Peavey Windsor Studio popping noise

[Gerhard Grass]

Hi to all,

I have here Peavey Windsor Studio (SE, Class A one 6L6GC) that
makes an intermittend popping noise (like making popcorn).

The noise occurs independet from the positions of the controls,
wheter an instrument is connected or not.
The owner told me, a friend made some "improvements" to the amp which I removed
immediately. (Sort of filter before the power xformer...)
Changed all the tubes without any effect.
As the popping occurs intermittend (sometimes every 5 seconds, sometimes after an hour)

Just noticed that the 6L6 ist glowing red, when not on Stdby.
Took some measurements:

plate voltage: 473V
VR38 voltage: 36V
R38: 400R (checked o.k.)
Ik: 36V/400R = 90mA
plate diss.: (473V - 36V) * 0,09 = 39W !!

Seems to be a bit too much (or am I completly wrong?)


Any help and suggestions appreciated !!
thx in advance!

greetings Gerhard

[MarkusBass]

If the tube is glowing red, isn't that a clue that the current is to high?
Here: Peavey Windsor Studio Preamp & Bias Modifications it is suggested to change the R38 resistor to 500 Ohms. I'm also curious what exactly you mean by "plate voltage". Is it voltage on the anode of the V3 tube, or voltage marked "PLATE" on the schematic?

Mark

[Gerhard Grass]

Hi Markus,

thx for answer. With "plate voltage" voltage on anode of V3 is meant.
Regarding the red glowing, I didnīt doubt the work of Peavey...
I will follow yout advice and change R38.
(Tried in the meantime a 5881WXT. Obviously this tube can handle the current a bit better.
Much less noise).

Will post results when the mod is done.

thx Gerhard

[g1]

Also check the grid voltage (pin5).

[Gerhard Grass]

Sry, forgot to mention.
Ug2 is 452V

[g1]

I meant g1 control grid (pin5). Should be zero volts and check that it measures same resistance to ground as schematic shows.
The schematic link is not working, can you zip it and respost?

[Gerhard Grass]

Resistance between grid (G1) and ground measures correct 1M.
Voltage between grid (G1) and groung measures about 115mV.

[MarkusBass]

I think that the name of the amp is Windsor and not Windor. This may be from Windsor castle: https://en.wikipedia.org/wiki/Windsor_Castle . It may also be from Wind Door but this is not likely.
The voltage on the grid should be almost zero Volts (as in all tube amps). This is not very interesting. Much more interesting is the voltage on R38. With this voltage you can calculate the current throgh the tube. And you already measured it (36V).

Mark

[Enzo]

Peavey made a Marshall-ish amp called the Windsor. It was ready for 6L6 or EL34. Windsor evokes a British image. Then they applied the name to this little amp as well. It also will take a 6L6 or an EL34.

[g1]

The voltage on the grid should be almost zero Volts (as in all tube amps). This is not very interesting. Much more interesting is the voltage on R38. With this voltage you can calculate the current throgh the tube. And you already measured it (36V).

I hope your choice of the word "interesting" was due to language differences and not because I bored you .
The reason I asked about it was in case the coupling cap C9 was leaky, putting DC on the grid, which would lead to the excess voltage across R38.
If that were the case, then adjusting the value of R38 would be treating the symptom, not curing the problem.

[MarkusBass]

I wish I could speak English better. I was looking for some word but couldn't find better than this one . Sorry for confusing you.

Mark

[g1]

Maybe you meant "significant" ?
Anyway, I guess we both are thinking the .1V at the grid is probably normal and not due to any C9 leakage?

[MarkusBass]

Maybe you meant "significant" ?

Yes, somehow I changed it to "important" and then to "interesting", which changed the meaning of the sentence . I'm still working on my English vocabulary.

Anyway, I guess we both are thinking the .1V at the grid is probably normal and not due to any C9 leakage?

It seems that description of the modification (available on the internet) does not explain the root cause of the problem. Maybe the amp was manufactured with some specific tube and with this tube the amp worked properly.

Mark

[J M Fahey]

I think that the name of the amp is Windsor and not Windor. This may be from Windsor castle: https://en.wikipedia.org/wiki/Windsor_Castle . It may also be from Wind Door but this is not likely.
The voltage on the grid should be almost zero Volts (as in all tube amps). This is not very interesting. Much more interesting is the voltage on R38. With this voltage you can calculate the current throgh the tube. And you already measured it (36V).

Mark

Well, after all Peavey called it's Celestion "inspired" speaker "The Sheffield" .

[g1]

If the tube is glowing red, isn't that a clue that the current is to high?
Here: Peavey Windsor Studio Preamp & Bias Modifications it is suggested to change the R38 resistor to 500 Ohms.

One person did report having to go as high as 750 ohms to get the tube running at proper current.