On 3/17/23 15:26, Iain Jamieson via Jukebox-list wrote:
Hi Everyone,
I have an AMI R2777B Basic Amp plus the R2728A power amp.
Screened on top of the chassis is 6973 for the output tubes. However, they are not 6973 tube sockets.
They are a larger 8 pin socket which looks to be factory installed.
Take pictures of the top and bottom and post to imgur.com. Send a link to the list. It's possible they're configured for octal tubes from the factory or it was converted if 6973s were unavailable. Could be 6L6, more likely 6V6 or 7591. Heater current for 6L6 is double that of 6973 and could overload the transformer.
Did these amps ever come out with say 6L6 tubes? The wiring on the sockets suggest it may be these as pin 1 and 6 are not connected, but I couldn't find any info to support this.
On the original 6L6 (and most octal metal can tubes), pin 1 is connected to the metal case and used as a shield. This was typically tied to chassis ground. Glass 6L6 tubes have pin 1 unconnected and it is often used as a tie point.
I noticed that you're in NZ. AMI jukes or parts for them outside of the US were often partially sourced locally, sometimes under the BAL-AMI label. In that case it's possible that your amplifier is substantially different from the USA version.