1967 Ampeg B-15NF

As received. It actually looked better than the Reverb pictures.

I’ve really enjoyed building amps, but it’s time for me to take on something a little more challenging. I found a 1967 Ampeg B-15NF head on Reverb listed as “Non Functioning.” It looks like it it’s either been in a salt water environment or someplace damp as there’s surface rust and other signs of neglect, but it appears to be mostly complete. The price was low enough that I can buy a lot of parts and still make it worthwhile. I expect it’s going to be very labor intensive which would likely put it out of the realm of having a tech restore it, but since I enjoy that kind of work it should be doable. I suspect it has never been worked on since the can cap shows a 1967 date code. It may not have been opened up - We’ll see once it gets here.

 1/23/26 - Received the amp and did a quick initial inspection. Power and speaker cords cut for safety. Non standard screws to chassis tray. Missing one tube cage nut. Externally dirty but corrosion is not as bad as I expected. Unblown 3A fuse installed. Pulled chassis. Inside is clean and looks to be 100% original! Power cord was 2 conductor, all caps have a 1967 date code. 

Internally it looked original and in good shape!

 1/25/26 - Performed initial chassis cleaning with WD-40, cleaned tube sockets with alcohol. Checking component values, 5.6M and 2.2M grid leaks are out of spec high. Removed chassis tray from top panel, removed shock mounts and shield plate. Planning on recovering chassis tray. Need to order tray material, tube cage gasket and ‘60’s style knobs. 

 1/27/26 - Checked values and transformers. Cleaned chassis with aluminum foil for rust and applied glass wax. Replaced 100/100 bias cap, switch, pot and jack hardware. 1/31/26 - Installed grounded power cable. Replaced coupling caps. Ordered new knobs, tube cage gasket and tolex for chassis tray.

 2/2/26 - Received parts order. Installed new electrolytic, speaker cable and cage hardware. Speaker cable had open to pin 1. (Whew - started pricing output transformers!) Surprisingly enough the old tubes work, although the 6L6s are seriously mismatched with one at 46ma and the other at 25ma. Ordered a matched pair of TAD 6L6WGC/STR.

Internal work completed.

 2/9/26 - Found a 1973 Eminence 15" square magnet on eBay. I figured I could recone it as necessary, but it actually seems to work pretty nicely.

 2/14/26 - Received parts order. Installed new tube cage gasket and knobs. (Nothing wrong with the old knobs other than being the 1967 type that apparently nobody liked.) Recovered tray and re-glued shield/schematic panel. 

 2/19/26 - Ordered a single baffle cabinet from Fliptops.

 This project turned out not to be as challenging as I originally thought. I think this amp lived in a garage or shed for quite a while. I'm guessing the cabinet got trashed somewhere along the way. The XLR speaker connector had been cut off and sloppily wired so the external speaker jack would work. The "death cap" was out of spec so I'm guessing someone got shocked and cut the plug off the power cable. All the amp needed was a recap, new power and speaker cables and a set of 6L6's. I've probably spent more time on cosmetics - cleaning up rust, new logo plate, new Tolex for the amp tray, etc. One thing I haven't quite figured out is how Ampeg rated these amps. The spec in the 1966-67 service manual claims an output of 25 watts, though most sources say 30 watts. With a 200mv 1kHz signal in I'm getting 39 watts clean. Even on a Variac dialed in for 6.3v heaters (115v line) I'm still seeing 36 watts RMS out. These are original transformers and in tolerance components so Ampeg must have really been under rating its amps.

Temporarily installed on old cabinet top.

After going through this amp I have to wonder about its’ history. The cabinet top had been cut and the speaker connector was cut and jury rigged in such a way that the external speaker jack would work as a 16 ohm connection instead of in series with the cabinet speaker. Did the cabinet get destroyed somehow? All this amp needed was a new power cord, speaker cable, capacitors and a sete of 6L6s. Total parts cost - $235. Add $150 for 2 hours labor and for under $400 you have an excellent little amp head. Add another $150 for parts and 3 hours or so of labor if you want cosmetic work done. That might be more than a person might want to spend going to a good tech, but it’s a no brainer for someone doing their own work. I’ll update this post when I get the speaker cab.

Resources used: Fliptops for all things Ampeg specific, Amplified Parts for various components, and EL34world.com for schematics and the 66-67 B-15NF service manual.