Count Bassie
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Count Bassie replied to Baloney Balderdash's topic in Bass Guitars
That's a little booger! Cool that it's nicely proportioned though. Get those fret sprouts filed though... Not cool to bleed all over the carpet! 😁 -
I think this game could be more fun if another rule were added.
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Ruth
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Kush
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You know there might be more than I've been led to believe, but it's possible this amp had been serviced with non-spec'd or alternate parts- which might have to do with why the output is so anemic. I'm not the tech though, and life's too short for some things... Also, as far as I've been able to find, there seems to be no Mk IV schematic in existence. ? Trace Elliot has a rabbit hole of hardly documented work. Thanks again for the files though!
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Yes, this one's a 250.
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Yep, this set goes back to the Mk V, and there are some significant differences between it and the Mk IV. Thank you for sending those though! I've downloaded them and I'll bet there will be another old tank added to the pile within the year, 😁. 👍
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I'm all about it, I'll look them up. Thanks again Matt! (Sent him a mssg... Ashdown, Peavey and BAS next...)
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Apparently there are some meaningful differences. The MK IV diverged from the MK V in the preamp I think, that's the report. He's been, as I say, reverse-engineering his way through some of it. I'm hoping to eventually get to someone who was part of the design team from that period.
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Alright then... My tech has the amp opened up again, as the volume doesn't seem to be what it should. Apparently the signal travels from several points between the power section and the preamp, and the preamp is quite complicated. At this point the gain on the preamp has to be all the way up to get even moderately significant volume. The model I have, the MK IV, doesn't have a schematic or any kind of plan available, so I'm starting to dig in and see if I can talk to any of the people who had a hand in the early designs. So far my tech has been essentially reverse-engineering his way through the amp, and it's exhaustive. I'd be very interested in hearing about any sources of first-hand info about the MK IV'S design. Thanks! It's off to Ashdown...
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Ready to receive... Went with gloss black, Rust-Oleum clear lacquer and #0000 steel wool.
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So it's been cleaned up, which took a lot more work than anticipated. The fan was caked with some kind of mud or sludge, and the preamp module was taken apart and gone through methodically. I almost didn't want to know what went on in the life of the guy who owned it previously... Anyway it's working, but it's not putting out nearly the power it ought to be. The tech has it back again, and is going through the op amps that get signal from the power supply. It's got a surprisingly small power amp I'm told, due to the structure of this thing. It seems the 250 through 500 models used the same transformer and big blue caps, but the number of power transistors was the difference in the final product. But, it sounds like I expected it to, which is great... Hopefully the output comes up to spec, and I'll install it into the sleeve. Pix to prove it happened! (Typos fixed!)
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Simply Ned
