Bogen Challenger

tonejones · Post by **tonejones** » Tue May 22, 2007 3:52 pm

Hey guys,

I guess I've got the bug, as I picked up a working Bogen Challenger CHB35a for cheap a couple of nights ago to mess around with.....

Now I'm wondering if I should try modding it out for the best guitar tone I can get with what's there already, or turn it into a double-powered 18 watter????

A slammin' 30-something watt Marshall sounds good, doesn't it (no pun intended, but I'll take it anyway

)??????

Seems like it would be perfect power-wise for club gigs.......

Here's a link to the schematic
http://www.schematicheaven.com/hifiamps ... chb35a.pdf
Ideas or suggestions????

Flames1950 · Post by **Flames1950** » Tue May 22, 2007 4:50 pm

Haven't seen "Leftee" here in a while and he bailed from Plexi Palace a while back. See if his profile has an e-mail address, or maybe Trampy or Michael Patrick have a contact address for him. He did something like five or six of those Bogens ("Boggies".) He'd know where to start!!!

tonejones · Post by **tonejones** » Wed May 23, 2007 12:55 am

kewl,

Thanx Flames.....

Maschinenmann · Post by **Maschinenmann** » Thu May 24, 2007 11:39 am

Flames1950 wrote:Haven't seen "Leftee" here in a while and he bailed from Plexi Palace a while back. See if his profile has an e-mail address, or maybe Trampy or Michael Patrick have a contact address for him. He did something like five or six of those Bogens ("Boggies".) He'd know where to start!!!

He moderates at the Fender forum.

http://www.fenderforum.com/forum.html

Flames1950 · Post by **Flames1950** » Thu May 24, 2007 5:12 pm

Didn't know he'd stepped up to the moderating plate at the FF!!! But I haven't hung out there in ages, it's all I can do to keep up with this place!!!

gldtp99 · Post by **gldtp99** » Sat May 26, 2007 3:10 am

I've done over 25 of these Bogen CHB series conversions in many different ways---- i've got a great sounding CHB35A with a Marshall model 1987-type preamp/PI--- i kept the 7868 output tubes (matched Sylvanias)---- i rebuilt the power supply to near Marshall specs (except for the 1st filtering stage which must be set up as Bogen did it due to the voltage doubler/rectifier system Bogen used on these amps---- this is assuming you would use the orig Bogen PT)---i haven't used filter chokes on these amps to keep costs down and i like the way they sound without them (Angus Young has his Marshalls modded to remove the filter chokes--- power resistors take their place).
Here's some pics of a CHB50 i did recently with a "Plexi" type preamp--- i experimented with 1" diameter filter cap cans on this one--
http://s46.photobucket.com/albums/f112/ ... A%20heads/
This one now has a custom faceplate and a Fender type jewel lamp in the rectangular hole one the front panel---- the Power and Standby switches are on the back.
I've done another CHB50/Plexi since this one with lower filtering values (a JJ 40/20/20/20@500V can and some extra axial e-caps) and a 6av6 7-pin tube in V1 (the triode section is very similar to 1/2 of a 12ax7)---- a very nice sounding amp , it goes from clean to harmonic-heavy distortion with a turn of the guitar vol pot.
This band used one of my older CHB35A/Plexi amps to record all the guitar parts on the song "Die Alone"--- it was recorded guitar straight to amp, no effects--http://myspace.com/laddersandsnakes----- this CHB35A has cathode biased 6L6GC output tubes (another experiment---- not really better than the 7868's) and is owned now by another local player.
These Bogens can sound very good and are great to experiment with but when i've run the CHB50's against my '76 Marshall 1987 the real Marshall still stands out--- and Bogen vs. my '81 JMP 2204 is no contest.
Leftee's Boggy amps were mostly Bogen CHA-33 based--- the CHA-33 is an older Bogen design with tube rectification and 6L6GC output tubes. Leftee has done some very cool work with these and also with some Bell PA heads, too..................gldtp99

tonejones · Post by **tonejones** » Sun May 27, 2007 2:26 am

Nice stuff gldtp99!!!!!!

gldtp99 · Post by **gldtp99** » Sun May 27, 2007 3:24 pm

You don't have to completely gut the Bogen circuit and rebuild another preamp design if you don't want to---- i traded a CHB35A to a friend recently for some wooden amp head cases he and his dad build--

I had them build these JMP-ish head cabs to fit the CHB-series Bogen chassis as well as the Hammond 16x8x2" chassis.
This CHB35A has all new filter caps, modded screen grid supply, and a modded but stock Bogen preamp--- two vol controls (each running 1/2 of V1---- different tone set-ups on each one)--- running into the stock Bogen Master Vol (not the greatest set-up for guitar -- but it works)--- i modded the bias circuit to make it adjustable (new bias cap, also) and it's running EH 7868 output tubes.
People seem to like the tone of this one but i like the "Plexi" Bogens better..............gldtp99

mrguitaroman · Post by **mrguitaroman** » Thu Feb 17, 2011 1:54 am

Do you have a schematic drawn out or step by step directions to converting the Bogen CHB-35 to the Marshally tone? I do mostly pedals and such, this is my first tube amp experiment.

gldtp99 · Post by **gldtp99** » Sat Feb 19, 2011 9:31 pm

Old thread---- no, i don't have a specific schematic or step-by-step instructions---- i worked from both the Bogen CHB35A and Marshall schematics as needed.
I'd suggest building a simpler tube amp until your tube amp skills are up to modding Bogen CHB35A's------converting old PA tube heads can be done so many different ways it would be futile to draw up a schematic----i've done dozens of them and no two have been built exactly the same----experimenting is a lot of fun once the basic tube amp building skills are in place.................gldtp99

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