#1
I got alot of hum in the power section of my cheap Peavey Valveking head.

I opended it up drained the caps, cheked the filament supply....

It is 32 Volts DC goind in series from the first filament (first
tube) to the last filament of the fourth tube.
On the last filament of the fourth power tube the voltage is 6vDC !!!!

Like this:
-------------

32v->(7- 2)->25v->(7-2)->18v->(7-2)->12v->(7-2)->6V

Then the Resulting 6vDC goes to V1,V2,V3 (12ax7)
(Those are in parallel)

What the hell????

The 12ax7 filaments feed from the "Resulting" 6vdc of the "Used" 32vdc
from the power tubes filaments !!!!

This means the power tubes HUM because of imbalance.
And if the first filament of the first power tube dies, the amp is disabled.

How the hell will I find the tube that broke the chain if all the other tube are also dead?

Questions please:
Where do I find 6.3v AC in the board?
Can I power the filaments with DC? 32vDC?
I've head of something like "Floating Postive center tap" but I thik I also need the 6VAC.

I can rewire the amp no problem, But I need some Pro suggestions from you guys.

Help Please...

Thanks.
Gear
Valveking 100W Head.
Framus 2x12 w/Celestion Vintage 30's.
Cort X-TH Neck-Thru Body 81/85 w/Original Floyd Rose.
Boss GT-10, GE-7, NS-2, Vox Wah, EHX Metal Muff, ProCo RAT, etc...
Last edited by ilya-v at Aug 29, 2009,
#2
Quote by ilya-v
What the hell????
It's series wiring on the heaters. Yeah, it's goofy. But that's what they did. Get over it.

Quote by ilya-v
This means the power tubes HUM because of imbalance.
lol, no. If the power tubes hum, it has nothing to do with "imbalance". Check your heater supply for ripple. Maybe one of the filter capacitors in the heater circuit failed.

Quote by ilya-v
How the hell will I find the tube that broke the chain if all the other tube are also dead?
Ohmmeter on the heater connections of each tube is the easiest way. Just pull each tube and check it.

Quote by ilya-v
Questions please:
Where do I find 6.3v AC in the board?
You won't find it. Your amp doesn't use a 6.3v AC.

Quote by ilya-v
Can I power the filaments with DC? 32vDC?
That's what's happening right now.

Quote by ilya-v
I've head of something like "Floating Postive center tap" but I thik I also need the 6VAC.
Yeah, biasing the heaters above ground is common. Almost as good at reducing hum as running them on DC.

Quote by ilya-v
I can rewire the amp no problem, But I need some Pro suggestions from you guys.
Rewire it how? You have DC heaters. The only way it could be better would be if the heaters were in parallel on a 6v DC supply. But unless you get a different PT or add another transformer just for the heater, you won't have 6v with enough current available to do that.
Meadows
Quote by Jackal58
I release my inner liberal every morning when I take a shit.
Quote by SK8RDUDE411
I wont be like those jerks who dedicate their beliefs to logic and reaosn.
#3
Thanks SomeoneYouKnew.

The 32vdc is not straight from the transformer, its generated by a Diode Rectifier
and a few caps.

Quote:
Can I power the filaments with DC? 32vDC?

Answer:
That's what's happening right now.

I mean individualy.


Can I use a Voltage Divider with two resistors to make the 32vdc to a 6vdc?
Would I have enough current to run the divided 6vdc in parallel to all the tubes?

If I'll have the 6vdc how will I wire it?
In parallel to all the tubes on one side but what about the other side? Ground?
Gear
Valveking 100W Head.
Framus 2x12 w/Celestion Vintage 30's.
Cort X-TH Neck-Thru Body 81/85 w/Original Floyd Rose.
Boss GT-10, GE-7, NS-2, Vox Wah, EHX Metal Muff, ProCo RAT, etc...
Last edited by ilya-v at Aug 29, 2009,
#4
Quote by ilya-v
Thanks SomeoneYouKnew.

The 32vdc is not straight from the transformer, its generated by a Diode Rectifier
and a few caps.
Yeah, I know.

Quote by ilya-v
Quote:
Can I power the filaments with DC? 32vDC?

Answer:
That's what's happening right now.

I mean individualy.
No.
12AX7s can run on either 6v or 12v. You can connect the two heaters in parallel or series.
6L6s can only run on 6v.

Quote by ilya-v
Can I use a Voltage Divider with two resistors to make the 32vdc to a 6vdc?
Would I have enough current to run the divided 6vdc in parallel to all the tubes?
Try to do that and your amp will give you one of these:


You'd be asking that circuit to deliver 5 times the current it was designed for.
Not taking into account the 14v for op-amps and relay stuff that's connected to that supply, it presently provides 32v @ 900mA for the heaters. That's almost 29 watts.

If you change your heaters to parallel and run them from the same supply, you'll be asking it to provide 144 watts. Where do the additional 115 watts go? The voltage divider has to turn them into heat. That's a LOT of friggin heat!

But don't worry. The resistor will never get that hot. Most of the power will already be turned into the smoke billowing out of your power transformer.
Meadows
Quote by Jackal58
I release my inner liberal every morning when I take a shit.
Quote by SK8RDUDE411
I wont be like those jerks who dedicate their beliefs to logic and reaosn.
#5
Thank you agian.

Of the record:
You are one damn arrogant dude.
Chill... write with respect.
Gear
Valveking 100W Head.
Framus 2x12 w/Celestion Vintage 30's.
Cort X-TH Neck-Thru Body 81/85 w/Original Floyd Rose.
Boss GT-10, GE-7, NS-2, Vox Wah, EHX Metal Muff, ProCo RAT, etc...