Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: maltikeks on November 03, 2022, 04:58:19 am
-
Hi,
somehow I ended up with a Mesa Boogie Dual Rectifier Roadster head, idk... it was a moment...
Anyway, I've read the Owner's manual, and there stands, that the EL is a Series EL, but...
When I plug in a cable in SEND jack I can still hear sound comming from the speaker. The FX LOOP switch is on, and I control it with footswitch. While FX is active the signal is on cable from SEND jack and in the speaker, while FX is off the signal is just in the speaker.
So... does that mean that there is something wrong with the EL? I'm not an english native speaker nor a guitar amp specialist, but I guess that if something is in series in a circuit it means that 100% of signal goes through this, am I right? There's no other meaning in english for a "series" term here?
I will be grateful for any help with this :)
Best regards
maltikeks
Edit: It only behaves like this on channel 3... other channels seem to have FX loop always active (with sound in the speaker)... the situation seems to be more fcked up than I thought... ehhhhhhhhhhh... I checked that with an osciloscope, cause I wanted to check how clean does the signal from SLAVE OUT is (really good tbh) and then I wanted to check the SEND OUT signal.
I will make some tests with footswitch, without it and then ask for help with the diagnose... :/ or maybe someone already has an idea...
Btw, anyone can help with schematic for this unit?
-
Boogie_dualrectifier.pdf (el34world.com) (https://el34world.com/charts/Schematics/files/Mesa_boogie/Boogie_dualrectifier.pdf)
didn't see the word roadster
if LDR3 is engaged, or the send jack is jacked sound could get through
-
(https://i.imgur.com/24PHzHY.png)
This is the best I can get, a screen from a YT video. Unfortunatelly, I can't find any schematic for roadster :(
Plus FX loop ON/OFF on footswitch works only on ch3, so now I wonder if footswitch is broken, or FX Loop, or both?
-
There's a switch on the return jack. When nothing is plugged into the return jack, the signal still goes through. The switch is NC, normally closed. Plug into the return jack and it opens the switch. Plugging into the send jack alone does not change this.
In your screen shot, see the wire from the send jack that goes to the return jack switch? It goes from the send jack tip to the return jack switch. The switch is on the return jack tip connection.
Plug into the return, still hear sound from the speaker?
-
There's a switch on the return jack. When nothing is plugged into the return jack, the signal still goes through. The switch is NC, normally closed. Plug into the return jack and it opens the switch. Plugging into the send jack alone does not change this.
In your screen shot, see the wire from the send jack that goes to the return jack switch? It goes from the send jack tip to the return jack switch. The switch is on the return jack tip connection.
Plug into the return, still hear sound from the speaker?
Finally, I had some time during this weekend so i checked this.
Yes, thank You, when return out is jakced the sound doesn't come through.
As for the footswitch, it turned out, that those individual per channel ON/OFF FX switches act like 'external section', so when at ON postition it can't be turn off with a footswitch, I don't think that is mentioned in the manual, but idk, maybe it's not clear enough just for me... :/
Right now, I'm trying to figure out how the SLAVE OUT works. In the manual stands:
"This 1/4” jack and control provide a signal derived from the speaker jack."
However, when the FX Loop control is switched to hard bypass, the slave out sends the very same signal (a lil bigger), that would normally come from SEND OUT. (and there is no such info in the manual). So I wonder how it's made and is it possible to make some modifications to make the SLAVE OUT less hummy, like cut it from that SEND jack and leave it connected only to the speaker (to put it in simple words).
I haven't looked inside the amp yet... :( hopefully I'll have some free time this weekend.