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Jay, is that an image of A IIB preamp card? And about the 2:90's, I kinda liked mine until I repaired and recapped it.

Ty for the replies! Yes, Mike told me that those 680 2w resistors can get pretty hot! lol. I had amp on stand by for a few hours while leaving room. Luckily I came back when I did! I believe they have upgraded the 680 to a wire wound 3 watt. Let me tell ya WB, I spent many hours tracing out the...

Ty for your reply! Yes, I will. Mine has a RP11A board. I should have noted that my PT is a 105. Not sure if that matters or not regarding the high plate voltages. Last time I was inside her, few weeks ago, those two 1k 2 watt carbon comp resistors on power board measured darn near perfect. Are...

Ty for your replies WB and Jay. I got my head wrapped around that. 👍. Those lil " explosions " from cathode to plate also releases random negatively charged electrons flying everywhere. Which I believe is why the positively charged screen helps to attract them. 🤔 I have a DRG C+. Say that my...

Ty kindly for the lesson. Please explain why you said my bias was cold. Did you base it on visual or my comments on my negative voltages on power tube grids? I was always so confused with bias due to the negative ( - ) before the number. Under and over biased. Taking myself back to my old...

I have a 33k , and a 10k in parallel ? with the two 47uf's. As you can see, there once was two resistors next to the 33k. It came from factory that way. After that reversed biased diode, that 470 is attached to one side of the 10k. Over on power out board, bias in, there are two 220k's...

Fantastic! Those voltages are real close to mine. As mentioned, I'm A DIY learner. That temp pot, is that for bias adjusting. If so, how and why did you do it on a " fixed" bias amp? I see ,I think, that the pot is hooked to the two 47uf, 100v bias caps. What was the purpose? Ty. Blessings, Jim

I'll be following. By your post, you are well trained in C+'s. I'm sure that you've done this but trace everything back to the diode and 220k on power board. For my own interest, when you say you bypassed the EQ card, you took the lead from the output of V1A and attached it to the grid of first...

Ty for the reply! And dang, I would love to know where I can get those darker red caps (.047 and .0005 uf ?) . Hard to find 600v caps that small. Blessings, Jim.

Looks awesome. Very neat and clean!! 👌👍 . I've always wondered what the two 100 ohm resistors do off the heater supply to ground. 🤔 And dang, I would love to know where I can get those darker red caps (.047 and .0005 uf ?) . Hard to find 600v caps that small. Blessings, Jim.

Old post but I'm thinking its just a preamp plate resistor.

Although I have no experience with III, when my C+ lost its lead channel, it was due to the plate load resistors failing on preamp board. But it appears that this approach has been done.

Ty for your reply. Yes , Aussie Brad. I just recently found him but his friend Lyle from Psionic Audio. Lyle ******* at Mesa constantly for using inferior components. When Lyle gets Boogies in, he immediately changes the carbon comp power tube plate resistors to metal oxides. And always...

Ty for your reply! I'll put those back in ! Hey brother, I gotta ask ya one more question then I'll find another tech's mind to pick on 🤗 . It may be a difficult question to respond to since there are so many amp designs but you mentioned putting good caps in critical spots to achieve optimum...

Lol. God bless you and your family. 💞. Take your time. I'm in no hurry. I just love to talk with techs. I learn so much!

Ty for your reply. You're way more advanced in electronics than i. I don't quite understand how you found it. I'm assuming it was pin 7 on V1B? Are you referring to the orange drops when you say creamy? lol. Yep! Lots of techs scoff at Mesa for using 400 v caps when a few more cents could get ya...

Greetings Jon! Hey , there are two updated C+ schematics out there. One has the ++ mods shown with optional component values in some spots and the other one doesnt . though they seem both correct, which is the most recent one? Tia, Jim

I have that same problem with my C+. My bass and mid pots have no DC ( well, .2 to .3 mv but that's no biggy). You said that you had no DC on pots. How did you discover? Did you lift one leg of orange drop and measure? The MK III schematic thats out there, how the heck can you read it!? The...

Ty!! And ty for info on bypass cap. 👍. Of course I have a question. Which direction is turning down? Towards ground lug? You are probably pulling your hair out by now with these questions. And I don't know what CCW means. I apologize. After this, I should have a handle on situation and will...

Thank you! You are very kind and a great help! I completely understand how to take the measurement once pot is dialed to my liking. I'm stumped on how to wire the pot to the two pads once 220k is lifted. One side of 220k is ground obviously and the other to grid with 1 meg. A pot has 3 lugs...