i've had a fender hot rod deluxe for...wow...its getting close to a decade now. i had no problems with it for the first half of it's life. then i started getting it tuned up, replacing some tubes more often, etc... now every time i take it in to my repair guy (who i don't know well) there is some new problem that costs me big time; i take GREAT care of my gear, so i just don't get it. i guess i just need some direction as to where to start learning about repairing my tube amp(s) myself. also, my current specific problem is completely random and continuous popping and crackling when my hotrod is up and running (tubes have little usage...maybe 15-20 max). i just don't want to take it to a guy that charges me $60/hour for labor when i can do it better myself!
Most likely it's in need of a "cap job", which is the replacement of the large capacitors in the power supply.
This isn't hard to do yourself, but it is quite dangerous because high voltages are stored in these caps (400-500 volts).
Fortunately, this is a very common repair and there's bound to be a lot of web pages describing what to do, and how to do it without something nasty happening.
This isn't hard to do yourself, but it is quite dangerous because high voltages are stored in these caps (400-500 volts).
Fortunately, this is a very common repair and there's bound to be a lot of web pages describing what to do, and how to do it without something nasty happening.
Hi juicy1484,
That is one young amp.
I look after a few vintage twins. They may need tubes and that's all. Your "service" guy may not know what he's doing, or is creating his own work for later.
A good service guy is your best friend. Your amp should not need any caps yet. It's easy to create all kinds of trouble, don't work on it yourself.
Now, your problem could be poor workmanship "down under", poor tube socket contacts or "not so good" tubes. For the old Twins, I use either 7581A's (beefed up 6L6GC) or 6L6EH from Electroharmonix. They stand up and sound great. If you have 5881's in there, put the proper tubes back in. (5881's only have a plate dissipation of 25W compared to a 6L6GC of 30W and 7581A/KT66 of 35W).
Given that your amplifier has been causing trouble for a while, find a known good technician, and use him.
One last comment. A good technician has a lot of training. He's actually worth more than $60 / hr, but normally doesn't get paid what he's worth. A bad tech gives everyone a bad name and isn't worth anything.
-Chris
That is one young amp.
I look after a few vintage twins. They may need tubes and that's all. Your "service" guy may not know what he's doing, or is creating his own work for later.
A good service guy is your best friend. Your amp should not need any caps yet. It's easy to create all kinds of trouble, don't work on it yourself.
Now, your problem could be poor workmanship "down under", poor tube socket contacts or "not so good" tubes. For the old Twins, I use either 7581A's (beefed up 6L6GC) or 6L6EH from Electroharmonix. They stand up and sound great. If you have 5881's in there, put the proper tubes back in. (5881's only have a plate dissipation of 25W compared to a 6L6GC of 30W and 7581A/KT66 of 35W).
Given that your amplifier has been causing trouble for a while, find a known good technician, and use him.
One last comment. A good technician has a lot of training. He's actually worth more than $60 / hr, but normally doesn't get paid what he's worth. A bad tech gives everyone a bad name and isn't worth anything.
-Chris
Hi juicy,
Repairing electronics is not something one can learn quickly in a few days or even months. However there are books that can help with the basics. I would suggest going to someplace like www.amazon.com and searching for "amp* repair". I just did and a lot of curious titles come up. Try eBay too as well as a general google search.
Also, even though your tubes are fairly new, they could still be the cause. I have little faith in some of the import tubes being sold today.
Victor
Repairing electronics is not something one can learn quickly in a few days or even months. However there are books that can help with the basics. I would suggest going to someplace like www.amazon.com and searching for "amp* repair". I just did and a lot of curious titles come up. Try eBay too as well as a general google search.
Also, even though your tubes are fairly new, they could still be the cause. I have little faith in some of the import tubes being sold today.
Victor
I've run across the problem of seriously bad crackles and pops on a Fender Twin Reverb 100W job belonging to one of the engineers I work with. He gave it to me to fix coz he knew I was into tube stuff and he was sick of what passes for a professional service at the local guitar shop. In that case it turned out to be output tubes with partially melted screens. Fenders run very high voltages and the older onesused 470 Ohm 2 Watt CARBON resistors to each output tube screen. These resistors go very noisy and drift massively in value. Replace the 470 Ohm 2 Watt carbon resistors with 1K 5W wirewound resistors. This is one of those s"standard" mods that all amp techs "in the know" do routinely but your official Fender Serveman won't. If the screens have been overstressed badly then you may have to change output tubes again, even if there isn't many hours on them. Best option for 6L6 Fenders is Winged C Svetlana 6L6GC. Cheaper but almost as good is the JJ 6L6GC. If as your post suggests, the amp has had a new set of output tubes recently then they may be OK BUT check those screen resistors. They may well be your problem.
Cheers,
Ian
P.S. If you want to get some books to learn about tube amp service then do a search on "London Power". There you will find "The Ultimate Tone" TUT Volume 1 and Volume 2 by Kevin O'Connor. Those 2 books will teach you heaps about how tube amps work and servicing and modifying your own tube amps.
Cheers,
Ian
P.S. If you want to get some books to learn about tube amp service then do a search on "London Power". There you will find "The Ultimate Tone" TUT Volume 1 and Volume 2 by Kevin O'Connor. Those 2 books will teach you heaps about how tube amps work and servicing and modifying your own tube amps.
gingertube, an acquaintance of mine has in his post-2000 made Fender DeVille also loud crackles and pops even when only the output stage is driven (plugging into the power amp input, which disconnects the input stages). I replaced all tubes, no change. Also since I'm bypassing the input stage that way, doesn't seem to be the problem of input connectors breaking their solder join with the PCB, which I've read about elsewhere for this model. Tilting the amp or moving it about tends to change the frequency of occurrence. I tried jiggling the tubes and tapping various parts, but didn't seem to be able to provoke the crackling this way (interestingly, connecting the probes of my multimeter to the B+ filter caps would create pretty much the same pop sound). I don't see how it could be the screen resistors since I put in brand new output tubes. No visible damage to any components. Any other suggestions?
Hi Nixie,
Resistors can often look just fine, but be bad. Don't trust your eyes! Measure the darn things. Also, they may be noisy without any outward signs. Tapping and a little freeze spray may allow you to find the defective part if you must. I will generally just change them if I suspect a problem. I always measure them and change them if they have drifted much.
-Chris
Resistors can often look just fine, but be bad. Don't trust your eyes! Measure the darn things. Also, they may be noisy without any outward signs. Tapping and a little freeze spray may allow you to find the defective part if you must. I will generally just change them if I suspect a problem. I always measure them and change them if they have drifted much.
-Chris
I've repaired a number of Popping and Cracking Hot Rod Deville's Hot Rod Deluxes, Blues Deluxes etc...
Pretty much every instance the problem was the Plate resistors on the Phase inverter. I tend to rebuild the entire phase inverter with higher quality resistors and caps for assurance that that area is not going to be a problem...
Pretty much every instance the problem was the Plate resistors on the Phase inverter. I tend to rebuild the entire phase inverter with higher quality resistors and caps for assurance that that area is not going to be a problem...
Nixie,
I've only just noted your post. Crackle and pops nearly always are sourced in the higher voltage areas. That means output tube screen circuits, phase inverter anode circuits etc. RenegadeAmps advise to check phase inverter anode loads is good. If you have an oscilloscope its relatively easy to check the signal at the output tube grids to see if the crackle and pop is coming from the phase inverter or from the output stage itself. Coupling caps are another possible source of the noise.
Good Luck,
Ian
I've only just noted your post. Crackle and pops nearly always are sourced in the higher voltage areas. That means output tube screen circuits, phase inverter anode circuits etc. RenegadeAmps advise to check phase inverter anode loads is good. If you have an oscilloscope its relatively easy to check the signal at the output tube grids to see if the crackle and pop is coming from the phase inverter or from the output stage itself. Coupling caps are another possible source of the noise.
Good Luck,
Ian
Hot Rod Deluxe late 90's
This HRD is making sounds that are incredible. With no instrument plugged in.
When you plug in to either channel you get no sound from the guitar but the beastly sound continues. It's as if nothing is plugged in. I have removed and tested/checked the caps...it is to new to have bad caps. They all test good on my Eico 950B.
What I think is wrong is a big guess....I have rebuilt my 76' Ampeg SVT and I would rather work on this whale or even an old V4...these new amps now days are, in my opinion...JUNK! Way too sensitive components. It's like looking at and working on a computer board...
Now back to my guess..All these damned lite op amps, TO-? whatever sizes of semi's blah blah..These are very voltage/amperage sensitive. I think something has time wise happened or something had been spilled on it or moist conditions has caused these sensitive little electronics to go bizurk!
Once you turn the master volume you get all this awful noise. The input volume control has no effect on this noise. It get's louder and louder only with the Master.
Also if you push in the Drive Mode button, the red lite lights but a new sound has now entered the arena.
What a nightmare..
I plan on checking the resistor and diodes only after I have removed them. These types of amps were meant to have the whole damned board replaced thus continued company income. The company and all their obscene incomes must survive at the buyers cost!!! They would rather see you buy a new amp and lalalalal!
Tube Head Ron
This HRD is making sounds that are incredible. With no instrument plugged in.
When you plug in to either channel you get no sound from the guitar but the beastly sound continues. It's as if nothing is plugged in. I have removed and tested/checked the caps...it is to new to have bad caps. They all test good on my Eico 950B.
What I think is wrong is a big guess....I have rebuilt my 76' Ampeg SVT and I would rather work on this whale or even an old V4...these new amps now days are, in my opinion...JUNK! Way too sensitive components. It's like looking at and working on a computer board...
Now back to my guess..All these damned lite op amps, TO-? whatever sizes of semi's blah blah..These are very voltage/amperage sensitive. I think something has time wise happened or something had been spilled on it or moist conditions has caused these sensitive little electronics to go bizurk!
Once you turn the master volume you get all this awful noise. The input volume control has no effect on this noise. It get's louder and louder only with the Master.
Also if you push in the Drive Mode button, the red lite lights but a new sound has now entered the arena.
What a nightmare..
I plan on checking the resistor and diodes only after I have removed them. These types of amps were meant to have the whole damned board replaced thus continued company income. The company and all their obscene incomes must survive at the buyers cost!!! They would rather see you buy a new amp and lalalalal!
Tube Head Ron
I am an authorized Fender repair shop, and I can tell you for sure that the last thing they are going to do is replace a circuit board for some little problem. They pay us to fix the amps. Here in the USA, that amp came with a 5 year warranty. That means that for the first 5 years you have it, Fender pays for any repairs, not you. SO I have no idea what your rant about profits is about.
There are a few op amps in this circuit, that is true. One drives and recovers the reverb, so if you turn the reverb off, it is not involved. One drives the Preamp Out jack, so if you are not using that, it is not involved. And there is one used as a buffer only when you use the Power AMp In jack, so again, if you are not plugged into that jack, it is not involved. There is one more over in the footswitch/channel switching circuit. It is not in the signal path.
If I understand you correctly, turning your master volume control down turns off this noise (right?), so that means the op amps are not involved. In my experience, the little op amps are not at all temperature or "current" sensitive. They do require a proper power supply, but then so do tubes and anything else that amplifies.
There have been some problems with this series of amps involving the dropping resistors for the +/-15VDC supplies coming loose. That can result in problems with channel switching and reverb, but doesn;t usually just make loud noise.
SO if you want to fix it, isolate the problem.
First characterize your noise. Is it a loud hum? or more like a screech? something else?
There is the clean channel, and there is the overdrive channel. The OD channel also has the "more gain" setting. Is your noise present in ALL channels? Or does clean work, but not the drive channel?
We established the Master turns it up and down, and the volume control doesn't. But do ANY of the other controls - volume, gain, bass, treble, mids - have ANY effect on the sound of the noise? DO they change its tone or level at all? This helps locate the areas affected.
Remove V1 from its socket. Did that kill the noise? Now remove V2 from its socket. Did that kill the noise?
And have you tried different 12AX7s in those sockets?
Have you explored the solder under the input jacks?
And at this point I'd like to hear your findings. But if I had to add a long shot, I might suggest removing Q1, Q2, just to see if they are faulty.
There are a few op amps in this circuit, that is true. One drives and recovers the reverb, so if you turn the reverb off, it is not involved. One drives the Preamp Out jack, so if you are not using that, it is not involved. And there is one used as a buffer only when you use the Power AMp In jack, so again, if you are not plugged into that jack, it is not involved. There is one more over in the footswitch/channel switching circuit. It is not in the signal path.
If I understand you correctly, turning your master volume control down turns off this noise (right?), so that means the op amps are not involved. In my experience, the little op amps are not at all temperature or "current" sensitive. They do require a proper power supply, but then so do tubes and anything else that amplifies.
There have been some problems with this series of amps involving the dropping resistors for the +/-15VDC supplies coming loose. That can result in problems with channel switching and reverb, but doesn;t usually just make loud noise.
SO if you want to fix it, isolate the problem.
First characterize your noise. Is it a loud hum? or more like a screech? something else?
There is the clean channel, and there is the overdrive channel. The OD channel also has the "more gain" setting. Is your noise present in ALL channels? Or does clean work, but not the drive channel?
We established the Master turns it up and down, and the volume control doesn't. But do ANY of the other controls - volume, gain, bass, treble, mids - have ANY effect on the sound of the noise? DO they change its tone or level at all? This helps locate the areas affected.
Remove V1 from its socket. Did that kill the noise? Now remove V2 from its socket. Did that kill the noise?
And have you tried different 12AX7s in those sockets?
Have you explored the solder under the input jacks?
And at this point I'd like to hear your findings. But if I had to add a long shot, I might suggest removing Q1, Q2, just to see if they are faulty.
Hi Enzo,
I was going to post something very similar to what you just did. I agree with you completely on all those points.
Hi Ian,
One point to consider about oscilloscopes. The newer ones, and especially the USB types, have a maximum allowable input voltage of 5 V peak. Not 5 V per division, 5 volts period! That means that with a X10 probe, your maximum applied voltage may be only 50 VDC maximum. The newer full oscilloscopes are very sensitive to input voltage. I killed one channel on my Philips PM3070 (expensive 'scope!), and one of my guys killed a Leader 100 MHz, dual channel with cursors oscilloscope. It was brand new as well. That was years ago now, maybe around 15 years?
If anyone will be working on higher voltages, use an older oscilloscope that has a more robust input amplifier. The new stuff is just too easy to kill. Of course, you can use a 1600 VDC film capacitor to couple your probe to a high DC potential, just don't let that cap charge or discharge through your 'scope! This takes a clear mind and attention to detail. Better to use an older oscilloscope.
-Chris
I was going to post something very similar to what you just did. I agree with you completely on all those points.
Hi Ian,
One point to consider about oscilloscopes. The newer ones, and especially the USB types, have a maximum allowable input voltage of 5 V peak. Not 5 V per division, 5 volts period! That means that with a X10 probe, your maximum applied voltage may be only 50 VDC maximum. The newer full oscilloscopes are very sensitive to input voltage. I killed one channel on my Philips PM3070 (expensive 'scope!), and one of my guys killed a Leader 100 MHz, dual channel with cursors oscilloscope. It was brand new as well. That was years ago now, maybe around 15 years?
If anyone will be working on higher voltages, use an older oscilloscope that has a more robust input amplifier. The new stuff is just too easy to kill. Of course, you can use a 1600 VDC film capacitor to couple your probe to a high DC potential, just don't let that cap charge or discharge through your 'scope! This takes a clear mind and attention to detail. Better to use an older oscilloscope.
-Chris
I'm with Chris on this one. Resistors can measure within tolerance and still be very noisy. This sound is often refered to as "frying bacon". I get a wooden chopstick and tap on all the resistors until I find a one that is noisy (microphonic). In some cases, as you get close to the bad one, the ones soldered to it transmit the vibration and appear to be microphonic when they are not. Replace the loudest one first. It should be very obvious. You'll have it figured out in less time than it took me to write this. (I chopstick faster than I type).
The last three posts are right on. I like to think about three troubleshooting aproaches, 1. make measurments 2. break device into sub circuts 3. signal substitution. This sounds simplistic but its easy to over look. making measurments implies having the schematic or just knowing about what values to expect. Breaking device into sub circuts can be powerfull indeed, (example) disconnect a series coupling cap, does this stop the problem. Signal substitution as in usuing the known test signal injecting approach. Hea I'm not trying to be sarcastic here, but the basics sometime escape us.
Hello guys, I'm new here, well I bought one hot rod deluxe, and when I turn the drive channel (red) up into the end come a big noise hummmm... this is normal? I took out the the tube from v1 and the noise was there yet, but when I took out the v2 tube the noise stopped, well I know that the problem is the 2 tube or some component near from there, I guess... I changed the v2 tube as well to see if was the problem but the same noise came from the amp, someone could help me please!!!
Thank you and sorry about my English...
Thank you and sorry about my English...
Didn't see if someone else said this, but I find it worthwhile to just replace all the pre-amp plate load resistors. I've seen it called the 100K mod online. I use 1W metal film or oxide resistors, and don't forget those phase splitter loads too. I've done amp repair for many years now, and this seems to prevent returns. The dissapation on these is typically .3W, but a shorted tube will take them much higher than their 1/2W rating.
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