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For what its worth. The Mark 4 verb circuit. http://guiguijones.free.fr/Electronique%20&%20Bouine/electronique/Schema%20Amplis%20Effets%20etc/Amplis/Mesa%20Boogie/mk4-2.gif

Ty for your timely reply!! And advice! I know where these components are , I had my head inside my chassis for years! 🕵 😞 👍. If I start with the 1 meg resistor (33), could I just put another resistor in series with it to add resistance? If so, what would be a good starting value? There was this...

I moved the send over by speaker outs. I temporarily put a 2.2k on end of black lead to send. The other two black leads on return, one goes to verb pot, the other connects in between 150k and 4.7k. 4.7k goes to ground. I never really had a chance to hear the effect of the added 2.2k. I was...

Ty for your reply! Dang, I was hoping that it would attenuate my verb some cause it sounds like crap. I kinda understand what you said 🤔. . if this link works, its the most accurate one out there. I spent hours tracing it and there are a couple errors. Anyway, the effects loop shows the jacks...

Ty!. Imo, you are very savvy with amp electronics.👍 . I posted this in a new thread but you can probably answer it. On my schematic of a C +, there is a later factory mod to the effects loop send jack in which a resistor is placed that goes to return jack (muting lug). Anyone know what this...

Greetings! On my schematic of a C +, there is a later factory mod to the effects loop send in which a resistor is placed. Anyone know what this would do? Does it reduce signal a bit for effects and reverb? since reverb is tapped off return jack.Tia, Blessings.

I checked again. Its the same. The picts blown up more than I thought. lol. Btw, what's that resistor for that feeds the LDR B cathodes? Thanks, Jim

Hmmm...? That puzzles me now. My C+ has a RP11 and I looked at its preamp PCB for comparison last night ( my OCD makes me do things like that) . My board has another trace thats not in your pict. Mine has eq. I'll check again to be sure. I wish those reverb leads were out of the way. lol. But I...

Just curious, is that a RP11 A board?

I totally agree. As mentioned, mine was used for Volume. And I like bedroom levels. This pot did Not satisfy. For lead drive, no problem. Like you said, for distortion, who turns the setting to zero to two. But, if its used to go to your clean channel , not sure how that would affect. Blessings.

The CTS pot has a " faulty" carbon resistance trace. My Master One pot on my C+ was a bit faulty. I got a new one from Mesa. After installing, from zero to 2 or 3, nothing . then suddenly it kicks in.I did NOT like that. Totally unacceptable. I removed it and took it apart. That's where I found...

I purchased the Delta Pro 12 A many years ago trying to match the old EVM 12. They're ok. Back then they were generally used for PA speakers. Their specs may have changed by now.

Man, I really want one of these. But they are pricey. I was told that this is the Santana tone.

Try Amp Repair Parts - Powered by Studio Sound Electronics Blessings, Jim

You're welcome! I was basing the 470 ohm of off the 50/50 schematic I've found. It does say 1 watt. I follow this amp tech on YT ( Psionic Audio) smart as a tack, and he always bumps up the watts on screens. To be honest, you know, I'm not sure. I need to comment him and ask him. Your theory...

May be used as a fizz cap to reduce brightness but they are usually in series with the two output coupling caps ( usually .1uf 400v are the coupling caps in older Marks. Orange drops) from Phase Inverter circuit.

Greetings. 470 ohm 1 watt . a 2 watt wud be a lil better. Tho it probably came with carbon comps, metal oxides take the blows better. Blessings.

Greetings! I hear that term a lot. " sag". What does that mean in amps? Tia! Blessings, Jim

Greetings. I just briefed it. The tone stack appears to be the same as Jrb32's. Blessings.

Greetings. I'm A bit late to the party as usual. Hope all is well. Its been a while but if you haven't done the bright mod, that orange drop on left side, third preamp tube, that yellow lead goes to the 270k resistor. That's where you put the 1000pf 1kv ceramic cap. Put it in parallel. One side...