elevate the heater supply.

What are you doing with SRPP stage?

Mr Blencowe (aka Valve Wizard) a good article on the SRPP and optimization of it.

The Valve Wizard- SRPP

see the blue link "The Optomized SRPP amp".
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Old 13th May 2013, 03:55 PM   #7
kaushik is offline kaushik  India
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I am planning to do a simple preamp



I am happy to get a 256V after rectification connected a 56K+redled (very tiny load )
i have not yet given power to the SALAS HV circuit.

worried about the filter cap rated 200V (it may blow i guess)
only way is to go market and put a 100Uf 400V part ,

i have a 2.2uf 400uF capacitor if i remove the 330uF , only 2.2uF will not be sufficient .
@TheGimp that page lists good info on 12Ax7 SRPP thanks
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Last edited by kaushik; 13th May 2013 at 03:59 PM.
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Old 13th May 2013, 04:11 PM   #8
kaushik is offline kaushik  India
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Click the image to open in full size.

Here is the pic of the board
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Old 13th May 2013, 04:30 PM   #9
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I used AC to my heaters and got pretty much zero noise.
I just used resistor dropper to get the right voltages.
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Old 13th May 2013, 04:53 PM   #10
AndrewT is offline AndrewT  Scotland
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your 200Vdc cap is no good for your 150Vac transformer.
I have shown that you could get well over 200Vdc even in average use conditions and around 240Vdc in worst case conditions.
You need to measure what you actually get from your tansformer and then apply the mains tolerance and loading effect to find the lowest voltage that will be the feed into your Regulator.
Your output should then be set to ~10V below your lowest input voltage.

But do you need a regulator?
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