Back in the Mark IV owners club

anomaly said:
Nice score. Apparently those transitional heads are not much different than a typical B revision circuit wise, but they do have a lot of the older components that the A revision uses. The Mark IV may be my favourite amp ever, I like it more than the Mark III red stripe I owned.
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Thanks ! I also had a red Stripe III and prefer the IV. To me it's more usable, the III I had had was insanely loud
 
found this on line
This particular example is a transitional model between "A" and "B". Very early 6000s serial number (0-6000 = Mark IV A; 6000-13000 = Mark IV B). They made around 200 of these w/ different circuit changes before settling w/ the "B" we all know. Small part of those 200 were exports like this one. Here's what is different in this one:
-Still has the 561137 PT used in Mark IIIs, early export Rev D/E/F Rectos and Mark IV A's
-The Phase Inverter is not like MK IV (A or B), but like IIC/IIC+
-The lead channel circuit is direct copy from Mark IIC+
-It has the more usable channel 2 (RY2) from the "B"
-It has the switching (including the Lead B+ switching for the preamp), Stereo FX Loop and OT (562004R1) from Mark IV "B"
-Older style unpainted chassis w/ separate faceplateDefinitely not your "run-of-the-mill" Mark IV.
 
How does the “stereo FX loop” work? Out R/L to some stereo FX and then one back to the Mark IV and one to another amp, then to cabs?
 
kmanick said:
found this on line
This particular example is a transitional model between "A" and "B". Very early 6000s serial number (0-6000 = Mark IV A; 6000-13000 = Mark IV B). They made around 200 of these w/ different circuit changes before settling w/ the "B" we all know. Small part of those 200 were exports like this one. Here's what is different in this one:
-Still has the 561137 PT used in Mark IIIs, early export Rev D/E/F Rectos and Mark IV A's
-The Phase Inverter is not like MK IV (A or B), but like IIC/IIC+
-The lead channel circuit is direct copy from Mark IIC+
-It has the more usable channel 2 (RY2) from the "B"
-It has the switching (including the Lead B+ switching for the preamp), Stereo FX Loop and OT (562004R1) from Mark IV "B"
-Older style unpainted chassis w/ separate faceplateDefinitely not your "run-of-the-mill" Mark IV.
Click to expand...
Ya, i've seen this exact description but when I looked at the guts of a transitional Mark IV it looked exactly like a revision B, not a thing was different in it that I could see. The transformer part is true though, some early Rev B's have the same PT as a Rev A.
 
going to see how it sounds through the Splawn today.
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, there is someone local to me selling the exact same cab but loaded with V30's
much cheaper $$$ than a mesa a cab , I Just don't know how the Chinese V30's will sound compared to Mesa V30's.
I gig this Splawn cab all the time with my Splawn head , but's got M75/J75 Scumbacks in it. Probably not the best speakers for a Mark IV.
 
I've found the MKIV to be much pickier on speakers where it really tends to prefer V30s. This is opposite of something like the IIC+ that sounds killer with every speaker. That said, tone is personal preference so one way to find out for yourself. :)

Generally speaking I'd be more concerned with what year the V30s were made & less concerned with what country they were made in. That said, the 04-19 "fizzy" V30s that a lot of guys don't like actually did still sound good with my MkIV, where I didn't like them with my other amps.
 
theres gotta be more than 200 transition a/b's out there. i feel like i owned 200 of em lol.

i know i had at least 3, and some pals have had one or two in their stables. they can't be THAT rare, or maybe i'm just a magnet for rare boogies. my first c+ was a 60 watt SRG factory b -> c+ conversion and there are said to be like 20 of those and even less were the 60 watt version, so who knows.
 
JimAnsell said:
theres gotta be more than 200 transition a/b's out there. i feel like i owned 200 of em lol.

i know i had at least 3, and some pals have had one or two in their stables. they can't be THAT rare, or maybe i'm just a magnet for rare boogies. my first c+ was a 60 watt SRG factory b -> c+ conversion and there are said to be like 20 of those and even less were the 60 watt version, so who knows.
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could very well be , I'm just going on what I've found online so far. I'm going to call mesa on Monday and see if I can get some info, I know certain years of them had problematic caps and LDLs? I want to know if I need to get this serviced as I'm holing on to this one.
 
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Just checked again without EQ. I wouldn't say it pops like some Rectifiers I had did. More like a click, but not thru the speakers like a pop.
 
I've got Aztech engineering near me, they do really good work with amps I'll have to call them tomorrow and see if he'd even do it. I watched a video on this , it's a pain in the butt job to do
 
Ok I pulled the chassis on this and this is what's in there (I have no Idea what I'm looking at it looks like the original "problem caps may have already been replaced? The seller told me the previous owner had it serviced but he did not get into specifics
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Indeed they have been, run flying leads and glued them on top of what I assume are the preamp filter caps.

Speaking of, looks like the date codes on those caps are 49th week of 1992, 31 years old. Mesa I don’t think skimped on the filter caps, they’re apparently good quality, they may still be fine but a good tech should know.
 
mnemonic said:
Indeed they have been, run flying leads and glued them on top of what I assume are the preamp filter caps.

Speaking of, looks like the date codes on those caps are 49th week of 1992, 31 years old.
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which caps? the blues ones under the black 4700's look brand new. the chassis has a date of 2/93 on it
 
VHTStark said:
Glad you tracked one down! How are you digging it so far? What are you planning on putting in it for tubes?
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it had groove tubes in it. I replaced all of the preamp tubes with JJ's and the two inner 6l6's (all JJ's) with a pair of mesa Str440's I had pulled from my Recto back in 2008. I've got (all NOS) a Mullard, an Amperex, an RFT, and a Tungstram. I didn't put them in because I'm not sure which tube would work best in which spot, but the JJ's aren't wowing me, I'll burn them in a bit an d see if they grow on me, but I've also got new EH, new Mullards and New tungsols (I have a sh*t load of tubes. Also a few shunguang Chinese 12Ax7's, the ones every one seems t go gaga over)
again not sure where to put what, I'm more at home with a Marshall type of circuit.
**** edited*** pulled the str440's sounded flat put all JJ's back in (6L6's) and pulled theV1 JJ for an RFT,and V3 JJ for one of the Chinese 12Ax7's.
Much better, going to try the Amperex in there somewhere just don't know which slot to put it in
 
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