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Post by Jerry P on Aug 5, 2004 20:29:04 GMT -5
Sorry the bias mod is all the technical info I'll be putting up. Bias points is too involved and can be dangerous.
Jerry
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Post by swakke on Aug 6, 2004 1:45:02 GMT -5
did the bias-mod last night, I installed a pot next to my 6L6's for easy bias-adjustment acces, that metal plate is one tough suckah to drill through though... works like a charm, even with the stock tubes. Why is everybody always saying there're brand-X stocktubes in the 5150, mine were Sovteks and Electro-harmonix...?
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Post by Jerry P on Aug 6, 2004 6:02:40 GMT -5
I didn't know people said that. They ship with Sovtek's and EH (made by Sovtek).
Jerry
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Post by swakke on Aug 6, 2004 6:15:21 GMT -5
harmony central is full of that shit, they should put a Bullshit-filter button on there somewhere...
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Post by AZ Guitar Repair on Aug 15, 2004 16:11:07 GMT -5
Jerry, will this bias mod work for the 5150II's? Thanks for the info/photos of the bias mod as well.
Scott Eivins
A&Z Guitar Repair
Eolia, MO 63344
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Post by Jerry P on Aug 18, 2004 17:51:33 GMT -5
This mod won't be the same for the 5150II. The 5150II already has the pot installed. The bias range on the 5150II is too cold though.
Jerry
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Post by A&Z Guitar Repair on Aug 19, 2004 10:17:54 GMT -5
Thanks for the response, Jerry. Scott Eivins A&Z Guitar Repair Authorized Krank Amplifier Dealer www.krankamps.com |
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Post by Tim G on Sept 18, 2004 15:13:42 GMT -5
I helped a friend of mine install the bias mod for his 5150 (thanks for the write up, everything went smoothly) But, I have one quick question. Using the transformer shunt method I was only reading 23ma prior to the mod. They way I am reading the schematic means its only running 11.5 mA / tube? Is that correct? (seems really low) I adjusted the bias up to a reading of 33 mA but didn't want to go any higher until I found out for sure I was reading things right. The transformer shunt method should show the current for 2 tubes and I am thinking I should be looking for a total current in the range of 64 - 66 mA. Am I heading in the right direction?
Thanks for any info
Tim
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Post by Jerry P on Sept 22, 2004 22:23:04 GMT -5
Using the transformer shunt method you are measuring the current draw for 2 tubes so you would want to be up in the 64-66ma area.
Jerry
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Post by Tim G on Sept 27, 2004 18:47:31 GMT -5
Thanks! Mod works great! Tone is fantastic.
Thanks
Tim
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Post by Sikester on Oct 18, 2004 13:04:44 GMT -5
Jerry,
I did the mod yesterday. Only problem is, I'm not getting any current (ma) reading on my meter. Yes!! I do know how to use one and have had electronic experience. The circuit is hooked up correct and the circuit resistance is accurate, but no current value. I have a mid priced Craftsman volt/ohmmeter i'm using. Should I use a meter that will read lower current values more accurately? I am using a tube Bias tester in the 4th power output tube FYI. Any help would be greatly appreciated. I do See you on the Peavey Website as well from time to time and your info is a big help. Thanks again.
Sikester
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Post by Jerry P on Oct 18, 2004 13:55:17 GMT -5
Jerry, I did the mod yesterday. Only problem is, I'm not getting any current (ma) reading on my meter. Yes!! I do know how to use one and have had electronic experience. The circuit is hooked up correct and the circuit resistance is accurate, but no current value. I have a mid priced Craftsman volt/ohmmeter i'm using. Should I use a meter that will read lower current values more accurately? I am using a tube Bias tester in the 4th power output tube FYI. Any help would be greatly appreciated. I do See you on the Peavey Website as well from time to time and your info is a big help. Thanks again. Sikester What type bias probe are you using? I'm not familiar with all of them but you usually are reading the millivolts scale when you use a bias probe. You shouldn't be reading ma. With most bias probes you are measuring the voltage drop across a 1 ohm resistor (built into the probe) which due to ohms law works out to an equivilent to the ma of current for that tube. You get no reading on any tubes or just that one? If it's just one then chances are you have a failed screen grid resistor. Does the amp work since the mod? Jerry Jerry |
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Post by eddmann on Oct 20, 2004 23:09:44 GMT -5
Hello, hope im not inturupting here. I just had a quick question. I would like to get the bias mod AND the lowered gain mod done, and I understand you now offer that "tone" mod in the package for $180.00? Well, I am about to install JJ tubes, but to get the mods done, do I have to send the whole amp head to you, or could I just send the board per the instructions? Sorry if I missed that in the webpage... thanks for any info...Eddie
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Post by Jerry P on Oct 21, 2004 1:25:22 GMT -5
Welcome! You're not interupting anything. Ask all the questions you like. To do both mods I would need the entire amp. The lower gain mod is the only one I can do with just the preamp circuit board.
Jerry
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Post by THANKS on Oct 21, 2004 10:42:55 GMT -5
Thnk you very much, thats good news, only 15-40 dollors to send in the head. I emailed this quesion in to, so sorry for the double take. But, you managed to answer both, and that my friend, is impressive. Looking forward to sending the goods, and recieving the GREATS....Eddie
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