Help!! - Ampeg V4B blew up at practice last night

[bhoff5150]

I have an Ampeg V4B reisue that blew up last night. Powered it up sitting on standby (it had a cabinet load plugged in). As soon as I turned it from standby to on I heard a very loud "static sound" and saw some distinct blue and amber light through the grill cloth. Power light then stayed on "red" even when coming off standby, but no sound. The indicator light does not flash, just stays lit in red or amber like its sitting in standby mode.

I'll take her to a tech to be checked out, but any chance this is just a bad power tube? Any thoughts as to the issue?

 

[beans-on-toast]

Yes it can be a failed tube. Maybe a fuse as well.

 

[Wasnex]

I have an Ampeg V4B reisue that blew up last night. Powered it up sitting on standby (it had a cabinet load plugged in). As soon as I turned it from standby to on I heard a very loud "static sound" and saw some distinct blue and amber light through the grill cloth. Power light then stayed on "red" even when coming off standby, but no sound. The indicator light does not flash, just stays lit in red or amber like its sitting in standby mode.

I'll take her to a tech to be checked out, but any chance this is just a bad power tube? Any thoughts as to the issue?

After this sort of event, IMHO it's best to have a tech have a look at the amp. The tech will open and inspect for visible damage, and check working voltages to make sure everything is okay.

It's possible the problem was caused from an intermittent connection in one of the tubes sockets. Either a tube was not seated properly or the pins in the tubes socket are loose and need to be retensioned.

One of my amps produced a bright flash of light and sent a sound like a loud explosion through my cab. I opened the amp and there was no apparent damage other than a blown fuse. I replaced the fuse and checked all working voltages. I retensioned the tube sockets before reinstalling the tubes. It has not had any further problems.

IMHO I got lucky as it's not unusual for this sort of event to blow internal components.

 

[bhoff5150]

After this sort of event, IMHO it's best to have a tech have a look at the amp. The tech will open and inspect for visible damage, and check working voltages to make sure everything is okay.

It's possible the problem was caused from an intermittent connection in one of the tubes sockets. Either a tube was not seated properly or the pins in the tubes socket are loose and need to be retensioned.

One of my amps produced a bright flash of light and sent a sound like a loud explosion through my cab. I opened the amp and there was no apparent damage other than a blown fuse. I replaced the fuse and checked all working voltages. I retensioned the tube sockets before reinstalling the tubes. It has not had any further problems.

IMHO I got lucky as it's not unusual for this sort of event to blow internal components.

Thanks for the advice, I will for sure have a tech look at it. Being the Ampeg junkie that I am, it was sitting on top of my SVT-CL, so I just fired that one up and had a good practice.....

 

[Basslice]

Bad news: Could be a lot of things

Good news: Those amps are relatively easy to diagnose and fix. Probably nothing too major, your tech will figure it out.

 

[CTBassGuy]

I have an Ampeg V4B reisue that blew up last night. Powered it up sitting on standby (it had a cabinet load plugged in). As soon as I turned it from standby to on I heard a very loud "static sound" and saw some distinct blue and amber light through the grill cloth. Power light then stayed on "red" even when coming off standby, but no sound. The indicator light does not flash, just stays lit in red or amber like its sitting in standby mode.

I'll take her to a tech to be checked out, but any chance this is just a bad power tube? Any thoughts as to the issue?

Hey @bhoff5150 , did you get your V4B sorted out? I just had the same thing happen to my V4B this evening while practicing at home and it freaked me out!

There was a buzz and red flash from the back of the amp and then the distinct "magic smoke" smell but no visible smoke. My amp won't come out of Standby now.

Any intel on what happened with yours would be helpful.

And can anyone suggest an amp repair technician in Western CT or north of New York City? I'm NOT going to dig into this myself...

 

[bhoff5150]

Hey @bhoff5150 , did you get your V4B sorted out? I just had the same thing happen to my V4B this evening while practicing at home and it freaked me out!

There was a buzz and red flash from the back of the amp and then the distinct "magic smoke" smell but no visible smoke. My amp won't come out of Standby now.

Any intel on what happened with yours would be helpful.

And can anyone suggest an amp repair technician in Western CT or north of New York City? I'm NOT going to dig into this myself...

what’s up CTB? Sorry to hear that we’re in the same boat.

I have not had the amp repaired yet, but I have had an older V4B and my SVT repaired in the past for similar issues. They both had a resistor fail that caused the problem. On my old V4B it was a “grid resistor” if I remember correctly. I don’t remember what the name of the SVT component t was that failed.

I’m in Cincinnati and our two best repair shops went out of business. We are now down to one so I do t have much choice in where to take it.

both times the repairs ranged from $140 - $210. Also be prepared to buy a new set of power tubes which can get expensive. Unfortunately, it’s just part of owning and using a tube amp. You gotta love it or leave it. For me, once I experienced the all tube Ampeg tone, there was no going back.

 

[CTBassGuy]

what’s up CTB? Sorry to hear that we’re in the same boat.

I have not had the amp repaired yet, but I have had an older V4B and my SVT repaired in the past for similar issues. They both had a resistor fail that caused the problem. On my old V4B it was a “grid resistor” if I remember correctly. I don’t remember what the name of the SVT component t was that failed.

I’m in Cincinnati and our two best repair shops went out of business. We are now down to one so I do t have much choice in where to take it.

both times the repairs ranged from $140 - $210. Also be prepared to buy a new set of power tubes which can get expensive. Unfortunately, it’s just part of owning and using a tube amp. You gotta love it or leave it. For me, once I experienced the all tube Ampeg tone, there was no going back.

Thanks for the quick reply, bhoff. I actually found an amp repair shop last night relatively close to me, (Bell Audio Labs in Bristol CT, recommended by @buldog5151bass) and will be dropping my V4B off with them today.

Hoping the repair cost is in line with what you experienced. As you said, it’s part of tube amp ownership, but the tone is worth it, IMHO. Also why I have a backup solid state amp, just in case…

I’ll report back with the details of the failure and the approx cost to repair.

 

[CTBassGuy]

Good result! Andrew from Bell Audio Labs in Bristol CT was able to fix my V4B in 1 hour while I watched, and cost was under $120!

There was a jumper lead on the board at P23 (I think, may have been P27) that somehow shorted and roasted a resistor next to it. Andrew replaced the resistor and jumper, cleaned the circuit board, and pulled up a number of the jumpers that were lying flat so that they had some space from the board. He also replaced a couple of jumpers that did not have enough give to came far enough up.

Had a happy surprise too, in that I found out that the amp had been re-tubed by the previous owner (I bought it used from GC) with a full set of JJ pre and power tubes. Fortunately, the short did not affect the tubes at all, so at this point, the amp very likely is even better than new!


Brought it home, plugged it in, green light came on, and the happiness ensued!

Thanks for the info in this thread, all; TB Community is great!

 

[agedhorse]

Forensically, I think the logic in how the failure occurred and the importance of the jumpers in the failure is way off base.

Jumpers do not need to be off of the PCB (and in general should not be) and my educated hunch is that the resistor failed and got messy around that jumper.

Otherwise, a reasonable price for the repair.

 

[JeezyMcNuggles]

what’s up CTB? Sorry to hear that we’re in the same boat.

I have not had the amp repaired yet, but I have had an older V4B and my SVT repaired in the past for similar issues. They both had a resistor fail that caused the problem. On my old V4B it was a “grid resistor” if I remember correctly. I don’t remember what the name of the SVT component t was that failed.

I’m in Cincinnati and our two best repair shops went out of business. We are now down to one so I do t have much choice in where to take it.

both times the repairs ranged from $140 - $210. Also be prepared to buy a new set of power tubes which can get expensive. Unfortunately, it’s just part of owning and using a tube amp. You gotta love it or leave it. For me, once I experienced the all tube Ampeg tone, there was no going back.

Hey @bhoff5150 , did you get your V4B sorted out? I just had the same thing happen to my V4B this evening while practicing at home and it freaked me out!

There was a buzz and red flash from the back of the amp and then the distinct "magic smoke" smell but no visible smoke. My amp won't come out of Standby now.

Any intel on what happened with yours would be helpful.

And can anyone suggest an amp repair technician in Western CT or north of New York City? I'm NOT going to dig into this myself...

How long have you guys had yours?

 

[CTBassGuy]

Forensically, I think the logic in how the failure occurred and the importance of the jumpers in the failure is way off base.

Jumpers do not need to be off of the PCB (and in general should not be) and my educated hunch is that the resistor failed and got messy around that jumper.

Otherwise, a reasonable price for the repair.

I’ll certainly defer to your expertise here, Agedhorse. It is quite possible I mixed up the order of events from Andrew’s explanation. The resistor clearly failed, however, as there was a burnt hole in the barrel.

How long have you guys had yours?

I’ve had mine since 2018, but I think it may have been made as early as 2013 (there is an Ampeg 2013 date on the back as part of their legal statement).