Just scored this guy at the flea market for a very, very fair price. It's a tube-powered Challenger 35A and a matching set of L123C-A speakers ... But the speakers open up like a clamshell and nestle the head inside for transport! It's even got a couple (broken) handles to carry it around.
The seller had already turned it on, so I figured it couldn't do any more damage to run it a bit before I opened it up. As expected, there's a little 60Hz hum (the power supply is a half-wave doubler), but it works! The aux input is working great; the hi-Z mic inputs don't do anything, so I figure the 6EU7 is probably dead. I'm going to rewire that socket for 6N2P, since I've got a pile of those.
Anyway, I've never seen anything like this, and I figured I'd share. I'll probably leave it stock and plug an amp sim pedal into it, at least for now. If I end up keeping it, I may swap the 7868s for something a little more friendly.
Oh, and it came with a Shure 585SA, an AKG D109 lavalier, and a little Realistic lavalier that uses a 7V button battery. Not a bad haul!
The seller had already turned it on, so I figured it couldn't do any more damage to run it a bit before I opened it up. As expected, there's a little 60Hz hum (the power supply is a half-wave doubler), but it works! The aux input is working great; the hi-Z mic inputs don't do anything, so I figure the 6EU7 is probably dead. I'm going to rewire that socket for 6N2P, since I've got a pile of those.
Anyway, I've never seen anything like this, and I figured I'd share. I'll probably leave it stock and plug an amp sim pedal into it, at least for now. If I end up keeping it, I may swap the 7868s for something a little more friendly.
Oh, and it came with a Shure 585SA, an AKG D109 lavalier, and a little Realistic lavalier that uses a 7V button battery. Not a bad haul!
An externally hosted image should be here but it was not working when we last tested it.
Before assuming the mic inputs need a rewired tube circuit, check to see if there are any empty "tube sockets" in side, where plug in transformers would have gone. Many amps of that sort used optional impedance matching transformers in case someone wants to use low-Z mics. But in their absence, and jumper plug was needed to complete the Hi-Z input circuit.
If I had an unwanted old Bogen or similar, I would likely take the transformers out before discarding it.
If I had an unwanted old Bogen or similar, I would likely take the transformers out before discarding it.
That's a good thought, but this guy only has hi-Z capabilities. No place to add a transformer.
I'm a little annoyed that my tube tester doesn't have a listing for 6EU7, so I can't even test the tube. It's original Bogen-labeled. But given that it's grid-leak biased -0.8V by spec), low emissions from being weak would be a double-whammy, because it would mess with both the current through the tube and its bias.
As for the other tubes, the 12AX7 tests almost like new, but it's a replacement from what looks to be 1984. The original 6C4 is used but still strong. The original 7868s are almost dead, reading 20% emissions. Not surprising for an amp that was probably left on all day, every day, for a long time.
A buddy of mine might have some 6GT5s, so if he does I'll pop those in and pull down the screen supply to 200V. Otherwise I'll convert to octal sockets and use something like a 6AV5 or 6DQ6 (I've got spare top caps).
I'm a little annoyed that my tube tester doesn't have a listing for 6EU7, so I can't even test the tube. It's original Bogen-labeled. But given that it's grid-leak biased -0.8V by spec), low emissions from being weak would be a double-whammy, because it would mess with both the current through the tube and its bias.
As for the other tubes, the 12AX7 tests almost like new, but it's a replacement from what looks to be 1984. The original 6C4 is used but still strong. The original 7868s are almost dead, reading 20% emissions. Not surprising for an amp that was probably left on all day, every day, for a long time.
A buddy of mine might have some 6GT5s, so if he does I'll pop those in and pull down the screen supply to 200V. Otherwise I'll convert to octal sockets and use something like a 6AV5 or 6DQ6 (I've got spare top caps).
Your 6EU7 may be just fine. (How old is your tester anyway?) Signal triodes like that can last decades and decades, they don't wear out like power tubes do,. Many many people have rewired sockets for 12AX7 in its place though.
TOp cap tubes? Is there room inside under the roof for those?
This listing from Reverb has interior photos and a schematic
Bogen Challenger CHB 35A 1965-1966 | Joyous Jake's Jamz | Reverb
The listing calls it 1965-66.
TOp cap tubes? Is there room inside under the roof for those?
This listing from Reverb has interior photos and a schematic
Bogen Challenger CHB 35A 1965-1966 | Joyous Jake's Jamz | Reverb
The listing calls it 1965-66.
It's a Lafayette TE-50, ca. 1964. Haven't opened it up to date the components yet - only had it a few weeks. But it seems to work fine, at least on a gross level (i.e., new tubes show up around 85%, and the 7868s show up at 10%). And yes, I know it's not really a great tester, but it's better than nothing!
Very true, and I wasn't equipped at that moment to check voltages to see how much it was actually conducting. There were no obvious issues with the circuit like burnt resistors or leaky caps. It did respond to big transients like attaching the mic or switching the mic on and off, it just didn't do anything with an audio signal. Which to me feels like a super weak tube. But I'll definitely do a real diagnosis, even if I am planning to rewire the socket anyway, just to be sure.
It's an oddly roomy piece. With the cap installed, the 6DQ6 would be about 3/4" taller than the 7868, so it would just fit. Would have to remove the chassis to replace it, though.
Seems like it was a relatively long-lived model. The traffos and tubes in mine all date to 1974. Even got a factory 3-prong cord!
That example has been modded - the octal sockets are new, and the front end (far right on the first gut shot) has been reworked. Because of the grid leak bias, it originally had capacitors on the input, and those are gone. Interesting choice to put the input jack all the way on the right, where you've gotta run it alllll the way across the chassis to the first gain stage on the left (not to mention drilling a new hole in the faceplate ...) If I set mine up for guitar, I'll put the 1/4" in place of the Mic 1 input on the back, which is right next to it.
Personally, I would have replaced all those paper caps, too.
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