The Fine Things are Always Hand Made
I recently purchased a "custom" AW27. I say custom because it was constructed by modifying an AW23 tuner and putting together two AW23 amp chasses. It sits on a custom made Napier cabinet. I couldn't be happier with it. They guys did a fabulous job on everything. It plays great and looks great. In fact, it looks like a new one.
Anyway, I have attached a schematic for it. It has some errors in it, e.g. I think the 2nd detector tube is missing and the 4th IF is shown as a 6B7 but it should be a 6D6. I hesitate to put this out to the community because of the errors, but I think it is pretty close to mine and possibly others. (the 6A7s have been upgraded to 6L7's in the VRE on mine). Hope this is helpful to some of you.
Jim and Eric were the master craftsmen on this. I won't share their last names. If they want to acknowledge and take credit for this fine work I invite them to do so.
PS My SN is U-616
Looks like the labels for the RF amplifier and the second detector were swapped. The AW-27 had a single power amplifier. Is the one you have biamplified and equipped with a separate woofer and mid-range+tweeter?
No, only one amp, but it does have tweeters with the main speaker. The RF amp is a 6D6. The 4th IF is actually a 6D6 so it needs a 75 detector which is not shown. Note there are only 18 speakers shown on the schematic rather than the 19 that actually exist. The missing one is a 75 which I believe is the 2nd detector?
Ok, I confused the RF tube with the RF AVC tube which I see is included and correctly labeled. The schematic shows 18 tubes whereas the original AW-27 sets had 19 tubes on the tuner (neon bulbs included in the count). The 6B7 second detector appears to be used to replace the 6D6 fourth IF plus the 76 detector tube employed in both the AW-23 and AW-27 tuner chassis.
Yes, mine has the 6D6 and 75 design which is like the other AW27's. I have 19 tubes on the tuner.
If the shown schematic is correct, the addition of the expander required the omission of 4 tubes in the original allwave 23 to keep the same chassis. Those appear to be the 76 second detector, the meter amp, and both 6C6 driver tubes, which moved to the amplifier chassis.
The use of a 6B7 for 4th IF and detector makes sense, and the tune meter amp wasn’t needed, replaced by the eye tube.
The other changes made would be to improve performance.
The schematic is not correct. As mentioned the 75 2nd detector is not shown and the 6B7 should be a 6D6. I have attached a spreadsheet that itemizes the changes made to the AW23 to achieve an AW27.
Thanks for this info. I have a second Allwave 23 that was seriously messed with by a previous owner. I have done a complete restoration, and it works. Brought it back to a stock Allwave 23. My first Allwave 23 is a slightly earlier version. First one is sr# K486, second is J497. J 497 has twin antenna posts and later antenna coupling system. K 486 is single antenna post with outboard coupler.
Anywhere I mentioned a 75 tube I should have said 76 tube. Sorry for any confusion.