electrolytic capacitors have they names because of its liguid in it, the electrolyte. In German we call them Elko (Elektrolyt-Kodensator).
Elkos do have a minus pole and a plus pole. For that its is VERY important to solder them with the right side. The minus pole on an Elko is marked.
The older Elkos get the higher is the probability that the electrolyte drains and the Elko loses more and more its capacitance.
For me that was reason enough to change the Elkos on my 38 year old TI-99/4A EU PAL 1981 V2. Additionally i changed the voltage controller 78M12
on the PSU-Board with the modern 12V DC/DC-Voltage Controller TSR 1-24120, because its much more efficient and produces a LOT less heat than the
78M12 with its huge heatsink. The black plastic at the Cartridgeslot is now muuuuch cooler.
But... this is only what i did. Some people think that they do not need an Elko-Change until a device gets problems. Make your on decision. Iam not
responsible of what you do! And remember this is an EU PAL Version for 230V. US-Devices for 110V do very probably need other parts.
These are the parts that i needed. This may vary on your TI-99/4A.
22µF/25V axial. Quantity: 5. Articlenumber on www.reichelt.de: VIS MAL203036229
100µF/16V axial. Quantity: 3. Articlenumber on www.reichelt.de: AX 100/25
10µF/25V axial. Quantity: 1. Articlenumber on www.reichelt.de: AX 10/35
3300µF/35V axial. Quantity: 1. Articlenumber on www.reichelt.de: COS 105 3300/35
1000µF/25V axial. Quantity: 1. Articlenumber on www.reichelt.de: COS 105 1000/25
470µF/12V radial. Quantity: 1. Articlenumber on www.reichelt.de: RUBY 16ZLJ470MT
47µF/16V axial. Quantity: 2. Articlenumber on www.reichelt.de: AX 47/16
4.7µF/35V axial. Quantity: 1 Articlenumber on www.reichelt.de: COS 105 4,7/50
12V DC/DC-Voltage Controller TSR 1-24120. Articlenumber on www.reichelt.de: TSR 1-24120
Modulator PHA 2037:
22µF/25V axial. Quantity: 3. Articlenumber on www.reichelt.de: VIS MAL203036229
0,47µF/63V radial. Quantity: 3. Articlenumber on www.reichelt.de: RAD 0,47/63
47µF/16V radial. Quantity: 1. Articlenumber on www.reichelt.de: RAD 47/16
Here we go:
This is how the mainboard and the psu-board looks before the changes:
Before i ordered the new Elkos, i desoldered the elkos on one side to better see its capacitances
Look at the huge heatsink on the 78M12 voltage-controller, left of the 3300uF Elko.
This is how it looks with the new Elkos and the TSR 1-24120:
The videochip got a heat-conducting pad
See the TSR 1-24120 at the right side of the orange Elko. It needs no heatsink!
After that i changed the Elkos in my PHA 2037 PbPr to SCART RGB Modulator and readjusted the rotary potentiometer.
Now look at the overall result. This is the picture quality on my LCD-TV.
Kind Regards from Germany