electrolytic capacitors for JCM 800

kaznjavator · 08-11-2008, 08:27 AM

Hi, I'm new here.
I have old JCM 800 super bass MKII, model 1992. I have been using it for the guitar (stumping to the chest), but lately sound is weaker then usually. I changed the tubes, biased it right, but sometimes sound is loud, sometimes it's not. I'm suspecting that electrolytic capacitors are gone bad, so in order to change them I must now which model are they, and value.
Can somebody help me?

bigragu63 · 08-11-2008, 10:06 AM

Hi, the value is more important than the brand. There are several different companies making replacement cap cans, and I'm sure you can get lots of opinions on which ones are best.

Here's a schematic I found for your amp. The Free Information Society - Marshall 1992m2 Electronic Circuit Schematic

It looks like you have two caps with a 50uF + 50uF value, and possibly two more with 100uF + 100uF values. Look at the chassis where the tubes are, and you should be able to see the filter caps. You should be able to read the values printed on them, but you might have to pull the chassis out of the cabinet to see the print on some of the caps.

Tube Depot has a good selection... Can Capacitors

Be safe! Don't ever touch anything inside the chassis until you discharge the caps!!!

Good luck.

kaznjavator · 08-11-2008, 11:39 AM

thank you
cheers

08-11-2008, 08:27 AM	#1 (permalink)
kaznjavator Junior Member Join Date: Aug 2008 Posts: 5	electrolytic capacitors for JCM 800 Hi, I'm new here. I have old JCM 800 super bass MKII, model 1992. I have been using it for the guitar (stumping to the chest), but lately sound is weaker then usually. I changed the tubes, biased it right, but sometimes sound is loud, sometimes it's not. I'm suspecting that electrolytic capacitors are gone bad, so in order to change them I must now which model are they, and value. Can somebody help me?

08-11-2008, 10:06 AM	#2 (permalink)
bigragu63 Member Join Date: Aug 2008 Location: New England Posts: 33	Re: electrolytic capacitors for JCM 800 Hi, the value is more important than the brand. There are several different companies making replacement cap cans, and I'm sure you can get lots of opinions on which ones are best. Here's a schematic I found for your amp. The Free Information Society - Marshall 1992m2 Electronic Circuit Schematic It looks like you have two caps with a 50uF + 50uF value, and possibly two more with 100uF + 100uF values. Look at the chassis where the tubes are, and you should be able to see the filter caps. You should be able to read the values printed on them, but you might have to pull the chassis out of the cabinet to see the print on some of the caps. Tube Depot has a good selection... Can Capacitors Be safe! Don't ever touch anything inside the chassis until you discharge the caps!!! Good luck.

08-11-2008, 11:39 AM	#3 (permalink)
kaznjavator Junior Member Join Date: Aug 2008 Posts: 5	Re: electrolytic capacitors for JCM 800 thank you cheers

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