Moddjobbs

Moddjobbs Tube amp repair, restoration, and custom builds in Dalton, MA. Over 25 years of hands-on experience with vintage Fender, Marshall, Ampeg, Hiwatt, Vox and more.
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Thoughtful service and real bench experience. Custom Tube Amp Building, Repair, and Restoration
Musical Equipment Repair Service and Sales
Audio Consultation

Fresh off the bench: a lacquered-tweed Blues Junior LTD that came in with weak, poor-sounding output, traced to a failed...
09/03/2026

Fresh off the bench: a lacquered-tweed Blues Junior LTD that came in with weak, poor-sounding output, traced to a failed power tube.
While it was here, it also received selected capacitor and component upgrades, a metal input jack and output-cable plug, along with a bias adjustment.
These little 15-watt amps are very common, and I see quite a few come through the shop for some TLC. This one is back together and sounding sweeter than ever!

Blues Junior owners, what have been your favorite mods or speaker swaps?

Go for the Gold! :)This ’65 Princeton Reverb is getting (among other things) a new Mojotone baffle and Celestion Gold.Sp...
07/23/2026

Go for the Gold! :)

This ’65 Princeton Reverb is getting (among other things) a new Mojotone baffle and Celestion Gold.

Speaker choice in these little amps is always a fun debate / discussion. I know everyone has their favorites.

What’s your go-to speaker for a Princeton Reverb and why?

This beautiful 1962 Fender Concert was on the bench today for some routine maintenance.Many many years ago when I was fi...
07/10/2026

This beautiful 1962 Fender Concert was on the bench today for some routine maintenance.

Many many years ago when I was first getting into tube amp repair (after years of guitar pedal repair and mod work), I replaced the original filter capacitors with I.C. electrolytics.

At the time they were a common replacement choice, but over the years they’ve developed a reputation for leaking. This set was beginning to show the early signs, so it was time for another update.

The amp received a fresh set of German-made F&T filter capacitors, and a few cathode bypass along with new power supply dropping resistors.

One of the things I enjoy about this work is that you’re always learning. Components, techniques, and best practices can evolve and change over the years, and I’m honestly happy to revisit my own work when experience points to a better solution.

It’s all part of keeping these amazing amps healthy and able to be enjoyed for the long haul! :)

Hello everyone! I recently added a free tube bias calculator for my website and figured I’d share it here in case it’s u...
07/10/2026

Hello everyone! I recently added a free tube bias calculator for my website and figured I’d share it here in case it’s useful to anyone else

https://www.moddjobbs.com/tube-bias-calculator

It handles both fixed-bias and cathode-biased amps, and calculates:

• Plate current
• Plate dissipation (watts)
• % of maximum plate dissipation based on tube type

And provides some useful information on zeroing in on your bias range quickly

I originally built it for my own use because I wanted something that was quick to use on the bench.

If you get a chance to try it, I’d genuinely appreciate any feedback from others. If there’s something you’d add, change, or if you spot anything that looks off, let me know. I’d like to make it as useful as possible without being too dense or inaccessible! :)

1994 Vox AC30 on the bench for electrolytic caps and power tubes.Spotted “A.I.” marked right on the PCB, which got me wo...
06/06/2026

1994 Vox AC30 on the bench for electrolytic caps and power tubes.

Spotted “A.I.” marked right on the PCB, which got me wondering what model was powering this thing back in the ’90s. Seems like Vox may have been ahead of the curve on this one. 🤣

70s Fender Champ getting fitted with a Jupiter 4 ohm alnico speaker.I always enjoy these little amps. Simple, classic, a...
05/04/2026

70s Fender Champ getting fitted with a Jupiter 4 ohm alnico speaker.

I always enjoy these little amps. Simple, classic, and a good speaker can really wake them up.

This one should be a nice match!

Working through a little different approach on a 1979 Champ with a really bad conductive fiberboard issue. Understood th...
04/20/2026

Working through a little different approach on a 1979 Champ with a really bad conductive fiberboard issue.

Understood that not everyone will love moving away from the original approach here, but I’ve seen enough of these to know that once the board gets conductive, they generally do not come back well.

So rather than pretend otherwise, I’m working through a clean discrete filter cap layout and started with a laser-cut paper template to test the idea before committing to anything.

Still in progress, but this kind of problem-solving is always fun when it can make a cool amp like this more stable and serviceable again!

One worth pointing out from the bench:This 1971 Super Lead came in with a 3-prong plug fitted onto the original 2-conduc...
04/10/2026

One worth pointing out from the bench:

This 1971 Super Lead came in with a 3-prong plug fitted onto the original 2-conductor power wire, along with some pretty cooked screen resistors and filter caps that were well past due.

From the outside, At a glance, that plug swap can look like a safety upgrade. In this case it’s actually a wolf in sheep’s clothing. A 3-prong end by itself does not make an amp properly grounded or safe. The mains wiring inside the amp still has to be reworked correctly so the chassis is actually at ground potential.

This one’s getting the AC side sorted out properly, along with new filter caps and the rest of the service it needs to be solid again! Looking forward to hearing it roar back to life! :)

Fender Deluxe Reverb on the bench for some well needed service! This one got fresh filter caps, a new reverb tank, and a...
04/09/2026

Fender Deluxe Reverb on the bench for some well needed service!

This one got fresh filter caps, a new reverb tank, and a new rectifier tube.

I also replaced the molded 1/4” speaker output lead with a hand-soldered metal plug. Those molded ends are a pretty common failure point on these, and it’s one of those small details that’s worth taking care of while the amp is apart.

Nothing flashy here. Just good maintenance and a few smart fixes to keep a good amp solid and dependable.

Had a little “Carr” show at the shop this weekend! Mercury V, and a Vincent in for some TLCDefinitely not textbook circu...
04/04/2026

Had a little “Carr” show at the shop this weekend!

Mercury V, and a Vincent in for some TLC

Definitely not textbook circuit layouts or builds, but then again these don’t sound like textbook amps either. Always interesting getting to look under the hood on amps like these!

Address

63 Flansburg Avenue Suite 250
Dalton, MA
01226

Opening Hours

Monday 11am - 4pm
Thursday 11am - 4pm
Friday 11am - 4pm
Saturday 11am - 4pm

Telephone

+14136134870

Website

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