Tube Layout For Better Mod??

[zozoe]

Howdy, I reworded the topic of this thread so as get a bite or two. I fully understand that this may be hard to answer, but of 2 different Bogen Challenger amps, one 10w using 2x6SF5,6SL7, 2x 6V6, & either a 5Y3 or 7Z4, and the other 18w amp with a modest set with only a 6AV6, 6AU6, ONE 6L6, & an EZ81, Just looking at the tube lineup, is it at all possible to tell which one might be more workable, & made into a 'rawker'? Both are PA amps made by the Bogen Co., with decent iron, not huge. I've never tackled anything like this before, but I want to give it a go.
Would any other info be useful for one to make a better assessment?
Thanks & be well~~
kenny

[pompeiisneaks]

If you want to get traction on this kind of thread, it's pretty common to include schematics of the amps you're referring to. People often need to see the schematic to understand how the amp is laid out, the component values etc.

In some cases the only thing you need to do to push an amp into a nice driven range is to change the tube bias point with some anode/cathode resistor changes etc. If we don't have the schematic, we can't tell what to do.

Also, defining 'rawk' is about impossible. What specific tone are you looking for? Heavily driven Marshall? ODS? TW?

We need to know more of what you want. We can't guess that you're looking for gain of 4 or 11.

~Phil

[thetragichero]

I'd also add it depends on how you're planning to build it. i pick up old organ chassis, completely disassemble, clean, and usually paint them and then build based on the transformer specs and what tubes I've got. a lot more planning but also a lot more control. single ended 6l6 and sounds fun (I've got one lined up myself)
but yes if you're just looking to hack into something a schematic is worth more than a bunch of typed words

[zozoe]

Here are the schematics I was able to dig up of the exact amps. Forgive the double entry of the second schm. Looking to do something that's clean & mellow, but past 5 or 6, get into old Gibson GA20/40, Premier, Danelectro or Supro 6V6 territory. No buzzsaw or uberdrive, but nice smooth harmonically rich OD. Maybe either of these amp's Phono pots could be used as a master, but I think I'd prefer 1 knob to do it all, unless there's a cool master that doesn't suck tone. My primitive, caveman thinking makes me think I'd want to drive the s*** out of the power tube(s)... I'm not going solely for volume, which each amp would be limited on, but the 'juice"~~
I did pick up a Western Electric 81B15 which has the exact tube configuration of my Gibson GA20 & 40, but I wouldn't expect them to sound at all alike two some tweaks....

Screenshot_20200714-141241_Drive.jpg

Screenshot_20200715-213844_Gallery.jpg

Thanks again!

[xtian]

That CH10 will be a very easy mod to start playing your guitar thru the Mic input. The EZ81 can have up to 50uF reservoir cap, so take advangage of that, and replace the paltry 5uF reservoir when you upgrade the filter caps.

[dorrisant]

What circuit do you want to mod to? Are you gonna keep it point-to-point, or fit a board in it?

[zozoe]

I think I'd like to stay with what's already in there, point to point, & receive guidance about a handful of components I could give my tech to work with, or ultimately attempt myself. Is this what's known as a Single ended circuit?

[zozoe]

XTIAN, I see that 5uF & the 10uF section, but just beef up the 5uF one & to what value? And what does having a bigger reservoir cap mean? At a glance, any other areas that can see definite value changes?
Thnx, Kenny

[Colossal]

XTIAN, I see that 5uF & the 10uF section, but just beef up the 5uF one & to what value? And what does having a bigger reservoir cap mean? At a glance, any other areas that can see definite value changes?
Thnx, Kenny

Read this:
http://www.valvewizard.co.uk/smoothing.html

Then read every link on the left side of this page:
http://www.valvewizard.co.uk/

[Phil_S]

XTIAN, I see that 5uF & the 10uF section, but just beef up the 5uF one & to what value? And what does having a bigger reservoir cap mean? At a glance, any other areas that can see definite value changes?
Thnx, Kenny

See if you can manage to remove the mic jack and install a guitar jack. Replace the 5uF cap with a higher value cap, anything from 20uF to 50uF. If I was doing this, I'd also change the 10uF cap to 20uF or 22uF while I was at it. Make these changes and see what you have. It may be enough that you'll stop there.

Use a cap that is appropriately rated for the voltage. I suggest a rating of 400V or 450V. Although the schematic suggests a 350V rated cap may be adequate, remember the CH-10 was made when line voltage was 110VAC. These days, it is common to see line voltage around 120V and up to nearly 130V. I've checked the line voltage in my house and it is often in the range of 125-129. This means that the whole circuit will run at higher voltages. If your line voltage is just 10% over 110, you'll see over 350V where it says 325V, so I'd say a 350V rated cap is not adequate.

Common cap values that you will find are 20, 22, 22, 40, and 50. This provides more filtering. The filtering removes ripple. When there is too much ripple, you hear a hum that is not wanted. Read this: https://en.wikipedia.org/wiki/Ripple_(electrical)

Caution: remember that filter caps retain a residual charge that can be lethal. Always discharge the filter caps when working inside an amp. Read up on what to do if you don't know.

[xtian]

XTIAN, I see that 5uF & the 10uF section, but just beef up the 5uF one & to what value? And what does having a bigger reservoir cap mean?

Phil beat me to it.

[zozoe]

Great, What is a Single Ended amp, & is this one, & are they easier platforms to mod? I just want to slam that 6L6 with some major juice, which i hope the AU6 & AV6 can deliver. Don't know what their gain factors are & if there any drop in subs that may better. Since I'm not after volume, but juice, would it make any sense to bring in that phono pot as a master w/o stifling the sound, as masters can do? I just want it clean to 3 or 4, them start to OD pretty quickly & get some rectifier sag helping out. PHIL, is it possible you could send me the direct links to all the things I could use to do what you recommend?
Thanks in advance!
Kenny

[zozoe]

Yeah, I've got the cap discharging routine down!
Thnx

[zozoe]

Screenshot_20200625-032634_.Gallery (1).jpg

While we're on the topic, this is a BOGEN HE10 that I also want to do the same to.... Any mods that jump out at you?

20200625_015725.jpg

[thetragichero]

one thing at a time man. don't be like me with 8 different amps in various stages of completion
spend that energy reading up (the merlin site you were directed towards earlier is a great resource)