Crate GX-15 not outputting sound anymore

[CowPunk]

Hello all, and sorry if this is a repeat question. I did a quick search of the forums, but didn't find anything specifically helpful.

Here's what's going on:
A few weeks ago I was having a jam session on my GX-15. Trying to be courteous to my housemates, I plugged in a set of headphones for the duration. Everything played as normal, and I played for about an hour and a half before shutting everything off again for the night. The next night, I had the house to myself for a few hours and excitedly powered everything on to get ready for a much louder jam session. To my disappointment, there was absolutely no sound coming from the amp on power. Usually when I flip the power switch I get a "pop" noise, and it has done that for at least the last 5 years or so. This time it was total silence. I fidgeted with it a while before I determined that the amp had just died. After about an hour it dawned on me that I should try to plug the headphones back in and see if I get any sound. So I tried, and the test was successful. I can still get sound out from the headphone jack, but not from the amp speaker itself.

As of now, I've used contact cleaner on all 3 jacks on the amp (input, headphone, and speaker). I figured if I was going to do one, I may as well do all three.
The speaker in the amp is rated at 4ohms, using a multimeter, I tested the impedance of the speaker to find that it is outputting 3.7ohms, which to my understanding is correct.

I can only be lead to believe that when I removed the headphones the first time, there was some type of switch in place that didn't send the signal back to the speaker. I'm relatively electronically-inclined, but I've never taken apart a guitar amp before, nor have I ever replaced or repaired any components on one. I wanted to post here to ask for any helpful suggestions, tips, or guidance to any other areas I should be examining first if there are any. Thanks in advance for any help any of you may be willing to offer!

[J M Fahey]

You did right.

Suspect is still the headphone jack.

Contact cleaner addresses one problem: dirty/rusty/grimey contacts but if leaf switch (the metal strip itself which is both pushed open by plug tip *and* makes contact with it) is worn/weakened then it might not make contact again with another metal strip in the jack which is the speaker contact.

You may push it down with a chopstick or plastic pen and it should restore contact, but it will be temporary, you must replace that jack with a new one.

Notice the top and right flexible contacts which touch the fixed left side ones when nothing is plugged:





There is a second possibility: the solder on the jack pin towards ths speaker is cracked so when you plugged the headphones it lost contact, so resolder all jack connections to PCB ... which you will do anyway when replacing the jack

[CowPunk]

Thank you Juan!

I'm glad to know that I was on the right track in my thinking. Since my original post I've removed the circuit board from the cabinet to take a look at things. I really just wanted to make sure that the capacitors were still in good shape (not swollen or leaking). Based solely on observation, I've noticed that the contacts on all three jacks show signs of oxidation. Since I already have the board out, I intend to just go ahead and replace all of the jacks.

This is where my inexperience shines brightly.

I tried searching Amazon for replacement jacks, but am blown away by how many different types of jacks are available--to the point that I don't know what I need to buy. Would you be able to point me in the right direction, both with types of jacks as well as brands? For example, the input jack and speaker jack both have 1 less contact than the headphone jack (much like the pictures linked above). I assume the third contact is actually the switch the re-directs the audio to the headphones, but that's just assumption.

Lastly, I've never soldered anything in my life. I understand the process, as it is similar to welding, on a much smaller scale, but I've never actually done it before. In an effort to not damage the circuit board, how do I break off the old solder points without causing any damage and with what type of soldering iron and wire would I need to buy?

With the aforementioned, is this project something that's worth doing myself or should I just go ahead and take the board to Guitar Center (the only shop I'm aware of in my town, unfortunately) and have them repair it for me?

[fastfolkert]

If you have access to a soldering iron, you might try to re-solder all pins of the jacks first. Just reflow the solder "islands".
In my experience with similar jacks, there's a good possibility this will cure your problem (together with cleaning the spring-loaded contacts, as you already did)

My 2c.

[J M Fahey]

You wonīt need *all* that is shown in these videos, just:
* 30/40W soldering iron.
* some 1mm diameter good solder for electronics use: lead-tin mi: 60-40 or 63-37 (better)
* one small roll of desoldering braid
* one desoldering pump

* optional a soldering iron stand as shown but if you will use it today and never again you can use a heavy glass or ceramic ashtray (so it stays there) to hold the iron while itīs hot but not in your hand and a ball of wet but squeezed cotton to clean the iron tip if you see grime or oxidation on it (after a few minutes)

almost forgot: buy a small experimenterīs board as shown to practice .
Next video: a better one on how to unsolder.

Although GC is an option, of course, itīs nice to practice and keep tools for some future use, even if only replacing some bad cable plug.
That alone is worth learning.

[J M Fahey]

This desoldering video actually has some errors but Iīm using it on purpose: the guy is using a *cold* iron (whether itīs low powered for the job or he just turned it on, you must leave it on at least 4 or 5 minutes) , solder must melt at once when touched (1 or 2 seconds tops), at the beginning heīs shown scratching solder with the iron tip, a guarantee to tear the pad off.

Iron works fine from minute 4:51 on, go back and forth and compare that to earlier attempt at , say, 1:31 .

Iīm including this nevertheless because thatīs a common beginner mistake.

A common misconception is to think: "Iīll use a smaller iron (say, 15W) so I donīt overheat the part.
The opposite is true: heat takes a few seconds to travel along the part leg, a hot one will be in-out in 3 or 4 seconds tops; a cold one will be there forever, so heat has ample time to reach the partīs "heart" and kill it, or melt far away plastic.

[CowPunk]

UPDATE/EDIT:

As it turns out, the guitar shop around here doesn't repair the jacks. They referenced me to another shop in the area with overwhelming bad reviews, so it looks like I'm taking the dive and buying a soldering iron today.

If you have an suggestions for replacement jacks, I'd be thankful. Elsewise, I'm off to Amazon to see what I can find.

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Thank you again for all the suggestion

I think for the sake of cost, I'm just going to take the board to the shop and have them repair it for me. I think it will probably come out cheaper that way.

I will get a soldering iron and a practice board in the near future, because I do want to be self-reliant in making my own repairs-So I'll bookmark this thread and reference it when I'm ready to make the dive into owning my own equipment. Thanks again for the recommendations.