Results 1 to 6 of 6

Thread: Ampeg SVT Classic Vintage control knob issues

  1. #1
    Supporting Member nevetslab's Avatar
    Join Date
    Apr 2010
    Location
    Burbank, CA
    Posts
    1,840
    Thumbs Up/Down
    Received: 666/1
    Given: 1,507/1
    Rep Power
    11

    Ampeg SVT Classic Vintage control knob issues

    Our Ampeg SVT Classic Vintage (1987 Limited Edition, #178 of 500) came back from a rental with the Volume knob broken and the Bass control's knob & shaft broken off. 1/4" dia Single-D Nylon shafts on all of the pots. I hadn't removed the rest of the knobs before ordering seven new Ampeg replacement knobs, though the set that was installed, all but the Volume knob from Ch 1 had their faces sanded smooth and new indicator lines cut into the surface. I vaguely remember having to do that though didn't remember why. After ordering the knobs, grumbling a bit about paying $4 per knob, I had removed the knob next to the Ch 1 Volume pot, then saw why. All but Ch 1 Volume pots had their Flat 180 deg rotated from that Ch 1 Volume pot. The indicator lines would be reversed. I hadn't spent time to search for an alternative knob type that had dual set screws. And, with another standard SVT-CL that had come in, I looked at it, whose single-D shaft all matched the one control that didn't require a non-standard knob.

    So, I tried a different approach this time. Using some 3M Mylar tape, I masked off the surface using the stock indicator line as a guide, leaving an exposed knob surface where I was going to apply some white enamel paint for a new line, then scrape off the old line, and use some very fine sandpaper (2000 grit) to remove the tool marks from scraping off the old line. As careful as I was, I still was greeted with seepage underneath the mylar tape. I did at least escape having it seep down onto the short radial surface above the fluted surface. Took a while to get thru the six knobs, and looking close, I wasn't all that happy with the results, but, after I had sanded the surface around the new line, and used a bit of nose oil with my thumb to rub into the sanded surface, it came out ok. At a glance, who's gonna know?

    Click image for larger version. 

Name:	FV-No Knobs-1.jpg 
Views:	17 
Size:	1.52 MB 
ID:	56587 Click image for larger version. 

Name:	FV-No Knobs-5.jpg 
Views:	15 
Size:	1.61 MB 
ID:	56588 Click image for larger version. 

Name:	FV-No Knobs-4.jpg 
Views:	14 
Size:	1.97 MB 
ID:	56589 Click image for larger version. 

Name:	Painting New Indicator Lines.jpg 
Views:	16 
Size:	1.25 MB 
ID:	56590 Click image for larger version. 

Name:	Painting New Indicator Lines-2.jpg 
Views:	19 
Size:	1.39 MB 
ID:	56591 Click image for larger version. 

Name:	Painting New Indicator Lines-4.jpg 
Views:	18 
Size:	1.14 MB 
ID:	56592 Click image for larger version. 

Name:	FV-New Knobs-1.jpg 
Views:	15 
Size:	2.35 MB 
ID:	56593

    Still more work than I had intended to do. Getting that preamp out of the cabinet was a PITA, since the bulk of the mounting screws are along the back flange on the roof of the cabinet, so either remove the power amp chassis, or remove the power tubes, and curse when you can't get anything but a right-angle ratcheting Philips screwdriver in where the two xfmrs disallow any size of normal scrrewdriver to remove those two. The front screws are right above the front side-wall cleats. No service loop on the bass control, which was the pot whose shaft broke. All in a days work.

    3 Not allowed! Not allowed!
    Logic is an organized way of going wrong with confidence

  2. #2
    Old Timer Leo_Gnardo's Avatar
    Join Date
    Sep 2012
    Location
    Dogpatch-on-Hudson
    Posts
    6,491
    Thumbs Up/Down
    Received: 1,489/21
    Given: 1,259/0
    Rep Power
    14
    Extra points for mentioning the use of nose oil. I call it nose grease. Great stuff innit? Absolutely indispensible.

    Old style SVT's, heck I just disassemble the whole thing if I have to get into the preamp. It's all such a big PITA innit? Beats scraping up hands & wrists trying to loosen the preamp mounting screws. There's no good shortcuts.

    1 Not allowed! Not allowed!
    Enjoy. Every. Sandwich.

  3. #3
    Supporting Member nevetslab's Avatar
    Join Date
    Apr 2010
    Location
    Burbank, CA
    Posts
    1,840
    Thumbs Up/Down
    Received: 666/1
    Given: 1,507/1
    Rep Power
    11
    Quote Originally Posted by Leo_Gnardo View Post
    Extra points for mentioning the use of nose oil. I call it nose grease. Great stuff innit? Absolutely indispensible.
    I got that trick when I had taken an oboe I had bought years ago that was claimed to be a Loree (but didn't look right) to RDG Woodwinds (formerly Robert Gilberts woodwinds) shop in LA, and while their seasoned repair man was looking for hidden details in the wood, he reached up with a finger and extracted a bit of nose oil and rubbed it into the surface to bring out the faint engraved numbers in the wood. Turned out to be a fake. YUP.....nose grease....indeed great stuff!

    0 Not allowed! Not allowed!
    Logic is an organized way of going wrong with confidence

  4. #4
    Senior Member
    Join Date
    Jan 2011
    Location
    NorCal
    Posts
    430
    Thumbs Up/Down
    Received: 77/10
    Given: 81/0
    Rep Power
    10
    I'm laughing. When my wife says, "do you have any Chapstick?" I say, "Here, kiss my forehead."

    1 Not allowed! Not allowed!
    --
    I build and repair guitar amps
    http://amps.monkeymatic.com

  5. #5
    Member
    Join Date
    Jul 2019
    Location
    boro
    Posts
    66
    Thumbs Up/Down
    Received: 11/0
    Given: 36/0
    Rep Power
    0
    Wonderful amp, very well built, better than 70s but nothing beats MTI's from early 80s.
    Just the squared look...

    1 Not allowed! Not allowed!

  6. #6
    Supporting Member Randall's Avatar
    Join Date
    Jan 2013
    Location
    Cape Coral, FL
    Posts
    2,472
    Thumbs Up/Down
    Received: 571/0
    Given: 104/0
    Rep Power
    9
    When I was young, an old timer showed me the nose oil trick on the parts where a fishing rod fits together.

    0 Not allowed! Not allowed!
    It's weird, because it WAS working fine.....

Thread Information

Users Browsing this Thread

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

Similar Threads

  1. Ampeg SVT CL Classic multiple issues
    By xtian in forum Maintenance, Troubleshooting & Repair
    Replies: 7
    Last Post: 09-15-2019, 06:02 PM
  2. 4 issues to be addressed on my 1990 Red Knob Twin
    By jalexquijano in forum Maintenance, Troubleshooting & Repair
    Replies: 5
    Last Post: 08-25-2017, 05:10 PM
  3. Laney VC15, treble control knob has decided to become an inverse volume control?
    By jm2 in forum Maintenance, Troubleshooting & Repair
    Replies: 13
    Last Post: 06-19-2016, 10:05 PM
  4. Variable control knob for sewing machine motor
    By gkwon002 in forum Tools and Coil Winding Gear
    Replies: 10
    Last Post: 07-06-2011, 05:32 PM
  5. Ampeg vintage svt help - need replacement hum control pot
    By jasonguitar in forum Maintenance, Troubleshooting & Repair
    Replies: 2
    Last Post: 07-20-2010, 10:59 AM

Bookmarks

Posting Permissions

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