fender hot rod deville mods

[Colas LeGrippa]

Hi ! Glad to be back ( after one week ). I am sure youre happy too, because you will surely laugh ( at me or at what I'll say ). Q: Wazzup ? A: a Fender Hot rod DeVille that a client brought to me for mods on the clean channel. He doesn't like the distortion channel. Kaka to him (that's what HE said, not me).  In fact he'd like the clean one to break up earlier, to have more bite, you know just the sharp edge that is interesting to play soft rock. I had 5 min. last night to take a look at it and the first move I did is replace the 6L6's  by 6v6's . Instant goodness, but still not enough. Next plan is to remove NFB. The other next ( if I can say ) is to jhook up in parallel with the clean channel 12ax7 cathode a resistor and a cap so that the total is 820R and 330uF, for extra gain. If you guys would have other ideas to share, youre right on the spot for that!

Thanks

Colas

[stratele52]

Hi Colas , yes we are glad to hear you back.

About the hot rod deVille  you are not afraid to burn the 6V6's?  There a lot of power for these tubes in DeVille, and too much voltage I think. You have to put bias very very low. Are you able to lower bias enough?

[Colas LeGrippa]

 i know 490V is too much for 6V6's, I did not have time yet to tweak the bias. I'll be back!

Colas

[Colas LeGrippa]

what I did:

-6V6's biased at 20mA each ( bias pot very effective, down to 0 mV and up to .......I did not try hey hey )
-NFB disconnected from speaker jack
-fender / groove tube 12ax7's replaced with JJ's

that is a very good beginning, in fact this amp sounds 50% better now on the clean channel. All I have to do now is tweaking the preamp cathodes with new values and replace the 10 in fender speakers by Eminence raging cajun. That'll be done.

I invite you though to submit your comments and ideas to improve the gain on the clean channel.

Colas ''get a grip'' LeGrippa from Montreal.

P.S.: kiss your wife, fellas, or the neighbour will. ( this is related to amp tweaking because if you're down in the basement spending too much time on your amps, your wife will become in need and meanwhile if your neighbour comes to borrow your lawn mower and SHE answers the door, you may not be aware of that and she will be so hot that they will be kissing while you test one of your amplifier, full volume up. )

[Colas LeGrippa]

I will try EL34's and KT66 also,  but the 6V6 will break up earlier, I think. Oh gee, I GOT TO plug in a pair of EL84's  with yellow jackets, that's gonna be killer. I'll be back with results.

I love you all.

Colas

[stratele52]

Hi Colas,

How much plate voltage you have with 20 ma bias ? You probably have too much for long tube's live.

And about the power , try the amp at maximum volume and see how much current you have on your 6V6 ( plate/ cathode with signal) .
This show you if there is too much power for the tube.

[stratele52]

What is the 6V6 's brand name you put in the amp ?

[Colas LeGrippa]

i have 490V on the plates of the JJ 6V6's with 20mA

[Colas LeGrippa]

wow this is really cool !

[sluckey]

Sounds cool to me too. Who's watching your wife? 

[jjasilli]

IMHO: This series of amps HR Deluxe; Hot Rod Deville, etc. have poor clean tone & worse overdrive tone, stock (unlike their little brother the Blues Jr., which sounds great stock).  Checkout the mods for the HRD.  They're posted here and on the internet.  Post again if you can't find them.   Good news:  These amps can be made to sound great.  Bad news:  the mods are extensive & a PIA to do on the cheap PCB; and the PCB is nothing but a lot of cold solder joints waiting to fail randomly as you work on the board.  Quality signal caps make a big difference.

Probably 6V6's seem desirable because of uncontrollable loud vol past 2 on the dial - a serious drawback.  There are fixes for that, including:  replace the linear taper Master Vol pot with an audio taper, and put lower mu preamp tubes in positions 1 and maybe 2.  You now have control over the vol/gain pots, and can still get overdrive.

[Colas LeGrippa]

Sluckey: prob. my right neighbour, but my pitbull is watching him so I'm not worried.

jjasilli: on the hotrod deville I'm working on, the bias pot can't bias the output tubes hot enough and is designed to stay way beyond the upper limit of 70% Sterile tone.
Signal caps are so tiny I am wandering how the signal can pass through!
The yellow jackets with EL84's do a great job, combined with the disconnection of the NFB. In fact, I think this amp would be a lot better if it was cathode bias type and that's what the jackets do. The clean tone is much warmer. Imagine with carbon resistors and orange drops caps.... but at this point, better strip out the whole thing and build a new one ! The trannies do a good job, it is the rest that suffer a lack of good parts. I have seen a couple of mods on internet, but nothing so special. Just removing the pcb is a hassle so I want to be sure any change is worth the work !

Colas

[Colas LeGrippa]

I promise I won't do that again

[phsyconoodler]

The Fromel mods for Hot rod Fender's are great,especially the reverb mod.
  To get more hair on the clean channel without changing anything,you simply insert a volume box into the effects loop.It allows you to crank up the clean volume and turn the overall volume down to a less than nosebleed level.Works pretty good for me.
  Volume Box? Simply a 100k audio pot inside a box with two patch cables and two jacks.One in the power amp in and one in the power amp out.You now have a master volume for your clean channel.
 The reverb mod? Simply remove R105 off the board.WWWAAAYYYY better reverb now.Before it's almost unuseable after '2' .

[Colas LeGrippa]

yeah I read about the master volume box, I'll go for it....I'll try at least and see what happens

I'll check the R105 on the schem...do I replace it with a bridge or simply take it out ?

[jjasilli]

Here's a more complete reverb mod, also killing an evil capacitor:  http://www.justinholton.com/hotrod/reverb.html

BTW:  I think I've done all the mods on this site to my HRD.  They are great!!!  But, once again, a PIA.

[stratele52]

i have 490V on the plates of the JJ 6V6's with 20mA

IMO Colas the bias is too hot and plate voltage too. Tubes will have short life.

Do another test ; play guitar in the amp with reading bias , turn volume for medium to high output.
 You'll see how much current flow in tube in playing mode . You will know if tube drive too much power.

[Colas LeGrippa]

stratele, better than playin guitar: I inject a 280mV, 1khz signal from my tone generator

for my client, tube life is no important: he prefers a good tone for a year, rather than sterile tone for....eternity.
after all, what would do tubes manufacturer without musicians craving  red plating tubes tone ?

[Colas LeGrippa]

..anyway the 6V6's are out to the profit of yellow jackets/EL84, bias pot being turned all the way clockwise, to the less negative voltage

[Colas LeGrippa]

orange sucks.

[sluckey]

orange sucks.

not as much as pink!

[Colas LeGrippa]

that's for sure!

[stratele52]

..anyway the 6V6's are out to the profit of yellow jackets/EL84, bias pot being turned all the way clockwise, to the less negative voltage

Less negative bias votage = very very hot bias .  In this amp 6V6's need probably full negative voltage, not less.

[stratele52]

stratele, better than playin guitar: I inject a 280mV, 1khz signal from my tone generator

for my client, tube life is no important: he prefers a good tone for a year, rather than sterile tone for....eternity.
after all, what would do tubes manufacturer without musicians craving  red plating tubes tone ?

And how much 6v6's ma you read at high volume ?

Yube life could last only fews weeks in worst case . Not enough mesurements to know. Tubes alway play very well before they come dead

[Colas LeGrippa]

stratele, I am telling you this bias pot has to be set at MAX LESS negative voltage, not fully negative. It has been designed to run the tubes cold with no possibility of running them hot.

[stratele52]

I think Nicolas we don't talk about the same thing.

[rzenc]

i have 490V on the plates of the JJ 6V6's with 20mA

I ASSume you read it directly from R66? If so, you are reading the current from both tubes. 490V * 0.02 A = 9.8W for BOTH tubes...Fender recommends 60mV (across 1 ohm = 60mA ), if your B+ did not sag when cranking, 490V * 0.06A = 30W. However, it may sag... which is why you need to read  B+ again after biasing.
HDR's seems to become alive when biasing them on the high  side...

Hope thie helps

Best Regards

R.

 

[stratele52]

i have 490V on the plates of the JJ 6V6's with 20mA

I ASSume you read it directly from R66? If so, you are reading the current from both tubes. 490V * 0.02 A = 9.8W for BOTH tubes...Fender recommends 60mV (across 1 ohm = 60mA ), if your B+ did not sag when cranking, 490V * 0.06A = 30W. However, it may sag... which is why you need to read  B+ again after biasing.
HDR's seems to become alive when biasing them on the high  side...

Hope thie helps

Best Regards

R.

 

+1 rzenc,   

That's a good point ,I thaugh nicolas put a 1 ohms resistor on tube's cathode for mesurement of 20 ma. But not sure.

[sluckey]

That's a good point ,I thaugh nicolas put a 1 ohms resistor on tube's cathode for mesurement of 20 ma. But not sure. 

And maybe he did. But so what? Even if his numbers are for one tube, 490V and 0.02A is 9.8W. And that's exactly 70% static dissipation for a 6V6. And 70% is what most of us shoot for in a fixed bias P/P amp.

And if those numbers are for two tubes (which I doubt), then he's running waaaaaay cool.

[Colas LeGrippa]

Mr Bothcaster, my name isn't Nicolas and my nickname is Colas.  I  don't want to argue with you but I know what kind of negative voltage runs a tube colder or hotter.
Sluckey, I was talking about 40mA for both tubes , anyway as I said in my last post. the bias pot is fully on the less negative side and I just can't bias hotter, Mr Fender Engineer decided so.

I love you all, but I prefer my wife !

[stratele52]

Sorry Colas for the wrong name , too long days at work this week