Fowler's Hot Rod Plexi #39

[purpletele]

Next Amp on the Bench

Mark shared his files for a famous HRP that he has his own twist on.  I am starting that amp with the Dual 50 in the works as well.

Since the layout and Schematic is live at TAG, I don't think Mark will have any issue.  I sent him $20 and a Cuban cigar. (Did you get those yet Mark)

[Glenn]

Get ready for a punch in the face!
Lol... I mean this amp is that. I built a 6v6 18 watt version of this.... love it.
Good luck with yours...Joe

[purpletele]

A little Progress

[nandrewjackson]

Looks like a nice build !


 

[MFowler]

No cigar yet


Looking good, can't wait for initial fire up and look on your face.


Mark

[purpletele]

No cigar yet


Looking good, can't wait for initial fire up and look on your face.


Mark

Mark,

I'll set up a camera for the start up.

Parts coming tomorrow that will allow me to get real close if not finish it up very soon.

[silverfox]

Don't rush it.

silverfox.

[purpletele]

Back on track, waiting for a few parts.

[purpletele]

Stand Back It's Start Up and Testing Time.

[MFowler]

Going to be fun for about an hour playing time!


Mark

[purpletele]

Update on the HR Plexi


Up and running and really quiet.  I had some issues with the speaker jacks I used for the FX loop, changed that out and connected the tips of the FX loop jacks and the amp roared to life.


I had an issue with MV that I found and corrected, a ground wire was not soldered well to the buss.

I am going to test the FX loop to see if the jacks are working correctly, I tied the shunt to the tip.

I really like the FX Loop MV.



 

[sluckey]

Hey man! You're really turning them out fast these days. Looks great! Can you post a link to Mark's schematic?

[tubenit]

Fantastic job on the build!  Looks excellent.

I am wondering IF this might be the schematic?

With respect, Tubenit

[DummyLoad]

Fantastic job on the build!  Looks excellent.

I am wondering IF this might be the schematic?

With respect, Tubenit

based on the layout attached to the opening post, i would say mostly yes, minus the "depth" control.


--pete

[sluckey]

Ha! It was hiding in between the pics. No fair!

[purpletele]

Hey man! You're really turning them out fast these days. Looks great! Can you post a link to Mark's schematic?

I seem to be on a roll.  I have the Dual 50 right on the tail of this #39. 

That will be it for a while, I have one heck of a cool collection of fantastic amps that are only worth half of their real value.  But I am rich in tone.

[purpletele]

Fantastic job on the build!  Looks excellent.

I am wondering IF this might be the schematic?

With respect, Tubenit

Jeff,

That is the schematic, it is hard to read but it helped me clarify some confusion on the layout. 

I have the amp running at full performance and it is a Beast, I am sure you would really like it.

Mark's layout has a couple of subtle jumpers that you cannot see very well, but are quite visible when loaded into Visio, so if anyone takes on this amp feel free to ask for clarification.

I like the long board layout, but the board ends up being 18", so you need a 20" chassis. 

Good fun amp project, tough to build in a JTM Chassis though.

BV

[MFowler]

Based on original schematic from Stephan (Darkbluemurder)


Added depth pot and power section is JCM800 2204 or 2203


Mark

[purpletele]

Project Update


I took a break from this amp and worked on another project.


After thinking about the instable voltage that I have on V4-6 I am wondering if I have a .1 Cap that is not holding it's charge. 

I also have a strange issue when I engage the boost it has a note decay that doesn't exist when not engaged.  I am wondering if i am on the right track to assess the voltage instability.


This amp is really going to be a beast if it is only pumping 7 cylinders.

[sluckey]

V4-6 should be just as stable as V4-1. And the steady dc voltage should be about the same on both plates. Maybe check the jumper between pin 3 and 8?

Can you produce a clean sound with that amp?

[purpletele]

V4-6 should be just as stable as V4-1. And the steady dc voltage should be about the same on both plates. Maybe check the jumper between pin 3 and 8?

Can you produce a clean sound with that amp?

Yes, the amp is quite responsive, so if I turn the gain down, thurn up the master and roll back the guitar volume it cleans up as anticipated.

[purpletele]

Here are a couple of photos of the target area


The voltage on V6-7 is 41 V

The voltage on V5-7 is 41 V

[sluckey]

Resolder the jumper between pins 4 and 5. Resolder the jumper between pins 3 and 8. Replace the plate resistor for pin 6. Any better?

[purpletele]

Resolder the jumper between pins 4 and 5. Resolder the jumper between pins 3 and 8. Replace the plate resistor for pin 6. Any better?

I did that work without results.  I changed the .1 Cap without change, I pulled the plate resistor and checked it and replaced it and tested, no change.


I changed the 100pF Cap tying the two tails together, I don't know if it was the process of refloating or if it was a bad cap, but I have 202 V now on V4-6, and the amp feels and sounds a tad better.


I was hoping that the voltage issue might resolve a decaying note issue with the boost engaged, but it didn't.  I am going to redo some of the work around that boost.

Update I didn't resolve the decaying note under Boost issue with the clean up work.  I may eliminate it altogether, I like it but I like using a variable clean boost on the board for that.


With exception to the boost, the amp is complete and sounds really hot! 

[purpletele]

Here is the new configuration for the Fowler #39 Beast.

The guitar has also been recently hatched.  I had a body made by Musicraft with super lightweight Swamp Ash.  They sent it to MJT for a nitro finish.  I like the Charvel necks so I bought one from Stratosphere.  It's a nice guitar, needs a little fret work, but it feels nice and it rips.

The amp is a living breathing monster, pretty fun.  The amp is really quiet.  My board is too tight to try to trouble shoot the Boost, I think it will be one of those things that goes away.

After the troubleshooting and resolving the chaotic voltage, I am getting 485 on the plates and I have the bias set at 36 mV.

[MFowler]

That boost switch engaged is where myself and the guys that have one of my HRP amps play most of the time for those harmonic Rock God tones.



The switch marked Boost is just switching a .68uf bypass cap in and out for a sweet boost.  Both the cap and resistor connect to ground and then each is wired to the mini switch with 4m7 resistor.  The mid boost is just switching between two 10k caps in parallel for either 5k or 10k.  I don't use it as much as the 2nd Boost switch.


Like you said you can lower the gain and crank up the master and it will clean up.  You could add a 1k8 resistor to the end of the gain pot to ground as a stop so it's easier to turn down on the fly the gain won't completely turn off that way.

Glad you have your amp up and running but it can sound better just keep working at it.  Resolder the terminals might help.


Mark

[Glenn]

Brian and Mark: does the boost add hiss?
I love mine but I get more hiss, the mid boost is ok but the slap in the face boost is great. I replaced the wiring but the hiss is still there
this is a great amp, and nice work on yours Brian

sorry didn't mean to derail

[purpletele]

Brian and Mark: does the boost add hiss?
I love mine but I get more hiss, the mid boost is ok but the slap in the face boost is great. I replaced the wiring but the hiss is still there
this is a great amp, and nice work on yours Brian

sorry didn't mean to derail

I don't get a hiss from my boost, I get a decaying note.  So if you hit a note and it is sustaining, it will just cut off. 

I also have a deep six feedback now when I hook up my FX cables.

I do like the boost, so I will find the issue of the decaying note.

[purpletele]

That boost switch engaged is where myself and the guys that have one of my HRP amps play most of the time for those harmonic Rock God tones.



The switch marked Boost is just switching a .68uf bypass cap in and out for a sweet boost.  Both the cap and resistor connect to ground and then each is wired to the mini switch with 4m7 resistor.  The mid boost is just switching between two 10k caps in parallel for either 5k or 10k.  I don't use it as much as the 2nd Boost switch.


Like you said you can lower the gain and crank up the master and it will clean up.  You could add a 1k8 resistor to the end of the gain pot to ground as a stop so it's easier to turn down on the fly the gain won't completely turn off that way.

Glad you have your amp up and running but it can sound better just keep working at it.  Resolder the terminals might help.


Mark

I'll keep working at it Mark.  I learned a few things about Turret boards this last go around.  I learned that I am not giving myself enough room to do clean work. 
I really like the amp! 

Just a few more tweaks and I'll be there.

[Ed_Chambley]

Nice work.  I love the CF Tone Stack.  Wouldn't want to lose any gain from the 4 triodes proceeding it.


Will it play clean, Sluckey asks?  Well I guess you could relay switch out 3 triodes in the preamp and make it similar to a 1987. 


Turn it up!  Gonna have a bit of tweaking to get it just right.  Take you time.  I can tell the how to build an amp understanding has grown a lot.  Good for you, maybe.  I hesitate to congratulate anyone on developing an Addiction.


really, nice work.

[purpletele]

Nice work.  I love the CF Tone Stack.  Wouldn't want to lose any gain from the 4 triodes proceeding it.


Will it play clean, Sluckey asks?  Well I guess you could relay switch out 3 triodes in the preamp and make it similar to a 1987. 


Turn it up!  Gonna have a bit of tweaking to get it just right.  Take you time.  I can tell the how to build an amp understanding has grown a lot.  Good for you, maybe.  I hesitate to congratulate anyone on developing an Addiction.


really, nice work.

I just took up Smoking Marlboro Reds and I love it.

I didn't, but it sounds funny. 

I am an addicted builder of things.  I am going to build a couple of Storage Facilities and that type of construction has gotten real specialized with Light Gauge metal studs.  Should be fun, I mange the deals for owners.

[PRR]

> I just took up Smoking Marlboro Reds and I love it.
> I didn't, but it sounds funny.

Smokin OPs:

[MFowler]

In my 100w versions for some reason I switched V1 to 12AY7 or 5751 to lower that hot gain.  The amp will hiss, it's a 4 gain stage amp. Actually 4 1/2 stages.


Mark

[purpletele]

That boost switch engaged is where myself and the guys that have one of my HRP amps play most of the time for those harmonic Rock God tones.



The switch marked Boost is just switching a .68uf bypass cap in and out for a sweet boost.  Both the cap and resistor connect to ground and then each is wired to the mini switch with 4m7 resistor.  The mid boost is just switching between two 10k caps in parallel for either 5k or 10k.  I don't use it as much as the 2nd Boost switch.


Like you said you can lower the gain and crank up the master and it will clean up.  You could add a 1k8 resistor to the end of the gain pot to ground as a stop so it's easier to turn down on the fly the gain won't completely turn off that way.

Glad you have your amp up and running but it can sound better just keep working at it.  Resolder the terminals might help.


Mark

That boost has me perplexed, but that happens quite often on these amps. 

I replaced the resistor as well as the .68 cap.  I had stripped it down to bare turrets and rebuilt it and resoldered the switch wires.

I get a static and a quicker cut of on note sustain.  The only thing left to replace is the switch.

Would I be getting a note decay from a switch? 

[MFowler]

Well that resistor and bypass cap is the bias for that preamp tube stage so funny noise is possible.


Mark

[purpletele]

I wrestled the boost circuit and finally won.  I changed every component without a change, changed the switch and resistor on the switch, no change.

I had 22 gauge hook up wire so I tried 20 gauge and that made the difference.  Maybe it was the surface area at the connections, or lack thereof that was causing the decay.

[purpletele]

Worked through the FX loop issues that I had.

I installed a switch to close the circuit when the FX loop is not in use.

The amp is working very well now, the boost and Mid boost are working fine and the amp is smokin.

Thanks for the help

BV

[MFowler]

try this

[purpletele]

try this

Thanks Mark.

I have to work, I'll be back later

BV

[EL34]

If you guys have any layouts you would like me to add to the .diy file library, let me know.

This is how custom boards are created from layouts
I can then make the custom board on my CNC machine

[purpletele]

If you guys have any layouts you would like me to add to the .diy file library, let me know.

This is how custom boards are created from layouts
I can then make the custom board on my CNC machine

I saw the video the other day, that is a nice tool.

I was going to try and copy the layout the Italian Guys developed for the Friedman Smallbox 50.  I placed the file in the Hoffman folder, but I haven't tried the new tracing program.

BV

[EL34]

I saw the video the other day, that is a nice tool.
I was going to try and copy the layout the Italian Guys developed for the Friedman Smallbox 50.

 I placed the file in the Hoffman folder, but I haven't tried the new tracing program.
BV

What is the Hoffman Folder?

[EL34]

I don't mean to hijack your thread
I was just playing around with this amp layout in DIYLC
Since I am using components that are sized exactly to the real life parts, I noticed a few things
The filter caps do not fit on the original board layout in the PDF


That's one of the handy thing DIYLC can do when you are creating a layout
You can get the board the exact length you need by using parts that are 100% scale
I added the PDF image as a background and then added eyelets and parts
The image is pretty large and may not look good scaled down here

[purpletele]

I don't mean to hijack your thread
I was just playing around with this amp layout in DIYLC
Since I am using components that are sized exactly to the real life parts, I noticed a few things
The filter caps do not fit on the original board layout in the PDF


That's one of the handy thing DIYLC can do when you are creating a layout
You can get the board the exact length you need by using parts that are 100% scale
I added the PDF image as a background and then added eyelets and parts
The image is pretty large and may not look good scaled down here

I found that out as well on my first board. 

Mark's boards are around 17" long.  The chassis that I had was about 17", I tried to compress it but failed miserably with the caps.

[EL34]

Mark's boards are around 17" long.  The chassis that I had was about 17", I tried to compress it but failed miserably with the caps.

Looks like you did what I would have done.
Used a 40x20x20x20 can cap 

[MFowler]

My boards are 19.75" long x 2.875 wide and I have changed my layout 4 times to better fit the wiring layout.


Mark

[EL34]

My boards are 19.75" long x 2.875 wide and I have changed my layout 4 times to better fit the wiring layout.


Mark

Yeah, that's a super long board

[Ed_Chambley]

try this

Is the wiring diagram stating to use a shorting switchcraft preamp out and a non-shorting power amp in.  I get this.  The connection points, to confirm. Preamp tip connected to the intersection R37 and C14.  Switch and tip connect.  Finally for the long run to the Volume pot use shielded wire and connect to the wiper prior to R37?


Please let me know as I have a 2204 I just added the boost to and tweaked it a tad.

[MFowler]

For Switchcraft I think that 1st example is wrong you could not use the power amp in by itself.  I would follow the 2nd example and put the switched jack on the send.

For Cliff jacks in a JCM800 I use the interrupt style effects loop.


See Ceriatone's layout

[purpletele]

My boards are 19.75" long x 2.875 wide and I have changed my layout 4 times to better fit the wiring layout.


Mark

Sure looks good now