Getting ready to do a Metro Loop install. Used to be in electronic repair ions ago and worked plenty with a soldering iron. But it has been a while. And never worked on tube amps.
It is an older 1987x prior to them coming with an effects loop.
I looked at the metro loop install instructions and they seem straight forward. I took the information from that and looked over the 1987x schematic and am pretty sure I know where to hook everything. Was just hoping someone might come behind me and double check what I was about to do.
The install plan looks right, but those are potentiometers, not switches!
I would use shielded wire to carry the signal and ground the shield at only one end, that being on the pot side of the wire.
While you are in there I would also replace the signal wire off of each stack of input jacks with shielded wire as these stock wires make for a lot of added noise at high gain settings.
To drain this amps 450 volt power supply to make it safe to work on just turn the standby switch on while the power cable is still plugged into the wall and wait about a minute and a half and then your safe and you unplug the amp from the wall outlet.
Now is also a good time to get some spray cleaner that has a lube in it and blast some down into all the pots since the open slots are facing you and easy to get at!
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
I should have been more clear, when I say "right middle lug of switch", Im talking the metro loop toggle switch for bypassing the loop.
Absolutely agree on the time to cleanup. While Im in there I was going to go ahead and replace the filter caps as well since the amp is over 20 years old.
Thanks!
Last edited by primal on Tue Jun 26, 2018 11:41 am, edited 1 time in total.
You may want to leave the filter caps alone while you are modding for the loop. More than likely your caps are still good... most Marshalls of that vintage still fine with the original filters. Are you having hum issues? If not, get the loop in there and functional before changing something that is already working. Just a bit if advice...
"Education is what you're left with after you have forgotten what you have learned" - Enzo
dorrisant wrote: ↑Tue Jun 26, 2018 11:35 am
Welcome to the forum!!
You may want to leave the filter caps alone while you are modding for the loop. More than likely your caps are still good... most Marshalls of that vintage still fine with the original filters. Are you having hum issues? If not, get the loop in there and functional before changing something that is already working. Just a bit if advice...
Thanks
It's hard to say if it's noisy. I mean it's not quiet, but given the amp is only played cranked I'm not sure it is really noisier then it should be. It was really more a case of, well, everyone says you should change the filter caps at 20 years and I'm going to be in there anyway.
Likely good advice to not mess with it until I know the loop is working!
