A Quick Viking 2 Question

[AF9J]

Hi Guys,

I'm looking to remove the last paper caps in my Viking 2.  Where C11 & C12 go is a dual capacitor that's only rated at 350V.  Only two of the leads are hooked up (in stead of the 4 leads that are on the dual capacitor.  So, in effect, only 1 capacitor is hooked up.  The schematic calls for 2, 15 microfarad elelctrolytics, rated at 450V.  I have 2, 20 microfarad electrolytics rated at 450V.  Am I right in assuming that under the 20% tolerance rule, these will work fine for my application?

73,
Ellen - AF9J
Plugging away at work 

[W1RKW]

Ellen,
20mfd shouldn't be a problem.  I doubled that capacitance on my V2 without any issues. There was an increase in the voltage but I would have seen that increase since the old cap was beat anyway and doubling it probably raised the voltage slighty more higher than nominal. I have found new caps to be usually be slightly higher in capacitance than what is stamped on their side but even that isn't doubling the value so you should be AOK. 

[Jim, W5JO]

Ellen, if you want to be really picky, then Mouser has some 16 Uf axial types you can put in.  However the ones you have will work fine.

[AF9J]

Thanks Guys,

BTW, I meant C10 & C11.

73,
Ellen - AF9J

[n2bc]

Hi Ellen,  back in the Viking's day most electrolytics were +100%/-50% tolerance - or even wider!  Put 'em in. 

[Tim WA1HnyLR]

Hi Ellen, I generally use 100 mfd 450 volt caps. The power supplies are solid stated . The LV supply comes up to 370V under load. It is advisable to use the LV supply for the screen voltage source for the modulator and eliminate the 20 bleeder resistor with the tap. This is a very poor means of supplying screen voltage. I take the screen voltage through a set of relay contacts as part of the  PTT system. 370 volts is a bit too high. I change the LV supply to choke inpoot . This lowers the supply voltage to about 260 volts. I clamped the bias at -24v with a string of shadio rack zeners . Aside from other audio mods such as changing the second 6AU6 to a triode connected 6AQ5 etc. Usually the filter cap used for the biass supply goes away . This should also be replaced with 100 mfd units @ 150VDC. Good luck, Tim WA1HnyLR