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In the Forum: Melquiades Amplifier
In the Thread: Bias help
Post Subject: Bais and filament voltagePosted by DA on: 8/19/2013
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Well, it looks like I got fucked by the transformer company.that realy sucks !!!  I have not talked to them yet ,but even if they agree to replace them it will take at least 6-8 weeks plus international shipping cost , import tax , VAT .

Filament transformer - if only the 6E5P is connected then I get 6.3v. Once I add the 6C33C voltage drops to 5.8 -5.9v.....
Bais transformer - only 415v instead of 440v...

How do you like the sound of the thing ?

Well can not comment on sound yet but it works (connected to a small monitor at my workshop ) sounds clean and nice...

The  output stage 200mA /187V. It is a bit too small but I will do. I do not know what the gap you have in your OPT. If it is limited to 200mA then stay there, you might crack the voltage to 200V if you need a little bit power from your 6C33C.

I use Lundhal 1627am /200mA  in D configuration . How to raise voltage if needed ? R22 ?
The DC drift at inputs – that shall not be

It is more then +- 0.5mV more like +- 2-3mV ,but I am not worried about it at this point.perhaps it has to do with the low current and voltage of gas tubes ?  If your transformer give too little voltage for bias supply then you need to adjust the volume of the R15 and R16 resistors or perhaps the R11 and R12 in order to have on the B and C point around 190V- 195V.  Replaced R15 and R16 but that did not work,even with 50 ohm resistors I only get 180v.
Anyway looks like the project is on hold for now and that (really) sucks.

Regards
Daniel

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