reverb goes to full deep at "2" '65 DRRI

Discussion in 'Amp Tech Center' started by O T Hill, Apr 25, 2016.

  1. O T Hill

    O T Hill TDPRI Member

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    Just bought a deluxe reverb that I plan to eventually use as a donor for a full on upgrade to the original specs (retro-grade?). The man that sold it had 2 amps, and wanted a bunch for them. They were 100% clean and had a good record of maintenance since new, had been crated to gigs and are both great sounding amps. For a price discount I let him pick the amp I would take home and I got the one with the replacement MOD reverb tank on board.

    Home, plugged in and happy with my purchase, except that the tank goes to full on reverb tank echo mess at anything more than 3 or 4 on the knob. Useless beyond that, a cacaphony.

    Of course I checked and it is the right tank for this amp. and it is mounted well and seems free to float without feedback from the cabinet.

    Without any experience with this amp model and little tank experience, I am just hoping you guys will share experiences that you might think I can learn from.

    It seems pretty straight forward from here- I suspect a faulty 20 dollar tank rather than a failing amp that is perfectly fine in every other way. Accutronics tank is on it's way as I write this.
     
  2. Wally

    Wally Telefied Ad Free Member

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    What tube is in V3? There should be a 12AT7.
     
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  3. Silverface

    Silverface Poster Extraordinaire Platinum Supporter

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    Like Wally said, it sounds like a wrong tube. Alternatively there could be a problem with a component or traces on the board. If there are good service records, exactly what service was performed and by whom? If it wasn't a qualified tech there' may be other issues you aren't aware of, especially if you don't know that much about amp technology.

    It certainly seems like since you just bought it you should be able to take it back and swap it for the other one - the seller dumped a defective amp on you. Did you contact the seller and ask if he ever used the reverb? Many people never turn it above 2 or 3 except to test an amp (I don't use Fender spring reverb at all, so I'd only know if testing it)

    Also - if you don't know much about this model, how do you plan to accomplish this:
    FWIW you'd be starting with a cabinet totally unlike the originals and a chassis that would need to be replaced to switch to a vintage-style hand wired circuit. It'd likely be less expensive to buy a SFDR!
     
  4. robrob

    robrob Poster Extraordinaire Ad Free Member

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    The reverb tank replacement might have been done in an unsuccessful attempt to solve the problem you have. I would swap in a correct replacement V3 and see what it sounds like. Since you have a replacement tank on the way that would be a good second troubleshooting step.
     
  5. codamedia

    codamedia Friend of Leo's

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    +1 for making sure the correct tube is in place but I am more inclined to suggest it MAY be working as designed.

    I have a TRRI not a DRRI but same family and basic principles. My experience with all of these amps is that the reverb goes from 0 - too much very quickly. My TRRI is stock with a proper 12AT7 for the reverb driver.... I cannot turn up the reverb past 2 or 3 - it's already in Dick Dale territory at that point.

    It's possible that the tube could be wrong, or the tank is wrong and it's causing the problem. But what you are describing is exactly what I expect from these amps. 0 - 3 on the reverb control is all I can handle, beyond that is a mess ;)

    Just my 2 cents...

    (I should add that the reissues are my #1 backline request so I play through a lot of different ones every year. My experience is not just with my TRRI, it's with all of them)
     
    Last edited: Apr 26, 2016
  6. BobbyZ

    BobbyZ Doctor of Teleocity

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    On my old Fenders with reverb I run 12au7s for reverb drivers. Supposedly that helps the taper but I really do it because I've got a lot of 12au7 pulls.
    Worth a shot and they're a cheap tube. (common in old organs you can get for free)
     
  7. chezdeluxe

    chezdeluxe Poster Extraordinaire

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    I don't think my issue was as extreme as that described by the OP but I did want a more controllable reverb on my DRRI.

    I had my tech change the linear pot standard on the amp to one with a log taper. The reverb now comes on more gradually.
     
  8. O T Hill

    O T Hill TDPRI Member

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    I understand the opinion, but respectfully disagree.

    Actually, no, not cheaper. And I really want to learn what I don't know so it won't be a chore. I am a toolmaker with access to a full metal shop so building a chassis won't be tough but I think I can modify the reissue easier. If the stock trannies stay in, the small parts can all be bought from one source so shipping isn't bad although I get some parts I don't need, otherwise I can still get all the components for less than the difference between this amp and any original 65 I have seen by far, with a big chunk of change for a better speaker and the better trannies and all the shipping leftover. And enough to take Mrs. O T Hill out for dinner and some live music and keep that end of the amp supply chain moving too.

    I have built a few amps although none with a reverb or tremolo circuit. I am not a very experienced amp owner so my personal experience with the DRRI is basically the time I spent looking at the two amps and the time I have on the one I brought home. I had never played through a 59 deluxe before I built one of them from a kit and now I build them from scratch. I have never played a princeton but have all the fixins and an old film o sound speaker cab waiting for me to finish my current 5e3. I have some experience with spring reverb but the two amps I have owned that had it were different both from each other and from this one, my blues junior was a weak reverb ( I think I remember that from the short time I owned it) and my Rivera era concert is a smooth roll on from 0 to 10. Thats what I wish I had now. The other DRRI amp is long gone but wasn't that much better, not even worth the extra gas to drive back let alone pay the difference and send back the tank I have ordered.

    I checked the tube again and it is the right one. I switched in an old 12AT7 I had here and it might be a bit better for the roll on, might be better for the total overload but once you get past the point of noise, less noise is still noise. Hoping the tank does the trick. I like the idea of changing the taper of the potentiometer, not sure if thats possible without some major tweaking but I will look into it, maybe.

    Like I said, this is intended to be a donor. it didn't cost me very much more than what I paid for just the cabinet and speaker for the first tweed kit I built. And I always wanted an amp that said "deluxe reverb" on it because an original blackface just like Duanes ( it belongs to Trucks now) is maybe the most drooled over piece of gear I know of. I am a fender fan boy, gotta admit the truth.

    If changing the tank doesn't get me where I want to be, I will make a trip to guitar center world, wade through all the teenagers and chinese imports and play on a brand spanking new DRRI. If the reverb is not better than mine, I win!

    thanks to all for the advice.
     
  9. BobbyZ

    BobbyZ Doctor of Teleocity

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    To each his own but I'd scratch build a new one and sell the DRRI.
    But I can build the chassis and cab. No denying that makes a significant difference in overall cost.
     
  10. Guitarteach

    Guitarteach Poster Extraordinaire

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    That has been my experience of fender reverbs nothing and then suddenly all Dick Dale.
     
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  11. EddieLocrian

    EddieLocrian Tele-Afflicted

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    True, I have tried ax, at & au tubes in the send&return v3/v4 positions and to be honest it didn't really make much difference to the reverb start point.

    What it did do was knock out a bit of hiss, which was nice, but only a fraction.

    chezdeluxe mentioned changing the pot - that sounds like it might actually do something. - Go with that!

    Ok - Eddie.
     
  12. codamedia

    codamedia Friend of Leo's

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    If you are planning a gut and build, changing a single pot should be a walk in the park. If you are doing a rebuild why not make this entire area your first step. Currently the pots and jacks are on a separate PCB.... get rid of that and put in real pots and jacks.

    I truly believe you will find that this is just how the reverb works on these amps.
     
  13. Johnny Cache

    Johnny Cache Former Member

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    The reverb runs hot for some reason on those amps. I don't know what tank it has in it but you can go from short delay tanks to long delay. Lesser is usually better, also the impedance has to be right, the wrong tank impedance will change the effect. The reverb tube can be changed you can try a 12AU7 and see if that helps. You can also change a few things in the circuit like a resistor or cap but I'm not sure how it's done, never done that.
     
  14. Johnny Cache

    Johnny Cache Former Member

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    I like Dick Dale!
     
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  15. Wally

    Wally Telefied Ad Free Member

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    Well, I have never had a problem with any true tube Fender reverb as far as the sweep of the pot is concerned. As for dropping out the front panel PCB and hardwiring chassis mounted pots, IMHO that is a no go because there are a lot of resistors and caps on the PCB. I suppose there might be a way to mount all of those components onto the pots; but if I were to pull that PCB, then I am going to pull the main board and rebuild it like a BFDR.
     
  16. codamedia

    codamedia Friend of Leo's

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    I could certainly be wrong, and I have only seen my TRRI PCB during a pot cleaning (what a pain) not a DRRI. I was certain it was just pots and jacks on that PCB, 3 ribbons connect to the main board for all the heavy lifting. If there are caps and resistors there then I agree... certainly not worth the effort on it's own.
     
  17. Wally

    Wally Telefied Ad Free Member

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    coda, the resistors and caps on the side of the PCB that faces the panel....at least that is the way it is on the DRRI, the VVRI, the CVR....every other RI type of Fender I have worked on. I have never modded a TRRI, but I have modded DRRI, CVR, VVRI....adn I had to pull that front PCb to get to the tone caps and the slope resistor. IF they had not placed these resistors and caps on that PCB, they could have easily have done what they did on the Pro Sonic.....mount all of the pots, jacks and switches on the chassis.
    You can see on the PCB layout that indeed the TRRI is built in the same manner.

    http://schematicheaven.net/fenderamps/65_twin_reverb_ manual.pdf
     
  18. chezdeluxe

    chezdeluxe Poster Extraordinaire

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    Wally my DRRI that had the linear pot changed to log is a first year issue from 1994.

    Has anything changed in the DRRI layout since then. My tech didn't make an issue about changing it and it works with a far more practical taper.
     
  19. Fred Mertz

    Fred Mertz Tele-Afflicted

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    If one could change the 100K pot to 50K, that would cut the wet signal going back by half. Maybe wire a 100K ohm resistor between the pot wiper and ground. I haven't been inside a DRRI, so I don't know how hard it would be to access the pot.
     
  20. Wally

    Wally Telefied Ad Free Member

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    The VVRI and its offspring the CVR, the BF RI amps, and now the SF '68 customs are all built this way. There is a front panel PCB with pots, jacks, switches and tone stack components. This PCB is wired to the main board. the tube sockets are chassis mounted and are hardwired to the main PCB.
    When I opened up a Pro Sonic, I was shocked to see the superior build quality, I figured that it would be built like the RI amps. No way....there are big chassis mounted dual gang pots, chassis mounted Switchcraft jacks that will last a lifetime.....all hardwired to the PCB. the tube sockets are chassis mounted and hardwired to the PCB. This is exactly the way the first Marshall PCB amps were built back in the '70's and early '80's. The Pro Sonic is the only amp that Fender has built in this manner.

    IN comparison to the Reissue builds, the Blues and Hot Rods can be bunched with most all other modern amps that are pointed at the 'consumer market' ....including the regular production Marshalls. (;^) Very inexpensively built compared to other methods. These less expensive methods of building bring some amps to the masses....and in some cases exorbitant profits to the corporations that sell them. These methods also, ime, bring a lot of amps to the repair shop.

    Fred, one simply has to remove all of the nuts adn screws holding the pots, switches and jacks to the chassis. then, delicately one can pull that front PCB away from the chassis. Do the work, and put everything back like it was....delicately----or one will be replacing a broken PCb-mounted pot. IT isn't any thing but time, and time is money, right? By the time you get the nuts off, one could have soldered the resistor on to the pot in an old DR, put the chassis back in the cab, loaded it up and left for the gig.
     
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