Fender Hotrod Deville ISSUE!

[skyyamps]

Hey guys, I just recently got a used 410 Deville. It played great for a few weeks but of course, there is now a problem. The amp has fallen victim to giant volume leaps during playing. This happens whether on the clean, drive, or more drive settings. I can actually hit the amp a couple of times and get it to bounce back to normal operation. The Channel LED on the amp will flicker to a dim red when the amp is being loud, and the channel selection will not work. Once i hit it a couple times, it will return to its respective color (red or yellow) and operate at a lower volume. This also happens regardless of whether the footswitch is plugged in. If the footswitch is plugged in, the lights will both turn off and will blink on and off depending on how loud im playing.

I have opened the sucker up looking for some disconnects or cold solder points, but I haven't found anything. I am suspecting its a problem in the relay/LED section. Any thoughts or ideas on where to look or what to look for?

Here is the schematic.
http://schematicheaven.com/fenderamps/h ... eville.pdf

Thanks guys!

[marcoloco961]

Bad volume pot????? chopstick it to see if it the problem, or just wiggle it up and down when the amp is acting up. Bad pots will jump around like that. Just an idea.

[Andy Le Blanc]

take a good look at the IC's around the re-verb and effect loop.

The power amp in jack might be all it is, spray cleaner or replace.

[Structo]

I agree, a lot of those amps use junk shorting jacks on the effects loop.
They get oxidised on the switch part and can get intermittent.
Problem is they are usually plastic housed jacks so you can't get in there to tension the switch leaf, or clean it.

You can test it by injecting another preamp out into your power amp to see if that is the culprit.

I know these companies try to squeeze every penny of profit out of the parts but a part like a jack that will be used a bazillion times is not the part you want to go cheap on.

Good luck. And if there is a way to clean the switch on the jack or tension it, that would most likely cure the problem.
Also, it is most likely a PCB jack, so a lot of times they lift a trace or break a solder joint on the PCB pad, because of flexing when you plug in.

[selloutrr]

Sounds like a voltage issue
refer to a schematic and cross check voltages
isolate the area that is acting up
check that sections components and work back toward the power transformer.

Failing tubes will cause volume issues as well.
Though the led points to a power issues. Diode, ic, cap, or pt

if you recreate it the chopsticks is very helpful to test for broken component leads and wire.

[rriddy]

I would check resistors r78 and r79. They are the 5w ones in the bottom middle of the main board. They set the relay and reverb voltages. Fender has since changed them to a 330ohm. I recommend checking if they're open and the solder joints. I've had over 40 of the hot rod series in my shop this year already and they almost always have either broken or cold solder joints either at those resistors or on the power tube sockets. Hope it helps

[bluesfendermanblues]

Hey guys, I just recently got a used 410 Deville. It played great for a few weeks but of course, there is now a problem. The amp has fallen victim to giant volume leaps during playing. This happens whether on the clean, drive, or more drive settings. I can actually hit the amp a couple of times and get it to bounce back to normal operation. The Channel LED on the amp will flicker to a dim red when the amp is being loud, and the channel selection will not work. Once i hit it a couple times, it will return to its respective color (red or yellow) and operate at a lower volume. This also happens regardless of whether the footswitch is plugged in. If the footswitch is plugged in, the lights will both turn off and will blink on and off depending on how loud im playing.

I have opened the sucker up looking for some disconnects or cold solder points, but I haven't found anything. I am suspecting its a problem in the relay/LED section. Any thoughts or ideas on where to look or what to look for?

Here is the schematic.
http://schematicheaven.com/fenderamps/h ... eville.pdf

Thanks guys!

Symptom:
This is a common fender blues blues deville/deluxe problem. The amp will shift between the clean and boost channel when it gets hot.

The reason is two cheramic power resistors (5w I believe) on the PCB, the gets wery hot and distrubes the peace.

Solution
I have repaired a friends blues deluxe. And know how to fix it.

I found the recipe on a long gone webpage: http://studentweb.eku.edu/justin_holton ... stors.html

However, I saved a copy for a rainy day:

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.

[Structo]

I was looking at that schematic.

It amazes me how much crap they cram into these more modern amps.

All the semiconductors and ribbon cables, etc.

It makes you wonder how all those vintage amps even operated.......

The schematic shows 485v B+ but only 30ma bias per tubes?

Looks like the guys have experience with these amps so I hope that fixes it.

[jaysg]

I was in one recently. I found it a pita to get the main board out...a certain amount of down & sideways pressure against a wiring bundle that's in the way. If you're into preventive maintenance, replace the PI plate resistors with 1 or 2W parts. Some or all of the plate resistors are stupid small.

[Andy Le Blanc]

I've been in too many newer fenders for bad plate resisters. I've heard they got a bad lot from a supplier.
you have to check with the client to see how much they are willing to blow
for the fix, it's a quick fix without full disassembly, won't flip the pcb with out asking, too much time.

The filter caps in the in the PS have the largest ripple rating in their price range.

everything but the iron is cheap cheap cheap.

[guitardude57]

The author of the fix has some terminology a little goofy.

The so called cold solder joint is a case of poor flow when soldered. IE, not soldered correctly.

A Solderability Expert will tell you the same. Most will tell you that the concept of Cold Solder Joints is BS. With the Solder Irons out there running at the correct temperature, the solder flows like it should. Heat the parts and the solder does what it is supposed to. If not, you are not doing it correctly.

This can be by hand or wave soldered.

A stress crack happens in the solder from over tension of the part in the "Thru Hole" and related traces. Use of a too low of a wattage value part resulting in overheating/expansion has nothing to do with the so called "Cold solder" joint.
This is a manufacturing defect.

So think of this not as a cold joint, but bad flow. It doesn't take a "ham fisted heat the shit out of the parts" to get the solder to flow. Most people get the feel pretty easy. Some of them even make name brand amps on production lines!

I have seen parts get so hot, that they literally melt the solder and the part drops off! Solder had nothing to do with it......Engineering defect.

Wrong values of parts.........If a 5 watt part overheats that much, sounds like some math is due, to find it needs to be a larger value. Hmmmmm Engineering again.

I agree that hard random angles of leads from components against the part can cause stress on the lead and premature failure. And it can happen inside the part, enough to make the hunt a bitch when looking at a normal appearance with a broken lead inside.

So if everyone watches how leads are bent, and irons are applied, we have less failures and nice shiny joints............

Ultimately, I'm glad that we can find fixes for issues the design guys miss.
We play them, we build them, we fix them!

[bluesfendermanblues]

guitardude57, you're right, a correctecly soldered joint won't go 'cold' from vibration or underdesigned resistor wattage.

However, the fix works like a charm on these amps. These resistors are indeed the weak link......plus the use of pcb in the first place.

The funny thing is that many people hold Fender in higher regard than Peavey. I you peek inside any new consumer tube amp, you see the same lousy PCB design similar to a digi camera.

[skyyamps]

Absolutely wonderful guys! I knew I could rely on you! I checked the resistors and sure enough, one lead was poking through the solder joint. I simply did a quick test and resoldered the lead securely. It totally fixed the problem as far as I can tell. I'll eventually replace the resistors, but for now, a solid joint works I think.

Thanks!

[bluesfendermanblues]

Absolutely wonderful guys! I knew I could rely on you! I checked the resistors and sure enough, one lead was poking through the solder joint. I simply did a quick test and resoldered the lead securely. It totally fixed the problem as far as I can tell. I'll eventually replace the resistors, but for now, a solid joint works I think.
Thanks!

Great!

[M Fowler]

I had a Randall RG-100 Classic on the bench last night the only thing this amp needed was some attention. The pots were dirty and the owner probably thought the PCB board was bad. Worked like a charm even for a solid state amp.