20 Most Recent Fender Hot Rod Deluxe Guitar Combo Amplifier - Page 6 Questions & Answers

Hello. You might have a "Tube rattle" problem. This is very common in these amps.
google "tube rattle" and you will find alot of people having the same issue.
There is some rubber tube dampers that you can buy to stop the rattling.
Hope this will help

/Daniel

Using a common lead pencil, gently tap on the smaller tubes in the unit, listening for noises and crackling to change and the drive channel changes.

It is normal to get a slight twang when doing this from the microphonics of the tubes, however, the crackling and up and down volume points to a bad tube.

BLK to CP3 (hot power in)
WHT to CP4 (neutral power in)

RED to CP11 and CP12 (high voltage, probably 280VAC)

GRN to CP13 and CP14 (6.6VAC filament power)

BRN to CP15 and CP16 (about 38VAC bias supply)

If you email I can send you PDF of schematic.

This sounds like a bad solder joint or cracked circuit board feeding the heater voltlaage to the left tube.

Pins 2 and 7 are the heater. LOOK for circuit board crack or bad solder to these pins.

Remember there is HIGH VOLTAGE in this unit so use ALL precautions for your personal safety as the voltages can be lethal.

This is likely a bad jack for the foot pedal, or a problem with the pedal and cable. The jacks are junk and even with the pedal unplugged the switch contacts on this jack will vibrate and cause your problem.

This often due to a cracked circuit board or bad solder joint. Sometimes input connectors are bad but those are easily discovered by wiggling the plug.

This is likely either a tube issue OR one with capacitors.

You need to characterize the loudness of the noises versus the settings of the controls as part of troubleshooting...

You can try tapping each tube with a pencil to see if one in failure will reveal itself.

pull the circuit boards and look for burnt capacitors

You can plug the output of the gt10 into the "power amp in" jack of the Fender. This bypasses the preamps in the Fender but uses a buffer amps in the Fender to drive the power amp. Please note that the reverb is STILL in the circuit when you do this. You can turn the reverb to zero if you wish to disable it.

The TL072 is shown having a must better distortion figure than the TL082.

DigiKey.com has them 50 cents. I would NOT substutute the 82 for the 72 in this case.

http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=497-2201-5-ND

Yes you could do that. The preamp output is just a BUFFERED output of the signal sent to the power amp. And the power amp input jack is BUFFERED before driving the power amp. These impedances are neither high or low being in the 1K to 3K ohm range.

The jacks for BOTH are mono jacks so noise pickup is possible if long cables are used. The external effects unit should be well grounded and operate off the same receptacle as your Fender for system safety. Use SHORT audio cables to minimize noise.

ALL the signal will pass through the effects unit when used this way... HOWEVER the internal reverb will still be in this path. You can kill this by turning the reverb control to zero on the Fender.

IF YOU ARE USING the footswitch, then likely problem is with cable and or the pug and jack.

IF YOU ARE NOT using the footswitch the contact switch on the jack for the footswitch is PROBABLY intermitent contact. These jacks are POOR quality in the music equipment. If this is the case in yours, open the unit and tighten the spring contact.

i am guessing on what the problem is , the post is very vague. i am guessing a channel switching issue. you need to check the "sugar cube" looking power resistors solder welds. they are probably cracked and arent making good contact. if you tap on the amp it will cut in and out, its probably these two resistors. they are usually 470ohm 5 watt cement resistors. what happens is they get real hot, and as they cool down they crack the little solder welds. i usually replace them with new and keep them floating up over the pcb to help them stay cool and off of the board to prevent further solder weld cracking, stock they are real close to the board. then put a little silicon under the resistor to hold it in place and to keep it still on the board. i just fixed a blues deluxe with this issue. while you are in there, cut out the resistor sitting right behind the reverb pot, this will make the reverb awesome. also solder the mid pot center leg to the mid pot leg that comes off of the bass pot leg to get better midrange control. very easy mods. check the master volume pot, is it a B100K? pull it and put an A250k in its place for better volume control. bias pots , etc. check my website yostamplifier.com.

There are FOUR controls that affect the volume of signals going through plus the tone controlling ones.
and your
You used the word "volume". Based on the schematic, and assuming you are talking about the control labeled "Volume" and not reverb, master or drive, I can give some hints.

OFTEN the resistance element in pots MAY have a bit of overtravel which can act like your unit, but USUALLY not as far upscale as yours appears..

If the control you are refering to is not the "Volume" but one of the others, then there are other things to look at.

The action you describe would be one of probablly an inverse signal leaking through and when you go up to 1.5 you are actually cancelling the leakage.

I SUSPECT you may have a cracked circuit board in the vicinity of the input jacks that is leaking the inverse phase of the input past the input triode tube stage.

Board cracks OFTEN occur near input jacks because people trip over cords... (save yourself by running cord through a handle before plugging in the plug)

This should be easy to find. Connect an audio generator to the input and use a scope to find the problem. Without a scope, use a capacitor to "ground out" suspected signal paths.

On the schematic they show a resistor (10 ohms) from ground near the input to the pot bracket. I have personally SEEN capacitive coupling to pot brackets feeding into the amps from this source sending in stray signals.

If this is connected to other equipment, a ground loop could cause problem, so test with nothing but the guitar connected.

In YOUR amp, take a pencil and tap teh sides of the tubes GENTLY, listening for any crackling... note SOME microphonics is normal in the preamp stages.

Since retubing it fixed it once, it is likely either a tube was bad OR a pin of a tube wasn't quite making so replacing the tubes cleaned it and made it work. Tubes DO go bad, especially when they are vibrated like in these amps... BUT don't just replace the lot, try to find which is at fault..

On your friends unit, LIKELY an electrolytic bypass capacitor for one of the reverb preamp stages has dried out and needs replacing.

I want you to do a test. while using the amp plug a pair of headphones into the preamp out... note you will only hear stuff on one side if they are stereo phones and the sound may be fairly weak... while the unit is operating correctely then unplug phones and use it. When it fades out plug in phones compare the level when it was OK... If the preamp output fades lower as well, then we know problem is in the preamp section...

We can do a lot of troubleshooting without opening the amp.

I see nothing in the scheamtics that should be an issue causing this...

Since it didn't fail for the tech, think "what was different?". Are you connecting something else? Foot pedal? Temperature? :Loudness of playing?

Now what else is in common to these two units... AHA! The guitar...

If your guitar has a battery in it, the 20 to 30 minutes fading would correspond to a battery failing and then recovering after you unplug the guitar for a while.

Here is a link that might help:http://www.geofex.com/ampdbug/ampdebug.htm Unless you have the tools and experience to work on your gear it is always best to take it to someone who is qualified to work on that particular amp. Your local Fender dealer should be able to recommend someone.

I have a friend who keeps getting me to fix his deluxe. Nice sounding amp but not super reliable unfortunetly. He had the same problems and his kept dieing in the middle of a gig. I can't tell you what exactly needs fixing over the net. You need a meter and the amp in front of you to fix it. And the power in these is more than enough to kill you so you need to take precautions. From your description and what you have changed etc then this is a board level fix. So if you don't have the tools then this is headed to a repair shop.

Usually the problem starts out in the power sections. So you need to measure the voltages and start spreading out from there. Too low on the high volt part and you get no volume, too low or none on the low volt section and you get nothing at all. I would suspect this is where the problem lies.

One of the possible problems is going to be the diodes and ceramic power resistors on the board. One or more of those will have to be replace. The parts are cheap say under $2 and are common. This section controls the power produced by the main transformer so it can cause anything from low volume to noise when acting up.

The other part of this is a opamp. I think it is a TLO72 (35 cents). If the power to those is off or they go then it can make zip for output. Usually these die with a nice squeel.

If you can get it to someone who can repair it then you might pay $100
to get it fixed. If there is no one close you could just try to find a mainboard on ebay or someplace and swap it out. Those can go for cheap to $$ like anything else.

There are amp techs who will just replace tubes and cost you money and not fix anything and then there are amp repair houses who fix them when they do these sorts of things. Usually any music store has a 'tech' but no-one who actually repair them. All they do is seperate you rfrom your moeny.

In refering to the schematic i find that the MOST probable cause would be a bad switch contact on the jack the pedal plugs into. There is a normally closed contact that passes the select signal within the unit to the control circuit. If the contact vibrates open, then the unit will switch. These jacks are a pile of.... prone to failure if you use them very much. With the pedal plugged in the switch is no longer in the circuit and control is solidly by the pedal.

If you remove the amp from the cabinet you can probably bend the spring contact to temporarily fix the problem, however, use that jack a bit and the problem will come back. You could cobble a good quality Switchcraft jack with switch as a replacement and add pigtail wires to the circuitry for a little better reliability.