Results 1 to 5 of 5
Like Tree2Likes
  • 1 Post By echo8287
  • 1 Post By g1

Thread: 1967 AB165 Bassman

  1. #1
    Junior Member
    Join Date
    Aug 2017

    1967 AB165 Bassman

    Hello all, new here. I've been reading a lot of the posts here for several weeks and I think I've landed at the right forum. I am an electrician/plumber by trade and enjoy playing the guitar for the past 45 years(old guy). Around thirty years ago, I bought this Fender Bassman for $135.00, thinking I would eventually try to make something of it. Serial number stamped on the back was A-29487. I've check the transformers and found them to be Schaumacher>Main(606-2-40)Choke(606-6-30)Output(606422). I have ordered new electrolytic caps,fuses, and a few resistors that are out of spec for it. I have never tried to fire it up. Only thing I remember from the guy I got it from was he had been playing it, that he had a tech add 2 more power tubes for more power and a couple of years after that, it had a problem and it popped the fuse. He did get a couple of caps changed,but it has many of the old brown caps still in it. I have pictures that I will try to upload. What I had in mind was to add the new caps and a few resistors and then try and troubleshoot it. The only thing I noticed looking at it,looks like a resistor might be burned up on the bias board. I was hoping someone here might help me with a schematic of an amp with 4 6L6's and there are only 3 preamp sockets. I didn't know if a bandmaster,showman,or a twin reverb might be more like the circuit I should be looking at. Thanks for any assistance, David
    Attached Thumbnails Attached Thumbnails img_0106.jpg   img_0107.jpg  
    Justin Thomas likes this.

  2. #2
    Old Timer
    Join Date
    May 2006
    Chill-Ville, VA
    I will openly admit, I'm biased. I own a BF AB165, mostly stock circuit-wise. I <LOVE> it. I even converted my Bassman 100 preamp to match my Bassman. Your fourth preamp tube hole was converted for an extra 6L6. So, going forward... first, 3-wire cord, ground plug, etc. Does the amp actually work and sound good as-is? If so, that's a good start. If the Power tranny & Output Tranny are indeed "stock," are they up for the task of powering a 100W amp? I used to know for sure, but I don't have info handy. One way to tell is checking the 6.3 heater voltage - does it sag much below 6V with all four power tubes? You <REALLY> don't want to blow a tranny up.

    I don't see any burnt resistors on your bias board. So,if it was <MY> amp... I'd see about adding a 5V transformer for a tube rectifier. I'd convert the other extra 6L6 back to a 9-pin socket with an adapter. Then I'd build the stock AB165 preamp, and twiddle it from there. I'd also add a bias adjust along with the bias balance. Then I'd see if I liked it.

    My personal amp had a few mods when I got it... the OT is from a Twin Reverb, so it's bigger than stock but not nearly as big as my Bassman 100's. The 220k feedback resistors on the 6L6s are gone. I may have changed one cap in the tone stack... I also jump the channels, since on only the AB165 and later Bassmans are the channels in phase, which I consider a big plus.

    Follow the layout for the model, along with the schematic. I'm sure others will say otherwise, and I realize I'm in the minority in favoring this particular model of Bassman (and all others that followed it)... if you have any questions, I'll answer as best I can. As far as 100W/3 preamp tubes, Bassman 100 (boring as-is) or Marshall non-mast we r volume ( a good time, but don't change to EL34s w/out extensive tranny tests.).


    Edit: your transformers are from 64/74, 62/72, and 66/76. Are there any other readable numbers on them? If they're stamped with Fender part numbers, we can figure out if they're up to your desires.
    "If you're using one of those Digiyuk module type things..." - Chuck H. -
    "When receiving a shock I emit a strange loud high pitched girlish squeak." - Alex R -
    "All I ever managed to do with that amp was... kill small rodents within a 50 yard radius of my practice building." - Tone Meister -

  3. #3
    g1 is offline
    don't forget the joker g1's Avatar
    Join Date
    Feb 2010
    Canada, somewhere north of Fargo
    It looks like the chassis has been cut & holes drilled to accommodate larger transformers, but the other numbers Justin asked for will be helpful.
    The part you said looks burnt appears to be the bias diode, not a resistor. Can't tell for sure from the pic whether it is burnt or not, they are mostly black.
    Justin Thomas likes this.
    Certified Dotard

  4. #4
    Supporting Member mozz's Avatar
    Join Date
    Oct 2015
    I second the checking of the power transformer. You can google the part numbers to see what amp it is from, or if it's original. Last year i worked on a friends bassman that was used as a test bed frankenstein. The previous owner burned out the filament winding using tubes which drew a lot more than the stock 6l6's. It does happen and you will be out a original fender transformer.

  5. #5
    Junior Member
    Join Date
    Aug 2017
    First let me thank all of you for your replies. I have Kevin O'Conner's Ultimate Tone and another book #3 and a couple of books by Gerald Weber, but I just started reading them again.I bought them a long time ago. So I am justing getting somewhat up to speed and don't fully comprehend a lot of this stuff. It is looking simpler every day though.
    I have just started looking at this amp, so I never have put the tubes in it to try it. It has had the cord changed to a 3 prong, and the death cap removed. The resistors on the tube sockets are newer ones. I figured it needed the electrolytic caps changed first. The part on the bias control was black and I didn't see any colors on it like a resistor. It might not be burnt. Can I check that part with an ohm meter? I'll try to take a better picture of that. I called Schmacher about the transformer numbers,but the guy that might know is on vacation. He'll be back next week. It's hard to remember but I thought the guy I got it from did mention that the trans was from a Twin or something other than normal. I have the tubes he gave me from 35 years ago and I have an old Hickok tube tester, I'll have to dig that out.

    Other numbers on the transformer>
    KO 22756, CSA 827, 606-2-40 these were stamped into the trans
    On the choke>
    125 C1A, 022699, 606-6-30 these were stamped into the trans
    On the output trans>
    125A32A, 606422 also had 76(was like a red stamp on the side)

    On the inside of the cabinet it has the AB 165 sticker.

    I was thinking if I could get it going, I'd see what it sounded like before changing it. I have a SF Twin, a Princeton with no reverb, and a Vibrolux all from the early 1970's. I really don't need 100 watts of power. 50 or less would be fine, so I might just change it back to near original,Mr. Justin.I normally play blues,classic rock, and some of the grunge stuff to keep up with 2 daughters. Thanks for all the assistance, David

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Similar Threads

  1. 1967 Bassman build
    By Randall in forum Build Your Amp
    Replies: 61
    Last Post: 09-20-2017, 08:12 AM
  2. 1967 Fender Bassman AB165: Oscillation on Normal Channel w/ bright switch engaged.
    By cluster in forum Maintenance, Troubleshooting & Repair
    Replies: 4
    Last Post: 06-26-2016, 02:02 AM
  3. 1967 Fender Bassman Head AB165 early Break-up. Help.
    By cluster in forum Maintenance, Troubleshooting & Repair
    Replies: 15
    Last Post: 11-25-2015, 02:41 AM
  4. Question about my 1967 Fender Bassman
    By Stratohawk in forum Vintage Amps
    Replies: 4
    Last Post: 11-22-2012, 07:56 PM
  5. Need help on Bassman AB165
    By StratTone in forum Debugging Your Build
    Replies: 6
    Last Post: 01-27-2009, 04:50 AM


Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts