#1
I'm pretty gear-illiterate so please bear with me. Any insight is greatly appreciated.

So I bought a used Fender Hotrod Deluxe from a local shop. The guy assured me that if I had any issues in the first week or so, they would cover it.

Sure enough, there's a problem right away. I'm running an EP Booster pedal through the amp, it's about halfway up, and the master volume's at maybe a 4. It's a loud amp, so this is approaching "show volume." Then I notice distortion. Not the "clean-ish" kind of overdrive one would want/expect from a Hotrod Deluxe with a pre-amp pedal. The clean channel sounds spiky, ugly, the sustain just deteriorates into fuzz. Nothing close to a "clean" sound is possible, even when I dial the volume back down to reasonable practice levels.

I bring the amp back to the shop the next day. We run my guitar through it, without any booster pedal this time, and the guy at the shop agrees with me. "Sounds like a bad tube," he says, which is what I assumed, but I've never heard what a "bad tube" sounds like before.

A week or two later, they call me and say it's fixed. They replaced a couple components, I guess a tube and maybe the "socket" that it attaches to? But I still get the sense they were never totally clear on what went wrong.

Anyway, the amp works fine for a month. I get it pretty loud while recording. All is well. I'm running the EP Booster through it still, as well as a RAT.

Then I finally bring it to band practice. Not running the EP Booster, but I've got my RAT running through it. Amp volume is halfway up, the volume on the RAT more like 75%. Again, "show volume." Within a song, I notice the dirty RAT distortion sounds a little *too* dirty. Turn off the RAT, and sure enough my clean channel sounds awful again. The same ugly, spiky, decaying kind of distortion. Ugh...

So now I'm suspecting there's just something busted with this amp. It's getting over-heated, blowing its tubes out... again, I have no idea about this kind of tech. But it seems a logical explanation.

I drop the amp off again. Flash-forward to today:

The shop's amp guy calls me and tells me he can't find anything wrong with it. He's running his strat through it, and not experiencing any of the distortion that I described. I'm going in on Thursday morning to look at it with him.

So I guess I'm wondering if any of this makes sense to any of you?
On the phone, the guy was asking me what kind of pickups I have. They are definite hot pickups, but could that really be an explanation? He's also asking me weird questions like "Why are you running distortion through this amp when it distorts naturally at high volume anyway?" Is it just me or is that an odd question? I mean the amp has its OWN overdrive channel, it's just kind of crappy, so surely I'm not an idiot for running pedals through the clean channel. Those kinds of questions are just unsettling me more.

Again, I'm way out of my depth here so if anything I'm saying is blatantly stupid, please tell me. If I'm being reckless with the gear somehow, tell me. I'm just trying to get a grip on this issue so I can be as helpful as possible when I go speak to the guy on Thursday.

If you've already read this far, thanks so much. Again, any feedback is greatly appreciated.
#3
I had an old one of those that I hated because the clean channel was so easy to push hard. My guitars made the thing sound like I had an OD pedal in front of it. Are you using guitars with humbuckers or single coils?
#4
Pull the tubes out and plug them back in again and tell me what happens. Sounds like it could be a dodgey socket. When you move the amp around a tube becomes unseated.
And yes, he's full of shit.
#5
Thanks for the replies so far.

Have you been letting the amp warm up properly?

Admittedly, I'm not always great about letting it warm up the recommended amount, but I do hit the standby first and give it at least a moment. Could that really be the cause of the damage/distortion? Would that effect disappear over time, because the guy's telling me it sounds fine now.

I had an old one of those that I hated because the clean channel was so easy to push hard. My guitars made the thing sound like I had an OD pedal in front of it. Are you using guitars with humbuckers or single coils?

My guitar has split-blade single coils by Lindy Fralin. Personally, I love the natural overdrive of Fender amps, it's why I wanted this one, but this particular sound is a whole other level of distortion. It sounds busted and burned out.

Pull the tubes out and plug them back in again and tell me what happens. Sounds like it could be a dodgey socket. When you move the amp around a tube becomes unseated.
And yes, he's full of shit.

The socket is what they changed last time, so I feel like this could be it. Maybe the tube was jostled back while in the shop, or on the way there.

And yeah, what is he talking about... to be fair, I think the amp guy I spoke to is pushing eighty or something. Supposedly the best in the state... I wonder if he's just an amp snob who thinks we young hooligans are wasting elegant technology with our loud stompy boxes. It was definitely a very dad-like line of questioning.
#6
Yeah, "why do you need that much distortion?" type of thing? That's the "full of shit" part I was referring to. LOTS of people used HRD's as a clean platform for pedals.


Put on a glove to protect you from the heat and give the tubes a gentle jiggle while on and turned up. If it makes noise, that socket is shot (or dirty)
Last edited by Cathbard at Nov 10, 2014,
#7
Quote by hombre_lobo
Thanks for the replies so far.


Admittedly, I'm not always great about letting it warm up the recommended amount, but I do hit the standby first and give it at least a moment. Could that really be the cause of the damage/distortion? Would that effect disappear over time, because the guy's telling me it sounds fine now.

No. The amp will warm up on its own, there's nothing you can do with the standby switch that's going to damage the tubes. I guess if you sat there flipping it on and off as fast as you could for a few hours. But a shorter warmup is nothing.

It sounds like the guy couldn't get the problem to happen again so he was just making sure that you weren't just hearing speaker breakup or natural distortion. It sounds like that is not the case. This does sound like a preamp tube or a socket. I'd have them check those again, especially since the problem seems to come and go. You don't need it showing up at a gig again. Sometimes this happens when a part heats up after the amp has been running hot for an hour or two. That means it's hard to replicate on the bench because some techs aren't going to sit around waiting for the amp to cook itself over an hour or two.
#8
Re-create the exact conditions at the shop so they can see what is happening and why. Get the amp nice and warm and wail away with OD pedals at your preferred settings with a pillow in front or something until it starts cutting out. I'm not clear about your setup but if you are running your guitar into TWO boost pedals and into the amp set to 5 it is possible you are hitting the preamp with too much gain and overheating the components. Rare but possible on a HRD due to it's circuit design. Maybe there is a better way to get the tone you are after thru that amp.

On my HRD I used a TS909 with volume and drive around 40% and amp never above 4. More gain than that just got mushy and lost definition.

Good luck!
#9
Thanks again, folks. This forum is always so helpful.

Quote by Cajundaddy
Re-create the exact conditions at the shop so they can see what is happening and why. Get the amp nice and warm and wail away with OD pedals at your preferred settings with a pillow in front or something until it starts cutting out. I'm not clear about your setup but if you are running your guitar into TWO boost pedals and into the amp set to 5 it is possible you are hitting the preamp with too much gain and overheating the components. Rare but possible on a HRD due to it's circuit design. Maybe there is a better way to get the tone you are after thru that amp.

On my HRD I used a TS909 with volume and drive around 40% and amp never above 4. More gain than that just got mushy and lost definition.

Good luck!


Could this sort of overheating cause distortion that would later disappear when the components cooled down?
#10
Quote by hombre_lobo
Thanks again, folks. This forum is always so helpful.


Could this sort of overheating cause distortion that would later disappear when the components cooled down?


Yes exactly. That is what it sounds like to me from your description. Just pushing the front of the amp too hard causing it to overheat the preamp circuit. It's a wild guess without hearing it but an educated guess as a long time Fender amp owner and techie. This may be why "old tube dad" was questioning your distortion settings and he just didn't express himself very well.

Try just one OD pedal and see if you can get your tone without melting the input preamp. Sometimes less is more.
Last edited by Cajundaddy at Nov 11, 2014,
#11
How the **** can you overheat the input of the amp with the output of a 9V pedal? I don't give a damn how many of them you have chained up, it aint gonna overstress a 12AX7. That's nonsense.
#12
Quote by Cathbard
How the **** can you overheat the input of the amp with the output of a 9V pedal? I don't give a damn how many of them you have chained up, it aint gonna overstress a 12AX7. That's nonsense.


Most of us already know what the problem "isn't" Cath. Now we just need to figure out what the problem "is". Got any good ideas? Cooked capacitor maybe? Here is a nice map:

http://www.prowessamplifiers.com/schematics/images/hotrod_deluxe.pdf
Last edited by Cajundaddy at Nov 12, 2014,
#13
could you be pushing it hard enough to distort the speaker? i haven't done it but, i have seen youtube. but that would always be going unless enough the speaker was left at low volumes.

just a shot in the dark.

after all that i would see IF they don't see a problem you could get another amp from them? that is if they think its fine, why not them let you take it if they think its fine, they can sell it and you have store credit. i have no idea on their policies but if they do tell them you will keep going back.
#15
Quote by Cajundaddy
Most of us already know what the problem "isn't" Cath. Now we just need to figure out what the problem "is". Got any good ideas? Cooked capacitor maybe? Here is a nice map:

http://www.prowessamplifiers.com/schematics/images/hotrod_deluxe.pdf


cath may have been blunt, but AFIK you really can't get a pedal or series of pedals to OD a 12ax7 i don't know if you were around, but there was this thread on hear a few years ago it was gain wars. people were stacking dimed fuzzes and ODs in order to get a square wave. i never heard of any damage to the amps or pedals, just their ears.

but i would do what cath said pull the tube and stick it back in.

or better yet spray Deoxit on the pins of the tubes and work it in and out.
#16
We are all in full agreement that if the 12AX7 is in good working order it won't likely be overdriven and damaged by pedals. There is a lot more to a preamp circuit than a single 12AX7 though.

Possible causes:
- One or more tubes going south
- Fouled tube sockets
- failing capacitor
- failing transformer
- failing speaker
- low source voltage to amp

These are the most likely problems from what little we know. Process of elimination.
#17
Quote by Cajundaddy
We are all in full agreement that if the 12AX7 is in good working order it won't likely be overdriven and damaged by pedals. There is a lot more to a preamp circuit than a single 12AX7 though.

Possible causes:
- One or more tubes going south
- Fouled tube sockets
- failing capacitor
- failing transformer
- failing speaker
- low source voltage to amp

These are the most likely problems from what little we know. Process of elimination.


i realize that. i have built a 1974x and jtm45 and have my final parts for my 5f1 at the ups store i need to pick up,. so i am familiar with amps, not near caths level though

i would go tubes, tube socket then check caps. i woudn't necessarily think it would be as likely to be a transformer in a combo than if it was a tube head. but i woudln't eliminate it entirely.

i thought about speaker distortion, and i think i typed t earlier in the thread.


OP what year is the amp>
#18
Agreed that it sounds like a socket problem. If you already had to replace one of them, it might be worth your while to go ahead and replace them all with some higher quality sockets, assuming a different one is the culprit this time.
#19
Quote by Cajundaddy
We are all in full agreement that if the 12AX7 is in good working order it won't likely be overdriven and damaged by pedals. There is a lot more to a preamp circuit than a single 12AX7 though.

Possible causes:
- One or more tubes going south
- Fouled tube sockets
- failing capacitor
- failing transformer
- failing speaker
- low source voltage to amp

These are the most likely problems from what little we know. Process of elimination.


And the winner is... failing speaker!

I went to the amp specialist's home this morning to recreate the problem by plugging in my RAT and getting it pretty loud, then turning off the RAT. Sure enough, the horrible buzz returned right away. We did some trouble-shooting, switched out all the tubes, replaced a cable, and ultimately plugged in a different speaker. No buzz on the other speaker, plugged back in the HRD's speaker, and the buzz returned. So, speaker it is! The guy seemed 100% certain.

Out of curiosity, what causes a speaker to go bad like this? I have to assume it was already bad when the previous owner put it up for consignment, and I don't blame the guitar shop for missing it because the problem only manifests once you hit a high volume, but I also want to be certain that I don't wreck the speaker the same way.

Anyway, ideally the guitar shop will cover repairs, or, rather, make the original seller cover them, which they did the first time they tried to fix this problem.

Thanks again for all your help! It was fascinating to see the debate this question created.
#20
Good to know! I had a Princeton Reverb once that sounded fine at moderate volumes but got really nasty when cranked up. Failed Jensen speaker also.

The easiest way to damage a speaker is sustained, uncontrolled feedback which quickly overheats the coil. They can also be damaged by just driving it really hard for hours. It is a wear item for most rock guitarists who play loud. A new speaker will fix you right up.