Double check me. 1987x Metro Loop install

[primal]

Used to work in electronic repair years ago but it's been a while and I had no experience with amplifiers. That said I think installing this should not be a problem.

Getting ready to install the metro loop into my 1987x. It is a 90's model that did not come with a loop installed.

After reading the instructions and going over the schematic, I have mapped out the points where I believe this will be installed and was hoping someone here could double check what I am getting ready to do.

I have attached a picture of the board along with notes on where I believe everything should be connected. If one of you knowledgeable folks could just double check me it would be greatly appreciated.

My biggest concern is the long wire run I would need to power the board. The PI supply node seems pretty far on the 1987x pub if I have mapped it out correctly.

Also, I am going to have to buy the proper drill bit to drill the wholes for this. Anyone have any recommendations?

https://imgur.com/a/qBkxh2c

[primal]

Now with the image properly embedded

[neikeel]

The loop is a great addition for time based effects on a plexi (or EQ pedal)

I now install them without the on/off switch (avoids the extra hole).

When drilling the holes I take great care to line them up with the existing jacks and make sure the hole centres are the same across all the jacks (more important on the 100w as some of those came with 4 jacks and it looks almost stock.

You can take the B+ feed off one of the two 10k 2w resistors mid board (just need a small resistor value to get loop voltage right, on the pcb amp this is not quite as neat as on turret board (or using the stand up PI turret!) but gives a shorter PS wire and less likely to create noise.

Good luck and please feel free to embed more pics as you go.

Oh and I use 3 or 4 drills in succession to minimise overheating and burring (dont forget to make a plasticine well inside the chassis to catch the swarf).

[primal]

Thanks for your reply!!!

Your timing could not have been better. It just so happens that today, I opened her up to get started. When I went to measure my B+ at the supply to the phase inverter (Labeled B+ in my picture), it measured 450 volts. So clearly that was not going to work.

I went to R12, one of the two 10k's in the middle and it was 330vdc. That I can work with.

I did notice that when I play, that voltage will drop all the way down to 290.

I will try and embed some more pictures as I go along.

Thanks!

[anthonymunoz]

Just wondering if you ever finished up this mod. I’m planning to do the same on my 1987x. Did connecting the B+ To the R12 on the PCB cause any issues? You had mentioned that your voltage would drop while playing.

Thanks. Just looking for some guidance before I get started.

[anthonymunoz]

Hi. I was wondering if you completed your install and how it went. I’m about to start mine and could use some advice.

[anthonymunoz]

Hey I was wondering how your install went. Did you happen to take pics? I’m about to start my 1987x and it would be great to see yours before I start.

Thanks!