Mark IIB to IIC+ Conversion

[Henz]

Thank you!

Not sure what you mean by extra 1M, I used a 1M instead of the 470k shown for R33 in the schematic below that I got from the sloclone site. The one between the caps on the right is R34 and the one in the top right corner is R33 as shown. If you're referring to R34 as extra, it was present in my Mark IIB EQ board which I based mine off. I think R33 was 1M on my IIB and my Mark IV.

The backward transistor is the darlington which is Q1 in the schematic below. It's the transistor on the far right in the picture I believe.
View attachment 430

Thanks Jay. I was referring to R33 as the extra 1 Meg. Mine has a 1Meg ,R34,as shown in diagram. And a 470k for R33. Just wondered why you did it. You did it cause your IIB has it? I looked at the schematic. Yours has the two mini toggles on each end .Nice!! . The MK IV schematic didnt have it ( the extra 1 meg) but Mesa is notorious for errors on their schematics. As I'm sure you know. Great job! Gotcha!!

 

[Jay Omega]

3D rendering of the preamp board from KiCad. The design is wrapping up, time to start building soon

 

[woodbutcher65]

Might want to add in the holes for the preamp tube sockets before sending that off the board factory. Even if you're not going to bend the socket leads over and solder them directly to the board you DO want those holes in there to allow heat to escape and not get trapped under the board.

 

[woodbutcher65]

About that high plate voltage... I now have a Mark III Blue Stripe that came to me with a problem, it was red plating the left pair of power tubes as seen from the rear. It was only a bad 0.1 uF orange drop coupling capacitor, and I replaced the pair. Easy fix, 20 minutes start to finish. And then I put in a brand new, true NOS pair of blue label Philips ECG 6L6GCs and fired it up and...lightning in a bottle. Not good. There's some VOLTAGE on those plates! Right at 500. Those tubes should be able to handle that. But maybe that one has been damaged in the 40 years since it was made. I need to test it. But a pair of Groove Tube Sovteks is running fine in the amp.

I do know that the amp has such an insane level of aggressive drive that I wouldn't convert it to a IIC+ if the job was free! I appreciate it for the utter insanity it already has.

 

[Henz]

About that high plate voltage... I now have a Mark III Blue Stripe that came to me with a problem, it was red plating the left pair of power tubes as seen from the rear. It was only a bad 0.1 uF orange drop coupling capacitor, and I replaced the pair. Easy fix, 20 minutes start to finish. And then I put in a brand new, true NOS pair of blue label Philips ECG 6L6GCs and fired it up and...lightning in a bottle. Not good. There's some VOLTAGE on those plates! Right at 500. Those tubes should be able to handle that. But maybe that one has been damaged in the 40 years since it was made. I need to test it. But a pair of Groove Tube Sovteks is running fine in the crackling
I do know that the amp has such an insane level of aggressive drive that I wouldn't convert it to a IIC+ if the job was free! I appreciate it for the utter insanity it already has.

Congrats on that .1 coup!ing cap! This doesn't apply to your repair but Someone told me a while back that after a recap, you should also replace those coupling caps as well. Anyway, I purchased a pair of Sovtec 6l6's . got em from the tube store a long time ago. Long story short. I recently tube rolled them in my C+ and while I was tapping and gently wiggling them, suddenly crackling from speaker. Couldn't get to switch in time. Blew fuse and 470 screen grid. Needless to say, I'm never touching them again!!

 

[woodbutcher65]

The time to wiggle power tubes in the sockets is when the amp is off. Use good contact cleaner on the sockets like Deoxit D5 or a similar quality product, insert and remove the tubes a few times, and then put them in and try not to disturb them when they're working.

Tubes can be finicky, especially when you're subjecting them to mechanical forces. Truth be told, much as we love them, they are a primitive mechanical product that almost seems like they shouldn't be as reliable as they are.

 

[Henz]

3D rendering of the preamp board from KiCad. The design is wrapping up, time to start building soon

View attachment 439

Dang! Pretty cool! Looks familiar!!

 

[Jay Omega]

Dang! Pretty cool! Looks familiar!!

Nope, nothing underneath

 

[Jay Omega]

Might want to add in the holes for the preamp tube sockets before sending that off the board factory. Even if you're not going to bend the socket leads over and solder them directly to the board you DO want those holes in there to allow heat to escape and not get trapped under the board.

The socket holes will be drilled so I only mark the centers in the artwork. No board factory, I’ll make the PCB at home as I’ve made the other boards

 

[Henz]

Nope, nothing underneath

You mean that you don't have the under traces laid out yet? And, did you figure a way to make it thru hole? Blessings, Jim.

 

[Jay Omega]

You mean that you don't have the under traces laid out yet? And, did you figure a way to make it thru hole? Blessings, Jim.

You had asked a question about whether there was a resistor underneath a capacitor on the EQ board.

It will be thru hole, but not plated. I’m going to use eyelets and vias

 

[Henz]

You had asked a question about whether there was a resistor underneath a capacitor on the EQ board.

It will be thru hole, but not plated. I’m going to use eyelets and vias

I can't wait to see finished board. And yes I did. But I deleted it. I looked at a different angle and you didnt. That one image of the eq card, twas just the reflection off of the shiny .1 . With my eq card, what would happen if I replaced R33 with a 1 meg? Mine has the 470k. I'm always curious and wanting to learn. Thanks in advance. Jim

 

[Jeffw5555]

I have designed PCB's dating back to the early 80's, but also repaired boards in the early 80's that were made in the 60's and 70's. ( I own a small company now and do my own boards for my designs) It is SO easy now to design boards and have quick prototypes made within a few days, and relatively cheaply.

Having repaired a huge amount of boards with eyelets, and know how cheap and easy it is to get proper boards made, I shudder to think why anyone these days would think of doing otherwise. The finished result of DIY in this fashion will look like amateur junk and be unreliable AF. Why would you invest this amount of time and energy for a junk result? The other thing you are forgetting is that modern masks have excellent insulating properties, very useful when you have hundreds of volts flying around tube circuits.

 

[meesa_jarjar]

I have designed PCB's dating back to the early 80's, but also repaired boards in the early 80's that were made in the 60's and 70's. ( I own a small company now and do my own boards for my designs) It is SO easy now to design boards and have quick prototypes made within a few days, and relatively cheaply.

Having repaired a huge amount of boards with eyelets, and know how cheap and easy it is to get proper boards made, I shudder to think why anyone these days would think of doing otherwise. The finished result of DIY in this fashion will look like amateur junk and be unreliable AF. Why would you invest this amount of time and energy for a junk result? The other thing you are forgetting is that modern masks have excellent insulating properties, very useful when you have hundreds of volts flying around tube circuits.

I'm curious, how is this different from SMD? I'm just barely beginning to explore the world of custom PCBs myself.

 

[Jay Omega]

I have designed PCB's dating back to the early 80's, but also repaired boards in the early 80's that were made in the 60's and 70's. ( I own a small company now and do my own boards for my designs) It is SO easy now to design boards and have quick prototypes made within a few days, and relatively cheaply.

Having repaired a huge amount of boards with eyelets, and know how cheap and easy it is to get proper boards made, I shudder to think why anyone these days would think of doing otherwise. The finished result of DIY in this fashion will look like amateur junk and be unreliable AF. Why would you invest this amount of time and energy for a junk result? The other thing you are forgetting is that modern masks have excellent insulating properties, very useful when you have hundreds of volts flying around tube circuits.

Thanks for the condescending feedback!

 

[Henz]

Thanks for the condescending feedback!

You have a great handle on this brother! With my 2:90, that green masking didnt help my issues with what caused the damage. I'm curious Jay, with all due respect, how are you gonna etch the underlying traces? Did you ever see one? For what its worth, if you ever need some advice as to what leads touch where underneath, I may be able to help you. But your knowledge is light years ahead of mine. Blessings, Jim. When you find the time, I need you to give me a very brief lesson on vactrols with regards to C+ schematics.

 

[Jay Omega]

You have a great handle on this brother! With my 2:90, that green masking didnt help my issues with what caused the damage. I'm curious Jay, with all due respect, how are you gonna etch the underlying traces? Did you ever see one? For what its worth, if you ever need some advice as to what leads touch where underneath, I may be able to help you. But your knowledge is light years ahead of mine. Blessings, Jim. When you find the time, I need you to give me a very brief lesson on vactrols with regards to C+ schematics.

I print my artwork onto transparencies via a laser printer and use presensitized double sided boards. Then I expose to UV and develop the image and etch the board in ferric chloride, so both sides are etched at once.

I’ve never seen the underside of an RP11, and never have I seen the top side of an RP11 without components. I’ve followed the component layout of an RP11 and schematics, the tracking piece comes together when you get going. None of the boards are intended to be copies of the Boogies, I’d consider them inspired by the Boogies.

I appreciate the offer, I may reach out for help at some point! The biggest unknown to me is the grounding, which is why I’ve went thru this effort to do a mock-up build. jrb32 sent me a picture of the underside of an RP10 a couple years back, that closed the loop on a big grounding question I had when I cross referenced with RP10 gut shots elsewhere on the net.

Sure thing, if you have Qs about the LDRs I can tell you what I know, just shoot me a PM

 

[JD]

Randal Smith back in the day etched his own boards did his own screen printing etc i wonder if he will be told he was building junk. keep up the great work Jay i am enjoying this come together and i bet it is part of the experience that at the end of the day you can say you did it all yourself.

 

[Henz]

I print my artwork onto transparencies via a laser printer and use presensitized double sided boards. Then I expose to UV and develop the image and etch the board in ferric chloride, so both sides are etched at once.

I’ve never seen the underside of an RP11, and never have I seen the top side of an RP11 without components. I’ve followed the component layout of an RP11 and schematics, the tracking piece comes together when you get going. None of the boards are intended to be copies of the Boogies, I’d consider them inspired by the Boogies.

I appreciate the offer, I may reach out for help at some point! The biggest unknown to me is the grounding, which is why I’ve went thru this effort to do a mock-up build. jrb32 sent me a picture of the underside of an RP10 a couple years back, that closed the loop on a big grounding question I had when I cross referenced with RP10 gut shots elsewhere on the net.

Sure thing, if you have Qs about the LDRs I can tell you what I know, just shoot me a PM

Ty Jay! Funny, I was JUST reading those older threads of Jrb32 and BoogieBabies and Wood Butcher about the under sides of those boards. They were also talking about tantalum caps as to what type and even if they should be used. Ty! I'll pm you my friend! Keep up the good work! Blessings, Jim.

 

[Jay Omega]

Got the preamp board etched, let the fun begin