Fuse Resistor Primer 101

[OleJeepGuy]

Hi All,
I, like many it appears, can be confused by the Fuse Resistors (FR) used in the Sansui vintage amps of the late '70s.

The Sansui 9090db I am currently working on has a few on the Driver Bd and Power Supply Bds: .33 ohm, 1 ohm, 4.7 ohm, 10 ohm, 150 ohm, 180 ohm, 330 ohm.

• First off, How can I (visually) distinguish between an FR resistor from a standard metal film Resistor? When I search eBay for these FR resistor values, I get very few hits. Are they really that hard to find?
• Is it OK to substitute a metal film R for a FR?
• Pro's and Con's of increasing/decreasing the wattage. ex: 1/4w to 1/2w. similar to reducing 10A fuse to 6 or 7 amp on these monster amps.

I'm sure there are other members that have other questions around Fuse Resistors.

My ask is for "those in the know" to reply with their knowledge so we the rookies can learn and not make a stupid mistake with these CRITICAL parts.

Thx, Hank

 

[LBPete]

Fuse resistors are called out on the board descriptions in the service manual. They are always a pale gray color. The driver board has a dozen or more of them. You should see them quite clearly. Don't bother trying to source them, just replace them with metal film resistors. In addition to their resistance value, pay attention to their wattage. Most are 1/4 watt but a few are 1/2 watt. Check the service manual for the wattage.

- Pete

 

[milo63]

The fusibles are raised above the board, most units have AK posts with lists.
There's a lot to learn, take it slow.

 

[Hyperion]

Pro's and Con's of increasing/decreasing the wattage. ex: 1/4w to 1/2w. similar to reducing 10A fuse to 6 or 7 amp on these monster amps.

The other way round, if you increase the wattage it's like increasing the fuse current rating. (which we should all know is a BAD thing).

The fusibles are raised above the board

Ordinary Metal Oxide resistors are also grey and raised above the board - best not to confuse the fusible resistors with them.

 

[OleJeepGuy]

Fuse resistors are called out on the board descriptions in the service manual. They are always a pale gray color. The driver board has a dozen or more of them. You should see them quite clearly. Don't bother trying to source them, just replace them with metal film resistors. In addition to their resistance value, pay attention to their wattage. Most are 1/4 watt but a few are 1/2 watt. Check the service manual for the wattage.

- Pete

Thanks Pete!

 

[OleJeepGuy]

Thanks all for your reply’s. Every little tid bit helps. Hank