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Fender Hot Rod Deluxe Repair Video
By Gary | March 10, 2008
This is an amp that was brought in for repair. Mainly dirt and worn tubes. I show some of the waveforms from the scope. I will go into more detail in later videos.
This type of repair is usually not that involved. A good cleaning, new tubes, bias, check tube sockets and circuit board.
These are good and loud once they are tuned up properly.
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Topics: amp repair (Fender) | 38 Comments »
March 13th, 2008 at 7:48 pm
This is not a repair video but a i will show you a few curves…..
Not really interesting…
March 15th, 2008 at 3:31 pm
Hello Colin,
It’s the first of a series, in the ones that follow I will talk more about the repair of this particular amp. Also as bloggers let me know what they want to look at will help. I get people asking for basic intro questions, so I thought I would start out keeping it simple but that could change with the response.
Thanks,
Gary
May 1st, 2008 at 2:59 pm
Hi Gary:
I found your great website while GOOGLE’ing “Fender Amp Repair”.
I accidentally broke off the stem of a volume knob/pot when trying to straighten it out. I now need to know how to replace a pot on a Fender Deluxe 85.
Do you have any resources that will instruct me on how to do this myself? Or do you suggest I take it into my local guitar shop?
Thanks.
Rod
May 1st, 2008 at 3:03 pm
Hello,
I’m almost positive that amp has pc mount pots. What this means is they are attached to a circuit board. For you to do it yourself would take a decent desolder sucker or desolder braid, a good iron, up on your solder/desolder chops. There is a video at the site on soldering. So it may come down to, do you want to invest in this equipment and practice a little desoldering before attempting or do you want to take it to a repair tech you like and have him/her do it.
You will also need to order the pot from Fender or a parts place without an account you will pay list price, I would assume this price on the pot and shipping will be in the ball park of what the tech will charge you so that is a wash.
So it’s kind of do you want to do it yourself or do you want someone else to do it. If it’s your only amp, you would want to be careful but if you have a cheapo to practice on you could learn a lot. I’m not trying to talk you either way, just letting you know what you’re in for.
Hope this helps!
September 2nd, 2008 at 2:43 am
Hi Gary, I have a Hot Rod Deluxe, I bought it new 10 years ago and have taken good care of it. However, it just blew a fuse the other day and it blows every new fuse I put in. After I switch power on then standby on, it hums for a second then the 3Amp fuse blows. I’d like to try to fix it myself. I’m experienced in electronics just not tube amps. Any recommendations? Literature/troubleshooting step-by-step?
I appreciate any info,
thanks,
Bob
September 2nd, 2008 at 5:09 pm
Hello,
Well it could be the supply going bad or you have a bad output tube. Usually if something can blow a 3 amp it’s going to be in the section that does all the work. The power supply rectifier or filter cap is where I would look. Even know your problem doesn’t kick in till you throw the standby on, if the power supply is marginal, when you throw on the load of the output section if could blow the fuse.
With that said, it could be an output tube has shorted, just stick in some used tubes and see if your problem goes away, if it does replace your outputs. I don’t really like to use new tubes to test things before I know what the problem is…
What kind of electronics work are you in?
Gary
September 7th, 2008 at 12:25 am
Hi;
I have a Hot Rod Deluxe that the reverb doesn’t work. When the amp was brand new it happened and the dealer said he found something loose and it worked again. Can you please tell me what might be loose? The dealer is out of business and I have no clue now.
Thanks!!
September 7th, 2008 at 2:18 am
Hello,
A lot of times if it’s a simple repair the problem will be down at the pan in the bottom of the cabinet.
The connections are male RCA plugs…sometimes just by twisting them back and forth on the female jack does the trick. If that doesn’t do it, mark what color goes with what female jack and unhook them.
Check inside the pan to make sure your springs are still connected. Sometimes the springs break off from the transducers (transformers) inside the pan.
Also find out which tube is the reverb tube and make sure it’s lit up with the rest of the tubes.
If it still doesn’t work, you got problems, take it to a tech.
Hope this helps,
Gary
September 7th, 2008 at 2:20 am
Follow up…
When you look inside the pan also look real carefully at the jack wires to the transducers, sometimes they pull away and have to be resoldered.
Gary
September 25th, 2008 at 11:45 pm
Bob from question #5: Hi, thanks for the info. Since then I took my amp to a repair shop, they replaced the output transformer and the 2 6L6 power tubes. I asked what could have happened and he said it was probably a shorted tube that took out the transformer. That kinda stinks if a failed tube can take out the xformer (total repair charge = $140.00) – I would’ve thought a tube failure would typically be an open rather than a short. Plus I don’t think trying to get 10+ years out of the tubes is out of line. The repair guy said I could’ve avoided it by replacing the tubes every couple of years. He gave me the bad parts if I wanted to test them myself.
Anyway, thanks for your time.
bob
September 26th, 2008 at 12:04 am
Hello Bob,
Yes, that happens, it’s kind of worse case scenario. I didn’t see it too much unless someone spilled a drink on it.
Output tubes can short and not take out the transformer or they can. Maybe in the Hot Rod the output trans can’t take a lot of beating.
As far as opening, if the input grid opened and went to 0 volts the tube could run red hot and fail and cause damage.
On the 10 years, that’s a bit much even for the old new stock but I’ve seen them go that long. I’m sure you amp is going to sound better, if your pre amp tubes are that old, I would replace them for the sound if nothing else.
If you want to learn some troubleshooting and you’re a tech, stick an ohm meter on the output trans primary. across the leads and one lead to one end of the primary and the metal of the output.. One of these examples will be a short. The secondary will look like a short on the 4 ohm…with an rms meter the 16 ohm should give you a small reading…
Gary
November 4th, 2008 at 11:05 pm
Hi Gary,
Actually I have the same problem as number 5
and 11, but with more info. Blew fuse. I pulled
the all tubes including the output tubes
and put in a new 3a fuse.
Its fine till I flip out of standby. Then
it hums with lots of static and will pop the
fuse after a few seconds.
I was able to measure B+(431v) before
the fuse went and it was only 165v. So I
located the connector cp18 (B+ to centertap)
and disconnected it. The B+ then measured 455v
with no output tubes, and it didn’t blow a fuse.
So do you think I’m in the same sad boat with
the output transformer? I should probable check
the plate diodes CR4,CR5. Maybe I’ll get lucky.
My output tubes are Ruby 6L6GCMSTRs and I bought them 2 years ago. I’m surprise that the output transformer could blow like that. When I measure the resistance of the primary transformer with the B+ lead disconnected; from centertap to either side I get 89 ohms on one and 109 ohms on the other.
Do you know what they should be? Seems odd they are not the same. No short to secondary.
(P.S I have a ET&EE degree)
November 15th, 2008 at 10:35 pm
Hello,
Sorry it took awhile to answer your post, I guess it was buried. It sounds like you may be on to it already with the transformer BUT you may be lucky with a diode or a Cap.
the ohms are close but 20 ohms off may be the clue. Also take a good sniff of the transformer, sometimes when they are burnt they got “the smell”.
Yes the hum could point back to the diodes or caps but then again one can pull down the other given time. The 20 ohm difference could magnify with power applied.
What I would do in the shop, at this point, I don’t even know what amp your talking about, rule out the power supply and then disconnect the output and jump in a known good transformer with alligator wire clips. Make sure you got the polarity right on the transformer.
Hope this helps.
Gary
November 16th, 2008 at 6:30 pm
Hi,
I am running into a similar problem with my HR Dlx. I was running the amp for about a year with a hotter bias for the output tubes. Fender recommends 60mA, Justin Holt recommends 68mA and I was running it at about 85mA per Eurotubes. Sounded great for about a year. Recently I noticed it didn’t sound very good and I found one of the 6L6 tubes was out. I replaced both 6L6s with Groove Tubes and it sounds better but not as good as it used to. It seems to distort sooner at lower volumes and I can’t bias it at any value above 70mA.
In any event, I checked the DC Voltages, and the resistor values around the output stage and everything looks good. No sign of damage to any components.
Finally I checked the OT primary windings to the Center tap and I see about 110 ohms on one side and 80 ohms on the other. This is similar to what Rick was seeing.
As Rick mentioned, it does seem odd that Resistance of the primary windings would be different to the center tap. I’m not sure what to make of this. How likely is it that both xfmrs failed the same way if they are indeed failed?
I wish Fender would just publish the actual winding spec for the xfmr. I’d hate to buy a replacement and then find out it is the same and not the problem.
By the way, I’m also an EE but I don’t remember enough xfmr theory to say it makes sense or not. Any help from either of you would be appreciated.
Thanks
Jimmy
November 16th, 2008 at 9:29 pm
Hello Jimmy,
I would say if you’re getting the same resistance reading this is not the problem. I would focus on the tube side of the one that went out. Check your voltages, I think you will find a clue there. Also check your bias circuit.
In my experience output trans don’t kinda fail, like gradually opening. They might but usually it’s obvious from the reading or the smell.
I did check my old trusty OT from a black face fender and there is a 7 ohm difference. Probably in fender’s design of today this difference in ohms per side is necessary.
Next time I talk to them, I’ll ask. If you don’t have a scope to check for leaky caps in the output tube circuit, your dc voltages will give you a clue.
In those amps the plate resistor takes a beating, check that out…if your bias is flaky with the reading check the cap, also if I remember correctly some of those voltages feed from off the tube board, check you connectors carefully, sometimes when a tube fails, the heat and current draw does damage on the connectors and boards in general.
Hope this helps…
Gary
November 17th, 2008 at 12:48 pm
I agree about the output transformer. I have checked everything else I can check with a DVM. The B+, Z and Y DC Voltages look ok. So do the screen Rs, and any other resistors associated with the output tubes. I found something that else that was strange though. The frame ground and the board signal ground are about 10mV apart. I’m wondering if something happened to the ground path somewhere because the schematic shows the two grounds tied together so there should not be any difference in voltage.
November 17th, 2008 at 4:22 pm
Hello Jimmy,
The 10mv difference could be a clue. A continuity check between the grounds should tell. Are you sure your dc voltages around both tubes in idle are the same? Also not being able to adjust the bias like you used to is a clue also. At this point a scope would be nice. For instance the difference in ground voltages produces noise, which could be AC where it should not be, so you might be reading noise from a leaky cap. I don’t know, speculating here, the continuity check will tell.
Also what I’ve seen often is when the input grid fails, resistor burns open or trace opens, the tube is wide open and draws a lot of current producing heat and damage before the tube fails, so eyeball that circuit and connectors real well, I’m sure you have already just referring back to earlier post.
Gary
November 21st, 2008 at 3:52 am
Gary,
No luck. I verified continuity and the grounds are connected. I don’t have a scope available so I’ll probably take it to a repair person I trust.
Thanks for your help.
December 16th, 2008 at 6:02 am
Hey Gary – this is not a repair question but rather one related to getting optimum performance from a Hot Rod Deluxe.
I bought a pair of 6l6GC power tubes that were matched at a # 16 plate current. I’ve recently heard that for a hot rod deluxe, 20-25 is ideal. Are the tubes under-conductive for my amp? Will the lower current comprise tube life, performance or sound quality?
Thanks,
Chris
December 24th, 2008 at 3:31 am
Hello Chris,
Sorry about the delay for some reason I wasn’t notified. I don’t have data sheets in front of me but the way I would look at it is like this.
#16 plate current (if) it is less than your 20-25 the tube will last longer and have a cleaner sound.
If it conducts more current it will clip sooner and distort. Some players want this and some players don’t
I usually go right in the middle which is probably where the 20-25 is, you try to get the best of both worlds in an amp like the Hot Rod Deluxe.
Hope this helps, in the mean time I will get the exact specs.
Gary
October 2nd, 2009 at 3:23 am
Hello Gary,
I have a faulty power tube socket on my deluxe. I’ve already switched my tubes around to make sure that both were working. i wanted to troubleshoot the sockets before hitting the repair shop. Any tips??
October 2nd, 2009 at 2:38 pm
Hello Aaron,
I not sure if you’re talking diode tube or output tube but regardless, this is one area you must know what you are doing before repairing. For example how to properly drain power filter caps, safety procedures like this and others are a must.
You also will need to be up on your solder chops if you need to replace a socket. If you are lucky, possibly a wire has come loose from a socket.
Cheers,
Gary
December 3rd, 2009 at 4:12 pm
Hi Gary,
Just surfing about after my recent purchase of a used Fender Blues DLX-re-issue. My initial complaint was a rattling bottle sound at mid to high volumes. I took it to my guy in Santa Clara, CA. who I advised to just replace all the tubes, which he did. I got the amp back and my distortion channel had no output, only clean side. Took it back and they replaced an apparent bad 12ax7. Another hour of playing and the power transformer went. To say I have a bad taste in my mouth at this point would be an understatement, but I need to get out from under as cheap as possible (already spending 350.00 for the amp and 200.00 for the re-tube-Another 200.00 to do this work is out of the question) I just ordered part from tubesandmore.com—Wondered if with a fair amount of soldering skills on my part if this is something I can tackle or are there fine adjustments (bias, etc.) that when I switch it on after replacement I’ll have issues with. Any help appreciated.
December 3rd, 2009 at 4:32 pm
Hi,
Sorry to hear about your problems. That sucks. Just for future note and this could not be your problem. Whenever you hear rattling at high volume, the first thing you check is to make sure the tubes are not rattling against the tube shields, especially whatever is securing the output tubes, there are remedies for this from rubber grommets to a bead of silicone.
Defective tubes happen. the pre amp tube had nothing to do with taking out the output tranny. Are you sure the output transformer is bad?
I don’t know what your solder chops are but it shouldn’t be too big a deal to replace, it’s just that it’s best to have bench equipment. For instance any time you do work in the power section you want to bring the amp back up slowly on a variac to check for excessive current flow. It’s a safeguard.
Do you want to spend a $100 bucks to get one? If not, can you get access to a bench? To just slap in another tranny can be done by experienced techs on the road with a few tricks but in your case I would get access to a bench. And yes you’re going to need to check bias and adjust and also if the output is bad, you need to find what caused it to go out or you will eat up your new tranny.
Just my 2 cents worth, and I know it sucks when you outlay money for an amp and all this stuff goes on. You just don’t want to throw any more money toward that amp unless it gets fixed right.
Gary
January 10th, 2010 at 6:39 pm
Hey gary I’m new to your site and am not how to post questions so I thought I’d try this I have a Fender Hot Rod Deluxe that is stuck in the drive channel I’ve tried the push buttons to no avail so any help would be appreciated
Tom
January 10th, 2010 at 7:12 pm
Hi,
If you’re using a foot switch make sure it’s not a foot switch issue. If you can’t switch from the control panel, more than likely it’s a switching FET. It’s a bit of work to replace correctly. Unless your solder chops are up to speed, I would say it’s shop time.
Gary
January 14th, 2010 at 3:50 pm
Hey there,
So the other day I was playing my Fender HRD and it started to smell like smoke. I was running a small pedal board into input 1. I turned it off and then came back and it didn’t smell and I thought I was safe. Same thing happened again when I turned it on a few days later. Could this be time for new tubes or something worse??
Thanks!
January 14th, 2010 at 4:58 pm
Hi,
Sorry to say, you got problems. Smoke is not natural, if I were you, I woudn’t turn it on anymore til it gets to the repair bench. The more you turn it on, current is going to go places that it wasn’t designed to go, thus causing smoke.
Now it may be a simple repair, like a resistor opening up but I would say it’s shop time. Just find a shop near you that your buddies recommend.
Gary
January 14th, 2010 at 5:34 pm
Thanks you so much! This site is a great find so keep up the good work!
May 11th, 2010 at 8:45 pm
I found this site while trying to diagnose my amp problem, and there seems to be good information! I have a fender hot rod deville and it’s been making some crackling sounds randomly over the last few weeks, and right before my gig this weekend the output volume went down (normally I’d run it around 3, but had to run it about double to get similar volume). Also, while on the clean channel it sounds distorted when I dig into it. I replaced the tubes today but nothing changed unfortunately. Also, there’s a quick blue flash in the left power tube when i take it off standby. Any thoughts/ideas would be great! Thanks.
May 23rd, 2010 at 12:43 pm
Hi,
If you replaced the outputs and you’re seeing a blue flash on power down along with the problems you posted. I would get the output section checked. You might have a component around the output tubes becoming unsoldered or breaking down.
Do it as soon as possible, problems in this section can put a strain on your output section.
Gary
July 7th, 2010 at 4:06 am
Gary,
I am looking at purchasing a Hot Rod deville but it has a problem. Clean and drive channels seem to operate properly but the more drive channel sounds like a motorcycle idling. I would suspect the preamp tube but not sure. What would you suggest?
Thanks,
Bob
July 7th, 2010 at 1:36 pm
Hi,
I don’t know, sounds like you could have more than a tube problem. Usually if they get old they will spit occasionally, sound crappy when you play, maybe a little hum but a motorcycle sound could be something else that’s hooked to the tube. Could be a filter problem also.
If you know how to switch tubes, like the two small on the end should be similar, make sure, 12ax7, if your problem changes channels, it’s the tube. Don’t bend the pins and turn the amp off.
Gary
July 15th, 2010 at 7:11 am
customer brought in a hot rod deluxe making load noise thought was one bad 6l6 removed6l6 turn on still load noise. used a .1uf orangedroptest for noise on the 47 uf cap center tap. removed red center tap no noise, its a load noise that i am not fermiler with been doing repair over 20 years.all diods test good. once and a great while. pulled all tubes noise returns with no tubes and center tap reconnected,i guess replace first filter section and replace output trans and tubes origanal tubeswere is old as amp sound firmiler? Jeff sss3061 fen
July 15th, 2010 at 12:21 pm
Hi,
What exactly do you mean by load noise? Also what happens when you pull the pre amps, have you seen the noise on your equipment out of the send? Just getting up to speed here. I know ground hums or low level noise ie static or spitting can be real brain teaser sometimes.
Gary
July 15th, 2010 at 9:49 pm
I apologize i meant loud noise, i have correct voltages, i can pull all tubes and still have that noise with no tubes in at all, but with preamp tubes in i have signal at preamp out.my thought is under load the first filter cap the 47uf 500v faults out, or the output trans is bad all rectifiers where check, just something in over twenty years i haven’t herd this particular noise before, if you have any other ideas let me know, i have never had a amp that i couldn’t repair so im sure i will get it.thank you Jeff’s repair
July 15th, 2010 at 10:05 pm
Hi i meant loud, removed all-tubes still makes loud noise like bad rectifiers or shorted cap or caps, but all diodes and caps tested good. with the tubes in, under a dummie load i have preamp outlooks and souds good.i geuse maybe under load the first cap 47uf 500v is the problem or the output trans is the culprit. never had an amp i could not repair just never heard this particular noise before, any way if you have any other ideas let me know. thanks for you time Jeff
July 15th, 2010 at 10:21 pm
Hi,
Ok, I understand now. Usually when situations like this happened to me it was usually because the customer did something like reverse the polarity on the output transformer or put a part in backwards. Drop it off and neglect to tell me they have been in it.
Now if this is not the case, it’s got to be the power supply, if you pull all tubes and it’s still humming, something in there is bridged, shorting two circuits. Seems like it would show up in your voltage measurements though if it was a cap problem.
With all the tubes pulled and making noises I don’t see how it could be anything in the signal path, like an open ground…hmmm
I know it’s easy for me to be an armchair quarterback. Let me know what you find.
I bet the person has been in it….
Gary