Members 1001gear Posted January 27, 2022 Members Share Posted January 27, 2022 My trusty sub, a Fender 80 w keyboard amp threw one of the two big caps - probably from sneezing in the cold weather. The amp works properly if I twist the one cap just right but it's really impractical to rig it to stay that way. Thankfully it's a simple design and some elementary tech-ing should get me under the board where I can reconnect it properly. So question, what do I need to know/do to avoid fried me? Thx in advance... 1 Quote Link to comment Share on other sites More sharing options...
Members 1001gear Posted January 27, 2022 Author Members Share Posted January 27, 2022 Oh and free likes to all respondents pro or con. 1 Quote Link to comment Share on other sites More sharing options...
Members gardo Posted January 27, 2022 Members Share Posted January 27, 2022 What , no pics? 1 Quote Link to comment Share on other sites More sharing options...
Members 1001gear Posted January 27, 2022 Author Members Share Posted January 27, 2022 Ok wait a few hrs. 1 Quote Link to comment Share on other sites More sharing options...
Members 1001gear Posted January 28, 2022 Author Members Share Posted January 28, 2022 Actually maybe this weekend. I gotta pull this thing out of its parking space and haul it out into the garage and stand it on its head so I can pic the innards. I have the chassis loose. That was the hard part. The thing just wouldn't slide out; swollen cab or something. Finally took a rubber mallet to it and pried it past whatever the hang up was. It won't go back in without a fight either. (fuq) Also there's a matter of a half dozen or so connections (they just need to be marked but eyy ) Quote Link to comment Share on other sites More sharing options...
Members gardo Posted January 28, 2022 Members Share Posted January 28, 2022 I would probably poke around with a volt /ohm meter to check for voltage. At least in the area I plan to work. Maybe even tape on a small piece of cardboard to cover the area that won’t be involved. You shouldn’t have the type of voltage a tube amp would use. 1 Quote Link to comment Share on other sites More sharing options...
Moderators daddymack Posted January 29, 2022 Moderators Share Posted January 29, 2022 It sounds to me like the cap should be replaced, not re-seated. Depending on the voltage rating of the caps, [and any cap can shock you], any caps anywhere near where you are planning to work should be discharged prior to poking around...so you need a discharge 'stick' similar to this What type of capacitor? [actually the type doesn't make much difference as long as it isn't a SMT wave soldered chip cap] If it is a can, tantalum, disk, whatever... do the 'old tech'* trick...just cut just the cap out, leave the 'legs', solder the new cap leads to the old 'legs', voila! No soldering to the board, no flipping the board...easy access to the part....as long as it doesn't sit too high [above profile] you should be fine. No, this does not meet NASA or DoD specs, but this gets done all the time on amp repairs.... *I learned this in the late 60s from a TV repairman, who used to build TV cameras for RCA in the 1950s. When I went into computer manufacturing in the 70s, I showed this to a couple of the 'bench techs', who had to 'tweak' PCBAs, typically a cap here or a resistor there...this saved tons of time and limited potential damage to the boards. oh, and 1k1G...save the 'likes' for themz wut needzem...everybody here hates the moderators anyway.... 2 Quote Link to comment Share on other sites More sharing options...
Members 1001gear Posted January 29, 2022 Author Members Share Posted January 29, 2022 This mod are Ohtey. OK here' the vaca tour: This thing: Them caps: This transfomenblat: This stoodul needs to catalog: The twisty thing might be on the RCAs but I forget. I'm pretty sure there's a plug for it. The board should pop off without those black screws unless stuff needs to be unsoldered - haven't checked. Only the right cap is loose and I'd really prefer to just melt it back in place. Also the volume pot needs replacing but it works. The reverb (spring) is not happening so I might go after that if this phase works. 1 Quote Link to comment Share on other sites More sharing options...
Members gardo Posted January 29, 2022 Members Share Posted January 29, 2022 I d give it a go . Could be a solder joint You should be able to look at the bottom of the board as long as you don’t go laying your hand on anything by accident. I’ve been inside a couple with no problems .Check for voltage and go for it Didn’t you once build an amp from a kit. . 1 Quote Link to comment Share on other sites More sharing options...
Members 1001gear Posted January 29, 2022 Author Members Share Posted January 29, 2022 I 'll probably get one of those cap deflaters DM mentioned. I recall "dont use a screwdrivel !" from somewhere. Is there any danger putting an iron to a hot cap? I mean like one leg at a time right? Quote Link to comment Share on other sites More sharing options...
Moderators daddymack Posted February 4, 2022 Moderators Share Posted February 4, 2022 On 1/28/2022 at 10:48 PM, 1001gear said: I 'll probably get one of those cap deflaters DM mentioned. I recall "dont use a screwdrivel !" from somewhere. Is there any danger putting an iron to a hot cap? I mean like one leg at a time right? best to discharge, although the 'can' caps you indicated are likely non-lethal, they could still potentially generate a numbing effect up your arm. [How do I know this? $#!+ happens......usually to me...]. IMHO, it is always preferable to discharge the caps before doing ANY work....safety first!* If you can flip the board, then yes, check the existing joint. Re-solder if need be, but make certain the 'pad' is intact and still connected to the 'lands'. Do not overheat! Clean and pre-tin the soldering iron tip before hand. *...and stop tracking mud all over my nice clean kitchen floor. Don't talk with your mouth full. Always look both ways before crossing the street...don't run with scissors... Quote Link to comment Share on other sites More sharing options...
Members gardo Posted March 21, 2022 Members Share Posted March 21, 2022 Was the operation successful ? Quote Link to comment Share on other sites More sharing options...
Members 1001gear Posted March 22, 2022 Author Members Share Posted March 22, 2022 On 3/20/2022 at 2:00 PM, gardo said: Was the operation successful ? Oh, hi there. Thanks for asking. Professional crastination sorry. Got interleaved with several Amazoning deals. Cheap speakers that actually sound good etc... Bought an itty bitty Behringer mixer/food processor with 3 actual band EQ. I stuck that between a DVD player and the stereo amp. The mids work wonders to alleviate driver compression and I even got classical stuff sounding good in the 80 to 100 db range. Pop music is already configured to play loud so no issues with drum practice. Still could use a graphic (using a geographic equalizer now) but I gotta say, if you need a good preamp, try a recording mixer. 😵 🤣 1 Quote Link to comment Share on other sites More sharing options...
Members gardo Posted March 22, 2022 Members Share Posted March 22, 2022 13 hours ago, 1001gear said: Oh, hi there. Thanks for asking. Professional crastination sorry. Got interleaved with several Amazoning deals. Cheap speakers that actually sound good etc... Bought an itty bitty Behringer mixer/food processor with 3 actual band EQ. I stuck that between a DVD player and the stereo amp. The mids work wonders to alleviate driver compression and I even got classical stuff sounding good in the 80 to 100 db range. Pop music is already configured to play loud so no issues with drum practice. Still could use a graphic (using a geographic equalizer now) but I gotta say, if you need a good preamp, try a recording mixer. 😵 🤣 Good idea. I have a small mixer somewhere that I should try Quote Link to comment Share on other sites More sharing options...
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