Search found 194 matches

by jrb32
Thu Aug 01, 2019 4:35 am
Forum: Vintage Amps (Before 1991)
Topic: Mark llB - difference between early and late models
Replies: 7
Views: 2017

Re: Mark llB - difference between early and late models

Amazing info! Any chance you could upload any detailed pics of the RP8 and RP9 boards? Since my earlier post on here I've managed to trace and map out the RP10 and RP11 boards for the IIC/C+ and all the Mk III boards along with schematics. Trying to document and date the development of the early Mk ...
by jrb32
Sun Jun 02, 2019 4:58 am
Forum: Vintage Amps (Before 1991)
Topic: MKIIC+ ++ mod
Replies: 3
Views: 696

Re: MKIIC+ ++ mod

No idea I'm just a repair monkey! I can figure out how to fix things or implement circuitry but understanding the exact difference certain values of components will make or design an amp... sorry! One day maybe :) I am on the understanding that putting the 100K in is indeed optional, BUT it does hav...
by jrb32
Fri May 31, 2019 2:05 pm
Forum: Mark Series
Topic: Original Mark II C+ vs. Mark II C Conversions, Any Differences?
Replies: 4
Views: 563

Re: Original Mark II C+ vs. Mark II C Conversions, Any Differences?

Depends on the board. If the IIC has an SP11A or RP11A (from about September 83 onwards) then a converted IIC+ will be IDENTICAL to a factory IIC+ in every physical way. Seriously. 100%. No question. If it has an SP10A or RP10A (the early IICs before this) then it will be identical from a circuit po...
by jrb32
Mon May 13, 2019 1:54 pm
Forum: Vintage Amps (Before 1991)
Topic: MKIIC+ ++ mod
Replies: 3
Views: 696

Re: MKIIC+ ++ mod

Need to add an LDR. Mesa moved from the Mk IIB to the MkIIC by putting in LDRs for channel switching to eliminate the pops that happen with channel switching. Get a VTL5C1 and wire it in. If you want it on permanently I'm not sure on the exact wiring, but if you hijacked the power off another LDR fo...
by jrb32
Thu Mar 14, 2019 4:28 am
Forum: Vintage Amps (Before 1991)
Topic: Mark III no distortion channel 3
Replies: 27
Views: 2657

Re: Mark III no distortion channel 3

In lead mode, volume 1 pull bright works. This does not have any effect when the amp is NOT in lead. I think you mean Lead Bright - Pull Bright on Volume 1 does actually work in both Lead and Rhythm modes, although it doesn't have much of an effect after around 8 on Volume 1. Apart from that I seco...
by jrb32
Wed Mar 13, 2019 6:20 am
Forum: Vintage Amps (Before 1991)
Topic: Buffers & the Mark II FX Loop
Replies: 2
Views: 942

Re: Buffers & the Mark II FX Loop

My first question—does this apply to IIC+ upgrades? (My amp is an '83 IIC upgraded to a + at a later stage) All C+ upgrades end up the same as all other C+s in the end from a circuit point of view and an FX loop point of view. Exactly the same. Anyone who says otherwise is misinformed. The preamp c...
by jrb32
Tue Mar 12, 2019 8:19 am
Forum: Mark Series
Topic: Converted IIC+ with Export Transformer
Replies: 7
Views: 1245

Re: Converted IIC+ with Export Transformer

At the end of the day - try it out if it's local! If it blows you away then buy it for the 2000-2500 price range. If not then don't. It's simple. It's well maintained, authentic and is the most desirable out of the non EQ models apart from a coliseum.
by jrb32
Tue Mar 12, 2019 8:16 am
Forum: Mark Series
Topic: Converted IIC+ with Export Transformer
Replies: 7
Views: 1245

Re: Converted IIC+ with Export Transformer

Yeah you 100% want an EQ to dial in tones. So you'd need to buy the Mesa Graphic EQ pedal separately and put that in the EQ loop separately. Looks a solid amp though and circuit wise it looks good with the correct maintenance done. It's also an RP11A which, although it was upgraded to IIC+ specs lat...
by jrb32
Fri Mar 08, 2019 5:45 am
Forum: Mark Series
Topic: Converted IIC+ with Export Transformer
Replies: 7
Views: 1245

Re: Converted IIC+ with Export Transformer

https://forum.grailtone.com/viewtopic.php?f=3&t=84402&p=521552 Price wise I'd rank them as follows from worth the highest to the lowest. (K=Coliseum D=Simul, H=100W, S=60W, R=Reverb, G=Graphic) KRG DRG HRG SRG KG DG HG SG KR DR HR SR K D H S Then based on that you can add in the following for more v...
by jrb32
Fri Mar 08, 2019 5:32 am
Forum: Vintage Amps (Before 1991)
Topic: Simul,s outer
Replies: 1
Views: 454

Re: Simul,s outer

I think 470s were used until pentode operation on the Mark IIIs and IVs came in. Then they used 2.7K. Someone out there might know the difference though. I'd stick with 470 though. For context Henz's power board is missing pin 1 on the power sockets, hence the reason to replace them. Just copy other...
by jrb32
Tue Mar 05, 2019 4:52 am
Forum: Vintage Amps (Before 1991)
Topic: Cap that shouldn't be?
Replies: 5
Views: 1090

Re: Cap that shouldn't be?

Stick with 470 Ohm. The more I think about it, the more I think 2.7K might be used for Pentode wiring as I haven't been able to find it used before the Green Stripe Mark III or the Mark IV but I could be wrong. 5W or similar rated 470 Ohm wirewound resistors would do the job properly and hold up bet...
by jrb32
Mon Mar 04, 2019 7:44 am
Forum: Mark Series
Topic: MK II C Mysteries
Replies: 3
Views: 1310

Re: MK II C Mysteries

RP11A IIC Schematic: https://drive.google.com/open?id=1_KWgnYKephAlJAnfH8IL9El8qHdo5nji RP11A IIC Layout : https://drive.google.com/open?id=1CALqxt8hsJK_ghfb4ZnNmY8LQ627h54b The IIC schematic for the RP11 is the best I can get it without tracing one first hand. Looks like there is some weird stuff g...
by jrb32
Mon Mar 04, 2019 7:43 am
Forum: Mark Series
Topic: Mark IIC to C+ Steps Required for Upgrade
Replies: 4
Views: 1312

Re: Mark IIC to C+ Steps Required for Upgrade

RP11A IIC Schematic: https://drive.google.com/open?id=1_KWgnYKephAlJAnfH8IL9El8qHdo5nji RP11A IIC Layout : https://drive.google.com/open?id=1CALqxt8hsJK_ghfb4ZnNmY8LQ627h54b RP11A IIC+ Schematic: https://drive.google.com/open?id=1SRE-Dthwda_-Wq0oRresd9D8matOy4qY RP11A IIC+ Layout: https://drive.goog...
by jrb32
Mon Mar 04, 2019 4:56 am
Forum: Vintage Amps (Before 1991)
Topic: Cap that shouldn't be?
Replies: 5
Views: 1090

Re: Cap that shouldn't be?

I think it's to do with the brightness and I believe Mike B confirmed with you that the early factory Simul Classes had this 1000pF around the 270K along with a 10pF cap instead of the usual 20pF for simul. I've added it to my list of mods and notes. Cheers.