When you say STK you confuse me, the two transistors you show in the picture should be 2SD525 or TIP41C if the mods have been done or 2SD234 if not.
What was the reason the service bulletins for the mod changing the two TO-220 was issued?
As I understood, overheating. They were cooking off their own solder joints or baking surrounding components. There's also the Main PS caps and replacing all the fusistors with flameproof resistors. The SB also includes the addition of a jumper wire across some AC line terminals in the rear, IIRC tying the 2 sides of the power switch together to reduce arcing internal to the switch.
I've also done the mods on CR-1020, although it doesn't need upgrades for the TO-220's on the PS sub asm board. Rob has been a great mentor for the n00bs like myself on stuff like this. Props to EW and Avionic as well. AK is full of knowledgeable and helpful members.[/QUOTE
Thought it might be the heat. I'm badly short of space and toying with the idea of placing an Altec 345A tubed amplifier on top of the CR 2020 using four or five 2 inch sections of small pipe foam insulation as spacers. I also would have a 12V fan running off a 5V transformer cooling the CR 2020. Right now I'm testing a cheapo fan. The trick is to insulate the fan from grill contact as much as possible for noise reduction.
Thought it might be the heat. I'm badly short of space and toying with the idea of placing an Altec 345A tubed amplifier on top of the CR 2020 using four or five 2 inch sections of small pipe foam insulation as spacers. I also would have a 12V fan running off a 5V transformer cooling the CR 2020. Right now I'm testing a cheapo fan. The trick is to insulate the fan from grill contact as much as possible for noise reduction.
I would be somewhat weary of a fan, But only because of the potential for dragging in dust and causing problems. I don't know the layout of the amp, though...so it may be ok as is. Even if its not a dusty enviroment, dust still winds up where fans are (ex. computers). But for noise effects, i'd actually run below voltage (unless it is a naturally quiet fan), or put in a potentiometer or rheostat to regulate yourself.
also: for heatsinks, sometimes places like Bgmicro and AllElcectronics (and various other small, odd parts dealers) have good heatsinks for cheap. especially for small-scale to-220 and the likes.
Simplest thing then would be to go to mouser online and check their catalog. Heatsinks are in the tools and power section. Do realize that if you put in anything larger be sure to use the mica insulators as there currently is a large voltage difference across the two sinks. Also, Radio shack uses to carry a nice 3/4" square heatsink with about five fins sticking out the back.
The bulletins are on the AK Yamaha database and if anyone does the mods to a 1020 please note that the 2 watt resistors are 10 ohms as opposed to 33 ohms on the 2020.
Just be sure to get the mica insulators or better still the gray silicone insulators.