Hi all.
I want to replace the rectifier for diodes.
The plate/anode voltage on the EL95 is 252vdc
And 240vdc on cathode.
Will the El95 be ok with the increase in voltage after the change if not what sort of value resistor would I need .
Thanks
I want to replace the rectifier for diodes.
The plate/anode voltage on the EL95 is 252vdc
And 240vdc on cathode.
Will the El95 be ok with the increase in voltage after the change if not what sort of value resistor would I need .
Thanks
Check the DC voltage on C1, especially if its voltage rating is below 350VDC.
If the filament voltage runs high, and the unit is set for 220VAC, you could connect it
for 240VAC instead of 220VAC.
Otherwise if necessary, a series resistor of around 250R 5W should work, but adjust the value
if needed to get around 250VDC on the plates. This will run hot, so keep it in free air.
If the filament voltage runs high, and the unit is set for 220VAC, you could connect it
for 240VAC instead of 220VAC.
Otherwise if necessary, a series resistor of around 250R 5W should work, but adjust the value
if needed to get around 250VDC on the plates. This will run hot, so keep it in free air.
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On My AG9016, I replaced the selenium bridge rectifier with a silicon rectifier and I added a small 10H choke with 300 ohms DCR after the first filter capacitor. The voltages are the same as the original schematic and the residual ripple is much lower. I also added a 33 uF capacitor in parallel to the one that levels the power tubes screen voltage. I left the original filter can capacitor in place because it still works just fine. I also measured it with a LCR - after almost 60 years it fares worse than a brand new Nichicon, of course, but it is surprisingly better than a typical no-brand filter capacitor. I had to replace the fuses, they weren't safe anymore.
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The nominal voltage in the UK unlike most of the EU is 230 volts rms not 220 volts , depending on where you live this can rise to 240 volts as "standard for the area " .
Just so there is no argument here I just measured mine going into my PC it stands at ---242 volts rms -- that's in Scotland.
Just so there is no argument here I just measured mine going into my PC it stands at ---242 volts rms -- that's in Scotland.
I assume you mean that the screen grid voltage now is 240 Vdc, so not the cathode voltage. What is the cathode voltage?
There's seems to be something wrong in the schematic with the value(s) of the screen grid voltage and/or the screen grid resistor.
With "+1" being 235 V and Vg2 being 230 V, the voltage drop over R22 (R52) of 390 Ohm would be 5 V. So Ig2 would be 5 / 390 = 0.0128 A, so 12.8 mA. Pg2 would than be 0.0128 x 221.5 = 2.84 Watt. But according to the datasheets, Pg2 max (at no signal) = 1.25 Watt, and Pg2 max peak = 2.5 Watt.
Even when the voltage drop would be just over 4 V (lower limit of the margins involved), Ig2 would stil be 4 / 390 = 0.0102 A, so 10.2 mA. Pg2 would stil be 0.012 x 221.5 = 2.26 Watt.
But if you calculate the current through resistors R1 and R2 between "+2", "+1" and "+", you get 13 mA and 1.9 mA. This would mean that about 11 mA is going to the two screen grids, so 5.5 mA per EL95. Those values are likely the correct ones.
There's seems to be something wrong in the schematic with the value(s) of the screen grid voltage and/or the screen grid resistor.
With "+1" being 235 V and Vg2 being 230 V, the voltage drop over R22 (R52) of 390 Ohm would be 5 V. So Ig2 would be 5 / 390 = 0.0128 A, so 12.8 mA. Pg2 would than be 0.0128 x 221.5 = 2.84 Watt. But according to the datasheets, Pg2 max (at no signal) = 1.25 Watt, and Pg2 max peak = 2.5 Watt.
Even when the voltage drop would be just over 4 V (lower limit of the margins involved), Ig2 would stil be 4 / 390 = 0.0102 A, so 10.2 mA. Pg2 would stil be 0.012 x 221.5 = 2.26 Watt.
But if you calculate the current through resistors R1 and R2 between "+2", "+1" and "+", you get 13 mA and 1.9 mA. This would mean that about 11 mA is going to the two screen grids, so 5.5 mA per EL95. Those values are likely the correct ones.
duncan2,
"Others will take the Low Road, and you and I will take the High Road" (242Vrms).
"And we'll be in Scotland Afore them".
I am Sorry to be so silly, but you reminded me of the Song Lyric.
And, I am an American, but my family originated from Isle of Skye (did I spell it right?).
And, being involved in electronics for 64 years, I could not "Resist".
"Others will take the Low Road, and you and I will take the High Road" (242Vrms).
"And we'll be in Scotland Afore them".
I am Sorry to be so silly, but you reminded me of the Song Lyric.
And, I am an American, but my family originated from Isle of Skye (did I spell it right?).
And, being involved in electronics for 64 years, I could not "Resist".
You will get a higher voltage with the Si diodes. Measure what you get now for the B+ voltage just after R1 in the supply before changing rectifiers. Install the Si diodes and measure again. If it's more the 10 or so volts higher, you can enlarge R1 a bit to lower the voltage. The voltage drop you see in the selenium measurement will depend on how many 'diodes cells' are in the selenium package.
Never been to Skye 6A3sUMMER but on my mothers side my grandmother came from South Uist and my grandfather from Tiree --they could speak "the Gaelic " .
A lot of Americans from the Southern States are originally Scots as they worked in the Cotton Fields after Culloden and "The Clearances " .
A lot of Americans from the Southern States are originally Scots as they worked in the Cotton Fields after Culloden and "The Clearances " .
The output of the selenium rectifiers does reduce as they age, so the comparison with the old voltage is not necessarily valid.
The key metric is the B+ voltage which is 248v on the schematic, and you measured 252v, so you are sufficiently close not to worry about it, I would say.
I fit a CL-140 Inrush Current Limiter on the amps I have tinkered with ...
CL-140
It adds a few ohms of resistance as well as a soft start, so gives an easier life for the tubes, IMO.
Maybe you could fit it from one leg of the secondary to the bridge, but is there a case for fitting it from from ground to the negative leg of the bridge?
The key metric is the B+ voltage which is 248v on the schematic, and you measured 252v, so you are sufficiently close not to worry about it, I would say.
I fit a CL-140 Inrush Current Limiter on the amps I have tinkered with ...
CL-140
It adds a few ohms of resistance as well as a soft start, so gives an easier life for the tubes, IMO.
Maybe you could fit it from one leg of the secondary to the bridge, but is there a case for fitting it from from ground to the negative leg of the bridge?
Referring to my Tubelab SSE, it should go between the positive of the bridge rectifier and the first electrolytic capacitor.
I have seen a case on another discussion where it was added between ground and the negative on the rectifier bridge, to lift the amplifier ground from the chassis ground, but I don’t think that will give you the right result here.
I have seen a case on another discussion where it was added between ground and the negative on the rectifier bridge, to lift the amplifier ground from the chassis ground, but I don’t think that will give you the right result here.
hello, j'ai acheté sur ebay un AG9016. J'ai remanié le câblage .Vérifié les capa de filtrage 50+33+33uF au capacimètre, j'ai lu 60+50+33uF.Il est rester en place, j'ai remplacé les 16 et 25uF. J'ai pris un fil de 0,6mm pour le 0V partant du pin - du redresseur vers la borne - de la capa de filtrage puis vers le point milieu du chauffage filament ensuite vers la masse 0V du CI coté de chaque tube de puissance et ensuite vers masse opt 1. DE masse opt 1 vers masse OPT2. De masse opt 2 vers masse HP G et HP D. Le tout forme une ligne . Il ni a plu de boucle de masse comme à l'origine. J'ai changé le câble secteur par un 2P+T, le châssis est à la terre. Refait aussi le câblage filament. Redresser , filtrer, réguler en cc les filaments de pré amplification. Il sonne mieux maintenant.
