Bogen Challenger CHA-35 Mono Tube Amplifier
Archived listing from the original vintage-amplifier.com. Prices, seller details and purchase links have been removed; this page is a reference record, and nothing here is for sale. About this archive.
This bogen challenger CHA-35 mono tube amplifier. This amp is in good cosmetic condition, chassis and transformers are clean. This amp looks to have been modified, One of the can caps went bad and it has added caps and resistors as a replacement, i have a picture that shows this. This amplifier was brought up to 80-90 volts on my variac where i was getting good output, There is a low hum that can be heard when the amp is turned all the way down so that will need some attention. i did not take it all the way to 117 volts because of original capacitors and the low level hum. I tested the amp using a cd player through the phono input and both mic inputs with a microphone. Tube complement are 2-6L6, 2-12AX7, I-6AV6, 2-5Y3 AND 2-6L6.
About this model
A Challenger with a history of repair. One of its original can capacitors had failed and someone had added replacement capacitors and resistors underneath; the seller brought it up to 80 or 90 volts on a variac rather than full mains voltage, because of the remaining original capacitors and a low hum at minimum volume.
That caution is exactly right, and it is the procedure the buying guide recommends. The listed tube complement mentions 6L6 output tubes, 12AX7s, a 6AV6 and 5Y3 rectifiers; it repeats "2-6L6" twice, so treat the exact count as uncertain until you see the chassis.
| Maker | David Bogen Company, USA |
|---|---|
| Series | Challenger (public address) |
| Inputs | Phono and two microphone inputs (listing) |
| Tubes listed | 6L6, 12AX7, 6AV6, 5Y3 (listing; count unclear) |
| Condition noted | Earlier capacitor repair; low hum at minimum volume (listing) |
Questions collectors ask
Why bring an old amplifier up slowly on a variac?
Old electrolytic capacitors can short or fail if full voltage is applied at once. Raising the voltage gradually lets you watch for trouble and can partly re-form tired capacitors before they are replaced.
What causes hum at zero volume on a Challenger like this?
Most often tired filter capacitors in the power supply. The seller of this unit stopped short of full mains voltage for that reason.
Sources: Wikipedia: 6L6.
