#189 50W Bluesmaster(Ripper?) Photos

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67plexi
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Re: #189 50W Bluesmaster(Ripper?) Photos

Post by 67plexi »

It look's real close to the Larry Carlton Dumble.


Steve. 8)
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stevlech
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Re: #189 50W Bluesmaster(Ripper?) Photos

Post by stevlech »

Both Larry's amp and #189 appear to have two stage OD unless something is different under the goop.
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ic-racer
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Re: #189 50W Bluesmaster(Ripper?) Photos

Post by ic-racer »

Overdrive entrance pot on front panel?
Cathode follower V2?
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martin manning
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Re: #189 50W Bluesmaster(Ripper?) Photos

Post by martin manning »

ic-racer wrote:Overdrive entrance pot on front panel?
Cathode follower V2?
I don't think so. All knobs are accounted for by the usual ODS arrangement, and V2 has separate plate, grid, and cathode leads on both sides.
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ic-racer
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Re: #189 50W Bluesmaster(Ripper?) Photos

Post by ic-racer »

martin manning wrote:
ic-racer wrote:Overdrive entrance pot on front panel?
Cathode follower V2?
I don't think so. All knobs are accounted for by the usual ODS arrangement, and V2 has separate plate, grid, and cathode leads on both sides.
If they are calling it a Ripper, one might need to do some poking around under the HRM board to tell. Just a guess.

CF WIRING IMAGE DELETED (errors, thank you Jelle )
Last edited by ic-racer on Thu Apr 30, 2015 11:35 pm, edited 1 time in total.
"You feel like you're floating on a football field filled with marshmallows." -Dumble
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jelle
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Re: #189 50W Bluesmaster(Ripper?) Photos

Post by jelle »

Without a grid to ground reference to the second triode grid, this will be rippin' nothing but farts.
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glasman
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Re: #189 50W Bluesmaster(Ripper?) Photos

Post by glasman »

martin manning wrote:Yes, that's clearly the case, it's a variable lift. Note also the "jazz cap" usually connected from the R/J switch to ground is going through what is usually the PAB relay, and the common lugs on the R/J switch are joined. Something different going on there for sure.
Funny, I did the same thing on some of my early SOD amps. I located the pot on the boost board (actually two of them). I have long since abandoned the practice.
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chris_sanford
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Re: #189 50W Bluesmaster(Ripper?) Photos

Post by chris_sanford »

martin manning wrote:
ic-racer wrote:Overdrive entrance pot on front panel?
Cathode follower V2?
I don't think so. All knobs are accounted for by the usual ODS arrangement, and V2 has separate plate, grid, and cathode leads on both sides.
Looks like a ripper to me. The lack of an OD entrance trimmer, and the "crossed" inputs to the OD grids are like the LC amp - where the OD drive is controlled by the level pot on the front panel.

Don't need a grid to ground reference for the typical dc-coupled CF stage.

Just my own speculation though.

-chris
Duble
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Re: #189 50W Bluesmaster(Ripper?) Photos

Post by Duble »

chris_sanford wrote:
martin manning wrote:
ic-racer wrote:Overdrive entrance pot on front panel?
Cathode follower V2?
I don't think so. All knobs are accounted for by the usual ODS arrangement, and V2 has separate plate, grid, and cathode leads on both sides.
Looks like a ripper to me. The lack of an OD entrance trimmer, and the "crossed" inputs to the OD grids are like the LC amp - where the OD drive is controlled by the level pot on the front panel.

Don't need a grid to ground reference for the typical dc-coupled CF stage.

Just my own speculation though.

-chris

I also think this is correct. Couldn't the second V2b Grid be connected to the plate, futher controlling the B+ of the CF stage, and the V2b cathode is connected to the HRM board, with a 100k to ground at the tonestack entrance junction in place of what would normally be a cathode cap/resistor to ground on the board?

The more I stare at the JCM800 schematic, the more this layout confuses me.

Just speculating of course.. Anybody have any more insight on this type of circuit? I'm sure would be greatly appreciated by everyone on this board.
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martin manning
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Re: #189 50W Bluesmaster(Ripper?) Photos

Post by martin manning »

I don't think there is a CF stage here since the two triodes have separate plate, grid, and cathode leads. The drive control does not replace the OD entrance trimmer since the lead from the Clean output to a V2 grid stopper is the same as usual.

Here's another possibility that is consistent with the photos: The two OD stages are reversed, with the HRM stack in between. The Drive control has the same function as before, controlling the drive into the second stage, but it is now positioned after the HRM.

(edited schematic diagram to swap stage outputs at coax connections)
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Last edited by martin manning on Mon May 11, 2015 10:56 am, edited 1 time in total.
chris_sanford
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Re: #189 50W Bluesmaster(Ripper?) Photos

Post by chris_sanford »

martin manning wrote:I don't think there is a CF stage here since the two triodes have separate plate, grid, and cathode leads. The drive control does not replace the OD entrance trimmer since the lead from the Clean output to a V2 grid stopper is the same as usual.

Here's another possibility that is consistent with the photos: The two OD stages are reversed, with the HRM stack in between. The Drive control has the same function as before, controlling the drive into the second stage, but it is now positioned after the HRM.
Hi Martin,

Don't get hung-up on the separate connections to V2B. If this amp is like the ones I'm familiar with, the front panel drive pot connects directly to V2A via shielded cable (note that in the pic) instead of via the regular wire from the circuit board, the new crossed over input wire connects to the grid of V2B to the plate of V2A (perfectly ok to leave a grid-stopper on the cf stage) and the V2B cathode shows a big resistor to ground. Sorry, I do not know what circuitry is under the goop, but suffice it to say, that it goes: OD relay>unknown stuff>front panel drive pot>V2A>V2B cf>TS. This much is easily confirmed (or denied) with a meter. Wish Charlie had had one with him!


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Charlie Wilson
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Re: #189 50W Bluesmaster(Ripper?) Photos

Post by Charlie Wilson »

This was the first Dumble I had seen in person. I didn't know anything about Dumbles but just felt like I should take some photos. It took me about half an hour to carefully remove the chassis from the head cabinet, it was wedged in pretty tight. When the chassis came out and I saw that blue goop I didn't know what think. If I only knew then what I know now. :D
CW
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martin manning
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Re: #189 50W Bluesmaster(Ripper?) Photos

Post by martin manning »

I don't know what to think about the CF hypothesis, it certainly sounds plausible, and a measurement showing a large Rk would confirm it. Still, that green grid wire that crosses to the other triode emerges from the goop exactly where the OD entrance trimmer would be.
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UltraHookedOnPhonix
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Re: #189 50W Bluesmaster(Ripper?) Photos

Post by UltraHookedOnPhonix »

As an aside...Sonny Landreth's ODS is also a BM and according to Alfonso Hermida, is #188.

http://www.thegearpage.net/board/showth ... ?p=8101716
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chris_sanford
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Re: #189 50W Bluesmaster(Ripper?) Photos

Post by chris_sanford »

martin manning wrote:I don't know what to think about the CF hypothesis, it certainly sounds plausible, and a measurement showing a large Rk would confirm it. Still, that green grid wire that crosses to the other triode emerges from the goop exactly where the OD entrance trimmer would be.
I agree with you Martin re: where the crossed connection hits the goop, but if you follow the blue plate wire from V2A, you will see that the plate connection could be even closer than the trimmer in terms of the board's real estate... even more so in the previously-mentioned LC amp pic.

chris
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