Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Sonny ReVerb on August 29, 2021, 11:12:40 am
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So I was living in an apartment complex a few years back. I went to the dumpster to throw out some trash and spotted an amp inside. I picked it out and took it home with me. It turned out to be a Fender Frontman 15G. I plugged it in and it didn't work, of course. I tried replacing the power MOSFET, but it still didn't make noise. I don't care for SS amps, but I thought I could maybe stuff some tube circuit in there someday.
Here's what I came up with. It's basically a Vibro Champ circuit with a diode rectifier. The front of the amp is largely unchanged, but the back shows it's true nature. The four knobs on the right are as labelled. The left 'Volume' is trem Intensity and the 'Gain' is trem Speed. The RCA 'Aux In' jacks are the trem footswitch jack. The 'Head Phones' jack is n/c.
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I first tried to keep the original speaker, but it was pretty lackluster, especially with the closed back. I decided to try a WGS G8C and open up the back. This helped the tone immensely, but it's still a small amp sound.
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One issue I failed to consider was a chassis mounting screw that ended up behind the PT. It took me about an hour with an angle screwdriver to get that sucker screwed in. I hope I don't have to open it back up anytime soon. I'm not sure I would recommend you try this at home, kiddos, but it was a fun, one off project.
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What about a screw or bolt with an allen wrench instead of screw driver? Since allen wrenchs use 90 degree angles
With respect, Tubenit
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That would definitely work better. I even thought about using a pin, because the screws at the back of the chassis effectively secure it. I was just trying to use original hardware. If I have to take it apart I'll come up with something better.
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Very nice build!!!!! :bravo1:
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That's really nice!
Last year my neighbor gave me a broken Frontman 15 and I did a similar thing; I stuffed an AC4 with Tremolo in the cabinet.
Funny, I'm now using the exact same speaker in mine. :icon_biggrin:
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Thanks, guys! That's a cool looking AC4! I'm happy with the WGS speaker. I've used a few of their other speakers, too (ET65, ET10, G12C/S). Haven't found a bad one yet.
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Looks like I will be taking it apart. I must have missed a solder joint or something is making contact where it shouldn't.
https://vimeo.com/597876692 (https://vimeo.com/597876692)
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I finally tore this amp apart this afternoon. The crackly noise turned out to be a bad solder joint on V1 pin 3. It only made the crackly noise when I tapped on it or at high volume settings (i.e. vibration). She's back together now and sounding the way she should. It's pretty frustrating tracking down these issues, even on an amp as simple as this. I've had pretty good luck on most of my builds. Keeping my fingers crossed...
I replaced the buried screw with a hex head. There's not enough room to get a socket wrench in there, but an open end wrench worked well enough.