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OLDER DECWARE GEAR SUPPORT >> SE84A, SE84B, SE84C, SE84C+,SE84CKC >> SE84CS Tube Flash, now both amps in-op!
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Message started by KellyB on 07/27/15 at 01:09:26

Title: SE84CS Tube Flash, now both amps in-op!
Post by KellyB on 07/27/15 at 01:09:26

I have 2 SE84CS amps that I use in mono for each channel. Turned on the right one yesterday & saw a flash, then had no power to any tubes. I then hooked up left amp to stereo mode & had music! Today I changed the left rectifier to the right in-op amp, didn't notice a flash, but now neither amp works in any fashion! I'm thinking I need new tubes, any idea how to proceed? How much would 2 matched rectifiers &/or 2 matched sets of tubes cost? Thanks in advance for any help!!! Kelly

Title: Re: SE84CS Tube Flash, now both amps in-op!
Post by will on 07/27/15 at 05:46:25

Kelly,

I am guessing the rectifier blew causing the initial flash event, and that this blew the fuse in that amp. So moving the other rectifier to the amp did nothing. If this is correct, you will hopefully only need a new fuse and rectifier for the amp that flashed, that amp's rectifier failing being the cause of the blown fuse. Or if your rectifiers are old, you may want to get two new ones. Price depends on the rectifiers you buy. If yours are brown-based Shuguang/Ruby 5U4Gs and you liked the sound, these are inexpensive.

Title: Re: SE84CS Tube Flash, now both amps in-op!
Post by will on 07/28/15 at 15:05:12

Sorry, I was not very clear on that post.

Once a rectifier failed in my SE34. I was trying a different tube type, a GZ34/5AR4 rather than the stock Ruby 5U4G. With just 75 hours or so, I decided to get a replacement from the seller with similar test scores and after some burnin, it sounded great. Early failure is rare, in fact any rectifier failure is rare in my experience, but I do like to roll tubes!

I have used mostly well-made NOS rectifiers though, and always buy matched pairs, checking that the scores are close, and the construction is exactly the same. My first foray into NOS was a pair of 50s RCA 5U4G-ST, and they came with slightly different construction from a respected seller. They sounded quite good together, but changing channels you could hear a difference. After that I was more careful, wanting each channel to start out the same.

Also, the rectifier does change the sound and can be used to tune the amp to taste, or upgrade the sound. And though many NOS tubes are expensive, you can find really nice ones cheaply also. There are likely threads on tubes for your amps in the forum if you have not already had a look.

Good Luck and I hope it is an easy fix!

Title: Re: SE84CS Tube Flash, now both amps in-op!
Post by KellyB on 07/28/15 at 16:13:20

Thanks Will, I'll start with the fuses. I've never been inside the amps!

Title: Re: SE84CS Tube Flash, now both amps in-op!
Post by will on 07/28/15 at 17:15:17

Hey Kelly. The fuses are pretty simple to get to if your amp is set up like my Decware amps. There is a fuse holder in the IEC inlet, so you don't have to go inside.

Unplug the amp and then pull out the Amp end of the power cord. Look into the space it came out of from the back of the amp... into the IEC inlet. Not far from the top you can see a little rectangular gap that a small screw driver tip can be put into. Gently pry the fuse cover/holder straight up. The fuse will be in the part that you pry up. Also, in the holder there is probably a little round area, where with luck, you will find a spare fuse. If you find the wire in the fuse is broken, if I recall correctly from Steve, this is what is supposed to happen to protect the amp from a rectifier short, and with any luck, no more damage would have been done. That the rectifier flashed points to this.

I am a little concerned about this: "I changed the left rectifier to the right in-op amp, didn't notice a flash, but now neither amp works in any fashion!" If the fuse is blown on the right amp, it would not work. But the Left still should using the rectifier that was originally in the Left amp. However, if you switched rectifiers, and tried the Left amp with the Right rectifier (that is shorted if this is correct theory), it probably blew the Left amp fuse too.

If you did try to start the Left amp with the Right rectifier, and both fuses are blown, it would seem that by replacing both fuses, and trying the amps with the rectifier that was originally in the Left amp... both would hopefully work, verifying that it was just the rectifier causing the problem.

Title: Re: SE84CS Tube Flash, now both amps in-op!
Post by KellyB on 08/02/15 at 09:21:28

Yes Will, that's exactly what happened! I replaced both fuses & put both rectifiers in their original amps & the right amp fuse blew again! I'll change the left amp to stereo mode & listen to that while waiting for a new matched tube set! Thanks again!!! KellyB

Title: Re: SE84CS Tube Flash, now both amps in-op!
Post by will on 08/02/15 at 14:32:16

Glad to hear it Kelly!

Edit: PS. May be best to avoid testing with a known bad rectifier in future, just in case! Since it flashed and blew a fuse....then it blew a fuse in the Left amp...had to be a bad tube. Great the fuses handled it!

If I recall correctly, I have only had one go bad. Hopefully this is your last.

Have fun!