Gibson Super Goldtone 30RV blowing fuses...

[busted_super_goldtone]

I've got a Gibson Super Goldtone 30RV that is, unfortunately, out of commission- one day, after playing (not excessively loud), it just quit working.
(Side Note: there was an electrical heater running in another outlet in the room at the time that might have caused a power spike)

The amp will turn on, and run in standby, but the moment i turn the amp "on", the 500mA fuse blows (violently), and no sound or signal can be heard. The two fuses on the "valve power board" (for standby, i assume) are intact, as are the fuses on the "main valve preamp pcb", and inline 'mains fuse' in the power cord connector... but I guess anyone that could give me any insight has already figured that out :]

Any and all help/advice would be greatly appreciated, as it's a crime against humanity to have this boutique gem sit in a corner and collect dust! Nobody has been able/willing to help, and shipping an 80lb amp off for repair seems infeasible at best.

Thanks in Advance,

Brent

[Enzo]

OK, it blows the high voltage fuse as soon as the high voltage is turned on. This usually means bad power tubes. REmove your power tubes and fire it up. If it no longer blows fuses, then buy a new set of power tubes for it.

[busted_super_goldtone]

thank you!

First off, THANK YOU!

I took out all the tubes, and the fuse didn't blow! I'll grab a new set, ASAP and hope this works. A Noob would assume at first, that the tubes were the problem, but they were all glowing, and (presumably) warm, so I wasn't sure...

I'll post an update after installing the new tubes, and hopefully, will be able to report how great my recently acquired 82' Gibson 335 sounds through it!

Just wondering... if it's not the tubes, is it possible that the fuse now isn't being blown because the circuit isn't complete? For instance, the power now isn't making its way past the tubes, and to, perhaps a blown capacitor (i have two the size of D batteries) on the power board following the tubes...

Thanks so much for your help Master Enzo, and any or all who follow!

Brent

[Enzo]

Current doesn't go through the tubes to get to capacitors, it goes to capacitors to smooth it out for the tubes.

The only thing left to worry about now is a possible open screen resistor if that amp has them. SOmetimes failing fuses take out screen grid resistors.

[busted_super_goldtone]

replaced my tubes to no avail...

So I just put in a sweet new set of JJ EL84's, and still no sound and blown fuses. Like I said, with no tubes in place, the amp will turn fully on without blowing fuses.

If you could, please describe this screen grid resistor (ie location, function, replacement) so that my ears will yearn no more! I see 4 "1K 5% 5W" labeled positions R15-R18 next to each tube socket, so I assume these are them. But also, there are 4 similar, but larger resistors that seem to correspond to each tube marked "W22 270R 5%"

British Audio, nor my local Radio Shack has neither of these parts, so if you know of a good place to get them, it would be appreciated.

Thanks!

Brent

[52 Bill]

The 1K resistors are the screen grid resistors and the 270R resistors are cathode resistors.

I don't think that a bad resisitor here will cause the fuse to blow.

Do you have the schematic for this amp? If you don't, it's available at the Gibson site. You will probably need it to refer to.

[busted_super_goldtone]

The 1K resistors are the screen grid resistors and the 270R resistors are cathode resistors.

I don't think that a bad resisitor here will cause the fuse to blow.

Do you have the schematic for this amp? If you don't, it's available at the Gibson site. You will probably need it to refer to.

Thanks friend!

I have the schematic for the amp, but I'm not the best at making all that much sense out of it against the board... I checked the continuity of the screen grid resistors, and they all read around/above 1000 -> same with the cathode resistors @ 270, so I assume that they're all alright.

Just recently though, a white, powdery, corrosive-type substance has appeared around the solder points (opposite) of the tube sockets on the power board , but they seem to be powering the tubes just fine, and there were no scorch marks on the tubes i replaced...

Any ideas what else could be causing this problem?

All help is much much much appreciated!!!

[52 Bill]

Just recently though, a white, powdery, corrosive-type substance has appeared around the solder points (opposite) of the tube sockets on the power board , but they seem to be powering the tubes just fine, and there were no scorch marks on the tubes i replaced...

Any ideas what else could be causing this problem?

White powdery substance? Is there any chance that this got wet/damp? Are you in a cold climate where the amp had gotten really cold, and then was brought indoors to a warm moist environment? You mentioned an electric heater earlier.

I downloaded the schematic for your amp, and I couldn't find any reference to a 500mA fuse. If you don't mind bringing me up to speed, where is this fuse located?

[busted_super_goldtone]

HT Fuses and Corrosive-type Substances

White powdery substance? Is there any chance that this got wet/damp? Are you in a cold climate where the amp had gotten really cold, and then was brought indoors to a warm moist environment? You mentioned an electric heater earlier.

I downloaded the schematic for your amp, and I couldn't find any reference to a 500mA fuse. If you don't mind bringing me up to speed, where is this fuse located?

The 'substance' in question looks almost like corrosion from an old battery... The chances of the amp getting wet are next to none, as it's been inside laying on my dining room table. Though it has been pretty cold lately, so there might be slight fluctuations in temperature, 55 - 70 degrees, but I live in north georgia, so nothing 'extreme', I suppose.

The electric heater was turned on, plugged into another outlet in the room, when the amp quit working. I mentioned it only because I thought it maybe possible that a power surge from the heater might have caused a problem with the amp.

The fuse I'm referring to is the HT Fuse, and is located next to the power cord, accessible from the outside of the amp. The fuse holder assembly has a power lead (red) that runs from the power switch, through the 500mA fuse, through another power lead, and to "TX1 RED" of the Power Board. Again, it only blows when the amp is switched from 'standby' to 'on'.

I've attached a pic of the power board... the power switch is seen in the top right, running to the HT fuse, bottom right. Also, in the pic is the reverse side of the tube sockets that are collecting this 'corrosion'.

I'd be more than glad to take more pictures of this thing, or provide anything else that might be of assistance!

Thanks Again!

[52 Bill]

OK, here are some thoughts.

It could be that one of your new tubes is also bad. You already tried with no tubes, and the HT fuse didn't blow. With the new tubes did the fuse blow "violently", like the original one did? Really black inside the glass?

Do you still have the original fuse? Was it marked T500mA (for slo-blo)? Are the new fuses that you are replacing them with the same type?

If all of the above is not the problem, it could be a bad tube socket or even a shorted output transformer.

Try powering up the amp with one output tube at a time, one socket at a time.

[hasserl]

Should it be a slow blow fuse and you're using a fast blow?

[busted_super_goldtone]

OK, here are some thoughts.

It could be that one of your new tubes is also bad. You already tried with no tubes, and the HT fuse didn't blow. With the new tubes did the fuse blow "violently", like the original one did? Really black inside the glass?

Do you still have the original fuse? Was it marked T500mA (for slo-blo)? Are the new fuses that you are replacing them with the same type?

If all of the above is not the problem, it could be a bad tube socket or even a shorted output transformer.

Try powering up the amp with one output tube at a time, one socket at a time.

MY EARS YEARN NO LONGER!

I absolutely effing love each and every one of you! While I feel like a bit of an ass for using the wrong fuses, I blame it mainly on my local radio shacky lackey, rather than my own stupidity... If I hand you something, and say that I want another, I expect that's what I'll receive!

My reverb didn't work for the first 10 minutes or so of playing, but it switched on (somehow) and everything is working wonderfully.

My new set of JJ's in this thing are enough to make a grown man cry; I'm simply smitten with the pure tone that drips from every orifice of this beast! My Strat Ultra now has an appropriate medium for expressing everything it has to say- and I assure you, there's a lot to say! Every subtle nuance is heard. My soul now has a voice!!

Thanks so, so, so, so much to everyone for their thoughts, efforts, and contributions!

Humbly, Brent

[busted_super_goldtone]

just when you think you've got it made...

i blew another fuse last night, replaced it, and it works again...

could it be possible that i just need to be extra careful with the output transformer and leave the amp in standby for say, 2-5 minutes each time i turn it off and on? that's the only time it seems to blow these fuses- in times of excessive switching...

[52 Bill]

The output tubes are drawing more current than the fuse will allow.

"excessive switching"? Please explain.

[busted_super_goldtone]

The output tubes are drawing more current than the fuse will allow.

"excessive switching"? Please explain.

excessive switching meaning, i power the amp up, let it sit in standby for 20-30 seconds, turn it on, play for five minutes, and switch it back to standby because i have to take a leak... come back in a minute and turn it back on.

or putting it in standby to switch out front end stomp boxes, rather than just unplugging the input jack on the amp....