Sourcing components for Sunn amp repair - Bi-amp pot needed

Discussion in 'Amps and Cabs [BG]' started by Andrew Wupper, Jul 11, 2017.

  1. Andrew Wupper

    Andrew Wupper Guest

    Jul 11, 2017
    Hi all,

    I did a search and didn't find any mention of a source for components to repair Sunn amps. I have a Coliseum 300 in need of a Electronic Crossover / Bi-amp pot. Parts list says it is a "Dual 100k" and I've attached a picture.

    Any idea where to get another one. One side of mine is broken away and no contact is being made.

  2. Stumbo

    Stumbo Guest

    Feb 11, 2008
  3. RSBBass


    Jun 11, 2011
    Try Mouser Electronics
    ezra1 likes this.
  4. What he said.
    Mouser can hook you up.
  5. Andrew Wupper

    Andrew Wupper Guest

    Jul 11, 2017
    OK, I'll try Mouser. However, here is what I have discovered so far. The pot I need is most likely an Alps brand pot. It is 100k ohms, dual and linear. These exact pots are no longer made, and haven't been in a while and are impossible to find. However, I found a pot for an SWR that looks identical and is also 100k, linear dual. So I ordered one to see if it will either work for me, or if I can combine the two pots (the shafts are different) and make one good new pot.

    Here is the link to the SWR pot I found:
    SWR Pot Vertical Mount 100K 10C Dual, 0064713000

    Any comments and suggestions welcome.

    Thanks y'all.
  6. Andrew Wupper

    Andrew Wupper Guest

    Jul 11, 2017
    Long overdue update. The SWR pot is an exact match, except for the legs, which I had to modify to fit the board and height I needed.

    IMG_3621.JPG IMG_3625.JPG IMG_3621.JPG IMG_3625.JPG IMG_3630.JPG
    Last edited: May 13, 2018
  7. Andrew Wupper

    Andrew Wupper Guest

    Jul 11, 2017
    My amp quit working at about the same time this pot broke, however replacing it did not revive the amp. So after some, education by youtube, and diagnostic work with my multi-meter, I determined that two of the six power output transistors had shorts in them. So I plan to just replace all 6 with new. Also a couple output jacks were broken and I will replace those as well.

    So, the transistors and jacks are on order. I'll update when I get them soldered into the board and flip the switch. Fingers crossed.

    IMG_5041.JPG IMG_5050.JPG
  8. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
    Have you verified that the rest of the circuitry is not damaged? Otherwise you can destroy those new transistors in a few microseconds.
    BassmanPaul likes this.
  9. Andrew Wupper

    Andrew Wupper Guest

    Jul 11, 2017
    I'm learning as I go with this. And, any advise on what to test and how would be helpful. I have tested the associated resistors and they test good.
  10. Andrew Wupper

    Andrew Wupper Guest

    Jul 11, 2017
    To put it into perspective, I paid $38.00 for this at a yard sale, not working. I and a friend replaced all the components that visibly were burned. We flipped the switch. It worked. I giged with it for 5 years.
  11. Andrew Wupper

    Andrew Wupper Guest

    Jul 11, 2017
    OH, and I replaced the bridge rectifier b/c it tested bad.