Bias Sampling Resistor 1 Ohm 2 Watt 1% Tolerance Blown KT66

Solutions, Advice, Mods, and Troubleshooting.

Moderator: longfxukxnhair


frank9310
Diamond Member
Diamond Member
User avatar
Posts: 1240
Joined: 04 Jul 2009, 13:56
Has Liked: 6 times
Been liked: 38 times
Contact:

Bias Sampling Resistor 1 Ohm 2 Watt 1% Tolerance Blown KT66

Postby frank9310 » 06 Jul 2010, 21:26

For those who blow a KT66, if your 1k/5W screen grid resistor is ok and all your tubes light up after replacing the bad tube but you are unable to get a bias reading and your amp sounds like doggie doo, check R83 and R84. It should read 1 Ohm if you touch both sides of it with your test leads (amp on or off).

If one or both are blown, replace with 1 Ohm, 2 watt 1% tolerance resistor ike this one. In fact, probably a good idea to keep a few of these on hand as Radio Shack doesn't carry anything with a 1% tolerance and Steve stressed that this is critical to getting an accurate bias reading. Otherwise, your bias reading could be 5-10% off if that's what the tolerance is on the Radio Shack part. I bought a 1 Ohm 10 watt 10% tolerance resistor at Radio Shack to hold me over till the real ones arrive but that's all they have http://www.radioshack.com/product/index ... Id=2062290

What you want is this one below...

http://www.newark.com/jsp/search/produc ... R0000FKE14

DISCLAIMER: If you are not a qualified service technician, do not attempt to do this unless you know what you are doing. The high voltages inside an amp can kill you dead.

Here's what it looks like replaced on the PCB. The original was smaller and blue with colored bands. It must have been the .75 watt one instead of the 2 watt one Steve recommends to use now.

Image
Image
Image
Image
"It may take talent to play fast, but it takes SOUL to say something between the notes....."

"Most people are about as happy as they make their minds up to be..." ~ Abe Lincoln

http://www.facebook.com/frank93101
http://www.facebook.com/areyouexperiencedband

Band page http://areyouexperienced.net/RobinTrowe ... clips.html

Electronic Press Kit (EPK) http://www.gigmasters.com/presskit.aspx?id=62115

munkyver
<100 Posts
<100 Posts
Posts: 54
Joined: 24 Nov 2015, 23:45
Has Liked: 4 times
Been liked: 17 times
Contact:

Re: Bias Sampling Resistor 1 Ohm 2 Watt 1% Tolerance Blown KT66

Postby munkyver » 10 Oct 2016, 03:38

Hello,

I think mine got caput in my 1959rr... reading about it in the internet, mine is a 1R 2 watt flame proof according to the schematic. Unfortunately, I wasn't able to find one here in Singapore and online as well. I was able to find a 1 watt but not flame proof. Do you think it will be ok?

Cheers,

Anitoli
Knighted
Knighted
User avatar
Posts: 4532
Joined: 05 May 2013, 12:35
Location: Lewiston, Maine
Has Liked: 2610 times
Been liked: 2688 times
Contact:

Re: Bias Sampling Resistor 1 Ohm 2 Watt 1% Tolerance Blown KT66

Postby Anitoli » 10 Oct 2016, 13:00

munkyver wrote:Hello,

I think mine got caput in my 1959rr... reading about it in the internet, mine is a 1R 2 watt flame proof according to the schematic. Unfortunately, I wasn't able to find one here in Singapore and online as well. I was able to find a 1 watt but not flame proof. Do you think it will be ok?

Cheers,
Yes that will be fine. In the event that the resistor sees enough current to blow it isnt going to last long enough to catch on fire.

Anitoli
Knighted
Knighted
User avatar
Posts: 4532
Joined: 05 May 2013, 12:35
Location: Lewiston, Maine
Has Liked: 2610 times
Been liked: 2688 times
Contact:

Re: Bias Sampling Resistor 1 Ohm 2 Watt 1% Tolerance Blown KT66

Postby Anitoli » 10 Oct 2016, 13:00

I have used the wire wound equivalent of that resistor and they work very well.

Return to “Roadhouse Repair Shop”

Who is online

Users browsing this forum: No registered users and 4 guests