Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: TIMBO on April 17, 2014, 09:49:30 pm
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Hi guys, I thought I stumbled across another vintage aussie built amp.
It was stamped with "rose music" that was originally Rose Morris & Co. who were in with Marshall awhile back. They then became Rose Music and built Goldentone amps here in Australia.
After investigating the amp, it became clear that although looking professionally made has no ties the "rose music" or goldentone amps. :sad2:
Not unhappy as the components are well worth the $250 I paid for it.
I reversed engineered it and as with a lot of these aussie built amp, there is always a bit of a twist to the circuit.
Can anyone spot any inspiration that the builder may have followed. Thanks
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oooooops, Forgot the schem :l2:
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For identification: that circuit board is probably factory made, and probably in Japan in the 1970s. Guya, Elk, other less-common brands. If the rectifiers are "green pills" then is sure from Japan.
You have the power supply drawn wrong. It is the Voltage Doubler. There's two kinds, Google will help.
Unless you find that some scrap of this is Very Collectable, I'd be inclined to chisel it back to iron and good(?) sockets/wires, lose ALL that iffy patchwork wiring, un-bushed holes, and vintage cheese-board.
> any inspiration that the builder may have followed
"Stuff it and see"??
The output stage is basic Fender but with EL34. Oddly the Presence network is permanently on.
The tone control IS classic Fender, you just drew it tangled. There may be small differences which I don't care to trace.
The mixer.... that's a LOW level mixer. It distorts easy. I wouldn't put it before a lossy tone control. For a few more parts it cudda been a 5F6A stage.
The preamps are unexceptional until you spot the 1Meg feedback from Vol pot to grid. That will give a LOW input impedance, perhaps 20K. (67K including the input resistors.) Which will suck the treble off a guitar. Which may be why the Presence network is permanently on.
If you prefer to do as little as possible, play as-is, then clip the 1M NFB around preamps. That may be bright, snip the 0.1u across the 4.7K to get no-Presence. That may be an OK amp. If it strains, mod the mixer stage to be more like the 5F6A (passive mix, gain, cathode-follower). 5F6A *works*. 5881 or EL34 is a matter of taste (and bias). Using a voltage-doubler supply is unimportant (and all you can do with this low HV winding).
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Thanks PRR.
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Look a Japan made amp not made in England , do not wort $250 IMO
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Hi guys, No luck on the maker or history...................
The amp itself is going to need a lot of TLC and the trannys are a waste for the circuit and Too heavy for the chassis. Some iffy wiring requires some fixing up. The best solution is to put the trannys to better use,so keeping in the aussie tradition of the build, is to build an iconic aussie amp. That being a Moody GA-40 that will suit the Huge PT well. Thanks
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Timbo,
Could it be a Phoenix amp? Jedistar is like a wayback machine for amps! Check this out:
http://www.jedistar.com/jedistar_amp_dating_p.htm (http://www.jedistar.com/jedistar_amp_dating_p.htm)
Also there is the Playmaster 116 that was a kit build from Electronics Australia magazine. However, scroll down to the pic of the 125. Maybe there was a source for parts and people built them as they wanted?
http://www.ozvalveamps.org/playmaster.htm (http://www.ozvalveamps.org/playmaster.htm)
Jim
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Thanks Jim, I looked into as much as I can find and still turned up Zip. I finally pulled it completely apart and other than the pots and the Ecaps having the DUCON makers mark which were the local maker of the day. I found stamped on a washer of the indicator lamps "ARCOLELECTRIC" made in England and that IS that. :icon_biggrin:
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Hi guys, The mystery is partly solved, I was looking through some aussie schems to compare a vibrato circuit with other builders and I found this http://www.ozvalveamps.org/fisonic.htm (http://www.ozvalveamps.org/fisonic.htm) (NO.3027) 60w and all the components were a match the only difference being the chassis and cab. Thanks
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The PCB is the same. Turned end-for-end and upside down.
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Het PRR, I though this amp was going to turn out to be a NOBODY build just some leftover parts used in what ever way it will fit into a poorly designed chassis.
I still think it is the case, but the circuit is similar to some of the other amps built around the same time by Phil Dreoni of Fi Sonic.
I may try to contact Phil for more info, because the cab design is not similar to any of his other builds.Thanks
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Do you have Rat Rods there? 3/4 of a 1937 Chevy body with a 1973 Dodge engine and a Mercedes grille?
That's my vote. Someone found two or more half-ruined wrecks in an amp-shop junk pile, and bodged them together. Apparently most of the electronics, complete, but laid out different to fit the chassis/cab.
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Hey PRR, I am hoping to contact the circuit builder tomorrow to get some info.
I was thinking much the same, that the cab was damaged and a new home was made for it. :w2: :dontknow:
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Hi guys, I was able to contact the builder and it turned out that one of his employee's had put it together and only a few were made.
So, I'll make a new chassis, with a better layout, tart up the cab a bit and it will be good to go.
I have the guys here http://www.guitargear.net.au/discussion/index.php?topic=40555.0 (http://www.guitargear.net.au/discussion/index.php?topic=40555.0) giving it the once over and the extra 1M resistors at the input was also getting them scratching their heads. Thanks
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Hi guys, MAN I can't believe its been that long since I got this amp. :think1:
OK, this is where I'm at............
Original cab stripped and joints reglued with new tolex.
Redesigned chassis to accommodate the PCB board to be up the right way.
Replacement PT smaller to fit. No filament winding so extra transformer for heater supply.
Reverb added and scrounged mustard cap to keep everything looking old and CC resistors as well.
New faceplate.
Sore finger (may loose fingernail) dropped pit cover on it at work :cussing:
The circuit as PRR pointed out is a bit iffy but the guy I bought if off gave it a bit of a thrashing when I picked it up and sounded good, so I have kept much the same as I was. As for the extra 1ms on the inputs I have deleted them for the moment.
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Looking good I know the feeling about time bought all my parts for the Da'lator back in July was finally going to get to it this weekend and was able to get a little work done.
Post some sound clips when complete.
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Hi guys, Nearing completion and I think I got it sounding pretty good for am old amp.
After some problems with the reverb its now working well.
A present it does have a ground buzz that is reduced when touching the guitar strings and a CC resistor fizz.
I'm just happy that I was able to get it working and sounding great.
Another one on the list for a sound clip.
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That is surely a labor of love. Interesting project and your relentless pursuit of finding the history is inspiring.
:icon_biggrin:
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Well done Timbo.
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Looks real good!
Very Nice Job!!!!
Brad :bravo1:
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Thanks guys, Just a few pics of the finished job.
A BIG thanks to Tone Junkie (Bill) for providing some of the MUSTARDS to get the it finished.
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Wow, speaking of the way back machine! That looks like the day it was sold! Great job!
Now young man.....how about some personal sound clips.... :m11
Jim
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Just for YOU, Jim https://www.youtube.com/watch?v=NmSf_dqPDM0&feature=youtu.be (https://www.youtube.com/watch?v=NmSf_dqPDM0&feature=youtu.be) :icon_biggrin:
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beautiful restoration!
--pete