tektronix 2235 AN overheating

[kapo16]

Hello from Athens

I purchase a 2235 UN in very good condition(cosmetic), but after 2 hours of working, ' a smell like plastic getting hot' came to my attention.
Inspecting the board noticed that the TL594 was replaced with the same type, and Q9070 is irf710.

1.Is it ok to replace the irf 710 with this mosfet: Qorvo
UF3C065080T3S as it has 100mh RDson?
2. What caps in the power supply would you suggest replacing?. All the caps seem original.

Thanks in advance.

Panos

[lucittm]

Your Tektronix 2235 could have been manufactured in 1983 or 1984. This means it is about 40 years old. Electrolytic capacitors have a useful life expectancy of 25-30 years. I would replace all the electrolytic capacitors, if possible. Especially the ones in the Power Supply. It would be good to have a schematic to assist with part identification.
The Service Manual is here:
https://tinyurl.com/4chvr997

Mark

[tunk]

Also see if there's any Rifa caps, they could be the source of the smell: https://youtu.be/MW_p8HzVAlY

[Gyro]

Also see if there's any Rifa caps...

Specifically PME271 Metalized Paper capacitors - Kemet (formerly Evox Rifa) make other film dielectric types that are absolutely fine with age.