Announcement

Collapse
No announcement yet.

Vox Cambridge 30 feeble tremolo

Collapse
X
Collapse
 
  • Page of 1
  • Filter
  • Time
  • Show
Clear All
new posts
Previous template Next
  • #1

    Vox Cambridge 30 feeble tremolo

    I have a Vox Cambridge 30 in with a complaint of no tremolo. I played it and I could hear some tremolo, not much but it was working correctly, kind of. After looking through the schematic for this thing I see that it uses the LDR method with an LT9914 isolator. Before just replacing it I want to fiddle around with VR11 and VR12 which look like they tweak the isolator input… maybe it's just out of adjustment. Does anyone know the setup procedure for these two trimmers? I'd hate to damage what could very well be a perfectly good LT9914.

    Vox Cambridge30R.pdf
    ... That's $1.00 for the chalk mark and $49,999.00 for knowing where to put it!
    Tags: None
  • #2
    Note carefully where they are set, so you can restore their settings. Then twiddle them to learn what they do.

    Yes, it could be just as simple as adjustment.

    If I recall correctly, one sets up the DC offset for the most room. The other sets a bias level of current through the LED.
    Education is what you're left with after you have forgotten what you have learned.

    Comment

    • #3
      Originally posted by Sowhat View Post
      I have a Vox Cambridge 30 in with a complaint of no tremolo. I played it and I could hear some tremolo, not much but it was working correctly, kind of. After looking through the schematic for this thing I see that it uses the LDR method with an LT9914 isolator. Before just replacing it I want to fiddle around with VR11 and VR12 which look like they tweak the isolator input… maybe it's just out of adjustment. Does anyone know the setup procedure for these two trimmers? I'd hate to damage what could very well be a perfectly good LT9914.

      [ATTACH]48737[/ATTACH]
      If it has the original opto coupler I would replace it regardless , they were notoriously unreliable .
      If you don't know where your going any road'll take you there : George Harrison

      Comment

      • #4
        I agree replace the opto coupler because if it has not failed, it will. I ordered mine from Cabin Tech Global LLC on Ebay. It was less than $10 including shipping.

        Comment

        • #5
          Just a close out on this thread but the LDR finally arrived from Big Bear and it was... ahhh... man! I forgot! but it was some brand X one that had about the same specs as the LT9914, looked about the same, maybe a little bigger. Once I got that thing in VR11 and especially VR12 actually did something, I could now trim the tremolo circuit. Problem is I don't know how the stock new tremolo should sound so I adjusted it to match my notion of what that might be. I talked the customer into having his line cord replaced because of the mysterious missing ground pin... it's like something grabbed it with a pair of pliers and just ripped it out! That didn't scare me one bit, I've seen that before.
          ... That's $1.00 for the chalk mark and $49,999.00 for knowing where to put it!

          Comment

          • #6
            Don't worry about being too exact on those two trimmer pots, just adjust to taste.

            I ALWAYS replace the whole power cord if the ground lug is missing or it has a hardware store plug installed. Nobody ever complained that their amp was too safe.

            BTW, those are surprisingly nice sounding transistor amps and VERY lightweight.

            Comment

            Previous template Next
            Working...
            X