Members RaVenCAD Posted May 30, 2017 Members Share Posted May 30, 2017 Alright folks, I need your tube knowledge. I THINK I know what's wrong, but it's always better to ask. So I went to play my Hot Rod yesterday and....... Nothing. It powers on, but it doesn't make any noise. I did some Google and saw a couple suggestions. First, plug into the effects return. If the power section is working, you'll get a very loud and clean guitar sound. I get nothing. The next suggestion was to plug into the effects send and run that into the effects return of another amp. Bingo! Sounded like a Hot Rod again. So, based on that, I'm thinking it's the power tubes. The last time I played it, it was perfectly normal and played at boring bedroom levels. No pops or crackles, everything sounded just fine. Link to comment Share on other sites More sharing options...
Members Verne Andru Posted May 30, 2017 Members Share Posted May 30, 2017 A buddy had a big Fender amp with a similar problem. I traced it to a couple of big resistors that had "broken" from their leads. Fender uses big, rectangle resistors on their output side that they leave long leads on so the heat dissipates better. Because they are not solidly mounted to the PCB they vibrate as you play and eventually the leads break and the amp goes dead. It's a tough one to spot visually but worth making sure everything is still connected to where it should be. Most times these problems have simple solutions - once you find them. Best of luck tracking it down. Link to comment Share on other sites More sharing options...
Phil O'Keefe Posted May 30, 2017 Share Posted May 30, 2017 It could be the power tubes or it could be something like what Verne was suggesting. If you don't know what you're doing inside a tube amp, such repairs are better left to a good tech - there's seriously high voltage inside of a tube amp that can KILL YOU, so please be careful! PS From your tests, the issue is most definitely in the power amp section somewhere. It sounds like the preamp is working just fine. Link to comment Share on other sites More sharing options...
Members RaVenCAD Posted May 30, 2017 Author Members Share Posted May 30, 2017 Oh yeah, I don't fiddle around inside tube amps. I like living too much. I'm heading to guitar center with the power tubes right now. They've got a tester. Should know a little more soon. Link to comment Share on other sites More sharing options...
Members Grant Harding Posted May 30, 2017 Members Share Posted May 30, 2017 Hoping it's just the tubes!! Link to comment Share on other sites More sharing options...
Phil O'Keefe Posted May 30, 2017 Share Posted May 30, 2017 Hoping it's just the tubes!! This - please let us know how it goes! Link to comment Share on other sites More sharing options...
Members DeepEnd Posted May 30, 2017 Members Share Posted May 30, 2017 Sorry to hear about your amp problems. Hope it's something simple and cheap. Keep us posted. Link to comment Share on other sites More sharing options...
Members thatsbunk Posted May 30, 2017 Members Share Posted May 30, 2017 I don't know if this helps, but I had a hot rod deville a few years ago that just died on me in the middle of a gig. Not gradual, but like all of a sudden dead like someone unplugged it. Fortunately a few bands were playing that day so I borrowed an amp to finish the set. Afterwards I gave the amp to a friend who was more electronic savvy than me to take a look at it. He gave the amp back to me in working order the next day & said he just replaced the pre amp tube & it fired right up. I didn't think tubes died right away- I was always under the impression that they die a slow death, but maybe that's something to look into? Link to comment Share on other sites More sharing options...
Members RaVenCAD Posted May 30, 2017 Author Members Share Posted May 30, 2017 Just got out of GC... BOTH of them were dead according to their Orange tube tester. How could both die at the same time? Could a power surge do it? We had a bad storm a few days ago, with lots of lightning. I didn't have them on a surge protector at the time because I had just moved them to another room. Maybe? The Marshall right beside the Hot Rod is fine though. Link to comment Share on other sites More sharing options...
Members Grant Harding Posted May 31, 2017 Members Share Posted May 31, 2017 Great! Does it sound better with new power tubes? What kind did you use? Link to comment Share on other sites More sharing options...
Members RaVenCAD Posted May 31, 2017 Author Members Share Posted May 31, 2017 Actually, it sounds exactly the same - silent. Wasn't the power tubes. Now I have no idea what to do for it. Link to comment Share on other sites More sharing options...
Members Grant Harding Posted May 31, 2017 Members Share Posted May 31, 2017 A tech should be able to easily troubleshoot and fix it. Link to comment Share on other sites More sharing options...
Members RaVenCAD Posted May 31, 2017 Author Members Share Posted May 31, 2017 Yeap, that's next. I can feel my wallet getting lighter... Link to comment Share on other sites More sharing options...
Members soundcreation Posted May 31, 2017 Members Share Posted May 31, 2017 On a side note....I agree people need to be careful with tube amps but there also seems to be a bit of a paranoia. They're not THAT dangerous. Just turn it off when it's warm. (and unplug it obviously) Simple as that. It will discharge. [YOUTUBE]sw9KnSFy3Fs[/YOUTUBE] Link to comment Share on other sites More sharing options...
Members gardo Posted May 31, 2017 Members Share Posted May 31, 2017 Really ,is it that simple. I have that paranoia you speak of. Link to comment Share on other sites More sharing options...
Phil O'Keefe Posted May 31, 2017 Share Posted May 31, 2017 You should always drain the filter caps manually as a safety precaution. And never ever work on the amp when it's plugged in unless you're a qualified tech. I used to manage a gear repair shop, and we had one guy (who I eventually had to let go) who it seemed like was getting zapped on a semi-regular basis. He never got killed or seriously injured, but he was lucky - if you've ever heard the snap! and yelp of pain of someone when a 600V cap bites them, you'll never want to be on the receiving end of it. Link to comment Share on other sites More sharing options...
Members soundcreation Posted May 31, 2017 Members Share Posted May 31, 2017 Yep. Done it myself many times. If in doubt grab a cheap multi-meter to test like he does in the vid. I have an old Gibson Falcon that I took to a guy to get a three prong grounded plug and to remove the death caps, and he messed it up. I ended up getting a shock from the chassis because he ran a wire to the wrong place. (and that's supposed to be someone who knew what he was doing...lol) There are no techs where I live so I researched it on the net and figured out how to ground it myself. I don't really even know how to solder, but you know....I gave it a shot. Wasn't the most beautiful solder job but it worked and now it's fine. Anyway....long story longer.....First thing I did was scour the net because I was paranoid about it too. Found that video....tried it out and yeah....now I'm not worried about the inside of a tube amp at all. Even if I don't know what I'm doing in there....lol. I'm more of a "wiggle it" to see if something happens. lol. Link to comment Share on other sites More sharing options...
Phil O'Keefe Posted May 31, 2017 Share Posted May 31, 2017 Yeap' date=' that's next. I can feel my wallet getting lighter... [/quote'] Check to see if there's a fuse on the circuit board - if the tubes went out, it could have taken a fuse out too. Not the main fuse - you're looking for one mounted on the power amp circuit board. If you find one, make sure you replace it with the same type and value. If it blows again when you power up the amp, then it's definitely time to visit a good tech. Link to comment Share on other sites More sharing options...
Members badpenguin Posted May 31, 2017 Members Share Posted May 31, 2017 You forgot to mention the cursing AFTER the snap sound! Been there, yeah, you curse.... a LOT! Link to comment Share on other sites More sharing options...
Members Les Paul Lover Posted May 31, 2017 Members Share Posted May 31, 2017 Just what I was about to say. If the power valves died, they probably took out the fuse too. They're usually time delay (or slow blow, same thing) fuses there, and are really cheap, probably £2 for 10 of them. Also, if you replaced the power valves, does your fender need biasing, or is it a cathode biased design? Link to comment Share on other sites More sharing options...
Members Busk Posted June 1, 2017 Members Share Posted June 1, 2017 I blew the power transformer on my Blues Jr. playing in a country with grid stability problems. It was plugged into a Furman power conditioner that was supposed to throw a breaker when there was a voltage problem. The upside is that I had Billm (RIP) upgrade the power transformer and mod it while doing the repair. Then I got a real grown up line regulator and never had problems again. However, it sounds like your power transformer is good. For working on amps. I usually drain the caps by touching the leads with an insulated handle screwdriver with shaft touching the metal amp chassis at the same time. Hopefully, this won't kill me... Link to comment Share on other sites More sharing options...
Members WRGKMC Posted June 1, 2017 Members Share Posted June 1, 2017 First thing I'd ask is if the power tube heaters are coming on. I would suspect they are since your preamp is working. Next you'd need to confirm you have B+ voltage. You have some B+ for your preamp tubes, usually less then 200Vdc. The power tubes will be over 400Vdc. Next the screen resistors are one of the weakest links. They can blow if the amp isn't being run with the right impedance. The power tube typically glow cherry red when they do. In your case the schematic says R64 & R65 should be your screen resistors and should have a value of 1.5K ohms. Next item is your inverter tube. If the screen resistors are good this would be my next item to swap. Its listed as V3A in the schematic. If this tube is bad you'll get no signal to the power tubes. I'd try swapping that one out and see what you get. My be an easy fix. From there you simply have to signal trace the amp. This is a hybrid amp containing several chips acting a buffers and channel switchers with its relay circuit. The biggest weakness of a hybrid amp is heat from the tubes. The SS components are low voltage and low heat and they simply don't work well with tubes which are high voltage/current, high heat. If you lack ventilation the SS components overheat and blow out. Tubes are likely fine. Its the SS op amps which buffer the signal most likely to be the culprit. I'd visually inspect to see if the screen resistors are good and swap the inverter tube. Maybe you'll get lucky. Otherwise the amp needs to be signal traced to find the culprit. The way that's done is you feed the amp with a test tone then use a small amp with a capacitive probe and listen to the signal each stage along its route. If you get to a component where you have sound going in and nothing coming out you found your bad component. The question from there is if its that one bad component or whether the components that supply voltage to it are also bad. It takes a knowledgeable person to test for voltages and make sure everything is kosher before replacing the bad part and powering it back up. Luckily the schematic is very detailed and it should be a fairly easy job for any competent tech.http://www.thetubestore.com/lib/thetubestore/schematics/Fender/Fender-Hot-Rod-Deluxe-Schematic.pdf I'd expect the repair to cost between $100~$200 depending on the parts needed. Most of that is labor costs, the parts themselves can be bought for chump change so long as they aren't something completely oddball where you have to get raped by the manufacturer to buy. Manufacturers often label parts with their own part numbers. They may be common parts but it can be difficult to know exactly what they are if you cant cross reference them. Link to comment Share on other sites More sharing options...
Members RaVenCAD Posted June 2, 2017 Author Members Share Posted June 2, 2017 Next item is your inverter tube. If the screen resistors are good this would be my next item to swap. Its listed as V3A in the schematic. If this tube is bad you'll get no signal to the power tubes. I'd try swapping that one out and see what you get. My be an easy fix. Are you sure it isn't called VX3? That tube doesn't appear to be lit up, but I figured it was just really dim where the amp wasn't being driven hard. Link to comment Share on other sites More sharing options...
Members RaVenCAD Posted June 2, 2017 Author Members Share Posted June 2, 2017 Check to see if there's a fuse on the circuit board - if the tubes went out, it could have taken a fuse out too. Not the main fuse - you're looking for one mounted on the power amp circuit board. If you find one, make sure you replace it with the same type and value. If it blows again when you power up the amp, then it's definitely time to visit a good tech. I read about that in other amps, but I can only find a main fuse on the back and it appears fine. Link to comment Share on other sites More sharing options...
Members WRGKMC Posted June 2, 2017 Members Share Posted June 2, 2017 I was just going by the schematic. It may be different then your tube chart. Its probably going to be the 12AX7 closest to the power tubes is its laid out like most Fender amps. Link to comment Share on other sites More sharing options...
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