Hi Jay,
I have added pics to my Google Drive, here is the link - Hopefully works ok. https://drive.google.com/drive/folders/1DTal-_lQXpSz-hBsA4dcv0DcAt4E2wqt?usp...
A bit of History, I purchased this Amp and Crossover from the USA to replace the missing audio gear as the Jukebox had been butchered and didn't have any audio gear in it.
Hopefully those pictures show enough detail?
Thanks
Iain
Date: Fri, 17 Mar 2023 16:12:21 -0700 From: Jay Hennigan jay@west.net Subject: [Jukebox-list] Re: AMI Continental 2 Amp R2777B output tube type To: jukebox-list@lists.netlojix.com Message-ID: a5c0fa7e-c9a2-623b-e4e5-1ccdd3a32879@west.net Content-Type: text/plain; charset=UTF-8; format=flowed
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.
-- Jay Hennigan - jay@west.net Network Engineering - CCIE #7880 503 897-8550 - WB6RDV
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On 3/19/23 12:23, Iain Jamieson via Jukebox-list wrote:
Hi Jay,
I have added pics to my Google Drive, here is the link - Hopefully works ok. https://drive.google.com/drive/folders/1DTal-_lQXpSz-hBsA4dcv0DcAt4E2wqt?usp...
A bit of History, I purchased this Amp and Crossover from the USA to replace the missing audio gear as the Jukebox had been butchered and didn't have any audio gear in it.
Hopefully those pictures show enough detail?
Based on the wiring, it looks like the sockets are indeed for a 6L6 or 6V6 tube. The components seem to line up with the connections. Pin 8 looks to be the cathode baased on the electrolytic and power resistor for self-bias. Pin 5 looks to be the grid based on the 100K resistor and coupling cap. Pin 3 has what looks to be the output transformer primary which would be the plate, and pin 4 looks to be the screen. Heater on 2 and 7 as with most octal tubes. This would be the standard pinout for most octal power tubes in the 6L6, 6V6, etc. family
If you look closely you'll see a pair of mounting holes punched in the chassis at each socket to accommodate the 9-pin sockets for 6973s. The riveted sockets suggest that it was made with the larger sockets at the factory. Possibly it could have been built either way or the larger holes were a factory modification due to unavailability of 6973 tubes.
So, the question is what tubes to use. Assuming that the design was for 6973s with a 450ma heater, the 6V6 would be relatively close but its maximum plate and screen voltages are lower than those of the 6973. 6L6 tubes would work but their heater current is twice that of 6973s and could overload the power transformer.
One option is the JJ Tubes 6V6S. They have a 500ma heater and plate and screen voltage ratings are in line with the 6973. Other 6V6 tubes will probably be fine, you could measure the plate voltage to be sure it isn't exceeded. I assume there were no tubes installed when you got the amplifier.
Some of the solder connections in your photos are kind of sketchy, you might want to clean that up.
On 3/19/23 12:23, Iain Jamieson via Jukebox-list wrote:
Hi Jay,
I have added pics to my Google Drive, here is the link - Hopefully works ok. https://drive.google.com/drive/folders/1DTal-_lQXpSz-hBsA4dcv0DcAt4E2wqt?usp...
A bit of History, I purchased this Amp and Crossover from the USA to replace the missing audio gear as the Jukebox had been butchered and didn't have any audio gear in it.
By the way, you've got a broken tube socket pin on pin 4 of the bottom socket in the picture ending in 08001. If you're careful you can straighten the barb from one of the unused contacts, slide it out the top, and replace it. Then re-bend the barb so the replacement doesn't slide out.
There's a lot of sloppy re-work you're going to have to clean up on that amplifier.
jukebox-list@lists.netlojix.com
-
Iain Jamieson -
Jay Hennigan