GX212 won't power up

[jstone54]

Hello everyone,

I'm new to the site, so I'm not quite sure if this is the right place, but I'll give it a whirl anyway.

I recently acquired a Crate GX-212 with what I'm assuming was a fault Power Transformer/power supply. When I got it, the amp would only come on after you hit either the top of the amp, or the power transformer.

After discovering this I proceeded to remove the chassis. I don't have a work shop and handled the whole thing pretty clumsily; setting it down kind of hard and having it slide and fall a few inches.

Once I got the chassis removed, which was a process of its own as I am new to the inner workings of amps, I proceeded to remove the power transformer. I got a little ahead of myself and didn't take a before hand picture of the wiring so I could replace it just right and schematics don't seem to be helping.

It's been a few days now and no matter what I do I can't get the power to come back on at all. I don't know if the transformer has gone completely caput, the wiring isn't right, or if I damaged the circuit board to badly.

Unfortunately I don't have pictures just yet. I can tell you that the transformer is 94-116-40. I'll be uploading pictures once I get out of work.

[Enzo]

Hi, welcome to the place.    A friendly tip:   Make the subject line your issue.  In other words "GX212 won;t power up" will get you better response than just "Help."   I'm not griping, just a suggestion.

And you now already know this, but I  still always draw a map or diagram of wires before I take them off of anything, and I have been working on amps over 50 years.  Never rely on memory.

Before, if you hit the top of the amp, it would come on.  Or if you hit the transformer.   Thing is, when you hit the transformer, it is about the same thing as hitting the chassis.  The transformer is bolted down tight to the chassis, so any hit you deliver to the transformer will also send a jolt through everything else too.  I'd wager it was not the transformer's fauly.

Something probably needed to be resoldered.  By not coming on, may I assume you mean zero signs of life, no power light, no nothing?   Or did you just mean no sound, but the lights come on?   I will assume completely dead for now.

To work, you need to get mains voltage to your transformer primary.  The part number you gave is for the universal/export power transformer.  Are you in the USA on 120v mains?  Or are you elsewhere on 240v mains?  The schematic shows wiring for both options.  A loss of power on the primary side can be from:
Bad/failing power cord
Bad/loose fuse holder (or even shaky fuse itself)
Bad/failing power switch
Wires off connections
Broken solder on any part of that

And yes, a bad transformer is possible, but really is the last thing on any repair list.  They fail rarely.

The white and black transformer wires are the primary.  For 120v, they go on posts J17 and J19.  If you have 240v mains, then the brown wire and white wire go on those posts.  DO you have mains voltage between those two posts? (Assuming the amp is plugged in, has a good fuse and is switched on)   If not, it should be simple eneough to find where it is interrupted.

I have no idea, but I'd bet the secondary wires are red.  But no matter.   You can check the transformer windings for opens.  Is the primary intact, does it have continuity?  Is the secondary intact?  Is there continuity end to and and to the center tap?

[jstone54]

Thanks for the welcome and the tip,

Normally I'm a little more thoughtful when it comes to taking something apart, (I'll take before pictures and draw maps) but I think I was a little too excited when I started this project.

I got the amp second hand so I was unsure of when the problem started or how. It had difficulty turning on and cut out when a guitar was played through it.

I'm adding the two pictures I have with me to this. One is just a general over shot of the circuit board with most of the wiring disconnected and the other is a close up shot of where the transformer wires are supposed to go. I've already re-soldered the J17 tab that was missing (this wasn't the problem, it came off when I was disconnecting some of the wiring).

[Roly]

Welcome!

Yup, that's an amplifier all right.

Now Enzo asked you two specific questions, and this is how it works, we ask questions, you provide the answers, then we ask more questions or tell you to do stuff and you report results.  Until you answer or provide results we can't move on to the next step.

By not coming on, may I assume you mean zero signs of life, no power light, no nothing?   Or did you just mean no sound, but the lights come on?

Are you in the USA on 120v mains?  Or are you elsewhere on 240v mains?

[jstone54]

My apologies!

There is no sound and no lights 100% dead and I am in the USA.

[Enzo]

Thanks, so then the question remains - is there 120v between posts J17 and J19?  That is where the transformer wires will go, but if there is no 120v there, connecting the transformer will not change that.

And again, we take this voltage reading with the amp plugged in and turned on.

[jstone54]

Ok, so I decided to check the fuse and its burnt out. So it seems I dug myself a pretty deep hole for an easy fix. Thanks Enzo for all of your help. If I still have problems when I get the fuse, I'll be back to bug ya some more. Have a great day.

[J M Fahey]

Build and use a lamp bulb limiter or I suspect you will burn truckloads of fuses.
Search this forum for it.

[jstone54]

New problem! The amp now powers on and emits sound, but it's very low and none of the potentiometers are working. Anyone have any Ideas?