Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: joesatch on March 27, 2022, 04:55:31 pm

Title: Massive resistor after Primary filter caps.
Post by: joesatch on March 27, 2022, 04:55:31 pm: What is this 10W 400R dale resistor for?
Title: Re: Massive resistor after Primary filter caps.
Post by: tubeswell on March 27, 2022, 05:46:11 pm: That's between the plate and screen supply nodes, so its part of the R/C filtering
Title: Re: Massive resistor after Primary filter caps.
Post by: sluckey on March 27, 2022, 05:46:41 pm: It's purpose is to drop voltage to the rest of the B+ string. 400Ω/10W is not MASSIVE.
Title: Re: Massive resistor after Primary filter caps.
Post by: shooter on March 27, 2022, 05:55:43 pm: I used I^2 R
100mA^2*400 = 4W
that's probably in the danger zone for the stuff downstream to be pullin
Title: Re: Massive resistor after Primary filter caps.
Post by: sluckey on March 27, 2022, 06:11:32 pm: Quote from: shooter on March 27, 2022, 05:55:43 pm
I used I^2 R
100mA^2*400 = 4W
that's probably in the danger zone for the stuff downstream to be pullin
Did you just make up those numbers? You ain't out in the bait shop are you? :wink:
Title: Re: Massive resistor after Primary filter caps.
Post by: uki on March 27, 2022, 06:16:09 pm: this is massive !!

(http://4.bp.blogspot.com/-lJsvI8H5wlg/VRnsQrviQTI/AAAAAAAAAk4/Lbc-rpeKyY4/s1600/IMG_1180(use%2Bthis).JPG)
Title: Re: Massive resistor after Primary filter caps.
Post by: joesatch on March 27, 2022, 09:37:33 pm: i believe i found the answer on the interwebs..
Title: Re: Massive resistor after Primary filter caps.
Post by: thetragichero on March 27, 2022, 10:23:16 pm: it is certainly cheaper, but can also be a design choice
Title: Re: Massive resistor after Primary filter caps.
Post by: AmberB on March 27, 2022, 11:43:08 pm: Pretty much standard procedure for Bogan tube amps...I've never seen one with a choke.
Title: Re: Massive resistor after Primary filter caps.
Post by: kagliostro on March 28, 2022, 01:58:22 am: If the position of the resistor on the schematic will be before the first node, also because on the schematic are indicated parallel connection, the purpose of that resistor can be SAG resistor (also the resistence value is compatible)

but as it is after the first node the only explanation is that to which refers Sluckey

--

(https://i.imgur.com/TZYf4xS.png)

Franco
Title: Re: Massive resistor after Primary filter caps.
Post by: shooter on March 28, 2022, 03:40:57 am: Quote
out ain't out in the bait shop are you?
:laugh:
there is logic behind the #'s
I was "looking" for 5W, then double n ship!
but to answer the ? :icon_biggrin:

Aside
we used foot long 1" diameter Resistors in a large Amp PS, they were ceramic coated, the PS's typical fail started with the Ceramic melting off and it goes down-hill from there!
Title: Re: Massive resistor after Primary filter caps.
Post by: AmberB on March 29, 2022, 03:18:28 am: When the ceramic melts off your resistors, you definitely have a problem...
Title: Re: Massive resistor after Primary filter caps.
Post by: Willabe on April 05, 2022, 12:20:13 pm: Quote from: AmberB on March 29, 2022, 03:18:28 am

When the ceramic melts off your resistors, you definitely have a problem...

:huh: :l2:
Title: Re: Massive resistor after Primary filter caps.
Post by: shooter on April 05, 2022, 01:11:01 pm: I looked for the pics but they are lost in space
the heat on the top of the box was enough to melt the Aluminum, and "etch" really nice colors into the cover.
I did a painting of it n gave it to the Boss :icon_biggrin:

the box was so hot I just left it for 12hrs.
after the field reported many such cases the real Engineers finally put down their coffee and came up with a fix.