Fender DRRI bias range mod

[Chuck H]

Well if the customer has a "bias probe" it's probably a plug in jobbie that he bought so he could play "pseudo tech tone master". Which pretty much puts the matter out of Randall's hands. So Randall's quandary is whether to give this guy the ability to blow up his gear by granting a request to change an adjustable parameter from *cold <> hot* to *cold <> melt*

I think I would try to explain to the guy about how the circuit has to balance voltage with current to keep the tubes in a reliable operating condition. Basically, make sure he understands that current is only half of the equation. Voltage may be the half he is ignoring. Then I would refuse the modification on those grounds. as in: "As your repair tech I can't, in good conscience, modify your amp so that it can be adjusted into an unreliable operating condition."

[Enzo]

1. Advise them what is proper.

2. Do what they want.

3. You can always just decline the repair.

[J M Fahey]

FULLY agree withb Enzo.
Just advise him on good procedure, do what he wants, cas $$$ and forget about him.
Who cares? ... youīre not his Mommy (I guess )
You canīt cure stupid so Plan B is just follow his folly.

IF it were something really dangerous, such as re-attaching a death cap, bypass a fuse or downgrade to 2 wire ungrounded cord, Iīs refuse based on liability issues, but ... letting him *need* a new pair tubes a year? orr even every 6 Months? who cares?

I lost **MANY** jobs by being honest beyond the call of duty ... ONLY result being they went to somebody else who did what they wanted and got the cash

To boot, a few bad mouthed me calling me an old fool who lived in the past or too callous to follow customerīs orders so I didnīt even get good Karma for my good deeds.

[SoulFetish]

FULLY agree withb Enzo.
Just advise him on good procedure, do what he wants, cas $$$ and forget about him.
Who cares? ... youīre not his Mommy (I guess )
You canīt cure stupid so Plan B is just follow his folly.

IF it were something really dangerous, such as re-attaching a death cap, bypass a fuse or downgrade to 2 wire ungrounded cord, Iīs refuse based on liability issues,

^^^^^ I absolutely agree with Juan on this point and follow the same policy. The liability issues alone make this an important and wise practice. I look at it on a personal level as a matter of character as well. Bottom line is I love what I do, and I care about my customers.
Juan's right in that you can't cure stupid. If someone wanted to go home and install lead water pipes because they're trying to recapture some of the some of those good times they had biting the window sills at grandma's house, there's not much I can do about that.
But, if a customer was insistent that I do something I know to be dangerous I won't even touch the equipment, and respectfully explain why. While that kind of dumb can be really frustrating to deal with, it certainly doesn't call for a potential death sentence. I certainly look back at some of the stupid shit I've done, and managed to escape with my life . Plus, what if someone else happened to play his gear at the wrong time and something tragic happened. I want no part of that.

[Randall]

Update. Customer came in with his amp today, nice guy. He brought his bias probe, so I hooked it up and measured the plate voltage. He was running the hotter tube at 25mA @ 416v = 80%. I explained all the bits about how plate voltage plays into it, and how to determine wattage with those readings. Also, how Fender sets them cool, and the 50 -70% thing. His amp had the 22K R59, and since he still wanted to play around with it, I tacked another 22K across it, making it easy to remove if ever decided. Now he can get as high as 40mA. I told him again and again that 30mA was way high and 40mA was probably going to explode high. It's in his hands now. If it does go boom, I'll get another paying visit.

[Jazz P Bass]

I had a jazz guy with a Fender something and he insisted the bias was too cold.

Cranked it up.

He came back the next week and asked me to put it back where it was.

I guess it depends on the playing style/ type.

40 ma's on a 6L6 is suicide.
I don't care what the plate voltage is.

[Tone Meister]

I had a jazz guy with a Fender something and he insisted the bias was too cold.

Cranked it up.

He came back the next week and asked me to put it back where it was.

I guess it depends on the playing style/ type.

40 ma's on a 6L6 is suicide.
I don't care what the plate voltage is.

Problem is, these are 6V6 which dissipate less than half the wattage of a 6L6. (I realize that was probably a typo)