Monoprice Stage Right 15W amp rebuild

vigilante398

Authorized Vendor
I was trying to decide which thread I wanted to keep spamming with this, then I remembered I have my own section here, so I can leave everyone else alone and post my garbage here.

I'll start with background: Six months or so ago I picked up a 15W "Stage Right" amp from Monoprice when they were on sale, and it came to about $203 shipped. You can't buy transformers and tubes for that, let alone a Celestion speaker, a reverb tank, a chassis, and a pretty well built cabinet. Hard to turn down when they come on sale. But I don't need a two-channel amp, especially a Marshall-voiced one. So this morning I decided to gut it and build something new inside.

I had thrown together a layout this afternoon, then when I got home I opened up the amp to take some measurements and adjusted the layout accordingly. One benefit to this being designed for easy assembly, it's incredibly easy to disassemble, I had it stripped down to a bare chassis with transformers in under 10 minutes.

So basically this will be the EF86 channel of the Matchless DC30 feeding into the 15W power section of the Matchless Lightning. You lose the reverb because I don't want to deal with it, but I left in an FX loop. Also the Monoprice has a lower voltage tap on the power transformer to feed the opamps for the reverb and FX loop (yes they're both opamp driven there's a handful of TL072 in there), and I decided to regulate it down to 12V and use it to drive LEDs. I had an idea I want to try out, and figured half a dozen LEDs would be useful. I will still have to drill a couple holes in the chassis to mount the PCB, but fortunately the chassis is aluminum and not steel, so it won't be too bad. I can reuse the existing holes for everything else I need. Once I've verified that this is a worthwhile project I'm planning to get a replacement faceplate so it looks nice and stuff.

Screenshot 2023-11-07 224021.png

Here's the chassis for now, still need to remove the power switch and jewel. I'm trying to decide whether I want to keep the attached power cord or if I'm motivated enough to cut a rectangular hole for an IEC power cable.

IMG20231107225315.jpg


The useless garbage.

IMG20231107225325.jpg
 
I was trying to decide which thread I wanted to keep spamming with this, then I remembered I have my own section here, so I can leave everyone else alone and post my garbage here.

I'll start with background: Six months or so ago I picked up a 15W "Stage Right" amp from Monoprice when they were on sale, and it came to about $203 shipped. You can't buy transformers and tubes for that, let alone a Celestion speaker, a reverb tank, a chassis, and a pretty well built cabinet. Hard to turn down when they come on sale. But I don't need a two-channel amp, especially a Marshall-voiced one. So this morning I decided to gut it and build something new inside.

I had thrown together a layout this afternoon, then when I got home I opened up the amp to take some measurements and adjusted the layout accordingly. One benefit to this being designed for easy assembly, it's incredibly easy to disassemble, I had it stripped down to a bare chassis with transformers in under 10 minutes.

So basically this will be the EF86 channel of the Matchless DC30 feeding into the 15W power section of the Matchless Lightning. You lose the reverb because I don't want to deal with it, but I left in an FX loop. Also the Monoprice has a lower voltage tap on the power transformer to feed the opamps for the reverb and FX loop (yes they're both opamp driven there's a handful of TL072 in there), and I decided to regulate it down to 12V and use it to drive LEDs. I had an idea I want to try out, and figured half a dozen LEDs would be useful. I will still have to drill a couple holes in the chassis to mount the PCB, but fortunately the chassis is aluminum and not steel, so it won't be too bad. I can reuse the existing holes for everything else I need. Once I've verified that this is a worthwhile project I'm planning to get a replacement faceplate so it looks nice and stuff.

View attachment 60065

Here's the chassis for now, still need to remove the power switch and jewel. I'm trying to decide whether I want to keep the attached power cord or if I'm motivated enough to cut a rectangular hole for an IEC power cable.

View attachment 60064


The useless garbage.

View attachment 60066

I just use a Powercon for retrofits, so much easier and arguably a much better connector to boot. My nibble tool-fu is strong when it needs to be though!
 
One of these days I'll get fancy and move into powercon, but I have soooo many IEC connectors and cables lying around.
You can hack the ends off your IECs and put on a Powercon, just sayin. I threatened to buy a Greenlee IEC punch for eons, but somehow it never made the top of my shopping list!
 
Oh oh. Trouble in paradise. A member of TGP is reporting receiving two Monoprices at the same time with shorted PT's!!!
 
Not sure what that has to do with this thread, but good to know I guess.
Well, meaning their PT's may not last long... The post was a guy reporting the same symptoms, a member that repairs amps had two different mono's come in around the same time with shorted PT's...
 
What became of this Project?
It ended up on the back burner. Typically if there's a project I'm doing just for fun that doesn't fire up on the first try it will get shelved until either I have free time or it becomes more important. I have a good handful of pedals in the R&D queue, and I still have a half-built SLO that's more important to me than this would be. That being said if the pop-punk project that recruited me as a guitarist ends up happening, I will have consistent need of a good sounding 1x12 pedal platform, so this would move up in the queue.
 
It ended up on the back burner. Typically if there's a project I'm doing just for fun that doesn't fire up on the first try it will get shelved until either I have free time or it becomes more important. I have a good handful of pedals in the R&D queue, and I still have a half-built SLO that's more important to me than this would be. That being said if the pop-punk project that recruited me as a guitarist ends up happening, I will have consistent need of a good sounding 1x12 pedal platform, so this would move up in the queue.
I like flipping around projects just because it feels like I'm working if I work on one too long. Plus being a (retired and loving it) programmer I'm used to 'hot issues' popping up and having to shelf stuff till the fire is put out.

Just got my Metropoulos repro 2203 chassis on Monday. Shelved the 5F6A for a few days to document the layout. Doing the inside dimensions first, then I'll transfer that to an external dimensions layout to account for tabs and metal thickness....

IMG_1539.jpeg

2203 Metro Chassis blueprint.jpg
 
I've been cleaning up the workshop/music room, and staring at my abandoned Monoprice 15W made me sad, so I'm taking another swing, but something a little simpler. This time it's a Matchless Spitfire, I basically copied the Ceriatone layout with some minor changes.

View attachment 69162
I have a Lightning on the build list. It's been there a long time, and it's going to have to wait even longer, lol...

1708633720932.png
 
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