Fender G-DEC Junior troubleshooting

[Boreas]

Don't judge me, but I have been a happy owner of a G-DEC Junior for many years. I bought it new for a specific purpose - a cheap modeling amp for my basement. I have several other Fender amps upstairs that I don't want to leave in the basement.

Here's the issue - over the last few months, the "Amplifier" modeling knob is slowly crapping out. Specific amp choices are louder than others, and some no longer work at all. Tweed and 2 of 3 Blackface settings no longer produce much, if any sound. I am going to tear it apart and try to clean the switch with Deoxit to see if it is just a contact issue. If this doesn't work, how can I tell if the problem is in the switch or the circuitry? I have never done much with SS amps before and expect I may may just junk it (and buy a Fender Mustang LT-25), but I would like to give fixing it a try. Thoughts?

 

[Jon Snell]

There is lots of digital processing going on in this amp, the digital bits are unlikely to be the issue.
Check the switch/controls first.
They don't like getting damp.

 

[Peegoo]

The switch you're having trouble with is a digital rotary encoder.

Fender cheaped out on this control on the G-DEC and Super Champ XD amps, and they just wear out.

While it's worth trying some cleaning solution in the control, in most cases it does not resolve the issue and the control must be replaced to return the amp to full functionality.

 

[Boreas]

The switch you're having trouble with is a digital rotary encoder.

Fender cheaped out on this control on the G-DEC and Super Champ XD amps, and they just wear out.

While it's worth trying some cleaning solution in the control, in most cases it does not resolve the issue and the control must be replaced to return the amp to full functionality.

Thanks a bunch!! That was my suspicion. It started dropping selections a year or two ago. I really never used it much preferring the "Clean Blackface" setting for just about everything. That is why I am thinking it might just need cleaning, but who knows.

Before I dig into it, is there much trouble replacing the switch? I downloaded a schematic and layout, but I have not set eyes on the switch yet - rainy day project. Expensive? Source?

I am hoping to trade it for a Fender Mustang LT-25 and hope I would get a few bucks for it. If not, I will just throw it on the pile of past mistakes and failures cluttering my house.

 

[esseff]

I've had two G-DEC 15s and one G-DEC 30. The main problem with these amps is worn or dirty encoder tracks causing selection jumping. Both 15s are now on my spares shelf; I've stripped them and cleaned the encoders twice, which extended their life but they've now reached the end of the road and spares aren't available. The Thirty is starting to give problems now.
You may have some luck with your Junior by cleaning the wiper tracks but who knows how long the fix will work...
G-DECS are/were great little jamming aids but the hardware eventually let them down.

Note - cross posting with Peegoo's comment!

 

[Jon Snell]

Lots to choose from here; https://uk.rs-online.com/web/c/passive-components/rotary-encoders/mechanical-rotary-encoders/?sra=p

 

[Peegoo]

Source?

Replacements became impossible to find starting about eight years ago. You can sometimes scavenge one from an old amp that broke somewhere else in the circuit, but that's rolling the dice.

You can crack it open and have a go like this:

 

[Boreas]

Replacements became impossiblle to find starting about eight years ago. You can sometimes scavenge one from an old amp that broke somewhere else in the circuit, but that's rolling the dice.

Thanks again. I just ordered a lot of 2 NOS on eBay for $9.50. I will try to remember to post my results when I get them and dig in to the amp.

 

[esseff]

Lots to choose from here; https://uk.rs-online.com/web/c/passive-components/rotary-encoders/mechanical-rotary-encoders/?sra=p

The closest specs I found wouldn't fit the circuit board. A shame because it wasn't expensive.

 

[Peegoo]

You found some on fleabay?

Do they look like this? They are a pretty specific part.

 

[esseff]

That part number seems to tie up with the G-DEC Junior manual on page 8. (It's a good link, I've checked it.)

https://www.google.com/url?sa=t&rct...unior-SM.pdf&usg=AOvVaw1mPBBhd8K6zuPipS8aKjpS

Encoders for my model aren't around any more (006972700 16 position 4 bit grey rotary).

 

[Boreas]

You found some on fleabay?

Do they look like this? They are a pretty specific part.

Well, it turns out no. The ones I bought are CTS... 3X3 vs 5 inline. Oh well, I'll just add them to the pile!

 

[Boreas]

Anyway, I couldn't wait. Opened her up and tore it apart expecting to have to replace the control. Some gut shots:

I applied contact cleaner to all pots and controls at the shaft as that was the only opening I could find with them in place. No access ports. But cleaning the control actually worked and I got my amp settings back - at least for now. I will continue to look for Fender replacements, but will also start saving for that Mustang amp...

Thanks all for the help! Next time, I won't bother tearing the amp apart since I can apply cleaner by just removing the knob. Learn something every day.

 

[esseff]

Well done, Boreas; you should get another few months out of it with any luck.
I had to bend the tabs back and lift the shaft out of the case to clean mine properly. Most of the problem was wear in the wiper tracks and I didn't expect them to last for much longer. I was right.
Fender's lack of spares back-up was disappointing. Apparently when the G-DECs were returned with skipping tracks under warranty, they simply threw them in the dumpster and gave out a new replacement. Hmmm - for want of a new cost-price encoder and a couple of hours labour...

 

[Boreas]

Well done, Boreas; you should get another few months out of it with any luck.
I had to bend the tabs back and lift the shaft out of the case to clean mine properly. Most of the problem was wear in the wiper tracks and I didn't expect them to last for much longer. I was right.
Fender's lack of spares back-up was disappointing. Apparently when the G-DECs were returned with skipping tracks under warranty, they simply threw them in the dumpster and gave out a new replacement. Hmmm - for want of a new cost-price encoder and a couple of hours labour...

Thanks! I just thought of something else - I use the other 16 point switches less often than the amp switch. When this one craps out, I could always swap it with one of the others if I can't find any replacements.

I guess Fender figured modeling amps were evolving so fast that people wouldn't be interested in having these fixed. Or more likely they went through these switches like crap through a goose...

 

[Peegoo]

Hmmm - for want of a new cost-price encoder and a couple of hours labour.

The production cost for the amp, delivered to retailers, was probably around 20-25% of retail. It was cheaper for Fender to junk the amp and send a new one than to repair it.

It's not just cost of parts, labor, and shipping. It's handling (accounting, inventory, etc.). Every penny counts.

Gibson found that out not too long ago

 

[Sax-son]

I too have a G-Dec jr amp lying around. It is dead as a doornail and complete junk. It worked well when it worked but started with a static noise and eventually completely stopped. I have owned many amps over the years, but all of them are still going. This is the only one that has died that I can't fix. It had to be a Fender.