1976 Boogie SP3 restore help

[James]

@sloanthebone just posted his IIB with a RP-9B. I'm jealous.

I have a few SP-9A's, SP-8B, RP-8C, maybe a RP-8B (I'll have to check) and the RP-9C is the one the thrash/metal guys seem to be discovering lately. I can't help but wonder if it's simply the IIB power section that not even the IIC+ can touch and then of course the 9C is the closest to the RP-10/11.

So that means there is a 8B, 8C, 9A, 9B and 9C at least. Most of mine are coli so it doesn't help with serial #'s but the early ones are 58x (long chassis IIB started at 550) and K12x and having only heard of one exception I don't think sub-K100 coli's exist.

74xx is almost 2000 amps into the IIB. It would be nice to see what's under the hood of 5575-6000 just to see if the 8A exists. It wouldn't make sense for the SP/RP-8's to span the IIA's and IIB's. So did the IIA's end on SP/RP-7x?

It's possible. I found the RP-9C to be in between the earlier and later amps.

The first MK series I owned was #7791. Pretty sure it was dated 9/10/81. I'm not sure what circuit that one had, but it was probably my favorite sounding IIB. I know it had all 12AX7s anyway.

Also, as Mike said there were only three versions, could the PCB layout have changed but not the circuit itself?

 

[user 41014]

It's possible. I found the RP-9C to be in between the earlier and later amps.

The first MK series I owned was #7791. Pretty sure it was dated 9/10/81. I'm not sure what circuit that one had, but it was probably my favorite sounding IIB. I know it had all 12AX7s anyway.

Also, as Mike said there were only three versions, could the PCB layout have changed but not the circuit itself?

We were pretty close on introduction Marks. Mine was 752x from 8/6/81. I couldn't remember the pre board in it so I just pulled the chassis and it's a SP-9A. That followed a decade of DC-2 with P12N, bell and all I cut my teeth on.

I thought about different layout when I saw your post because of the 5 boards I know of. At the same time I don't want to hold someone to remembering what they did 4 decades ago. Record keeping didn't seem their forte back then.

Changes in the pre-amp layout to match changes in the power section? Changes that the legend in his own time doesn't consider significant enough to be more than tweaks potentially?

What is the date on your 74xx and can you give the 3rd number? We just found the rough transition from SP-8B to SP-9A unless one of our amps have a random back plate grab. What stands out is only a hundred or so amps between them. The 58x coli has the RP-8C but is there even a SP-8C and was the RP-8C gone as quick as it came? It could be less than a hundred exist. Anyone got SP/RP-8C's to share?

I think it's time to plot this loop mod circuit vs the other SP-9A's I have and hope the different S vs K power sections don't come into play. There is that dual tube out to the power section config with the 6FQ7 on the coli.

 

[James]

We were pretty close on introduction Marks. Mine was 752x from 8/6/81. I couldn't remember the pre board in it so I just pulled the chassis and it's a SP-9A. That followed a decade of DC-2 with P12N, bell and all I cut my teeth on.

I thought about different layout when I saw your post because of the 5 boards I know of. At the same time I don't want to hold someone to remembering what they did 4 decades ago. Record keeping didn't seem their forte back then.

Changes in the pre-amp layout to match changes in the power section? Changes that the legend in his own time doesn't consider significant enough to be more than tweaks potentially?

What is the date on your 74xx and can you give the 3rd number? We just found the rough transition from SP-8B to SP-9A unless one of our amps have a random back plate grab. What stands out is only a hundred or so amps between them. The 58x coli has the RP-8C but is there even a SP-8C and was the RP-8C gone as quick as it came? It could be less than a hundred exist. Anyone got SP/RP-8C's to share?

I think it's time to plot this loop mod circuit vs the other SP-9A's I have and hope the different S vs K power sections don't come into play. There is that dual tube out to the power section config with the 6FQ7 on the coli.

If that one is a standard 60 watt model, I wonder if they went straight from SP-8B to SP-9A. Is V2 a 12AX7 or 12AT7?

That's definitely true for custom work. Having thought about it, maybe he was referring to the base circuit. Meaning there was a reverb (RP) version of each SP board, but the circuit was otherwise the same.

743x. I forget the exact date, but I'm pretty sure it's an April 1981 build

I've never seen an RP-8C. I do know the 82 I mentioned earlier had an SP-8X. I think it might have been the 8A, but not entirely sure

 

[user 41014]

If that one is a standard 60 watt model, I wonder if they went straight from SP-8B to SP-9A. Is V2 a 12AX7 or 12AT7?

That's definitely true for custom work. Having thought about it, maybe he was referring to the base circuit. Meaning there was a reverb (RP) version of each SP board, but the circuit was otherwise the same.

743x. I forget the exact date, but I'm pretty sure it's an April 1981 build

I've never seen an RP-8C. I do know the 82 I mentioned earlier had an SP-8X. I think it might have been the 8A, but not entirely sure

Here's the RP-8C. As we're seeing with the SP-3 and RP-4x updates to R or S can happen while the other continues on till they use up boards or find the need to change. I have not personally seen a SP-8C.

But both of us have SP's and 743x to 752X is only a hundred amps, plus the big brothers and coli's. On the other hand if 743x is April that's 4 months for only 100 amps and that doesn't seem right.

My tube labels are 12AX7 but my gut is the 12AT7 was personal preference when built. Reverb driver maybe? V2 seems like a lower gain tone shaping if a 12AT7 was used there and seems out of place in the evolution of the Mark gain. They are interchangeable but maybe different load/cathode R's were used? I'll try to pay more attention to the non-ax7 tube labels.

You meant SP-9x on your '82 right?

 

[user 41014]

This list might help and it suggests there may not be any SP/RP-7x. I don't know if there are any SP/RP-5's either. Maybe there are so few 8C amps Mike didn't include it in his "3 versions" leaving the 8B,9A and 9C as the main versions as I haven't seen the 9B myself and don't know how long it lasted. And 8A???

@sloanthebone - do you have a pic of the RP-9B in the 10/82 #8231 HRGX?

10/76 A70x SP-3
3/77 A922
8-77 A1239
9-77 A1307
3-78 A1747 SP-3
6-16-78 A2086 (6-11?)
2/79 ? RP-6A PWR-4B
2/28/80 4829 RP-6A
4/28/80 5108 RP-6A
8/22/80 5654
2/19/81 6521
? 58x RP-8C coli
4/14/81 K110 looks like RP-8C tracing
April 81? 743x SP-8B
? K119 ? - Brad Whitford
? K12x SP-8B
8/6/81 752x SP-9A
8/18/81 K152 looks like RP-9A
8/26/81 K17x SP-9A
10/5/81 61x RP-9A big brother
10/7/81 none RP-9A coli
11/13/81 8151
K22x SP-9A
K23x SP-9A
1/26/82 8551
1/83 10543
10582 ? - black knobs

And here's a shot of A13 since I was looking thru pics.

 

[sloanthebone]

Let me know if this gets you what you need…….

 

[user 41014]

Let me know if this gets you what you need…….View attachment 962
View attachment 963
View attachment 964
View attachment 965
View attachment 966
View attachment 967
View attachment 968
View attachment 969
View attachment 970

F***ing A- thank you!!!
But now I want one lmao

 

[sloanthebone]

F***ing A- thank you!!!
But now I want one lmao

What is it about this one that makes you want one?

Also, do you know what “HRGX” stands for?

I am building a headhsell for it too. Just waiting for some parts from MESA which just shipped. If it turns out the way I want, I will post a thread.

 

[user 41014]

What is it about this one that makes you want one?

Also, do you know what “HRGX” stands for?

I am building a headhsell for it too. Just waiting for some parts from MESA which just shipped. If it turns out the way I want, I will post a thread.

Sweet. That sounds awesome. The IIB has a special place in my heart. Every single amp is different but I would at least like one of each preamp revision. Yours with the RP-9B and the SP/RP-8A were two that I hadn't seen so they were like wolverines in the wild at least to me.

The SP-9A loop mod was my 1st followed by the breath-making SP-8C coli. Yours is the missing link to the 9C's that have become a focus in some circles. On top of the loop mod S I have 3 coli's with the SP-9A so I'll prob loosen up on the one I serviced or the 2 Charlie Daniel's ones and look to add the SP/RP-8B like yours, a 9C since I've never owned one and explore the IIA finally.

Side markings on chassis are the options available when new.
Power section:
S or SS = sixty or super sixty - they get **** on in the aftermarket but the 2-6L6's that mesa puts out (Mark, DC, Express, etc) are truly little expressive bombs
H = 60/100W
D = 15W class A/ "Simul-class" 75W designed for outer EL-34's
D comments- a) DRG was the "fully loaded" options and we live in a more is better world so along with your X which is useless to any non-international gigging user the aftermarket commands the highest price regardless if it's the best amp for you. b) The last Mark III, the green stripe brought a change to the "simul-class" power section- 25W class A / 85W by changing a tube pair from triode to pentode. The green stripe, like the Mark IVA were not available generally with options and Mesa sold blue stripes to anyone wanting options until the Mark III finale.
K= coliseum 180W unless one stupidly wanted simul-class to dilute the beast.

Then:
R= reverb
G = graphic EQ
X = export tranny and even tho the mains options may be useless iron matters and this tranny is known to be a good one. IIB's in general used big medicine iron. Thank you Schumacher- where did you go?
07, 23, xx = week of production, I believe the start of production. Not always present the finish date is marked on the chassis underside in the circle of tube sockets.

C! stands for crank it!
What kind of headshell? Tolex or hardwood? I've always wanted to make a cherry one, maybe a blue-stained maple or even pine that would probably really soak up a stain.

 

[James]

Here's the RP-8C. As we're seeing with the SP-3 and RP-4x updates to R or S can happen while the other continues on till they use up boards or find the need to change. I have not personally seen a SP-8C.

But both of us have SP's and 743x to 752X is only a hundred amps, plus the big brothers and coli's. On the other hand if 743x is April that's 4 months for only 100 amps and that doesn't seem right.

My tube labels are 12AX7 but my gut is the 12AT7 was personal preference when built. Reverb driver maybe? V2 seems like a lower gain tone shaping if a 12AT7 was used there and seems out of place in the evolution of the Mark gain. They are interchangeable but maybe different load/cathode R's were used? I'll try to pay more attention to the non-ax7 tube labels.

You meant SP-9x on your '82 right?

Just checked. 743x is actually 7/23/81. Might have been that the other one was April 1982, but I don’t have that one anymore. Serial was in the 8600 range

I suppose that’s possible about V2, but I don’t think I’ve ever seen an 81 with a V2 12AT7. Only 82 and 83.

I’m fairly sure it was SP-8X. I remember thinking that it was the second variant (this was when Mike told me about the differences) but looking inside and seeing a number that suggested something earlier.

It definitely sounded different from both the 81 (SP-8A) and 83 (RP-9C)

For reference:

5-76 A53X RP-4D
9-77 A131x SP-3
9-77 A1338 SP-3
8-78 A(????) SP-3
9/10/81 7791 SP-??
?-?-83 1050x RP-9C

I might have some pictures of the 82 IIB from when I sold it. I'll see if I can find them

 

[sloanthebone]

Sweet. That sounds awesome. The IIB has a special place in my heart. Every single amp is different but I would at least like one of each preamp revision. Yours with the RP-9B and the SP/RP-8A were two that I hadn't seen so they were like wolverines in the wild at least to me.

The SP-9A loop mod was my 1st followed by the breath-making SP-8C coli. Yours is the missing link to the 9C's that have become a focus in some circles. On top of the loop mod S I have 3 coli's with the SP-9A so I'll prob loosen up on the one I serviced or the 2 Charlie Daniel's ones and look to add the SP/RP-8B like yours, a 9C since I've never owned one and explore the IIA finally.

Side markings on chassis are the options available when new.
Power section:
S or SS = sixty or super sixty - they get **** on in the aftermarket but the 2-6L6's that mesa puts out (Mark, DC, Express, etc) are truly little expressive bombs
H = 60/100W
D = 15W class A/ "Simul-class" 75W designed for outer EL-34's
D comments- a) DRG was the "fully loaded" options and we live in a more is better world so along with your X which is useless to any non-international gigging user the aftermarket commands the highest price regardless if it's the best amp for you. b) The last Mark III, the green stripe brought a change to the "simul-class" power section- 25W class A / 85W by changing a tube pair from triode to pentode. The green stripe, like the Mark IVA were not available generally with options and Mesa sold blue stripes to anyone wanting options until the Mark III finale.
K= coliseum 180W unless one stupidly wanted simul-class to dilute the beast.

Then:
R= reverb
G = graphic EQ
X = export tranny and even tho the mains options may be useless iron matters and this tranny is known to be a good one. IIB's in general used big medicine iron. Thank you Schumacher- where did you go?
07, 23, xx = week of production, I believe the start of production. Not always present the finish date is marked on the chassis underside in the circle of tube sockets.

C! stands for crank it!
What kind of headshell? Tolex or hardwood? I've always wanted to make a cherry one, maybe a blue-stained maple or even pine that would probably really soak up a stain.

Awesome! Thanks for the explanation.

The headhsell is made from oak and will be stained black cherry with a wicker front.

 

[user 41014]

Awesome! Thanks for the explanation.

The headhsell is made from oak and will be stained black cherry with a wicker front.

Your welcome. Post that head when you're done- everyone appreciates a good head! Black cherry is exactly what I've wanted to build.

@GJgo Is it summer in Grand Junction yet?
Hey, does your RP-9C use a 12AT7 for V2? And is there a date on it since it has to be about the last 9C? Speaking of last mades did you get the blue stripe back yet?

 

[user 41014]

Just checked. 743x is actually 7/23/81. Might have been that the other one was April 1982, but I don’t have that one anymore. Serial was in the 8600 range

I suppose that’s possible about V2, but I don’t think I’ve ever seen an 81 with a V2 12AT7. Only 82 and 83.

I’m fairly sure it was SP-8X. I remember thinking that it was the second variant (this was when Mike told me about the differences) but looking inside and seeing a number that suggested something earlier.

It definitely sounded different from both the 81 (SP-8A) and 83 (RP-9C)

For reference:

5-76 A53X RP-4D
9-77 A131x SP-3
9-77 A1338 SP-3
8-78 A(????) SP-3
9/10/81 7791 SP-??
?-?-83 1050x RP-9C

I might have some pictures of the 82 IIB from when I sold it. I'll see if I can find them

Maybe a transplant? I don't hear people frying these boards but anything is possible with enough knowledge to be dangerous. Like me ha! That does seem weird.

Well our introductory Marks just became exactly 2 weeks apart, just by random chance we nailed down the introduction of the SP-9A board to August 1st 1981 give or take a week and the serial numbers actually make sense. Thanks for the other amps for reference.

Happy 4/20 to all.
It was Godzilla's bday and he would be a grandpa now.

 

[user 41014]

If the SP-8C exists it is in extremely limited numbers. Makes me wonder how many RP-8C's exist.

The board in K152 looks like the tracing of a RP-9A dated 8/18/81 giving the look that the RP transitioned about or at the same time. The nearest back I have pics of is K110 dated 4/14/81 and I can't see the print but it looks like a RP-8C.

If there are 3 main circuit versions what board makes up the bulk of the 5500-7500 is my next question. It obviously ends with SP-8B and RP-8C. People in general seem to distinguish the 9C as more gain making me believe there is enough difference between the 9A and 9C as being 2 of the 3, but to my untrained eye who knows? Maybe they are the same circuit, different layout and small tweaks to voice the gain.

 

[user 41014]

If that one is a standard 60 watt model, I wonder if they went straight from SP-8B to SP-9A. Is V2 a 12AX7 or 12AT7?

V2 12AX7:
8/6/81 752x SP-9A
8/26/81 K17x SP-9A
10/5/81 61x RP-9A
(Thanksgiving finish likely) 8231 RP-9B (10-81 start)

V2 12AT7:
12/28/81 K22x SP-9A
1/26/82 K23x SP-9A

Not a large sampling but I looked on the CD coli's and they are 12AT7's. They are SP-9A's while the original August '81 SP-9A's I have are AX7 for V2. The RP-9A from October and RP-9B I figure was finished late 11/81 still show AX7. But that 12/28/81 coli with SP-9A must reflect they started a 12AT7 V2 from the looks of it and who knows how long that lasted. I don't have pics of a '82 RP.

Looks like we nailed down another transition since my 10/5/81 is RP-9A and at some point in November they were using RP-9B. A good guess is there are only a few hundred RP-9A's and shortly after they transitioned to RP-9B they changed the V2 valve.

 

[James]

If the SP-8C exists it is in extremely limited numbers. Makes me wonder how many RP-8C's exist.

The board in K152 looks like the tracing of a RP-9A dated 8/18/81 giving the look that the RP transitioned about or at the same time. The nearest back I have pics of is K110 dated 4/14/81 and I can't see the print but it looks like a RP-8C.

If there are 3 main circuit versions what board makes up the bulk of the 5500-7500 is my next question. It obviously ends with SP-8B and RP-8C. People in general seem to distinguish the 9C as more gain making me believe there is enough difference between the 9A and 9C as being 2 of the 3, but to my untrained eye who knows? Maybe they are the same circuit, different layout and small tweaks to voice the gain.

I've not seen enough amps to know, but it seems like there are fewer 9Cs. I'm not sure when those appeared, but it looks to have been in 1983 at least.

I would say the 9C does have more drive than the previous IIBs. The voicing is a bit different too. In some cases I prefer it to the IIC+, as it still retains some of the earlier sound and is a bit more neutral overall.

 

[GJgo]

@GJgo Is it summer in Grand Junction yet?
Hey, does your RP-9C use a 12AT7 for V2? And is there a date on it since it has to be about the last 9C? Speaking of last mades did you get the blue stripe back yet?

Nope. Weather is still rough here. Winter coat today!

My RP9C came set up from the factory for AT7 in quite a few slots- see pic. However, when Mike B loop modded it, it came back set up for AX7 in all V1-V4.

The '99 blue stripe should be done any day now. The + mod check has been cashed!

 

[user 41014]

My RP9C came set up from the factory for AT7 in quite a few slots- see pic. However, when Mike B loop modded it, it came back set up for AX7 in all V1-V4.

The '99 blue stripe should be done any day now. The + mod check has been cashed!

Nice- I bet that little sixty is going to squeal like a stuck pig!

I wonder what the thinking was going AT7 through the B's. For all my B's it looks like I have a tight date range on most of them with a focus on AX7. Maybe you should drop off your B that has a C K-number so I can become acquainted with a 9C!