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Sunn Musical Equipment => Q & A => Topic started by: F6Forry on October 13, 2008, 02:38:23 pm

Title: 200 S head problem (fuze blew)
Post by: F6Forry on October 13, 2008, 02:38:23 pm

I picked up a 200 s amp and cab at a local auction- Not tested at auction. There was no fuze in the holder so I put a 3 amp in at turned it on. Tubes litup nice so after 10 minutes I hit the stand by switch on and the fuze blew. I'm thinking a short somewhere? Any problems with this model? I figure to pull the chassis and look for loose wires. I have a tube tester and a stock of tubes but am newish at electronics. Thanks.

Title: Re: 200 S head problem (fuze blew)
Post by: mckinnon audio on October 13, 2008, 06:27:50 pm

  Hi there,pull all the tubes,replace the fuse and fire it up again.If the fuse blows again you probably have a bad filter cap,(leaky or shorted) or some resistors associated with the powert supply or output stage.It could also be a bad trans.(power or output) hopefully not.Be careful if you take the amp apart,there are some high voltages in there,good luck Mel.

Title: Re: 200 S head problem (fuze blew)
Post by: djc on October 17, 2008, 08:45:20 pm

mine did exactly the same thing.  the power tranny in mine was blown.  replaced that, redid the cap with an SDS board and the thing has never failed me in 2 years.  turn it on, plug in and play.  adjust the three knobs as needed.

Title: Re: 200 S head problem (fuze blew)
Post by: basiklybass on October 20, 2008, 04:23:29 pm

Yep, replace the power caps...and all the rest while your at it. Check the power tranny leads for damage, it is probably blown as well. Triode has a nice replacement

Title: Re: 200 S head problem (fuze blew)
Post by: Isaac on October 27, 2008, 10:35:22 am

Was the fuse you put in a slo-blo fuse? I had a similar issue recently, and eventually figured out that I was using a standard fast-blo fuse instead of the slo-blo the circuit requires.

Title: Re: 200 S head problem (fuze blew)
Post by: F6Forry on October 29, 2008, 02:11:32 pm

Not sure what you mean  by slo-fast blo fuze? I used an AGC 3 that I had on hand. I got a fresh pack of AGC 3's from Littlefuse at my auto parts store. I see they are made in China-UGH! I'll have to stick one in and follow #1's procedure.

Title: Re: 200 S head problem (fuze blew)
Post by: Soundmasterg on October 29, 2008, 05:39:26 pm

They make slo-blo and fast-blo fuses in each value, and for a power supply application, you want a slo-blo fuse so the AC fluctuations that always happen don't make the fuse blow all the time. For an output transformer fuse like in a Marshall amp, you would want a fast blow fuse.

Greg

Title: Re: 200 S head problem (fuze blew)
Post by: F6Forry on October 30, 2008, 08:22:24 am

Okay, I get the difference-Whats written on the slo blo fuse? I went to Radio Shack and all they had was 250v 3 amp so I went to Auto parts and got a pack of 3 amp AGC for a lot less. Thanks for all this info,I'm learning more about this electronical stuff.

Title: Re: 200 S head problem (fuze blew)
Post by: mckinnon audio on October 30, 2008, 09:24:17 am

  Hi there,for slo/blo fuses the letter designation is MDL or MDX.Sometimes the body of the fuse is porcelin,sometimes it's glass.The AGC designation is for regular,(fast blow) fuses.The letters mean auto glass container,when these were first made it was for the auto industry,way,way,way back,think model-t.Good luck,Mel.