1985 Ampeg SS-150 guitar amp components

[KillerBee]

Was attempting to cleaning some scratchy pots on an old 1985? Ampeg SS-150 guitar amplifier and found all these white powder coated components (resistors?)

one says .33 ohm 5% 10W

What would I order to replace them with - assuming I should?
(The amp still works now - except for a blown speaker)

http://i.imgur.com/rJkSS4f.jpg?1
http://i.imgur.com/hoX61xD.jpg
http://i.imgur.com/3HuNsgG.jpg
http://i.imgur.com/uFTzQn3.jpg

 

[PottedMeat]

...huh, never seen sandstone power resistors look like that before. i've always seen them with the potting compound make a concave surface with respect to the body.

maybe the heat caused the compound to bulge out.

i'd consider replacing them if the powder can easily be dug out.

you're looking for 0.33 Ohm 5% tolerance 10Watt sandstone/ceramic resistors.

something like this:
http://www.mouser.com/ProductDetail...=sGAEpiMZZMtbXrIkmrvidHiKlRtT248UGmCvJgLpnbo=

 

[KillerBee]

wow - thanks for the quick reply PottedMeat
just the info I needed

I was expecting to see a bunch of bulged out capacitors but they all looked good visually.

I did find a couple of Ampeg SS-150 schematics in my googling -
not that I know much about using them tho

the SS-150 PowerAmp Schematic
http://i.imgur.com/c4QNpB9.jpg

and the SS-150 Pre-Amp Schematic
(same board as the SS-70 Preamp)
http://i.imgur.com/u1OJC48.jpg

 

[mindless1]

They should be fine but flip the board over to confirm that heat hasn't degraded the solder joints as that is the more common failure on PCB mounted high power resistor arrays.

The PSU isn't a switching type which explains the long capacitor life. Many of the electrolytics might be coupling caps in the audio signal path, which with a drift (drop) in capacitance over time could affect accurate frequency response but so long as it sounds "right" I wouldn't be in a hurry to replace them.

 

[KillerBee]

They should be fine but flip the board over to confirm that heat hasn't degraded the solder joints as that is the more common failure on PCB mounted high power resistor arrays.

The PSU isn't a switching type which explains the long capacitor life. Many of the electrolytics might be coupling caps in the audio signal path, which with a drift (drop) in capacitance over time could affect accurate frequency response but so long as it sounds "right" I wouldn't be in a hurry to replace them.

Thanks for the reply mindless,
Since the amp still works most of the time ,have been kind of too cautious about messing with it. Have only sprayed out the pots and brushed off the resistors w/o replacing them. Did a tap test on all the components and only one part which made noise was one side of the reverb tank connection - hoping a reheating of the joint will fix it. Else think I should bring it to a pro who has proper test equipment and knowledge - any guitar picking electronics gurus in Maryland here?

 

[KillerBee]

update ...
Unplugged the wire from the noisy joint to resolder it and the board terminal came out with it. Resoldered it and put everything back together with no mysterious spare parts left over and all good now.