Fender Hot Rod DeVille 410 cutting in and out

[HeXeD]

Thought maybe one of you pros could help me figure out my issue

AMP: 1997 Fender Hot Rod Deville 410

Issue:
At first I noticed my sound would just cut out.. and back in randomly. It could happen 30 times in a minute, or once in a week. It was completely random. When the issue occured and not immediatly correct itself, I would jiggle the jack going into the amp. This easily fixed the problem. As time went on I would find it more difficult for it to produce sound by jiggling the jack. As of the past 6 months or so, it is almost impossible to fix the cut outs. When it cuts out you can barely hear the sound coming out the speaker, it is there however. The sound also sounds like it is static as it goes from regular to cuting out. Sometimes it is also accompanied by a pop with an echo.

What I have done:

1. I have tried different cables
2. I have tried both inputs on the amp
3. I have tried the overdrive channel, bright button an any other combination of settings on the amp to figure this out.
4. Tubes have not been changed.
5. I have done the jack replacement on input 1 and 2 to metal input jacks thinking that this is the most common issue with this amp. I made 100% my solder points were perfect, closed it up and hooked up the power and my guitar. It seemed like for about 30 seconds it was working fine. Then the cut outs started again. What is weird about this time is, (and this could have been the case before I just never noticed) if I strum the strings HARD.. the amp seems to play.... LOUD.. which is good. But if I lightly strum or pick, the amp cuts out again. So I'm not sure if I was dealing with a jack issue PLUS some other issue, or if there were never issues with the jacks to begin with.

From all the reading about tubes I didn't think changing the tubes would be the issue. Unfortunately in the past 7 years or so I haven't played much so the tubes really aren't being beat up all the time. But the amp IS from 1997.

Now I am stuck.. so what do you think? Am I just going to have to give it over to a repair shop and pay anywhere between 25-50% of the worth of my amp?

[Euthymia]

After your 1. and 2. up there, the next (for free) thing to try on one of those Fenders is jumper the "preamp out" and "power amp in" jacks with a known good cable. The shunt switch on those gets dirty. Also the shunt switch on the "ext" speaker jack can get grubby and intermittent and cause similar symptoms.

[HeXeD]

Ok, I tried that but it was still doing the same thing even when I jumpered the Pre Amp out and power amp in jacks.

What I did do which was recommended in another thread was hit the amp on the top (not TOO hard) and go figure it cut back in and seems to be "ok". It went back out after 30 seconds but then after I hit it a second time, it stayed on and I jammed for about 15 minutes with no issue.

What do you think the issue is?

[Robert M. Martinelli]

Hi and welcome!


Since you already ruled the S/R jacks out, my educated guess is that your amp could suffer the (in)famous dropper resistors issue. This issue is very common on the Hot Rod series amps (especially on the Hot Rod Deluxe, whose droppers have to drop the voltage from +/-48 to +/-16V). In a nutshell, the PS section creates the dual voltage needed for the preamp by means of a couple of Zener diodes and dropper resistors (R78 and R79). The dropper resistors tend to overheat to the point that the solder joints can melt, and whatever solder left often crackles creating such problems.

Search the forum and you'll surely find quite some threads/posts dealing with this issue.

Hope this helps

Best regards

Bob

[pontiacpete]

I would check for bad solder joints on the tube sockets and the main pc board.

[HeXeD]

Ok.. I have checked R78 and R79. The solder points under the pcb for those two resistors seem fine. I have notcheck pontiacpete's ideas so those are next. Just got it cracked open again so let me know what you think. I will check the other threads I have come across.

[HeXeD]

I have checked under the PC board and the tube solder points. The tube solder points look great.. at least they look like every other solder point with no visible cracks. That leads me to R84 and R87. On both resistors there is one solder point each that looks.... ugly. It is still that silver color.. no burning.. just looks pitted and messy looking. I'm not quite sure if this is the culprit.. and I find it funny that hitting the top of the amp would jostle it working.. but then again I'm not a pro at this. Just a DYI type of guy competent enough to not electrocute himself.

[HeXeD]

Ok, took a pic of the board as best as possible and marked the two suspect solder points. Any ideas?

http://i.imgur.com/R2bts.jpg

You can click on the picture to zoom in...

[Enzo]

Just to make an old man happy, resolder all the power tube socket pins, no matter how nice they look.

If those solder joints look iffy, then just resolder them. No point in trying to decide if they are bad or not. Reesolder them either way.

We already know that whacking it causes changes, so there is a loose connection somewhere. SO next time it happens, plug the guitar into the Powr amp jack. Does that come out strong? Or is it gone that way too? This will isolate to the preamp or the power amp.

And with the guitar plugged into the input jack, when it happens, wiggle each tube in its socket. ANy help?

[HeXeD]

I just got finished resoldering the two power tubes (I think it was like 8 points per power tube), and the two points I thought looked funny. I left the pre amp tubes alone as I assume by "all the power tubes" you mean the the two big ones. Sealed everything up and turned it on. Sounded fine. Gave it the slightest bump on the top to test for the loose connection and then BAM.. back to the cutting in and out. So I did what you asked Enzo and plugged my guitar into the "power amp in" input and low and behold... there were absolutely NO problems. Switched it back to input 1 or 2... I would get barely any volume unless I whacked the top of the amp to bring it back to life. Any new ideas?

PS. As I had said.. These are the original tubes so is it 100% the fact that I don't need to change the tubes? Everything I know about the symptoms do not include the symptoms (except for the low volume part but I assume smacking my amp wouldn't fix anything if any of those tubes were bad.

PSS. I have never hooked my guitar directly into the power amp in. Is this a workaround for myself until I fix input 1 and 2? What am I missing by playing through this jack? Bypassing all of the fx?

[Prairie Dawg]

Something's loose fo sho. What I'd do before I ripped it apart was start probing around with a chopstick or dowel and see if you can locate the source of the pain. Pull the chassis out and check all the flying leads for integrity. Then start checking the back side of the circuit board for bad solder joints and stuff that's never really taken the solder like it should have. You'll find it, because it is there.

[HeXeD]

WOW.. This is where I say "huh???". Like I said, I am competent enough to not electicute myself but your post seemed a but over my head..

1. What's a chopstick or a dowel? I hope that is just some sort of analogy to some method of "finding the pain"... cause if it isn't you're going to have to deconstruct that sentence for me.

2. When you say pull the chasis out, you mean the actual metal chasis that is under the pcb or are you talking about the pcb? or the black cover? Cause you mention to check the flying leads.. Flying leads as in the ribbon cable? And when you say integrity... do you mean probing the points with a multimeter? or just checking the solder points and any other anomolies?

As far as checking the back of the circuit board, I did that. All of the points looked very nice except for 2 which I resoldered. I also resoldered the 2 power tube jack solder points by request of Enzo. There is a picture of the back of the pcb and it is pretty large. I doubt anyone could see anything out of the ordinary but I figure I would post it with the 2 dirty looking points.

Oh I also forgotto mention, I also resoldered point R78 and R79 just in case. I'm sure I can take hours out to resolder ALL of the points on the back of that thing, but that seems pretty excessive. But if it is what people think I should do please speak up.

Thanks for all of the help so far everyone

I

[Enzo]

A chopstick is a long thin piece of wood used to eat Chinese food... seriously. A dowel is a long thin piece of wood. All it means is with the amp running, we want to push on each little part to see if moving it makes something happen. This helps us locate problems of your sort. We need of course to use something insulate, both to protect you and to protect the amp from being shorted out by something metal. There are many alternatives, but a chopstick is something most of us have around somewhere. The plastic body of a BIC pen would work too, just keep the little metal point of it away from the board.


I almost never actually pull the metal chassis from the cab on these. Not while running, of course, but pulling the nits off controls and jacks, and a few screws, and probably cutting a tie wrap or two, and the board can be wedged out from under the top lip. Then it can be flopped down to get at the solder side.

FLying leads? Any wire that is not a copper trace on a circuit board. Integrity just means that if it is supposed to get from here to there that it in fact does. For example, I may solder two things together, and I could check the integrity of the joint with an ohm meter. But if I see a broken off conductor in a ribbon cable, that is a lack of integrity right there.

SO being careful, amp assembled and running, back panel removed for access, and some sort of signal appl;ied to the input, flex the ribbons to the tube boards. Flex any other wires that leave the board. Chances are the power wiring is OK since it is common to teh power amp and preamp. Your problem is in the preamp. That was the purpose of plugging into the power amp. we now know the power amp is OK.

DOn't know what you resoldered, but common failure points aside from those two resistors and the tube sockets, would be controls and input jacks.

[Moreland Amps]

# 1 Try new preamp tubes that is an easy fix!! I always try tubes before I get started taking an Amp apart , but I always have extra tubes to work with , do you have another amp thats working try the tubes from it !! I think I read that you have not switched tubes ???


(Quote from first post!! ) From all the reading about tubes I didn't think changing the tubes would be the issue.

[HeXeD]

# 1 Try new preamp tubes that is an easy fix!! I always try tubes before I get started taking an Amp apart , but I always have extra tubes to work with , do you have another amp thats working try the tubes from it !! I think I read that you have not switched tubes ???


(Quote from first post!! ) From all the reading about tubes I didn't think changing the tubes would be the issue.

This is HILLARIOUS. It has been so long that I tried to tackle this problem that I forgot about this thread so a big sorry to everyone for resurrecting such an old thread.

I was doing a google search and saw this thread. I thought to myself "Damn.. this guy has the EXACT same problem I have. After a few entries I realized I was reading a thread I created.

So on to the problem. In the last 3 years I have just been fixing the issue by banging the shit out of the top until it turns back on. I replaced the tubes but that didn't do anything unfortunately.

I tried the chopstick test (had several) and no matter where I hit, it never cut in and out. I basically hit every solder point on the board.. every capacitor.. every tube solder. Nothing.

I'm really thinking that it is time to bring it to a professional (they apparently have a good Fender repair shop in Dallas). What do you guys think? I hope in the last 3-4 years someone else has joined this forum and notices the same problem. I will continue to investigate this issue through google some more, but I am the type of guy who REALLY wants to know what the problem is.