196? Fender dual showman 80 w tube amp

[bobbybunante]

I have this amp. Believe it to be about a 1968 model. I inhertied it from my dad. A few years back I took it to Chicago and had it "fixed."
The tubes and the caps were all replaced because the amp had a loud hum after it warmed up. A while back, the amp started acting up again. What it does now, is while being played at low volume it seems to sound fine. When you turn it up there is a crackling and a decrease in volume. Have played head thru several diff speaker cabs. Problem is not speakers. I have limitted amp knowledge but do have moderate understanding of electrical circuitry.
So, where should I begin?

[52 Bill]

Is the crackling constant or is it caused by the signal?

How long ago was the amp worked on and retubed?

[bobbybunante]

The cracking occurs when you strum the instrument at increased volumes.
It was retubed about 4 yrs ago.

[52 Bill]

It could be, depending upon how much use it has seen, that a tube has failed. But it could also be that something has come loose inside, and is not making solid contact.

Turn the amp on, and try giving it a good thump with your fist. Does the crackling happen? Try tapping on the tubes and then wiggle them in their sockets. Any noises?

Generally, the order of things for you to check are tubes, dirty tube sockets, and then bad or broken solder connections.

[bobbybunante]

Thanks Bill, I will try those now and see what happens. Will post more later.

[bobbybunante]

Ok, when I turn the amp on while watching the tubes, the tubes ignite inside when powered up and the amp pops real loud. When I switch it on standby the amp goes silent as it should, when I switch it back off of standby, the thing pops real loud and there is a blue flash in two of the tubes.. Whatever is wrong seems to be worsening.
The sound still sucks.
This thing has been in my family since the early seventies. Until I took it to Chitown, it has never been altared by anyone. This was a really sweet sounding amp and I'd like to get it back that way.
Anyone in Chicago area good at doing service on these things & looking for some work?
Bumping the amp does not effect anything.

[52 Bill]

First off, when you power up the amp, you should follow this procedure: Both the power and the standby switch should be off (down). First turn on the power switch. This warms up the tubes and builds up the voltage in the power supply. After the tubes have warmed up (maybe 20-30 secs.), then turn on the standby switch.

That being said, the thump or pop at turn on could be many different things, including the power tubes. The blue flash is fairly normal, and I wouldn't be too concerned about that.

It sounds like it needs to be checked out by a tech, who can bring it back to life.

[Satamax]

http://www.geofex.com/ampdbug/ampdebug.htm

[mac1amps]

I've been a full-time tech. in the Chicago area for 35 years (and a player for 45+ years). I've serviced literally THOUSANDS of Fenders over the years (along with Marshalls, Ampegs, Voxs, Hiwatts, etc., etc.). I'm sure I can help you out.......Hmmmm, I don't know if it's considered "cool" to post my business phone # on this site though. I'm CURRENTLY located in Berwyn (JUST West of the city)......My shop goes by the name Mac/Amps.......'just thought I'd let you know

[Bruce / Mission Amps]

I've been a full-time tech. in the Chicago area for 35 years (and a player for 45+ years). I've serviced literally THOUSANDS of Fenders over the years (along with Marshalls, Ampegs, Voxs, Hiwatts, etc., etc.). I'm sure I can help you out.......Hmmmm, I don't know if it's considered "cool" to post my business phone # on this site though. I'm CURRENTLY located in Berwyn (JUST West of the city)......My shop goes by the name Mac/Amps.......'just thought I'd let you knowSome techs who contribute here don't do this but I think it is fine to put contact info to your signature as it adds credibility to your posts and tech replies.
Many readers here have a very small amount of electronic knowledge and are looking for local pro help.

[mac1amps]

Thanks Bruce, in that case (since I don't currently have a "signature" set-up with my replies), the phone # of my shop is: (708) 484-8338........Mac/Amps.....(my name's Mac.......No, I don't service computers;)

[bobbybunante]

Thanks mac, I'll give you a call in the next few days about this.