What to do with broken amp?

  • Thread starter Thread starter RideTheCrash
  • Start date Start date
RideTheCrash

RideTheCrash

Member
About two years ago my brother got one of those bass starter pack things that came with a Fender Frontman 15b (it's 38 watts though, not 10...like I keep reading on the internet). The input jack got very loose after a while, though cables were barely put in and out of it, they usually stayed there.

So one day no sound will come out, just a very loud obnoxious buzz sound. My girlfriend's father repaired it...I guess the deal was the little wire connected to the jack had come off (he made it sound like it had rough use on the jack, which it didn't...probably just a piece of shit). He said if it broke again there was no more that could be done unless you really wanted to do a big job or whatever.

Well go figure, the thing worked for a while...the cable was taken out one night for a practice, he came home, pulled her in...and the same buzzing was back with no sound. That was a while ago now, it's been months and it's been sitting in his closet. They figure they might as well toss it this week if it's of no use.

Well, me being a packrat myself, I don't see it as total junk. I wouldn't mind getting it working again, because it's a waste of an amp and brother need anything fancy...plus he's been using my '70s Yorkville bass combo...so you know. Of course I can take the speaker out of there, it's 8" but might as well.

I opened up the back of the amp tonight and I didn't see any little wire connecting to the input...not even hanging off something like it was broken, it was like it never existed.

This is the inside (was hard to get a decent picture, and beware of the size of the picture for you users on slower computers).
http://www.freewebtown.com/smsessions/frontmanjack.JPG

The black thing on the right is the jack...is there any way to fix it up without it being a pretty big job?
 
Replaceing a jack is no big deal if you are at all handy with a soldering iron. If you don't trust yourself to do it, any repairman should be able to fix it in a few minutes and it shouldn't be too expensive. Also a repairman can tell you if there is anything else wrong, depending in if there is or not, and how much it will cost to fix you can decide if it's worth it or if you want to scrap it.
 
I have been carrying a one of a kind broken amp around with me for thirty years now. One of these days I am going to have it fixed.
 
Oh yeah, see the deal this wire or whatever had already been soldered back on once so he claimed 'there would be nothing left to solder on to'.
 
The drag with this is that it's a relatively simple fix that will cost more than that particular amp is worth to have done at a typical shop. :( It's more of a mechanical repair than anything else. If the traces on the PCB are damaged, then they'll have to be bypassed with wires. Most amp nuts would replace it with a Switchcraft-style chassis-mount wired jack, though if I were doing the repair, I'd just wire the existing jack back into the circuit separately from the board just to prevent this from happening again.

That's a really idiotic way to mount a jack, I must say, even by the standards of PCB-mounted jacks, as it looks like the slightest mounting looseness will cause it to break from the PCB in use. What was Fender thinking?
 
If you go here to the Fender schematics site and download the .PDF for that amp (sorry, for some reason I can't scrounge a direct link with this Linux browser), you'll see that this is a bone-simple fix. Look in the upper left corner of the schematic.

All you have to do is remove the jack from the PCB, wire the tip lead to the junction of R1 & R2 and run the other two leads to chassis ground (yours looks to be a later revision than the '99 circuit, but the needed connection should be clear on examination or by metering from up top).

Done.
 
Last edited:
Thanks. Unfortunately I wouldn't know how to do any of that, not sure if it's worth having him look at it again..hmm.
 
Another possibility...check with the electronics department at your local community college, sometimes you can get repairs done by students just for the price of parts and a replacement jack should be less than $10.
 
Dani Pace said:
Another possibility...check with the electronics department at your local community college, sometimes you can get repairs done by students just for the price of parts and a replacement jack should be less than $10.
Click to expand...
The jack probably doesn't even have to be replaced. I don't think that the board even has to be removed. The jack just has to be cut loose from the board (assuming that it's not making good contact there because of being busted loose from the traces) and wire jumpers run as described above. A five-cent, quick-and-dirty repair that'll cost you $80 at a shop because of the bench minimum. The contacts in the jack may have to be tweaked to give firmer contact with the plug, perhaps, I dunno.

If the jack is physically damaged, it can be replaced with a standard Switchcraft-style, normally closed 1/4" phone jack, a Radio Shack kind of part.

Honestly, I could have done this repair in less time than I've spent writing about it in this thread.
 
When you refer to the wire jumpers are you referring to the post where you mentioned R1 and R2? I know nothing about this sort of thing.

So I would break off whatever connections off left from the jack to the board...and then I don't know where to go from there. Are there any sort of pictures I can work from?
 
It is really as simple as disconnecting the jack from the board, then using wire to make the connections that you just cut. The idea is to connect the jack to whatever the next component in line was. You use wire to get that done.
 
I see where you're getting. So I would just get some wire, and solder (I assume) it to the jack (not sure where, seems like there are a few places it'd connect) and solder the other end to...whatever the next component in line is. Which I don't know.

So basically I need to know now:

1) Where on the jack is it soldered onto?
2) I don't know what the next component in line is
 
RideTheCrash said:
I see where you're getting. So I would just get some wire, and solder (I assume) it to the jack (not sure where, seems like there are a few places it'd connect) and solder the other end to...whatever the next component in line is. Which I don't know.

So basically I need to know now:

1) Where on the jack is it soldered onto?
2) I don't know what the next component in line is
Click to expand...

you would solder one end of a wire to a lug on the jack and the other end to the first component in line on the pcb, as mentioned above.

take a look at the schematic and see if you can make sense of it. reading a schematic is fairly simple though you might want to search on google for something like "how to read a schematic". a schematic is just a map of connections and components. you just need to find out what all the little symbols and letters are.
 
Last edited:
Think for a second.


The part of the jack that attatches to the board is the connection. The board has traces (the lines on the circuit board) if you follow the traces, you will find the next component.

You need to follow the 2 traces that the jack was hooked to. Then connect the 1st connection on the jack to where that trace went, and the second connection to where that went.
 
RideTheCrash said:
I see where you're getting. So I would just get some wire, and solder (I assume) it to the jack (not sure where, seems like there are a few places it'd connect) and solder the other end to...whatever the next component in line is. Which I don't know.

So basically I need to know now:

1) Where on the jack is it soldered onto?
2) I don't know what the next component in line is
Click to expand...

If you will be soldering to the circuit board or another component that is connected to it, you will need to be careful not to heat the board up so much as to to melt the plastic or lift the copper traces. What I think works best is a very hot iron and touches of very short duration.
 
ggunn said:
If you will be soldering to the circuit board or another component that is connected to it, you will need to be careful not to heat the board up so much as to to melt the plastic or lift the copper traces. What I think works best is a very hot iron and touches of very short duration.
Click to expand...

good advice. let the iron get nice and hot and make the connection quickly. make sure the soldering tip is cleaned and tinned too. it will also make things easier if you pre-tin all of the lugs/wire ends.
 
RideTheCrash said:
I see where you're getting. So I would just get some wire, and solder (I assume) it to the jack (not sure where, seems like there are a few places it'd connect) and solder the other end to...whatever the next component in line is. Which I don't know.

So basically I need to know now:

1) Where on the jack is it soldered onto?
2) I don't know what the next component in line is
Click to expand...
I essentially answered these in a previous message.

This isn't a "head" problem, it's a "hands" problem. The fix is as electronically simple as it can possibly be (again, look at that schematic and you'll see what I mean), but will require a bit of manual dexterity to do without removing the whole dang PCB to do this the "right" way. If you have good dexterity and can normally do delicate work, give it a try. If not, run this fix by someone who does.

Your "hot" lead on the jack is the one that comes from the contact that grabs the tip of your plug on the guitar cable. It looks like the uppermost lead off the jack in your picture, but check. The lug coming off that is where you'll be soldering your hot wire.

I'd just unscrew the nut off the front of the jack to get it loose from the chassis, reach in and clip the jack leads off the circuit board with a pair of diagonal cutters (watch out for the light blue capacitor right above it) and remove the jack from the amp.

Then I'd inspect it thoroughly to see that it was making good contact with your cable plug when it was inserted. It appears that you just have two leads on the jack that are connected to anything in the picture -- the tip and the ground.

To see where the top lead was going if you can't clearly see the back of the PCB, you can just shine a flashlight behind the PCB in a dim room and it will light up the traces like an X-ray so you can see them from the front. You can also figure this out with a meter.

That tip lead on the jack should have been connected to a trace running over to one of those resistors to the left of it in your picture (surounded by those dark blue electrolytic capacitors that should carefully be pushed aside to give you some room to work). What you'll have to do then is just wrap the stripped end of an insulated wire around the exposed lead of that resistor up on the top of the board and solder it. This is simple to describe, but requires some soldering skill to do properly because of the tricky location and the need for cleanliness, speed and a good tight connection prior to soldering. The other lead from the jack has to go to the circuit ground, which is accessible in a lot more convenient places on the PCB. Remount jack and rock out.

This kind of bonehead repair covers about 80% of professional amp servicing -- just simple (or kludged, like this) replacements of obviously damaged parts and connections. Really.
 
TravisinFlorida said:
good advice. let the iron get nice and hot and make the connection quickly. make sure the soldering tip is cleaned and tinned too. it will also make things easier if you pre-tin all of the lugs/wire ends.
Click to expand...
To do the repair the way I described, pre-tinning will make it very difficult, as you have to do a lot of wrapping of the wires, which is very hard or impossible if they're tinned because they become too rigid.

A tiny dab of flux, on the other hand, will do the same job and better in this kind of situation. Everything has to be superclean, tinned or fluxed. Pick one. :p

Speed is completely essential in this particular kind of fix to avoid overheating the component and/or loosening the PCB solder joint -- second only to a tight "mechanical" connection of the wire prior to soldering.

When I was doing this sort of stuff for a living, I doubt I ever had contact with a PCB solder joint for more than a third of a second.
 
Yeah I see the need for having to be quick and precise because of possible overheating. I understand like 99% of what you're saying, took me a second, but it makes sense. I think I'll explain what to do when I take it to my girlfriend's dad and he can solder that on, because I'd melt something for sure...

Thanks guys.
 
You must log in or register to reply here.
Back
Top