Fender Deluxe 85 Repair - No Sound

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by leray1, Jan 1, 2018.


  1. leray1

    leray1 Member

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    I was given a Fender Deluxe 85 and it powers up, but I get no sound. When I tap on the top it makes noise. So I took out the board and see some obvious issues (see pics). Anything else I should be worried about? By the way, this is my first attempt at repairing a board.

    [​IMG]20180101_120725_resized by leray1, on Flickr

    [​IMG]20180101_120756_resized by leray1, on Flickr
     
  2. Kyle B

    Kyle B Supporting Member

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    The resistor might actually be OK i.e. it might still work, just crumbled a little due to time & heat (replace it anyhow of course)

    I would check that the output transistors are good before putting power on it after replacing the cap.

    I'd also replace ANY electrolytic cap (like the one that exploded) if it shows any sign of leaking or bulging.

    Note EL caps (like the one that exploded) are POLARIZED. Meaning you have to get the +/- correct when you put a new one in. Fail to do that, and you'll see more wax paper strewn about your board (because they'll likely also explode...)
     
  3. leray1

    leray1 Member

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    Thanks! Where's a good place to get replacements?
     
  4. xtian

    xtian Member

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    Mouser.com or Newark.com is good for radial caps and 5w power resistors.
     
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  5. VaughnC

    VaughnC Supporting Member

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    You might have a basket case. One important thing to keep in mind is that an electronic componant can look good to the eye and still be bad. So, just replacing the parts that are visually bad most likely won't fix it as you need to get to the root cause. Very likely the output transistors were overheated...but you can test their junctions with an ohm meter or just replace them all with the shotgun approach. But there could be other issues that could fry your new output transistors the first time you apply power to the amp. Solid state electronics tends to be less forgiving as tubes...once a PN junction is fried, it's a goner. Good luck with the project!
     
  6. Blue Strat

    Blue Strat Member

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    FYI, the CORRECT way to do this is with test equipment and a schematic. Signal generator, oscilloscope, DMM, etc. You may get lucky and fix it by random replacement of components, or not. As Vaughn mentioned, replacing defective components is fixing the symptom...not the cause. Best of luck!
     
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  7. leray1

    leray1 Member

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    This morning I changed the two resistors and that one capacitor and I got sound, great sound (much better than my Peavey Studio Chorus). But, it was intermittent due to the fact that I didn't clean any of the pots before putting it back together. I took it back out, gave the pots a deoxit and let them dry all afternoon.

    I just put back together and all seems well, really well. This amp really sounds good. I do get a pop when I turn it off. The loudness of the pop correlates to the level of reverb. When the reverb is at 0 there's really no pop at all.

    Worst case, it blows again and I take it to a real tech to have it restored. For now I'm going to enjoy it while it lasts.
     
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  8. fenderpro

    fenderpro Member

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    Great that you got it up and running with minimal servicing. I had a similar experience with a Princeton 1 12 Plus recently.
    I was all set to jettison the chassis and use the cabinet and speaker with a different head. it turned that one wire had come
    unsoldered. now the amp is totally usable. gotta love it when that happens...
     
  9. TEPR

    TEPR Member

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    Haha guitar denter is a new one to me!
     
  10. leray1

    leray1 Member

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    Still going strong...I replaced the reverb tank on it today and it no longer pops when powered off. It cleaned up a few other issues - it's quieter and it no longer wants to feedback at low volumes.

    I've got replacements on the way for the two power capacitors and the rest of the ceramic resistors...should be here in about a week.

    Aesthetically, it was missing two knobs, the four bottom metal corners and the piece on the back that allows you to store cables and what not. The knobs are on their way, the corners arrived today and I made a piece for the back out of a pine plank (painted it black).

    All I'll really need to complete the refurb is a foot switch.
     
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  11. leray1

    leray1 Member

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    I've been playing through this amp since the last operation. Today I went in and changed the filter capacitors (2200uF, 50V), the other three ceramic resistors (.47ohm, 5W) and a couple other, smaller capacitors (2.2uF, 50V) and the fuse blew as soon as I turned it on. I double checked my work - everything was plugged in properly, the capacitors are oriented properly, I didn't see anything that would cause a short, and all my joints look great. Where should I start to diagnose the problem?
     
  12. Tron Pesto

    Tron Pesto Member

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    .47 ohm resistors? I tried looking at a schematic to see where they would be and I could only find a lousy image so I couldn't track them down.

    Recheck the values of those resistors - they seem awfully low. I don't know this amp, but those values sound suspect. It's an odd value. A Fender tube amp could have a 47 ohm resistor in the long tail phase inverter section (which is 100 times the value of a .47 ohm resistor), but that really doesn't apply here.

    One possibility is if that resistor value is 1/100 of what it should be, you could be drawing much too much current somewhere and causing the fuse to blow.

    Another possiblity is did you confuse a capacitor with a resistor? 0.47 (mfd) is a fairly common coupling capacitor value and if you put a resistor in place of a coupling capacitor, that would certainly cause some problems. (I did see at least one .47 mfd coupling cap in the schematic...)

    (Update - I DO now see the .47 ohm resistors in the schematic - so if those are what you changed, then it probably isn't that - but recheck you solder connections)
     
    Last edited: Feb 10, 2018
  13. leray1

    leray1 Member

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    I thought that too. But they are supposed to be 0.47ohm. I tested the ones I took out and the ones I put in and they measure the same. If you look at the parts list for this amp, they are R80, 81 and 82, description: Resistor WW 5W 10% 0.47ohm. The smaller capacitors I changed shouldn't be the issue since I changed one of them the first time and just did the rest this time.

    I'm suspecting the filter capacitors. I ordered them from amazon and they were supposed to be Nichicon, but they are ChengX. I just filed a complaint with Amazon.
     
  14. Tron Pesto

    Tron Pesto Member

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    ChengX - that's a new one on me! Pull them and check them to see if they are shorted. Yeah, there are a lot of mystery radial caps out there. I just did a google search on them and there is a lot of "stay away" discussions about them.
     
  15. pdf64

    pdf64 Member

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    Unless you're happy to play pot luck, it's wise to buy from reputable, established suppliers that can provide trace-ability back to the manufacturer, eg Mouser.
     
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  16. leray1

    leray1 Member

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    The "audio grade" Nichicon capacitors are rated for 85C, but the capacitors in my amp are rated for 105C. Should I stick with the non-audio grade Nichicons that are rated at 105C?
     
  17. Kyle B

    Kyle B Supporting Member

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    My approach to selecting radial caps is one that acknowledges caps are usually the weak link, so I target long life and high operating limits. Forget BS like 'audio grade'. This is a guitar amp. Not hi-fi.

    I like Mouser, but lately Digikey has the bigger snap-in caps while Mouser doesn't. (Though Digikeys website seems markedly slower)

    As wisely mentioned...do not buy components for something you care about from Amazon or Ebay. Don't get me wrong....love Ebay for some things like knobs and screws .... but not electrical parts. Stick with the big name distributors and you'll be stacking the deck in your favor. You'd be shocked at the amount of counterfeiting in the electronics business.

    In regards to 'how to select a capacitor'.... My take on it is, the better ones cost fractionally more than cheaper ones, but will last ALOT longer. Do the job one time and be done with it.

    To that end, I target capacitors that are rated 105C or higher. ESPECIALLY in tube amps. Further, I target capacitors with long rated lifetimes. (Absolute minimum 2000 hours, but aim for 5000+. NEVER a 1000-hour rated cap)

    What kills EL caps is HEAT. The hotter they get, the shorter their lives. And it's a HUGELY accelerating relationship Like 10 degrees lower operating temp gives you 10x longer life, etc....

    Most of the heat is internally generated inside the capacitor - That 105C rating is not 'ambient environment'.... it's the internal operating temperature of the capacitor. The heat results from the ESR (Effective series resistance) of the cap. This is a value which is RARELY made available to you without reading into detailed engineering information. You want a low value.

    So the trick is this.... if you are looking for long rated lifetimes (like 5000+ hours) and high rated operating temps (105 or above), both of those things are natural results of low ESR. So you don't really HAVE to dig into specifications so long as you can meet both those criteria.

    Another goal is to target higher voltage specs than you need. If the cap you are replacing is a 50V cap, see if you can find a 100V replacement that fits. Operating so far from the devices limits generally will result in a dramatically longer lifetime.

    I also stick with JAPANESE capacitor manufacturers exclusively. Nichicon, Panasonic, Rubycon, United Chemi-Con etc... I'll use an Illinois only if nothing else is available. Definitely would not use "Cheng-X"!!!!! This is for RADIAL PCB-mounted caps.... for axial caps like those found in P2P amps, I really like to use F&T --- Those are made in Germany. IMHO - As a society, the Japanese are very good engineers with high quality standards. But the Germans are over-the-top anal about excellence in engineering. I'll take a German-made whatever over anybody else's whatever any day of the week.

    In the last 3 weeks, I've replaced approximately 200 electrolytic capacitors in 3 pieces of gear. Two Engater Renegades and a Presonus 24.4.2 mixer. One Renegade had like 7 or 8 leaking capacitors. The other had only 1. The Presonus had over FOURTY. Note none of these pieces of gear is over 8 years old.... pretty ridiculous to have that many leaking caps at such a young age. So I replaced nearly every EL cap in each one of these - all with high quality JAPANESE parts. (You can guess where the cr*p I pulled out of 'em was made).
     
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  18. leray1

    leray1 Member

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    Thanks so much, Kyle. Even though I've already ordered replacements for everything from Mouser I've met all your recommendations, except for the higher voltage rating. I've got Nichicon Caps (5000 hour, 105C), Yageo resistors and Littlefuse fuses heading my way. But I did it the hard way and pored over spec sheets for a good while. I also got refunded for the ChengX caps. Again, thanks. I'm hoping to receive the replacements later this week and be back in business this weekend.
     
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  19. leray1

    leray1 Member

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    I'm happy to report that I received my replacements from Mouser, swapped them out with the others and I'm back in business. Thanks for all the help!
     
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