Fender Blues Deluxe troubleshooting? FIXED! How to Dumblize?

[tubenoob]

The heaters are definitely on when it fades out, the filaments are glowing and there is voltage everywhere there's supposed to be.
I have the board pulled at the moment...don't really know what to do but I'm looking at it.

[tubenoob]

After messing with this thing all day I got it working.
There's a .1 1000v cap called R51 on the board right around the power supply area that had a cold or broken solder, it was causing the problems I think, cause when I wiggled it all he'll broke loose and when I retouched it with solder everything was fine.
It was definitely susceptible to vibration so that seemed to be it.

It the process I replaced a lot of parts that didn't need replacing.
And I changed a couple of things.
The am p sounds pretty good but I have a feeling it could sound better.
One thing I did was change the slope resistor from 100k to 68k on someone's suggestion, I think it sounded better before so I'll probably change that back

So now I want to make it sound better.
I see there is a mod to use the unused triode and while the Drive channel isn't that great, I'm not sure more gain is going to make it better.
It has kind if a crispy crunchy overdrive tone, I've heard you can dumblize these to some extent, how is that?

[martin manning]

Glad you found the culprit.

Yea, that 91k in the PI section always goes as both of those plate resistors need to be 1 watt, not 1/2 watt like they are...

I'm still not buying this 1W thing. What is your reasoning? When I do the math I don't see the plate resistors being in any danger of exceeding dissipation or voltage limits. Someone alluded to a batch of bad parts getting into these at some point, and that I can believe.

For the bias adjust, I would do something like in the mark-up below.

[tubenoob]

I thought maybe I could share something that might be helpful to someone.
On this version of the Blues deluxe there is no boas adjust pot and no bias test point.

I followed the trace from the power tubes cathode and found that on the main board there is a jumper wire maked Wxx that is a perfect spot to insert a 1 Ohm precision resistor.

Where the 27k bias resistor is located, I removed the resistor and replaced it with a 25k trimmer a 15k tail (the wiper tied to one leg and a 15k resistor comin off it) that fits right into the spot where the resistor was and now I have a way to check the bias and adjust it, imagine that!
It was pretty far off too...the negative voltage was -44.7 and at that voltage with the groove tubes that are in it, the current draw between both tubes was only 60mA, so I adjusted it to about 38mA per tube (assuming they match) and it sounds good.

So now I'm thinking of using that unused triode and basing the two triodes like a high plates ODS.
Anybody see a problem with that idea?
I was going to take the Duncan's amps blues deluxe mod and tailor the values to match the ODS.220k/150k OD plates arrangement, with snubbers, etc.
Any feedback on this idea would be appreciated.

[xtian]

It has kind if a crispy crunchy overdrive tone, I've heard you can dumblize these to some extent, how is that?

I played this amp for years, then sold it, and am now playing one again because of my church gig. I have slowly made friends with the drive channel! Start by turning the Treble all the way down, and the Bass down a bit too. Keep the Drive fairly low. I find this to be quite acceptable with humbuckers.

[tubenoob]

I hear you, and I agree that you can dial in an ok overdrive tone with eq and presence settings but for me it kills the clean tone. I couldn't find a balance between clean and overdrive so here's what I did.

First, I abandoned the idea of adding the unused triode, I got as far as cutting the traces and running the wires but I decided that adding more gain is probably not what I'm looking for and to focus on the existing circuit for now so I have the wires stubbed out and grounded in a sort of ugly way but it's back to the original circuit in that regard.

Added 330pF ceramic snubber from the plate to the cathode of v2a to roll of some highs in drive only
Added .001uF bleeder cap across the outside lugs of the Master pot to further roll of highs.
Changed tone stack caps to .02 mid 225p series orange drop, .02 bass 225p series orange drop, 270pF treble silver mica,
Changed the slope resistor from 100k to 56k, just following tweed bassman logic.
Increased the NFB resistor from 68k to 100k because to me it makes the cleans better, more Hendrix.
Changed the bright cap from 750pF to 360pF
Changed the C4 Drive cap from 750pF to Mallory PVC .001uF to fatten overdrive a little.
Changed the PI resistors to .5w carbon film
Changed the PI tail from 6.8k to 10k, more in line with bassman spec
Changed the .1uF coupling caps to new quality film caps for no reason other than they seemed old and crappy next to all the new parts.
Changed to PI entrance cap to .02uF PS6 series orange drop
Changed other coupling caps to PS6 orange drops and plate resistors to Dale RN65 precision.
Changed 470R screen resistors to 1k 3w Dale wire wound
Removed 1.5 grid resistors from 6L6s.
Biased it at 42mA pr/

I have to say it sounds really good considering what it is.
I got the nice shimmering Hendrix like clean tone, not too bright or too flubby, mids can dial down or up nicely.
Switch to overdrive and before with the cleans how I like it the OD was crispy and and shrill.
Now it's fat with great bite and body, it's more than just useable it's good. Great sustain, fat and punchy with bite and not flubby with good articulation.
I think my friend is going to be impressed, I am.
It sounds crazy to say this but it makes me want to get one for myself now that I know what to do with it.

[Stevem]

Martin it's that it seems most manufactures rate there 1/2 watt resistors for no more than 350 and most PI plate load resistors are being hit with way more than that, no?
Also I have replaced far more open PI plate load resistors than I have plate load resistors from other sections of the preamp.
Yup, 6 of those open 91k resistors in 2 years time in folks amps!

[JazzGuitarGimp]

Way to go tubenoob! If you're not careful, you're gonna have to change your user name!

[martin manning]

Martin it's that it seems most manufactures rate there 1/2 watt resistors for no more than 350 and most PI plate load resistors are being hit with way more than that, no?
Also I have replaced far more open PI plate load resistors than I have plate load resistors from other sections of the preamp.
Yup, 6 of those open 91k resistors in 2 years time in folks amps!

See in this post: https://tubeamparchive.com/viewtopic.ph ... 379#312379
The main points are that exceeding 350V is not likely, even in the PI plates, and 1W parts are not necessarily rated any higher in voltage than 1/2W parts. Were these 91k resistors you've replaced perhaps part of the batch of bad parts someone mentioned?

[tubenoob]

Way to go tubenoob! If you're not careful, you're gonna have to change your user name!

Thanks! This is fun stuff. With both the Fender and the Vox
I had no idea at all where to begin or what to do and I wished that there was more feedback being thrown my way because I'm so impatient, but there was enough to get me asking the right questions and thinking it through and I surprised the hell out of myself fixing a number of problems so far, this is a great place to learn...thank you very much!