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Hot Rod Deluxe

email - sdguitaramp@gmail.com
Rossville, GA 30741

Fender Hot Rod Deluxe and Deville Channel switching problem. More drive issues. The 470 ohm 5W cement resistors in the +/- 16V supply are the cause of so many problems...The main problem is that the resistors get so hot that they form cold solder joints.... For a permanent fix you'll need to order a few parts. VintageJon, an extremely reliable tech at the FDP, wrote that Fender put out a bulletin recommending that these resistors be replaced with 330 ohm resistors of the same type—the old value was 470 ohms....https://sites.google.com/site/guitartubeamprepair/Home/feed-back/hrd SEE BELOW

Hot Rod Deluxe channel switching problem


My friend's Hot Rod Deluxe no longer switches channels. He said when he pushed the control panel button last week, it seemed like it was switching back and forth quickly, the LED flickered with it, and then it just stayed where it stopped, which is the LED is off.

The amp still works fine, as far as playing it through that one channel.

I used the footpedal switch from a DeVille to test it, figuring that maybe the panel switch was whacked, but the pedal might work. No go. The foot pedal LEDs both change (channel and drive) but nothing happens in the amp.

Apparently, the "More Drive" switch isn't functioning either, but is that because it doesn't work unless the non-working channel is kicked in?

Having looked at the schematic, I see that both switches are in the same circuit. What I can't figure out, yet, is how exactly it works. I assume that circuit somehow switches the relays (K1 & K2?) to change "channels" and kick in "More Drive"? I am also guessing that since neither seems to work, it may not be the relays, but something in the switching circuit (that is disconnected schematically from the main circuit)? (I'm trying to follow the logic through this thing, and am not even sure, yet, if those relays do a task each, or both work together. If the More Drive circuit isn't engaged until that channel is engaged, I suppose a bad channel relay would prevent both?

Anyway, before my head explodes, has anyone run into this before, or does anyone have an idea of the (or some of the) likely culprits that may cause this?

Thanks in advance.

Take a look at R78 and R79. The HRDx has a long history of channel switching troubles. You could just try re flowing the solder joints for these resistors and that may fix it. The resistors themselves might be bad. A lot of times the leads were over stressed and became open inside the component. I have replaced quite a few of those 5 watt resistors in the last few years.
Or I could be wrong, and you may have a different problem entirely. But it is an easy, quick fix to try.

Hey Steve,

Thanks again.

Interesting article here. I get the impression that a number of problems are derived from this one issue.


I'm having the same problem on my 10-year old HRDx, and though I haven't had it fixed yet, I believe I've found the answer.

From The Unofficial Fender Hot Rod Deluxe Owner's Guide!
By Justin Holton

How to Replace +/- 16V 5W Resistors

"The 470 ohm 5W cement resistors in the +/- 16V supply are the cause of so many problems in the Hot Rod Deluxe/Deville it's unbelieveable. Are your channels randomly switching on you? Are you getting an uncontrollable squealing/feedback sound that appears after the amp's been on a while? Is the reverb dropping in and out?

The main problem is that the resistors get so hot that they form cold solder joints. Cold solder joints are caused by physically stressed leads that are subjected to vibration and repeated heating and cooling cycles. (They are very common on PCBs which use a wave soldering method like the Hot Rod Deluxe.) If your amp acts fine when you first turn it on, but after a few minutes starts showing the aformentioned symptoms, then you likely have one or two cold solder joints. These are characterized by a dry/dull appearance; a good solder joint will appear shiny and clean.

The DC voltage from the resistors power the channel switching relays, the effects loop opamps, and reverb opamps. Once the joints get hot they'll stop conducting for random periods of time. This is what causes the channels to switch and the reverb to drop out. The cold solder joints also cause your amp to "feedback" whether a guitar is plugged in or not—particularly the More Drive and Drive channels. I think this is actually some type of oscillation, but I don't know exactly why it's caused. Still, doing this procedure fixes the problem.

Another problem is how the resistors are prepped. Look at all the other resistors in your amp. The leads come straight out of the component, bend at a 90 degree angle somewhere on the lead, and then are soldered onto the PCB. The 5W resistor's leads are bent as soon as they come out of the body. You should never bend leads like this. This puts stress on the inside of the component and causes it to crack. Remember, some resistors could be burned up, cracked, and totally disfunctional and you'd never know from looking at the outside. The only way to test it is with a multimeter.

Now that you know why your amp's acting flaky, how can we fix it?

1. For a permanent fix you'll need to order a few parts. VintageJon, an extremely reliable tech at the FDP, wrote that Fender put out a bulletin recommending that these resistors be replaced with 330 ohm resistors of the same type—the old value was 470 ohms. Apparently Fender now uses 330 ohm resistors in newer amps to prevent this problem, but I haven't seem this implemented. Someone emailed me and said it was better to use a higher resistance rather than a low resistance, but I have not been able to confirm this yet. The disagreement is over how the resistor drops voltage. All the RadioShacks in my area do not carry any 5W resistors over 1Ω. Chances are yours won't either. It'd be good to call them first to save you the time and gas. The largest values I could find there were 10 ohms! Click here to buy better quality power resistors right off of Mouser. If you have trouble with link, then do a search from the main page. Its Part # is 280-CR5-470-RC.

2. Drain the power supply's filter caps! This is for your own safety. If you don't know how click here. Your life may depend on it!

3. If you've drained the filter caps, and I hope you did, the back panel should already be removed. Now remove the chicken head knobs, black screws, washers, nuts, etc. Whatever you have to do to get under the PCB. It's also a good idea to remove the green ground wire that's on the same side as the input jacks. This will make getting under the PCB easier. Be sure to store these parts safely so none are lost.

4. Look for the two problematic resistors (R78, R79). They are in at the bottom-center of the PCB. (They look like two white blocks, and are right next to the bias pot.) Now that you've found them on top, you'll need to find the location of their leads on the bottom of the PCB. This is essential if your fix is temporary or permanent.

5. (a) For a quick fix, "touch up" the solder joints by adding a little solder to all four joints. This will keep you problem free for awhile, but not for good. For a permanent fix: unsolder the two 470 ohm 5W resistors. You may need to clip the tips of any leads under the PCB—if they're bent in a hook shape. (Probably all of them.) If not, it'll make this step more difficult as they get hung up when you try to pull the resistors out. (b) Be sure to remove as much solder as possible with a solder sucking device. If not, you could damage the solder points which are just a thin piece of foil glued to the PCB. Then you'll find yourself running a lot of jumpers—like me. Also, it can get awkward trying to unsolder on one side and remove on the other. It's always nice if you can keep someone nearby to assist you.

6. Take the new 330 ohm resistors and bend the leads—but not right where they come out of the component. This is the proper way to "prep" a component. This will take stress off of the inside of the resistor, which will keep it from cracking and failing prematurely. (a) NOTE: The "prep" in the picture to the right is exaggerated for clarity. You don't need to bend your leads that far out, though you can if you want to. Just don't bend them right where they come out of the body. That's the most important thing to remember. (b) A good trick is to place a miniature screwdriver right against the body of the resistor and bend the lead around the screwdriver at a 90 degree angle. (c) This prep will be far closer to the body than you could get it with your fingers, and it will look more professional than any wildly prepped leads bent further out.

7. If you have some Silicon Rubber Sealer apply some under the resistor. Use it to prop the resistor up off of the PCB a little. This will help keep the resistor from vibrating when it's trying to dissipating heat, which in turn will prevent cold joints from reforming. Solder the resistors into place. NOTE: Be sure to give the silicon 24 hours to cure before turning on your Hot Rod. Once it has cured it will be completely inert to electrical current.

8. Screw everything (PCB, jacks, knobs) back into place. If you've done everything correctly you should be problem free for a long time.

Unleash the tone of your Hot Rod DeVille. The Hot Rod DeVille and Deluxe are the best selling tube amps of all time. The amp sounds good and is pretty reliable, other than a couple common problems. After these mods your amp will sound fantastic and be more reliable. The classic Fender tone is released through these changes. The flabby bottom darkness is gone, what you get is full warm classic tone with nice top end sparkle. Complete kit with detailed instruction book with photo's includes all the following mods. This Mod kit is for any version of the Hot Rod DeVille, both Made in USA and the current Made in Mexico versions, both 2x12 and 4x10 configuration.
I also have mod kits for other amps and pedals, see my other items for sale!!!
Tone Stack - Get rid of that farty bottom, honky mids, and lack of clarity. High Quality Sprague Orange Drop Caps with corrected values for the Bass and Mid Cap and corrected value for the slope resistor.  What about the Treble cap? replace the cheap ceramic cap with a high quality Silver Mica cap. The result is an amp that sounds huge and warm with nice top end sparkle, not dark and buried in the mix.
WARNING: Performing these modifications WILL void the warranty on your amplifier. Working on amps can be deadly if you do not take proper precautions. Follow these instructions very carefully. If you are at all unsure of your ability to perform these modifications STOP and take your amp to a professional to be modified. You can also send your amp to me for modification.
No Warranty: This kit and the instructions included do not include any warranty of any kind. The modifications to your amplifier are at your own risk and you agree to completely hold harmless the seller of this kit against any and all claims. Tube amplifiers contain parts that operate at very high temperatures and deadly voltages. If you are not sure of your abilities to perform these modifications then do not perform them.
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Twin Mod - Fix the mids on the amp and get rid of that flabby bottom. This mod enables you to take all the mids out of the tone allowing more flexibility and versatility. This is accomplished with just a short jumper wire but the result is far better control of your tone.
Brightness - Like to play at low volumes but find the amp too dark? The brightness mod adds sparkle to your tone at low volumes. As you turn your amp up the brightness mod loses its effect so the amp never sounds brittle at high volumes.
Lead Master Volume - Ever wonder why this amp gets extremely loud after you turn it up past 2. Fender uses a linear taper pot for the Master Volume when it should be an audio taper. This mod gives you usable control of the drive channel so you can get good tone without playing at stadium volume.
Power Resistors- Many problems with the Hot Rod DeVille especially the older ones are from the power resistors that control switching. Two new power resistors installed properly will avoid many problems down the road.
Plate Load Resistors - Replace all the plate load resistors with 5% 1/2 Carbon Comp resistors. This amp can develop a loud crackle/static that is caused by the plate load resistors. This mod fixes or prevents this problem and using the same carbon comp resistors found in vintage and boutique amps you add rich harmonic overtones.
Reverb Mod - Why does the reverb in this amp become a complete wash after turning it up past 3 especially at low volumes? This mod makes the reverb more controllable, fuller, and more natural. This is an easy mod that is nothing more than clipping one wire but the result is amazing.
Switchcraft Input Jack - Your input jacks are soldered directly to the circuit board, apply some tension when the amp is plugged in and you could cause major damage to the circuit board in the amp. This mod gets rid of the wimpy plastic input jacks and replaces them with high quality metal switchcraft jacks that are panel mounted and NOT directly soldered to the circuit board. Included is a shoulder washer and isolation washer so the input jacks do not ground directly to the chassis and prevents ground loops. The jacks come pre-wired with high quality, Teflon Coated, Silver Plated Solid Copper Core wire. The solder I use is Silver bearing. This is the same quality you will find in high end boutique amplifiers costing thousands of dollars. Newer Hot Rod DeVille amps have a better quality Neutrik input jack which are better than the older amps but they are still attached directly to the PCB.
Proper Lead Dress - Take a look inside a boutique tube amp and you will see all the wires carefully twisted and placed for greatest reduction in oscillation and noise. The Hot Rod DeVille has all the internal wires zip tied together. I give clear instructions on dressing the leads inside the amp for optimal performance, this results in lower noise and less chance for oscillation.
Included in the kit is all the components necessary to get your amp in top shape and the detailed instructions to make the changes easy. If you have a basic understanding of electronics and soldering skills you can do these mods in less than an hour.