# DRRI went *POP*



## vadsy (Dec 2, 2010)

A friend texts me yesterday after his band practice and says he's having amp issues. He plays through a Fender DRRI, several years old and all stock, doesn't travel past 4-5 on the dial. He tells me that in the middle of jamming the amp made a pop sound, got very hissy and went down to a very low volume. I confirmed he was still getting a guitar signal through it but it wasn't much. 

Anything that stands out to the techs in the crowd? Any checks that can be easily performed visually or with a meter before taking it in to a local tech? Tubes? OT? Caps?


----------



## zurn (Oct 21, 2009)

I would definitely check the tubes before anything else or maybe a another speaker.




vadsy said:


> A friend texts me yesterday after his band practice and says he's having amp issues. He plays through a Fender DRRI, several years old and all stock, doesn't travel past 4-5 on the dial. He tells me that in the middle of jamming the amp made a pop sound, got very hissy and went down to a very low volume. I confirmed he was still getting a guitar signal through it but it wasn't much.
> 
> Anything that stands out to the techs in the crowd? Any checks that can be easily performed visually or with a meter before taking it in to a local tech? Tubes? OT? Caps?


----------



## Church-Audio (Sep 27, 2014)

vadsy said:


> A friend texts me yesterday after his band practice and says he's having amp issues. He plays through a Fender DRRI, several years old and all stock, doesn't travel past 4-5 on the dial. He tells me that in the middle of jamming the amp made a pop sound, got very hissy and went down to a very low volume. I confirmed he was still getting a guitar signal through it but it wasn't much.
> 
> Anything that stands out to the techs in the crowd? Any checks that can be easily performed visually or with a meter before taking it in to a local tech? Tubes? OT? Caps?


Its most likely tubes. I would want to take it to a tech make sure that the amp gets chopsticked for bad solder joints ( the tech should know what that is ) and get the tubes checked out. It could be a bad screen resistor as well. I never charge more than 2 hours labor to fix these amps the older ones, older than 2011 have circuit boards that must be removed in order to service the amp. The newer HRD deluxe amps have solder pads on both sides of the board. If its an older one I would have the tech inspect the solder joints on the whole amp to reflow them as needed that makes this amp very reliable again. 

I don't recommend ever putting in new power tubes for a end user without taking it in for service by a qualified tech. the reason being you could have internal damage that will damage your new tubes! costing you more money than if you just took it to a shop in the first place. If you must try tubes you can try substituting a known good preamp tube one at a time on the amp and see if that helps. The fact that it has not blown a fuse is a good sign. I would be surprised if it was a output transformer. Also make sure your plugged into the correct speaker jack  The wrong jack will lower the volume big time but you have pops and hissy so that says preamp tubes or power tubes. 


Take it to a tech the short answer


----------



## Keefer (Feb 15, 2011)

That _does_ sound like an output tube has let go, or they have come loose from the socket, or has a dirty connection. I would start by pulling the output tubes out, and re-seat them. If the issue is still there, replace them. 

If, after replacing the tubes and the issue is still there, get it to a tech. It could be dry caps as well.


----------



## nonreverb (Sep 19, 2006)

Power tubes is usually what it is and they'll be Sovteks. Best to have a tech check the screen resistor as it usually goes with the tube.


----------



## Church-Audio (Sep 27, 2014)

vadsy said:


> A friend texts me yesterday after his band practice and says he's having amp issues. He plays through a Fender DRRI, several years old and all stock, doesn't travel past 4-5 on the dial. He tells me that in the middle of jamming the amp made a pop sound, got very hissy and went down to a very low volume. I confirmed he was still getting a guitar signal through it but it wasn't much.
> 
> Anything that stands out to the techs in the crowd? Any checks that can be easily performed visually or with a meter before taking it in to a local tech? Tubes? OT? Caps?


I would check out JJ 6v6 or my favorite right now TAD 6v6 both tubes will sound great in that amp. I would also break down and spend the $20 on a new rectifier tube while you were at it. Right now sovtek are the only ones making a good replacement gz34.


----------



## WCGill (Mar 27, 2009)

There are *no* good replacement GZ34's.


----------



## nonreverb (Sep 19, 2006)

Indeed.....unless you have a cache of original Mullards lyin' around....



WCGill said:


> There are *no* good replacement GZ34's.


----------



## vadsy (Dec 2, 2010)

The amp went to see a tech yesterday afternoon. Hopefully he figures things out and it isn't a terribly troublesome fix. In the meantime I heard he picked up a little Princeton for this weekends show.


----------



## Wild Bill (May 3, 2006)

nonreverb said:


> Indeed.....unless you have a cache of original Mullards lyin' around....


You know, I'd be tempted to just wire in some diodes! 

After all, the only thing a tube rectifier contributes to tone is sag from the voltage drop. The GZ34 has the least voltage drop of any other tube rectifier - 20 volts, if I recall. A few 1N5408's and maybe a 100 ohm 10watt resistor to simulate what little sag is involved and I doubt if human ears could tell the difference. Especially when you consider that tube rectifier sag is a function of how hard you crank the amp. These days most guys are playing at such low volumes that no tube rectifier will show sag anyway!

If we were talking 5Y3's or 5U4's of course it would be a different story.

Wild Bill/Busen Amps


----------



## nonreverb (Sep 19, 2006)

I believe that's what Weber does with their Coppertop SS plug in replacements.


----------



## Church-Audio (Sep 27, 2014)

WCGill said:


> There are *no* good replacement GZ34's.


When I say good I mean wont blow up right away or best new tube we currently have available  Although there are some new rectifiers out there now they are just this tube in a different package. Or the JJ in a different package for much more money. Case in point the Tungsol ez34.


----------



## WCGill (Mar 27, 2009)

I haven't tried the Tung Sol, although I've had good luck with the other Tung Sol branded bottles. I've done all the other new production GZ34's and think it's a total crap shoot, and only a matter of time 'till they go south, esp. in more demanding apps. Nothing compares to the old Mullard.


----------



## Church-Audio (Sep 27, 2014)

My attitude on new production rectifiers is change them when you change power tubes. Nos is a much different story. The JJ gz34 is also good.


----------



## LydianGuitars (Apr 18, 2013)

I've made diode rectifiers in a tube base for my B&K 707 tube tester. They're pretty easy to make out of the old tube base.


----------



## Church-Audio (Sep 27, 2014)

I personally like to have a tube rectifier in my amp and not a solid state device. I perfume the way an amp reacts with real tubes.


----------



## nonreverb (Sep 19, 2006)

As long as your taking into account the rise in B+ voltage or adding a resistor to approximate the tube rectified, B+. The rise in voltage could possibly throw the calibration out.



LydianGuitars said:


> I've made diode rectifiers in a tube base for my B&K 707 tube tester. They're pretty easy to make out of the old tube base.


----------



## LydianGuitars (Apr 18, 2013)

nonreverb said:


> As long as your taking into account the rise in B+ voltage or adding a resistor to approximate the tube rectified, B+. The rise in voltage could possibly throw the calibration out.


I have. In the B&K 707, you need to re-calibrate and that's about it. They're a great tester and a real workhorse when the switch bank is cleaned out. I sold a few I rebuilt a few years ago and kept one.

Other testers like Hickoks need a little more attention if you replace the rectifiers with SS. Its been a while since I've done tube testers (they can be a lot of work and hate to work on testers) but I remember the Hickoks being more sensitive to changes in B+, but that's nothing a little tweaking can't fix.


----------



## nonreverb (Sep 19, 2006)

I have a Hickok 539C which is perfectly fine the way it is...


----------



## Adcandour (Apr 21, 2013)

This thread keeps reminding me that the Dirty Rotten Imbeciles were the sh!t back in the day.


----------



## nonreverb (Sep 19, 2006)

Spike Cassidy 'n all....



adcandour said:


> This thread keeps reminding me that the Dirty Rotten Imbeciles were the sh!t back in the day.


----------

