Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: rzenc on September 11, 2011, 05:01:09 pm
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Got these on the bench...
Marshall 9200 - 2 channel 100W power amp - tubes are sovtek 5881 - seems to be factory original.. preamp tubes are ECC83, ECC81 - looks like chinese tubes...
Marshall JMP-1 preamp...
Friend bought them used back in 1998 - sold in 2003 - bought again last week... He told me it is sitting for about 5 years in the basement without use...Previous owner dropped both units on the floor - scratches on the faceplates and rack-ears...Also fired it without load attached :dontknow: and some stuffs he was not proud to tell us :l2:
Tested tubes in my amp and they are varying all over the place.
Since tubes are locked inside the cage, I had to check height on some tubes - 6L6GC variants - and besides Sovtek 5881, the only tubes that seems to fit are TAD 6L6WGC - small bottles - "C" is a little too long...
I will replace all e-caps since it has been on storage for such a long period.
Do you guys have EXP with this set up? It's dead clean inside - no one has been there since it left factory..
9200 schema:
http://www.el34world.com/charts/Schematics/files/marshall/9200_2x100w.pdf (http://www.el34world.com/charts/Schematics/files/marshall/9200_2x100w.pdf)
I have used JMP-1 a lot on a studio with metalhead bands but never opened one up..
JMP-1 schema:
http://www.el34world.com/charts/Schematics/files/marshall/jmp_1.pdf (http://www.el34world.com/charts/Schematics/files/marshall/jmp_1.pdf)
Thanks in advance
Best Regards
Rzenc
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what a load of garbage that 9200 is. sorry, but i don't equate a greater parts count to better tone. that thing has to be a nightmare to service. sheesh! sand state current sources? you'd think they were designing a hi-fi and got side-tracked into building a guitar amp.
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what a load of garbage that 9200 is. sorry, but i don't equate a greater parts count to better tone.
Agreed... Less is more
that thing has to be a nightmare to service.
Yeah...tight as hell...
sheesh! sand state current sources? you'd think they were designing a hi-fi and got side-tracked into building a guitar amp.
Had the same feeling when I saw the schematic...They could have used a EF86 instead, at least it would be glass-friendly :laugh:
Maybe we can come up with some cool mods...I will talk to my friend tomorrow...
Is there any reason why R40 - 56K noted as 1/2W metal oxide - must be metaloxide??
P.S. DL: I 'm still working on the .dwg file... did not forget..
Best Regards
Rzenc
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P.S. DL: I 'm still working on the .dwg file... did not forget..
cool! thought you gave up.
Maybe we can come up with some cool mods...
honestly, i wouldn't know where to start... maybe a gut it out and start over... :-\
Is there any reason why R40 - 56K noted as 1/2W metal oxide - must be metaloxide??
looks like R39 and R40 are 1/2W - metal oxide used in power supply - flame proof.
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P.S. DL: I 'm still working on the .dwg file... did not forget..
cool! thought you gave up.
Not that easy pal!! :occasion14:
About the mods, I will first bring it back to life..them we see...
Thanks for the info about the resistor...
Best Regards
Rzenc