Some while ago I obtained a small laboratory oven intended to use for Ceracoting and later powder coating.
It’s an old oven, probably build between 1977 and 1980 or so. It has a small heat exchanger to pre-heat the incoming fresh air when the vent is opened and inside you find an old-fashioned but reliable mercury contact. The contact is operated by a long metal pin which changes length when temperature changes and it can be calibrated using a small positioning wheel. The oven operates best when place level.
The oven has 2 resistant wires for heating, parallel connected and operated by separate switches.
There is also a third resistant wire near the metal temperature controller pin. Its was placed serial to a big capacitor, I did not find out yet what the use is and removed it when rebuilding the temperature control. Does anyone know its purpose? Please leave me a message….
The build quality is amazing. Very common in that area for German industrial products. The outside frame is stainless steel, the panels painted aluminium and the edges are bend 180 degrees to fit seamlessly and rigid.
When I was looking for information regarding this oven I contacted Memmert, the company still exist. The UN450 ovens look awesome and make my wish for one 😉 They were very helpful and found some old schematics. What an excellent service! Unfortunately the last person with knowledge regarding this oven retired a few years ago, not really strange keeping in mind my oven is 40 to 50 years old.
The video above showed a really well engineered door locking mechanism… beautiful isn’t it?
After issues with a short in the electrical wiring I decide to replace the mechanic temperature control and the isolation which was damaged in some areas.
First I bought one of those Alie express solid state PID kits, a Rex-c100, but I had no patience for the delivery and with Chinese cheap stuff you get what you pay for…
Luckily I found a Jumo iTron 702043 PID controller, it’s a whole other level compared to the Chinese product.. Jumo is also a long existing German brand like my Memmert oven also a third generation family company. As a Euro-chauvinist that suits me well!
I had a decent solid state relay laying around, unfortunately a 24v control voltage so I had to add another component for 24v supply.
The results are satisfying. The PID has an auto-learn option which learns how to keep the temperature steady and examine the characteristics of the oven. It takes his measurements from a Jumo 2 wire PT100 Sensor.
Scematics Memmert TV30 oven
If you own a Memmert oven as well please leave me a comment, I am curious how many others are using these ovens and whats is their experience.