Sometimes They Come Back | Part 2: The Hot Rod From Hell | (And Hot Rod Volume Taper Myths)

Preventative Maintenance on Hot Rod Amps:

Easy "Mods":

[RedArrow]

I like the way you hold on to the segment, when you trim a component lead, that wants to fly into the bowels of the amp.
Good FOD Control.

[ckturvey]

Sorry that this amp came back, but I did enjoy and learn from both videos. I have a newish HRD series 4 I purchased in May of 2021 and its been working reliably with the common behaviors that you and others noted in these amps. I did open the back and visually inspect the board. Unlike the HRD Series 4 you are working on, the 5W resistors (R78 and R79) raised up off the board and have insulating tubing on the leads. Now this is the only change I saw to improve reliability. Maybe a few more of the low or zero cost changes will be made in the HRD Series 5 or 6 :). On the touchy volume controls, one zero cost "mod"I have been using at gigs and practices for the last few months is plugging into the 2nd lower gain input. Once I dealt with my inner 15 year old guitarist ("You used the LOW gain input?!?! How could you!?!)), I was able to run the clean channel at 3 or 4 on the knob compared to 2 to 3. I also noted the tightening of the bass which helped playing clean on the neck pickup. Thanks again for the great videos!

[joekrutzsch]

Thanks for the volume pot explanation. I have seen multiple claims online saying that the taper was the reason the control is so sensitive as to be unusable.

[jimmyjoefine]

$300 to repair a $350 amp. That's really sad. I just bought a 1965 Epiphone Galaxie for $200, and $35 worth of parts later, it's rocking hard. And it can be maintained and serviced indefinitely. There are plenty of affordable options out there that are not circuit board based tube amps. Love your work, Lyle, and thanks for being the best amp repair channel on YouTube!

[ScottKDrums]

Man, a part of me wishes I could Ship you my Deville for all of these upgrades and futureproofs

[BradsGuitarGarage]

Just had the same thing on a Super Twin. Came back with a dodgy solder joint on a 10k dropper.

[blakesimpson]

Another great video. This one had us on pins and needles waiting to see the outcome. Seemed liked it was going to be the ribbon cable when you hit that spot on the board. Interesting find. Good work as always! There are just soo many things to go wrong in these mass produced amps...

[BradsGuitarGarage]

Don't buy a crimping tool. You've got a Piergiacomi PNG5000 on it's way!

[JzuHax]

Nice video, as always. Also, replacing the original speaker with an inefficient (which is good!), cheap, and decent-sounding Jensen MOD 50 will give you even less volume and more control. This, along with a 12AY7 in V1, allows me to hear the power tubes slightly break up while rehearsing or on stage, which never happened to me before.

[Curtislow]

Good follow-up on a techs methods and thoughts. I can remember my Dad explaining similar scenarios in his B&W TV repair days.

[cloudconnect]

Not all "audio" taper pots are the same. Some will match (logarithmically) to our ear, better than others. Cheaper ones often have a sweep that is somewhere between a linear and logarithmic. There is a science to it that is probably not relied on as much as it should be in the engineering stages.

[jeffamichaels]

I'm really enjoying watching. Glad i have a great tech. But it's nice to learn.

[kengevers]

Funny, while watching the video, I thought it would be the speaker plug, plugged into the wrong jack. Now I see you found the problem. Good catch, but I have had the same problem with a speaker change out, and the customer plugged the speaker cable into the other, auxiliary jack. 😀

[r.weaver]

I like using a 5751 in V1 on my Blues Jr. headroom seems to stay a little cleaner at a higher volume.

[mrbigg]

Ready to get my two amps done with your mods.

[goodun]

Those loop-forming pliers you referred to are *expensive*, something like 150 bucks; I noticed that Brad in Australia has a set.

[waynemallette]

Do you recommend using the Dr. Watson Lion Tamer?

[Satchmoeddie]

I vehemently HATE lead free solder. "IF" I have to use it, it is usually on a bonded ceramic terminal block in Tektronix test gear, and that Tektronix spec stuff was 6% silver. I use denatured alcohol to remove flux. I have had flux remover bleach some plastics out badly, including circuit boards. One side benefit was my cordless drill had a big beached out splotch on it, so I knew it was mine from 50 yards away. Lead solder is like vinyl asbestos floor tile. As long as it is not giving off dust or smoke and you keep it out of bodily orifices and cavities, it's safe.

[johnwilliamson]

The 12av7 /5965 has the same gain as ay but higher conductance like a 12 at . 5965 works as a good cathode follower there is some room to play with the gain there.

[tjminasi]

Note to self: check/change dropping R when replacing leaky HT filter caps. Huh.