Randall RH100 issue

[bry melvin]

Even though the amp is new I would replace ALL the jacks:

I've been buying returns from musicians friend fixing them and reselling them:

About half of the returns are bad jacks  corroded contacts.

A lot of these "new amps" have spent a long trip in a container from China!

Only do this if your soldering skills are good.  It's very easy to damage the traces on these amps  So if you doubt your desoldering techniques don't try to fix waht aint broke

[Blacksack]

Well, I am not very confident in my desoldering skills (or soldering, for that matter) on circuit boards.  I got back down and took a few pictures of the headphone jack.  One with it plugged in still, one with it unplugged and one of the underside so a person can get a good idea of how maybe contacts (legs?) it has.  I wonder if Randall (or the guitar manufacturer) builds these with the specific connectors or if this might be a common component available from a retailer with the litte connector and everything ready to go already.  I looked, but to no avail.

[J M Fahey]

You will not find the little board as shown.
Maybe you can find the exact same jack, *somebody* must have it, but sometimes catalogs don't have good pictures to help you choose.
Not even Randall shows the headphone out schematic, just a little square where the little board is plugged.  :duh
I would just bypass the whole thing (losing the headphone option, which sounds *horrible* anyway) and solder the speaker out jacks straight to the proper points in the PCB.
The little "phones" rectangle shows 4 pads which *should* be labelled so in the PCB:
PA+ / Ext+  <-- join them with a small piece of wire  and
PA-/Ext-   <-- do the same
Now you have bypassed (and killed) the headphone out.
Cover the jack with a piece of tape, so nobody ever uses it.
Now to the "4 ohm out" , do a similar thing:
just in case, post pictires of it, both above and below the PCB.

We are bypassing and killing two troublemaking connections, which anyway are never used.

[joecool85]

If you do Juan's method, I would take it one step further and remove the "phones" plug and board all together and simply wire nut the appropriate wires together.

[Blacksack]

I apologize for letting this sink into the oblivion for yet another couple weeks.  I have some photos to upload before I started wire nutting, soldering or anything else.  I am not exactly sure what points I need to connect together to bypass the phones jack and the 4 ohm.  The first picture is a close up of the 4 ohm board and the wire connections on it.  There is a ground switch on the left and the two jacks for the 4 ohm parallel.  The second photo is a close up of where the two big wires meet at points labelled SP+1 and SP+2 on either side of a large coil-butron labelled L1.  The third photo is a larger, overall shot of the whole unit, the phones jack belonging in the upper left hand corner and the 4 ohm board in the lower left hand, respectively. 

[joecool85]

I apologize for letting this sink into the oblivion for yet another couple weeks.  I have some photos to upload before I started wire nutting, soldering or anything else.  I am not exactly sure what points I need to connect together to bypass the phones jack and the 4 ohm.  The first picture is a close up of the 4 ohm board and the wire connections on it.  There is a ground switch on the left and the two jacks for the 4 ohm parallel.  The second photo is a close up of where the two big wires meet at points labelled SP+1 and SP+2 on either side of a large coil-butron labelled L1.  The third photo is a larger, overall shot of the whole unit, the phones jack belonging in the upper left hand corner and the 4 ohm board in the lower left hand, respectively.

Can you post a picture of the bottom of the board that shows where the phones and output jacks are?

**edit**
By "bottom" I mean the underside with all the soldered joints.

[J M Fahey]

Me neither.
Draw a schematic of what´s on the jack board.
Label parts as they are in the PCB, wire colors, connection points, etc.

[Blacksack]

Yes, I can do that.  I think there are five seperate PCBs, the tiny one with the phones jack (pictured in an earlier post), the larger one with the 4 ohm paralell jacks, an Identical one on the other side with the speaker outputs and the send/return jacks, a larger one in the center where the two large black round ...apparatuses... are and finally the largest PCB with all of the control knobs.  I'll take a photo of the underside of the 4 ohm PCB and try to label what is what.  Taking photos of the other three would require some intense dissasembly, I'll do it if it will help.  Lemme know, and thanks again!

[Blacksack]

So, my guess would be that the amp is switching grounds here, as I think the black and the blue from the 4 ohm are both grounds and the black and the blue on the "phones" jack look to both be grounds.  Here are some photos, two more of the "phones" jack PCB (top and bottom) and two of the 4 ohm PCB (top and bottom).  If they are just swapping grounds on me, could I just run the correct wire directly to ground on both jacks to bypass the jack switch?  Ugghhh...

[Blacksack]

So, does this sound like the right path?  If so, which one needs to be grounded, or do they need to be tied into each other and then grounded?  Or am I totally off base...?  :loco

[joecool85]

So, does this sound like the right path?  If so, which one needs to be grounded, or do they need to be tied into each other and then grounded?  Or am I totally off base...?  :loco

I think you are on the right path.  To check, try using a wire to "jumper" the appropriate pins and see if it does what you want it to.  If it does, solder the wire in.

[Blacksack]

I tried jumping the phones connector. I wiggled the cables. I plugged and unplugged connections on the circuit board. I rigged this connector to that ground, on and on and on. I can't get the damn pile of crap to work! So then, I plug my cab into the 4ohm output instead of the "line out" jack. Everything works and sounds normal. What is the 4ohm jack used for normally and can I just use it as my dedicated "line out"? And does this make anything more evident as far as the problem?

[joecool85]

I tried jumping the phones connector. I wiggled the cables. I plugged and unplugged connections on the circuit board. I rigged this connector to that ground, on and on and on. I can't get the damn pile of crap to work! So then, I plug my cab into the 4ohm output instead of the "line out" jack. Everything works and sounds normal. What is the 4ohm jack used for normally and can I just use it as my dedicated "line out"? And does this make anything more evident as far as the problem?

"Line out" is for connecting to a PA or recording device, your speaker cab should always be connected to "speaker" etc.  In this case "4ohm" is where you would connect your cab.  Out of curiosity, have you been trying to drive the speaker cab with "line out" this whole time?

[J M Fahey]

I can't get the damn pile of crap to work! So then, I plug my cab into the 4ohm output instead of the "line out" jack. Everything works and sounds normal.

You must be joking         

[phatt]

Just plowed through all this,,, phew

Best bet is remove both H/phone socket and line out,,, then take the speaker hot directly to the *Speaker out socket* (I''m assuming the speaker common is already soldered to that socket)

Oh do remember that speaker common is ground lifted so it's not chassis or circuit common.
If you do ground it the amp will run hotter.
Phil.