Challenger CHB 35

[plexi50]

I got this Bogen Challenger CHB 35 this afternoon. Someone did add 1/4" input and speaker out jacks a long time ago. But as far as the circuit goes it is completley stock.  I just change the bias coupling caps as the original blackcats were looking old and tired. I had one tube starting to redplate but that has been cured now. I want to keep this amp simple without making a bunch of alterations. Are there any benificial changes that you can think of?

 

[smackoj]

I did a lot of changes to a Bogen CHA 20 including mounting a 5 volt heater Tranny so I could swap out diff. rectifier tubes. The Bogen originally had a 6X5 if I remember right?  I also changed the output tubes to 6L6 from 6V6 and when I got it going the OT was sorely lacking any type of bass response. I put in a David Allen (Heyboer I think?) and it sounds very nice. I kept the orig. tube sockets but had to do some modding to get a jack mounted for the speaker plug because Bogen used the contact strip with screws which was too clumsy for a gigging amp.

I can't really say about leaving most of the circuit wiring in one because I basically gutted mine and built a turret board with a Fender Pro type output design.

good luck, Jack D

[SoundmasterG]

The CHB 35 is like half of the CHB 100, which I modded. The 7868 tubes are cool, but the preamp leaves something to be desired. The power supply uses a voltage doubler, so you are kind of stuck with that. The OT is a bit undersized but not too bad. If you make it a single channel in the preamp then there are all sorts of options for what to do. I started over with my amp...only kept the chassis and transformers....but if you wanted to stay close to stock mostly, I'd say leave the power amp and redo the preamp. Rewire for different tubes. They can sound good with a bit of work....

Greg

P.S. The EH 7868's are very nice tubes...as good or better than old stock for tone and so far are holding up great.

[plexi50]

Well i went hog wild as usual on the CHB 35. Just wasnt satisfied with tone. I built a 5E3 Tweed Deluxe. Pair of 6V6GT power tubes. Need to swap out the output transformer and PT. The OT isnt very loud. I think the OT impedance is why. I read the 7868 tube data and i think im reading 3000K impedance. Or the OT is bad, One of the two. It should be blowing smoke i would think with a 35 watt OT.

[PRR]

> 7868 tube data and i think im reading 3000K impedance

No, the datasheet shows 6600 for a *pair*. (3K for just one.)

If you already octalized it, 6L6 might be a better fit for 7868 PT and OT. Nothng new about 6L6 in a Deluxe.

[plexi50]

Much better idea PRR. Brought my power tube plate voltage down to a decent 450VDC. Changed out the OT. Wasnt working right. Volume was half of what i thought it should be. Sounds loud and full now. More tommorrow

[gldtp99]

I love to see what others come up with when rebuilding CHB series Bogens--- i've re-done many, many of them in many different ways.
Too bad your orig OT was no good---- usually these CHB35A OT's are good sounding units -- CHB35A iron with 7868, 6L6GC, or EL34 output tubes usually provides a good amount of volume.
I'm considering using a CHB35A PT/OT set I have on hand to build a moderately gain enhanced non-MV Marshall circuit for one of my customers------ he bought a 25 watt JCM 800 build (#34 Mod) head w/JJ 6V6S and a 50 watt 2204-type build (circuit tweaked for smoother treb response and slightly de-gained)-------- he says that the 25 watter doesn't have enough headroom with his band and that the 50 watter sounds great but is too loud when he dials it in for the tone he likes.
Both of these heads have Lar/Mar PPIMV's but he doesn't like to use them---- but he does like Resonance controls (in another amp i built)---both heads also have Metro Zero Loss FX loops (he likes to use rack effects in the loop).
This guy is a very good player but is particular about exactly what he likes in an amp----- we tried progressively adding preamp gain and NFB tweaks to the 50 watter but he likes the headroom, and very good ability to clean up with guitar vol pot, rather than earlier preamp break-up------ he much prefers power stage distortion over preamp distortion-- the 50 watter is a very loud amp when cranked up (pretty much how he uses any amp--- he likes the power stage "working")--it's interesting working with him and he has bought several of my amps over the last yr or so----i've offered to take the 25 watter back, in trade, but he doesn't want to give it up.
So......... the "in between" 7868/7591 19 watt dissipation output tube with similar-sized iron seems to be the way to go here------ I've tried to limit my builds to more common tube types but, in this case, I'll be using EH 7868's because i have them on hand.
Or i could go with JJ 6V6S x 4 with a different transformer set and scrap the CHB35A iron and 7868 x 2 idea.
Desisions, decisions....................................any other ideas ?............................gldtp99

[plexi50]

Im surprised myself that the 7868 OT was weak. I expected a loud and proud OT. Even before making any changes it seemed to be holding back. All of the tubes were excellent testing. Even after the 5E3 Deluxe build it was weak as can be. Top volume was like 2 on the pot. I will check it out more when able. I was pressed to go marshall again but i am more tweed and blues these days. Nothing like that SRV / Gary Moore soul tone. So many build option. Hard to make up my mind sometimes. I think i kept it simple

[gldtp99]

Nothing wrong with the 5e3 circuit family--- I include 6L6GC (5e5) versions and the later BF Princeton and Princeton Reverb circuits in this family, too----- one of my favorite "circuit families" to build--- I recently rebuilt another Challenger CH30 with a BF Princeton Reverb circuit--- without actual reverb but with the reverb recovery gain stage----- i'd always used parallel triodes (done in different ways) in V1 for added fatness in prior builds of this type but i thought i'd try using the reverb recovery stage in this one--- has Vol, Treb, and Bass pots--- fixed bias and has NFB loop------- Magnetic Components Super Reverb-type PT and BF Bassman 4/8/16 ohm OT----- 5U4GB rec and 6L6GC x 2 outputs----- this set-up has more compression to the tone and is very easy to play--and still sounds "fat"---a local player has a deposit on it already.
The Tweed Bassman 5F6A/ early Marshall NMV/ Marshall MV/ modded Marshall (incl extra gain stages and diode clipping) is another of my favorite "circuit families" along with Brownface and Blackface Fender circuits to build.
But having said all that--- i'm currently doing a gut/rebuild of another Sound City 120 into a EL34 x 6 Hiwatt circuit---two local bands are interested in this one to use as a bass head........................gldtp99

[nichesound]

 
I have a couple of Bogen amps that I am finally getting a chance to rework, CHB 35/50/100 and the first one I am working on, the 35, I have kept transformers and put in sockets for an EF86 and 8pin output tubes.  I also have changed out the 7 pin for a 9 pin Phase inverter.  This amp sings on both channels. 
I will post the work soon, as I am adding a 6.3v/3amp heater transformer so I can safely put in the EL34's for versatility.  I have added a few features to make this amp work with other tubes, and a switch for the Negative Feedback.  I see a lot of people chiming in on voltages for this amp.  I like that I have that extra voltage to work with.
I have added decent components, and wired it with basically grounding that is individually fed to ground area with separate ground wires where needed.  It has bias check points and can individually adjust each tube's bias.
The amp is quiet, and though the only thing I have to work thru is since I am using NFB, taking the EF86 from volume wiper to the PI input that has the 12AX7 on it, I get some cross talk thru the wires  and can actually use the volume control on the EF86 to add some depth to the 12AX7 circuit.  Having both options has opened up the amount of cool this amp purveys.  All told probably less than 2bills for a fine sounding head.[/b]

[nichesound]

I forgot to mention, I will post the layout as soon as I am finished.

[Platefire]

I've done a CHB50, CHB10A & CHB20A. The 50 I did 5F6A, 10A a 5E3 preamp/tone stack--left the power section as is and the 20A left the tone stack and power section stock but rewired for a normal fender type input and relocated the MV to pre PI. Good results on all but on the 50 the OT was bad and ordered one of Doug's baseman OT and it made a wonderful difference in overall sound. Kept the original power supply in all three. Good fun and experience!! Platefire

[jjasilli]

I got this Bogen Challenger CHB 35 this afternoon. Someone did add 1/4" input and speaker out jacks a long time ago. But as far as the circuit goes it is completley stock.  I just change the bias coupling caps as the original blackcats were looking old and tired. I had one tube starting to redplate but that has been cured now. I want to keep this amp simple without making a bunch of alterations. Are there any benificial changes that you can think of?

What do you want to do with the amp? I'm using my CHB-20A un-modded for its original purpose:  a PA amp.  It sounds great for acoustic guitar & voice and much better than SS units.  I also have a CHB-35 that needs a re-build, which I will use as a back-up PA.

If you have no use for a PA, then as a guitar amp IMHO the stock Baxandall (James) tonestack is too dark and needs to go FMV.  Arguably the 400V B+ supply to the power tubes is too high and could be dropped 100V!  If you search the forum PRR posted a clever mod to the remote volume circuit.  A major appeal of PA amps is that the multi-input channels can be converted to cascading gain stages, etc., but these little Bogen's lack that option.  However, there's plenty of room to add more tubes & a filament tranny.