Vintage Mark-style PCB and chassis kit

[rarebitusa]

From what I remember, the forward voltage is much higher on the Xvive VTL5C1 so it won’t really turn on when used in parallel with the Vactecs. There is also a 750 pF ceramic cap that could’ve failed, the pot switch, or the associated wiring. If you turn the power on to the amp, leaving the amp in standby, pull the treble shift and put it in lead mode. Read the resistance between the vactrol LDR terminals (the side closer to the big power supply electrolytic cap). If it’s reading 1-2k, your LDR is still OK. You should read approx 10M if you push the treble shift back in

Man thanks... I really appreciate the direction!!!

 

[Jay Omega]

Getting closer

 

[Hoplite22]

Getting closer

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OMG man ... that looks awesome !!! So exciting !

 

[Jay Omega]

Only thing left is to wire the input jack and front panel pots. The last of the parts will be here Saturday so if I’m lucky I’ll be done wiring this weekend

 

[Hoplite22]

Only thing left is to wire the input jack and front panel pots. The last of the parts will be here Saturday so if I’m lucky I’ll be done wiring this weekend

View attachment 4437

Exciting times !!

 

[Graydon]

Having done this myself on a few occasions, I can appreciate the amount of work that goes into the design and layout of a project like this. Great work! Very nice!

 

[Jay Omega]

Having done this myself on a few occasions, I can appreciate the amount of work that goes into the design and layout of a project like this. Great work! Very nice!

Thank you!! It was quite the project indeed and the primary reason why I wanted to make it available to others!

 

[Graydon]

I've done amp kits also (18 watt kits) so if you have any problems or questions, feel free to ping me.

 

[Jay Omega]

I've done amp kits also (18 watt kits) so if you have any problems or questions, feel free to ping me.

Very cool! I greatly appreciate the offer and I may take you up on that

 

[Jay Omega]

The amp is alive!!

There are a couple minor things to investigate still but I'm happy thus far. I'm loving the pentode / triode switch, the amp is noticeably more compressed in the triode setting and pentode has some serious oomph. I've also had fun with the "Mid-Gain / Harmonics" switch that I incorporated as a middle pull function, it switches in a cathode bypass cap on the fifth gain stage of the lead mode. I tried a 680 nF in this position as that is what I found present in my JP-2C. I've wondered if this was in JP's HRG that the JP-2C was based on or if they added it during development for another reason. With the 680 nF it acts as another high frequency control option which has been fun for sculpting.

Question for anyone with a simul IIC+ amp - does yours have the bypass cap installed on the V4a plate resistor? If so, is it a 1 nF or something different? I have a 1n in there for now like the HRG but I'm thinking about reducing - would like to be consistent with what Mesa does in the spot.

 

[Jay Omega]

The circled green capacitor is the one I'm wondering about if this is helpful, I'd love to hear what value these are for anybody with a IIC+ simul amp

 

[Henz]

The circled green capacitor is the one I'm wondering about if this is helpful, I'd love to hear what value these are for anybody with a IIC+ simul amp

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Hey, Mine has a 1n 1k v. Factory installed. It contradicts some schematics. Some say Delete on Simul Class. So, i dunno. MB told me its a bright reduction mod.

 

[Jay Omega]

Hey, Mine has a 1n 1k v. Factory installed. It contradicts some schematics. Some say Delete on Simul Class. So, i dunno. MB told me its a bright reduction mod.

Thank you sir! Yes, I’ve seen pictures of multiple C+ amps with and without a cap installed there. I agree that it rolls off the high end

 

[Henz]

The amp is alive!!

There are a couple minor things to investigate still but I'm happy thus far. I'm loving the pentode / triode switch, the amp is noticeably more compressed in the triode setting and pentode has some serious oomph. I've also had fun with the "Mid-Gain / Harmonics" switch that I incorporated as a middle pull function, it switches in a cathode bypass cap on the fifth gain stage of the lead mode. I tried a 680 nF in this position as that is what I found present in my JP-2C. I've wondered if this was in JP's HRG that the JP-2C was based on or if they added it during development for another reason. With the 680 nF it acts as another high frequency control option which has been fun for sculpting.

Question for anyone with a simul IIC+ amp - does yours have the bypass cap installed on the V4a plate resistor? If so, is it a 1 nF or something different? I have a 1n in there for now like the HRG but I'm thinking about reducing - would like to be consistent with what Mesa does in the spot.

That 680 nF , did you tap off of the V2B cathode? I tried a 2.2uf there a few yrs ago. I had a hard time making it switchable. And it really only added white noise to my ears.

 

[Jay Omega]

That 680 nF , did you tap off of the V2B cathode? I tried a 2.2uf there a few yrs ago. I had a hard time making it switchable. And it really only added white noise to my ears.

Yep! To make it switchable, you could do something like your lead bright pull on V4a cathode. 2.2uF is what Boogie used in the Mark IV for the mid gain harmonics switch if memory serves, as you drop the value below 1uF you will start to notice highs being accentuated

 

[Jay Omega]

I’ve noticed that the paint on the chassis hasn’t been holding up as well as I’d like, it’s been coming off with minor handling. A little disappointing, but the metal shop didn’t do a great job centering the graphics anyway. Now I get to figure out a faceplate plan for these!

 

[Fastforded]

Nice work, be cool to see a YouTube video

 

[Jay Omega]

Nice work, be cool to see a YouTube video

Anything in particular you'd like to see? I'm not much of a video production person but I think I can come up with something

 

[Hoplite22]

View attachment 4522
I’ve noticed that the paint on the chassis hasn’t been holding up as well as I’d like, it’s been coming off with minor handling. A little disappointing, but the metal shop didn’t do a great job centering the graphics anyway. Now I get to figure out a faceplate plan for these!

This is not the way that Mesa do it anyway.
Mesa use thin aluminium plate thats been powdercoated and then the white paarts are screenprinted on and then baked. Then that gets glued onto the front of the chasis.

 

[Henz]

View attachment 4522
I’ve noticed that the paint on the chassis hasn’t been holding up as well as I’d like, it’s been coming off with minor handling. A little disappointing, but the metal shop didn’t do a great job centering the graphics anyway. Now I get to figure out a faceplate plan for these!

maybe some kind of clear coat. Something not too shiny.