@RRK: I've noticed that my 70W R7s MH lamps, don't reaches greenish color of mercury during run-up, when only the mercury being ionized. This in contrast to 400W MH lamps, that reach greenish color during the mercury phase.
Is this related to the higher mercury pressure of the lower wattage MH lamps compared to the higher wattage ones?

I’m glad it wasn’t more serious. You now have first hand experience as to why enclosed rated (non protected) lamps should never be operated in open fixtures. If you get a new lamp and use it in an enclosed fixture, you should be good to go.

Unfortunately, I don't have enough space to place fixtures in my home, and some fixtures seems difficult to buy.

Lower wattages of MH lamps run at especially high pressure, so are surprisingly more prone to violent explosions than larger ones. I was more lucky, playing with some seriously beaten up 70W Philips CMH's, so far nothing bad happened. One died silently, probably finally developing through arctube corrosion.

Generally, CMH lamps rarely explode. For new ones the risk seems to be close to zero.

I have bought 2 new lamps and they can work properly. It seems that that second-hand lamp is indeed close to EOL.

And some powerfloods too. Nice find!

This old style small format Walmart in Houston MS has AE Series 25s on Union poles! Saw in a YouTube video.

Walmart

No, am in Utah

Are you in Cali?

Terminology is somewhat overlapped. There was a discussion on these some time ago. Usually, diac is a small low-voltage transistor-like 3-layer non-linear device typically in use for triggering SCRs and starting CFL ballasts, while SIDAC is a self-triggering TRIAC meant for generating strong pulses at high voltage itself, like in lamp ignitors, gas boiler ignitors, also used in overvoltage protection circuits etc.

Three days after a heatwave:
https://www.youtube.com/watch?v=lnCRYLrQV2s

Rainy and cold.

Yup, I have a photo of that exact fixture in my gallery (an admittedly subpar picture, but still) already.