Fender Hot Rod Deluxe Humming+Distorted Low Notes on Clean Channel

[BoomTexan]

So, basically as soon as I turn it on, there's this humming sound that increases in pitch and loudness the more that the tubes power on. Video:
It sounds like when you take the jack out of your guitar and there's the HRMMMMMMMMMMMMMMMM sound going, but it's constant.
I was asking around on Reddit and they said it was probably a tube, but they couldn't diagnose whether it was preamp or power amp for sure. I plugged into the Power Amp In plug and it had the same distorted bass thing going on. Do y'all think it's likely a bad power tube?

Next issue: I doubt if I'm going to keep this amp for long, I'm probably just going to flip it, because it's far too loud for home use. Also, reliability issues (as in this post) are a big deal for me, because tube amps are expensive and I don't have much money. So, all these things considered, should I go for a cheap pair of tubes? (link removed) I could get these for around my pricepoint, or I could get a non-matched JJ tube and hope that both of my tubes aren't blown. Do any of you guys have any experience with buying these older tubes online?

 

[corliss1]

Isolate as much as you can with the knowledge you have. Pull the preamp tubes one by one, starting from the right when looking at the rear of the amp. If that doesn't fix the problem, the issue is in the power section.

My bet would be a capacitor problem in the power supply, as a failed capacitor will greatly effect bass response more than treble.

 

[tubedude]

These symptoms are typical of bad filter caps or lost bias voltage. If your power tubes are glowing red, it's the bias voltage.
Don't buy tubes. Take it to a tech. It's cheaper than following advice on reddit.

 

[nathan5782]

I bought a pair of 6L6 tubes from the same eBay vendor for my 67 Bandmaster and one of the tubes was bad. It burned up a diode on the rectifier, he gave me a refund.

 

[Timbresmith1]

Sounds like filter caps. I’m hearing 120hz buzz and bass notes oscillating as if there is insufficient current to sustain the note.

 

[Happy Enchilada]

I had a couple of HRDs a few years back. Used 'em hard for worship services. They were heavy, bulky, and hard to get any decent sound out of at reasonable volumes. Much happier with Quilter Aviator Cub. I am now happily tube-free and my back is thrilled.

 

[MuddyWolf]

Those amps are cool but have lots of places where grounding fails over time. It's usually not bad tubes or stuff the user can fix. Find a tech.

 

[BoomTexan]

These symptoms are typical of bad filter caps or lost bias voltage. If your power tubes are glowing red, it's the bias voltage.
Don't buy tubes. Take it to a tech. It's cheaper than following advice on reddit.

Sorry for the late reply, but how much does the typical tech cost for an issue like this? I don't have much money at the moment, would it be feasible to take it to one? Is it a quick fix or will I be stuck with like a $200 fee and no solution?

 

[corliss1]

A re-cap of a HRD in my shop is 2 hours labor plus parts, so it's usually in the $140-175 range, depending how it goes.

 

[King Fan]

Ooh, yeah, money, dang. Depends, I bet. And not all techs are as reasonable and competent as our friend @corliss1 . Reading posts here over the years, we see cases where a nice tech fixes a single, simple problem for free, but others with a $400 bill for a lot of work we can tell wasn’t needed. And some expensive tech trips that didn’t fix a thing.

Smart folks, what does it tell us that the noise starts instantly on power-up, then gets louder on warmup?

 

[tubedude]

Tha it needs a tech.

 

[jhiatt1]

Sounds more like a filter cap failing. The stock IC filter caps are crap and tend to leak. The tubes could also be a factor. Best bet is to swap all the tubes and get better filter caps. On my HRD I put in the F&T filter caps. Matched power tubes and mixed and matched pre amp tubes. 12at7 in V1 12ax7 in V2 and 12ay7 in V3. That is my personal preference. You can mix it up how ever you want.

 

[jhiatt1]

I replaced the filter caps myself, however I have a lot of experience with amplifiers, mostly Military radio amplifiers, but some radio and guitar amps as well. I am pretty confident in my skills. DO NOT ATTEMPT TO DO IT YOURSELF IF YOU ARE NOT CONFIDENT!!!!!! You could really end up damaging your amp and really be screwed.

 

[jhiatt1]

I replaced the filter caps myself, however I have a lot of experience with amplifiers, mostly Military radio amplifiers, but some radio and guitar amps as well. I am pretty confident in my skills. DO NOT ATTEMPT TO DO IT YOURSELF IF YOU ARE NOT CONFIDENT!!!!!! You could really end up damaging your amp and really be screwed.

 

[jhiatt1]

I replaced the filter caps myself, however I have a lot of experience with amplifiers, mostly Military radio amplifiers, but some radio and guitar amps as well. I am pretty confident in my skills. DO NOT ATTEMPT TO DO IT YOURSELF IF YOU ARE NOT CONFIDENT!!!!!! You could really end up damaging your amp and really be screwed.

 

[jhiatt1]

Sorry for the multiple post. The site kept reloading on me.

 

[BoomTexan]

I'm going to get some new tubes and hope that fixes it. If not, I guess I'll have to take it to a tech or sell it as-is. Its weird, because I bought it 4 days ago and it wasn't causing a problem when I tested it.
I really don't want to take a loss on this amp...
The HRD is very common, surely there must be enough resources online for me to do it myself, right?

 

[King Fan]

I'm sure someone here could point us to some pics, and if you don't know already, you can read up on draining the filter caps before working on the amp. Not hard. The question is gonna be how difficult it is to access and desolder/resolder the caps in the modern layout.

 

[corliss1]

If you have tools and you're familiar with high voltage, sure. Some people say they are a pain to work on - I think it's just how modern stuff is built. Pull all the top knobs, washers, under the ground screw, undo the screws on the board, cut the wire bundles and spread them out, make sure not to pull on the reverb wires, then you can just get enough clearance to get to the back of the board.

It's not an easy job for a first project though, as you can quickly toast the circuit board if you linger with the soldering iron.

A full set of tubes is what, $50 for power tubes and then $20 each for preamp, so you're at $110 on a gamble? I'd rather take it somewhere instead of hoping that fixes it. I also outlined above how to help isolate which stage of the amp it is by pulling tubes.

 

[peteb]

Here is D Labs pulling the board.




the filter caps are the big ones.


pull the board to solder from the back side?