New Problem after installing choke and PPIMV

[jobewan]

Hi,

I just installed a choke and the PPIMV mod on a TubeDepot 18 watt kit. Can anyone tell me what effect a choke will have on the voltages at the two can cap terminals? Also, will the MV make much difference in voltages at various test points?

I turned the amp on for the first time with the power tubes in it tonight, just before dinner. I got this god awful popping noise - seemed at max volume and the vol knob made no difference. I pulled the power in a panic, and have not done anything further. I would appreciate some help.

One other question. I had read somewhere that it was a bad idea to ground to the PT posts. So I installed a couple of star grounds and moved anything that was previously on the PT ground lug to these nmew ground points. Is there any problem with that? I was operating under the assumption that a good short distance ground location is better the running a long wire, but now I am questioning that logic.

Thanks all, any help is very much appreciated. Looking forward to a nice long weekend of amp building fun!

Joe

[Daviedawg]

This is not a full reply to your issues. But I would say that moving your grounds off the PT is a good thing. Local star grounds is a good thing as well. One for the power supply, power amp and PI and one for the preamp is how i normally do it with the preamp one as close to the input as possible. In the download section look for JMP's (Josh) layout for Lite II. That will show a good example of grounding as well.

The PPIMV is on the signal path so should not affect the voltages at the valves to any great extent if it is wired as designed.

Do you have a schematic of the circuit with the choke in it? Without that it is hard to give a full answer.

Finally it sounds to me like there is an issue somewhere which is causing your noise and volume problem. A serious look at the installation following the schematic and marking it off as you go is how I would approach it.

Good luck.

Dd

[geoff 1965]

hello Joe,
good advice from Dd,i have the PPIMV fitted to my 18W and like Dd said it's in the AC signal path so should'nt affect voltages but check you have it wired correctly i.e. the signal path of one el84 going to one half of the dual pot - C14 to lug 1 "input" then lug 2 "output" to R25, also it pays to use good quality coupling capacitors from the phase inverter to prevent any DC getting to the grids.check with your multimeter,don't rely on new components being good!
the choke filters any DC ripple from your B+ but will have resistance so will drop your voltage a little but not as much as the 2K2 series resistor across the can capacitor,did you note the voltages across the can before you removed the 2K2? also have you used the tubedepot TR-CK-02 choke and do you know the resistance across it?
it will help if you post your voltages etc and any pics of your amps internals,good luck.

british18w_schematic_v5 (1).pdf