Fender Hot Rod Deville Conversion over to Handwire HELP!!

[John]

And honestly, that's a confusing way to draw it. I got spoiled reading Doug's schematic.

[tubenit]

Thanks John!   Finally saw it and corrected the SCH schematic in the earlier post.

I still am NOT familiar with a bridge rectifier looking like that before that I can remember?

With respect, Tubenit

[John]

You're welcome. I got stymied by the way a voltage doubler was drawn on a Heathkit schematic. After following it closely and wiring everything just like it said, and having it work, I'm still befuddled by the drawing!

[USAampsRus]

You guys Rock!


With much Respect

Anthony

[tubenit]

So is this a half wave voltage doubler?   


And NOT a bridge rectifier?

[66Strat]

It's a bridge rectifier. You have an error in your schematic

Ah OK,  finally caught the error and corrected it.  I will say I am NOT familiar with this type of bridge rectifier & I'm not recognizing it to be like any of the solid state rectifiers that Doug illustrates in his Library of Information.

And I don't see a separate ground for negative end of the rectifier ?   It appears it's using one of the high voltage wires as a ground?

With respect, Tubenit

The Fender schematic is drawn in a confusing manner. It took me a while this afternoon examining it to figure out what they were doing.

[USAampsRus]

 I felt the same thing very confusing it was giving me a headache.   

[66Strat]

So is this a half wave voltage doubler?   


And NOT a bridge rectifier?

Plain Jane bridge rectifier. Just drawn in a confusing manner by our friends at Fender. Probably some kind of schematic drawing software.

[PRR]

> So is this a half wave voltage doubler?    And NOT a bridge rectifier?

It is a plain old common Full Wave Bridge.

You can draw it with diodes slanty. -OR- you can draw it with diodes horizontal. Hoffman drew in an all-purpose graphics program with arbitrary orientation. The common circuit drawing software does not do slanty, so we use that tangled-up layout. But they are exactly the same.

[sluckey]

Some may like to stack the diodes vertically... 

[tubenit]

Gentleman, thanks for your help with this!  I will confess some embarrassment in not being able to see that for myself.   

With respect, Tubenit

[tubenit]

USAampsRUS,

Looking at the "back" of your DeVille combo/chassis with back off  ................. your input jack is on the right in your "tweed" style chassis.

Sluckey's Plexi 6V6 layout will work for you.  And he has all the documentation you need to make your own layout board.  I saw Doug's board material with a hacksaw and it's very easy & quick to do it that way and it makes very little dust.

It's easy to make your own turret board using Doug's layout board material and staking tools.   http://el34world.com/Forum/index.php?topic=9800.0

Presuming that you have enough room in your chassis & have measured space and compared it with size of Doug's layout boards .........

Hoffman's  5F6A Bassman will  work.   Hoffman's Plexi 50w will work.  Both have input jack on the right looking at back of combo.  Hoffman's sells boards for these and has a Bill of Materials, schematic, etc .......  These are in his Library of Information & his boards are in his online store.         

http://el34world.com/schematics.htm#Hoffman_Plexi_50_                     

You would change the input jacks to a single one if you're using Sluckey's Plexi 6V6 schematic. While there is no need to change the Bassman or Plexi 50w to cathode biased, you could still do that using one of Hoffman's boards IF you wanted to?

With respect, Tubenit

[USAampsRus]

Good Morning,

That sounds like the way to go. Ill order both Boards to have on hand. 5F6A & Plexi 50w. 
Can't Hurt.
Life by the Drop.!
I can see Clearly Now.
Doyle Bramhall

Im Gonna Start the Parts List  here in the next hour.

Thanks everyone for all the help on this Project!

And if for some reason this does Not Work out for me ........at least i tried.

Thanks Again,

Anthony

[66Strat]

Gentleman, thanks for your help with this!  I will confess some embarrassment in not being able to see that for myself.   

With respect, Tubenit

There's no need for embarrassment. The original (Fender) schematic was drawn very poorly IMO and the connection dots were not very clear.


Nice job on the schematic of your ideas for the OP.

[66Strat]

Good Morning,

That sounds like the way to go. Ill order both Boards to have on hand. 5F6A & Plexi 50w. 
Can't Hurt.
Life by the Drop.!
I can see Clearly Now.
Doyle Bramhall

Im Gonna Start the Parts List  here in the next hour.

Thanks everyone for all the help on this Project!

And if for some reason this does Not Work out for me ........at least i tried.

Thanks Again,

Anthony

Hi Anthony,

There's no need to buy two boards. They are very similar circuits. IF it were me, I would buy Doug's Plexi board and modify the circuit (component values) to land somewhere between 5F6A Bassman and 1987 Marshall. That part is easy. The areas that need work IMO are in the power supply and bias supply.

The HR Deville schematic shows 485 volts B+ supply to the output transformer center tap. IMO this is getting outside of the sweet spot for 6L6 tubes. I would add a dropping (sag) resistor (200 ohm, 15 watt) immediately following the bridge rectifier to get the B+ at idle down to around 460 volts. At maximum signal this would drop the B+ an additional 25 volts or so, simulating the sag effects of a tube rectifier. Additionally, I would tweak the dropping resistor values in the B+ rail to provide 385 volt DC supply to the PI and 325 volt DC supply to the preamps as reflected in the 5F6A schematic.

The cathode follower in both Marshall and Bassman circuits have DC voltage of about 180 volts. This is almost double the 100 volt DC cathode to heater rating for the 12AX7 tube. The peak AC plus DC rating is plus or minus 200 volts. I would look towards adding a DC voltage divider in the power supply to reference the heaters 90 volts above ground. This would allow the 12AX7 cathode follower triode and other 12AX7 triode sections to operate within the cathode to heater voltage ratings. The 90 volt reference is within the 200 volt heater to cathode rating for the 6L6 tube as well.

I would rebuild the negative bias supply on a new board and revise the circuit so that the negative voltage supply is not dependent upon the wiper connection. I would swap the 100K resistor and 25K potentiometer locations and reference the wiper of the 25K pot to ground. This way, if the wiper connection fails, the bias voltage goes to a more negative (colder) operating point.

Good luck with your project. It looks like a lot of fun.

Regards,
John

[USAampsRus]

Well thank you
John.

I still have a lot to learn and i'm enjoying the feedback here.

Anthony

[USAampsRus]

Here is an idea to consider.  Having said that,  follow Sluckey's advice on this and NOT mine.  Steve is far more knowledgeable then I am.

This is how I would consider approaching the conversion.  Note the things that are different from original schematics.  Please look over this carefully.  I think you can still use Sluckey's layout with this idea. 

On Sluckey's Plexi

1)  changed to cathode biased instead of fixed biased

2)  changed grid resistors from 1.5k to 5.6k  (for 6L6 grids)

On  original Fender  DeVille schematic

1)  did NOT use fixed biased circuit because of using  cathode biased instead of fixed biased

2)  Suggested different dropping resistor  between  node  B & node C     (changed it from 6.8k original to 33k/3w)
     The reason for this was to get node C from 413 v on LTPI plates closer to 270v on LTPI plates   (I think it will end up in the 300+ range)

3)  Instead of original 10k resistor on DeVille,  maybe try a 22k/2w?     This is to try to get node D from original 364v to closer to 232v

4)  Adding a node E with a dropping resistor of 10k/2w between node D and node E.  Trying to get node E headed towards 217v range

I would be shooting for something like:

Node A =  471v like on Deville      Node B = 468v like on Deville   Node C = 300+?      Node D= as close as reasonable to 232v
Node E =  as close as reasonable to 217v

Hopefully, Sluckey will weigh in on this.  Again, follow his lead on dropping resistors and everything else.  You certainly do NOT have to have a cathode biased amp.   I think it might make the conversion an easier project to do so, but maybe not?

With respect, Tubenit

EDIT:[/color]   I've added an ExpressSCH editable schematic & the same schematic in GIF format.  In the schematic I just added, I changed two more things which are simply a personal preference and not necessarily "better".   I don't care for the 47p "snubbing cap" as I think it muffles the tone, so I changed to a 220p "enhance cap" across the 82k LTPI entrance resistor.  The other thing was simply to add a passive effects loop for reverb or delay pedals.

I also have an editable ExpressSCH layout for this schematic that uses paralleled turrets or eyelets. NOT an improvement on Sluckey's great layout, just different.

can i use a 22k/3w instead of the 22k/2w i dont see any?

thx

[tubenit]

Yes.

However, last night I found this old Hoffman Plexi 50w schematic that had voltages on it.  I don't remember what the original source was that I copied this from?   You will need to check that this schematic matches the Plexi 50w schematic in Doug's Library of Information?  Print them both off and circle the differences on one of the sheets to note what might not be the same.

Looking at Plexi 50w volts on the power tube plates, you have 476v.  Your DeVille was 472v.  Close enough, IMO!

Note that there are voltages listed on the attached schematic that will help you determine if your build has voltages that are within normal limits of what the Plexi 50w should have.

So, in light of that,  I think you can copy the resistor values on the B+ rail of the Hoffman Plexi 50w.   

AND if you are going fixed biased (instead of cathode biased) then I think you can use the fixed biased system of the Plexi 50w which connects to the HV (high voltage) wiring instead of using a dedicated bias wiring circuit that was originally on the DeVille?

Hopefully, some others will edit/correct this thinking or affirm it.

With respect, Tubenit

[USAampsRus]

 tubenit


Good Job on the find for Hoffman Plexi 50w schematic.
so you think this this is close enough?476v. And the DeVille being 472v?

Thanks Agin
Anthony

[tubenit]

you think this this is close enough?476v. And the DeVille being 472v?

 

Close enough, IMO!

So, if you use Hoffman's Plexi 50w layout, schematic, bill of materials, etc.......   you should have a proven build that sounds great.  Take your time. Post questions as you have them.  Study the pictures on his build projects.  Study his grounding scheme.  Doug has given you a ton of excellent information so you can be successful with this.

http://el34world.com/Hoffman/files/CommonHookups.pdf

http://el34world.com/charts/grounds.htm

I've edited Hoffman's Plexi 50w to show the hook up with the Deville transformers  * see schematic and CHECK for ERRORS

with respect, Tubenit

[sluckey]

You can't use Doug's bias supply connected to the HT winding of that Deville power transformer.Just use the dedicated bias winding with one lead connected to ground and the other lead connected to R36. R36 will need to be decreased considerably. I'd try 1K initially. Maybe make a note on the schematic calling it the bias range resistor.

[tubenit]

Sluckey,   Thanks for the help on this project!

Is this correct the way it is drawn now using the Deville dedicated bias supply?   I am understanding this to mean one of the brown wires (either CP16 or CP18 but not both) goes to the bias supply circuit and that the brown/yellow wire goes to ground  (CP17)?

http://el34world.com/charts/Schematics/files/Fender/Fender_blues_deville.pdf

And if he is using the original 6L6 power tubes, would this bias circuit work ?   (understanding the bias range resistor may need to be changed?)

With respect, Tubenit

EDIT:   Corrected schematic bias wiring per Sluckey's follow post.

[sluckey]

You're looking at the wrong schematic Jeff. This is a HOT ROD Deville, not a BLUES Deville. They are different.

Here's the correct schematic...

     http://el34world.com/charts/Schematics/files/Fender/Fender_hotrod_deville.pdf

Connect one brown to ground and connect the other brown to the bias circuit. The bias circuit will work ***IF*** there is approx. 40 to 50 VAC between the brown wires. If the voltage is considerably less you'll need to use a simple voltage doubler rectifier. Or, consider using EL34s only since they require less bias voltage than a 6L6.

[tubenit]

Thanks for your help, Steve!   Always grateful for your stellar input on the forum.  You bring so much good to this amp building community. 

With respect, Tubenit

[USAampsRus]

Thank you so much everyone going out of your way with this project.

Can't thank you enough!!

I'm going over all the info that's been provided in the last few days.
Been Busy with My friend at the Docs.

Now i have time Again to get back on track here with the project.


Anthony