Yet another CRT mod: upgrade liquid capacitors to solid caps

[LukeEvansSimon]

In CRT based displays, the picture tube itself lasts a very long time and a CRT rejuvenator and CRT brightener can be used to further prolong their life. However, there is a component in CRTs that ages faster than all other components, the liquid electrolytic capacitor. When they start to go bad, the picture quality can deteriorate. Even worse, other components in the circuit can become damaged when an electrolytic capacitor goes bad.

The liquid electrolytic capacitors in your CRT display should easily last about 15 years before some of them need to be replaced. CRT displays can have anywhere from 50 to 250 liquid electrolytic caps in them, so it is a pain to have to replace them all. So wouldn't it be great to be able to replace them with something that will last for at least 100 years more? That way you never need to worry about replacing them again?

Advances in solid polymer electrolytic capacitor technology, as well as solid stacked film capacitor technology means there are now compatible alternatives to liquid electrolytic capacitors for most of the liquid caps in your CRTs. I gave this a try when I re-capped a consumer Panasonic CRT. [Here](https://docs.google.com/spreadsheets/d/ ... sp=sharing) is the full capacitor list with links to Mouser for replacements for all 74 liquid electrolytic capacitors in the TV. Details of how different capacitor tech varies in life expectancy can be found [here](https://www.illinoiscapacitor.com/tech- ... ators.aspx).

A summary of what I did:

39 liquid caps were replaced with 125c solid polymer caps. These have a lifetime 100x longer than the liquid caps they replace. So they will not need to be replaced in my lifetime.

20 liquid caps were replaced with 105c film caps. These also have a lifetime that is 400x longer than the liquid caps they replace!

2 "105 celsius" liquid caps were replaced with "150 celsius" liquid caps. There were no solid or film caps that were drop-in replacements for these. However, 150c liquid caps have a lifetime 16x longer than 105c liquid caps.

2 "105 celsius" liquid caps were replaced with "125 celsius" liquid caps. 125c liquid caps have a lifetime 4x longer than 105c liquid caps. So these 7 caps will last for another 60 years.

11 "85 celsius" liquid caps were replaced with "105 celsius" liquid caps. 105c liquid caps last 4x longer than 85c liquid caps.

How did I select the capacitor replacements? Well, I examined the schematic in the CRT's service manual and checked if the liquid electrolytic capacitor was being used as a coupling capacitor. If so, then I tried to find a film capacitor with the right size, capacitance, and voltage. Film capacitors have been around for a very long time, but they have always been huge in size. The recent advancements in technology allows them to be miniaturized. Kemet has the R82 series that is the same size as liquid electrolytic caps (except a rectangular shape as opposed to a cylinder). Wima has the MKS2 series, same thing: mini sized film caps. Both are top quality brands for capacitors. Film caps are good for coupling because they are ultra low ESR and low current leakage. Film capacitors can also handle crazy high voltages.

If the liquid cap is being used as a decoupling capacitor, then I still try to find a film capacitor replacement. However, above 10uF, film caps are too large in size to "fit" into a circuit as a replacement for liquid caps. This is where solid polymer caps come in. Solid polymer caps are ultra low ESR, support high capacitance, but they have high current leakage, so they are not good replacements for coupling capacitors... but they are great for decoupling.

If the capacitor is bipolar, then I try to find a film replacement because film caps are naturally bipolar.

Is this overkill? Yes, but collecting CRTs is in and of itself, overkill. So why not future proof these babies so they last a lifetime?

[Ikaruga11]

Awesome! Do liquid electrolytic capacitors go bad even if they're not being used and have very low hours? I've heard the caps used in PVMs and BVMs are far higher quality than the caps in consumer CRTs and should last a lot longer.

[LukeEvansSimon]

Awesome! Do liquid electrolytic capacitors go bad even if they're not being used and have very low hours? I've heard the caps used in PVMs and BVMs are far higher quality than the caps in consumer CRTs and should last a lot longer.

Liquid caps age even when not used, but they age very slowly. Their life expectancy is mostly determined by the amount of time they spend at higher temperatures. The higher temperature rating of the liquid cap, the longer it will last.

Top brand consumer CRTs use high quality brand liquid caps. The Japanese CRT TV brands such as Sony, Panasonic, and JVC use high quality Japanese capacitor brands (Rubycon, Nichicon, Panasonic, and Chemicon). However, the consumer CRT TVs from these top brands use fewer capacitors overall so there is less redundancy in the circuit’s voltage smoothing, and they use very few capacitors rated for more than 85c. Pro CRTs use more capacitors, so as the caps age, there is so much redundancy in capacitors, the circuit ages more gracefully. The other obvious difference is pro CRTs use many more 105c rated caps. These last 4x longer than 85c caps.

Regardless, even pro CRTs need to be recapped eventually to prevent more serious circuit issues from developing. Caps are used to smooth the voltage flowing through the circuit. As they age, they are less effective at smoothing and so the power flowing through the circuit becomes more noisy, which accelerates the aging of components. Replacing a capacitor is easy. Replacing a jungle chip, horizontal output transistor, or vertical oscillator transistor is very hard because the parts are no longer manufactured. Caps are abundantly produced. Why wait for one to fail and then have your jungle chip or horizontal output transistor melt?

Recapping a CRT is time consuming and a real chore. The mod I describe ensure that you won’t ever have to recap the CRT again. Hell, your kid that inherita your CRT collection won’t have to recap it either if you use the mod.