Ceriatone Plexi 50 Build (First Build)

sdn25

Active Member
Joined
Apr 24, 2022
Messages
188
Reaction score
77
The 50 watt 68' Plexi, my Dream Amp!

Hey guys, this is my first ever amp build I've done, learnt a LOT along the way. It is officially completed as of today as I have received the head cabinet and finally eliminated all the issues that came up with it and caused heartache for the past 2 weeks 🥲, resulted in a blown OT and a blown set of power tubes 😬 but hey, we all learn somehow right?
Gotta hand it to the guys over at the workbench forum they helped me tremendously.

There were some changes I made to the circuit as well but they were all personal preference:
- 0.0022uf Bright channel coupling cap
- 47k NFB off the 4 ohm tap,
Also ended up with a OT upgrade to a heyboer 8025A-H as suggested by @william vogel since I had blown my original OT.

Do let me know if you guys have any cool suggestions as well !

Took me all in all about a month to finally have it completed and It sounds absolutely AMAZING. Here are some pictures for you guys to enjoy :) .I hope its of decent quality.
 

Attachments

  • amp pics1.jpg
    amp pics1.jpg
    962.7 KB · Views: 23
  • amp pics2.jpg
    amp pics2.jpg
    549.8 KB · Views: 22
  • amp pics3.jpg
    amp pics3.jpg
    488.8 KB · Views: 19
  • amp pics4.jpg
    amp pics4.jpg
    530.3 KB · Views: 20
  • amp pics5.jpg
    amp pics5.jpg
    684.2 KB · Views: 22
Joined
Aug 18, 2021
Messages
21
Reaction score
54
Congratulation! It looks really neat! I’ve also recently started my first amp build but I have chosen the “all access” version of the plexi 50w kit.

You can see my build progress here:
 

sdn25

Active Member
Joined
Apr 24, 2022
Messages
188
Reaction score
77
Looks real nice, congratulations! Im sure you meant 0.022uF coupling caps. Play it loud!
Thank you man ! I indeed am able to play it loud as I use a load box.

Btw I mean 0.0022, the stock cap was a 0.022, I wanted that extra bite.
 

sdn25

Active Member
Joined
Apr 24, 2022
Messages
188
Reaction score
77
Congratulation! It looks really neat! I’ve also recently started my first amp build but I have chosen the “all access” version of the plexi 50w kit.

You can see my build progress here:
Thank you! I tried my best in terms of cleanliness but could be better.

Your build is looking really clean so far dude, hoping it goes all well for you.
 

BenTobith

Member
Joined
Jan 6, 2021
Messages
59
Reaction score
23
Thank you man ! I indeed am able to play it loud as I use a load box.

Btw I mean 0.0022, the stock cap was a 0.022, I wanted that extra bite.
That's a good choice, in my experience. I believe the 1987 circuit used a 2.2nF in the High Treble channel signal path by default, I'm wondering why that wasn't the case with the kit? Or maybe some earlier models used double 22nFs on the channels?
 

marco_giampa23

Well-Known Member
Joined
Feb 11, 2020
Messages
368
Reaction score
401
Location
STRAYA
How did you blow a set of tubes and your OT? Asking so I hopefully dont make the same mistake in the future
 

sdn25

Active Member
Joined
Apr 24, 2022
Messages
188
Reaction score
77
How did you blow a set of tubes and your OT? Asking so I hopefully dont make the same mistake in the future
When measuring the bias current using the bias test points at the back of the amp, I set my meter to read mA rather than mV. The meter set to read current gave me a skewed reading with which I set it to 33mA, in practice that was about 70 is mA which then caused overcurrent in the OT, shorted the primary windings, and blew a set of tubes as they were red plating.

just make sure that when you have current sensing resistors installed to help you easily set bias to not use the current setting on your DMM but rather voltage.
 


Top