OT - Fender Twin Reverb Reissue Problem - Reverb and Crackle

mikemaddux · March 13, 2010, 03:44:28 AM

Well, my Twin reverb reissue started to make this funny crackle on certain frequencies....and I noticed when the reverb is on 10 and I should be swimming in reverb, the reverb is barely there (like it was on 2 or so)
I thought...ehhhh.....no problem......new set of tubes..........its about that time. 5-6 years.
so, I took it in the shop that I work at, and tried out a stock twin reverb reissue and compared the sound to my amp with the same exact tubes from the dead stock twin reverb and it still had the same problem.
all combinations of tubes, for example:
my power amp tubes with stock preamp tubes
my preamp tubes with stock power amp tubes
replacing one of my tubes at a time with the stock tubes
cleaned out the preamp tube sockets with de-oxit
Now im not gonna go and open this up, because I really dont know what im doing inside a tube amp and I dont really feel like dying tonight. But do you guys have any ideas?
Thanks!

Hides-His-Eyes · March 13, 2010, 06:35:32 AM

Reverb tanks do die, it's a sensitive bit of equipment.

Boogdish · March 13, 2010, 09:16:45 AM

1. Reverse the red and white reverb cables. If these are backwards the reverb will sometimes just barely work. Probably not the problem, but it'll take you 30 seconds to check.

2. Take your reverb tank out of the cabinet, out of the bag and visually inspect it. There's not a piece of foam in there is there? Are there springs unattached or feeling ridiculously loose? Before you put the tank back in the cabinet, turn the reverb up and flick the springs with your finger. If the sound isn't very loud (this should be louder than your regular reverb sound in a normal working Fender blackface reverb) then your problem is in most likely in your recovery stage or the output transducer on the pan. If the sound is very loud then the problem is most likely in your driver stage or the input transducer on the pan.

3.Try a different pan (this is easier to do while your old pan and cables are out of the bag from the last test). If a new pan doesn't solve it, I would try replacing the tube(s) one last time and if that doesn't solve it, take it to a tech.

mikemaddux · April 06, 2010, 08:49:35 AM

Well, the Twin Reverb went to the doctor today......I should get it back in about a week or so

Ill let you guys know what the issue ended up being...

MikeH · April 06, 2010, 09:28:37 AM

I'm taking all bets!! 3:1 on a solder joint gone bad, 7:2 on a bad component, 15:1 on a bad reverb OT, 20:1 on a bad reverb tank. Place your bets! Place your bets!

*Note: I am not actually taking any bets

GibsonGM · April 06, 2010, 09:45:51 AM

Knowing Fender, bad solder joint that led to arcing, 1/2 fried plate resistor or some such thing. Give me 10 on the first option!

MikeH · April 06, 2010, 11:30:39 AM

Yeah, probably should be more like 1:3 on the bad joint/component.

I had a similar problem recently with my reissue super reverb- lots of strange noise coming from the reverb section. Turned out to be the preamp tube feeding the reverb was going rogue. Fortunately for me that was a very easy fix.

wavley · April 06, 2010, 03:23:16 PM

I'm with the bad solder people, I used to see this all the time in Fenders when I worked at the shop.

mikemaddux · April 28, 2010, 04:48:20 AM

Well I got it back from the shop and it still has barely any reverb....

The tech said there was some components in the channel 2 driver section that needed to be replaced.

I'm gonna take it in and try it with a new reverb pan and see if that solves the reverb issue....

Paul Marossy · April 28, 2010, 10:29:58 AM

When I first got my Twin Reverb, it had no reverb at all. One of the tiny wires inside the reverb tank had broken. All I had to do to fix it was solder that wire back on. Maybe you have one of those wires hanging by a thread? Might be worth a check.

wavley · April 28, 2010, 11:15:50 AM

Quote from: Paul Marossy on April 28, 2010, 10:29:58 AM
When I first got my Twin Reverb, it had no reverb at all. One of the tiny wires inside the reverb tank had broken. All I had to do to fix it was solder that wire back on. Maybe you have one of those wires hanging by a thread? Might be worth a check.

This is a REALLY common problem in the Blues Jr, they use those push in connectors that cut through the insulation for the wires in the tank and the wire eventually just breaks off. Just remove the old wire piece, push the new in and done, or better yet just solder it, that's what we used to do at the shop.

Paul Marossy · April 28, 2010, 11:27:47 AM

I was also going to ask if anyone checked the RCA cable. It could be that the cable is shot, too.

Top Top · April 28, 2010, 08:07:29 PM

If the reverb is there but just very quiet, doesn't that rule out wires that are broken/not connected to the tank?

Paul Marossy · April 28, 2010, 08:37:33 PM

Quote from: Top Top on April 28, 2010, 08:07:29 PM
If the reverb is there but just very quiet, doesn't that rule out wires that are broken/not connected to the tank?

Yes, but those wires inside the reverb are very small in diameter. One them could be hanging on by a strand and is not actually broken yet. So it is still making a connection, but not much of one. When my own reverb tank had a broken wire in it, I could get the reverb to come on momentarily if I shook the amp a little bit. That's when I knew it must be a broken wire or something.

It could be other things. In my own Twin Reverb, the stripboard warped and one of the coupling caps was actually broken as a result. So it would make loud popping noises when the amp warmed up. It was apparently arcing inside. Replaced the cap and it was all good again.

It could be any number of things causing the problem. The RCA cable could be bad, or one of the RCA jacks has some kind of problem. Or maybe one of the solder joints has become "cold" because the stripboard warped and it was dodgy when it left the factory, so that pushed it over the edge.

Much of this of course assumes that it's an old Twin Reverb, not a reissue... which I see that the amp in question isn't an old one.

wavley · April 29, 2010, 09:17:55 AM

This can also happen if the send wire is fudged up but the return still works, the vibration of the cab can induce some vibration of the springs thus giving you a tiny bit of reverb return.

Being that this is a reissue, did the tech take the board out and resolder it? New Fenders have a TERRIBLE problem with solder cracks. I would also suspect the ribbon cables coming from the controls to the board. I looked at the schematic http://www.fender.com/support/amp_schematics/pdfs/65_Twin_Reverb_ReissueE73.pdf and there any number of components being bad that can cause this, but I would look at the simple stuff first. Also, I would check the tube sockets of V3 and V4 to make sure that they aren't the problem.

Paul Marossy · April 29, 2010, 11:01:14 AM

Quote from: wavley on April 29, 2010, 09:17:55 AM
New Fenders have a TERRIBLE problem with solder cracks. I would also suspect the ribbon cables coming from the controls to the board.

I've heard a lot about cracking solder joints in the new Fender amps. That's another good possibility. Ribbon cables are less likely to fail, but it's possible that it might have a dodgy connection in it.

wavley · April 29, 2010, 12:01:52 PM

Quote from: Paul Marossy on April 29, 2010, 11:01:14 AM
Quote from: wavley on April 29, 2010, 09:17:55 AM
New Fenders have a TERRIBLE problem with solder cracks. I would also suspect the ribbon cables coming from the controls to the board.

I've heard a lot about cracking solder joints in the new Fender amps. That's another good possibility. Ribbon cables are less likely to fail, but it's possible that it might have a dodgy connection in it.

The only reason that I suspect the ribbon cables is because they are the pierce the insulation type cables. The Mackie 1604 mixer makes me suspect ribbons more than I should sometimes, they were on like Rev. G or H when I left the shop four years ago. It was the joke around the shop when somebody brought a 1604 in that had been in the prior year that it was time for the new cable revision, and it was usually true.

Paul Marossy · April 29, 2010, 12:19:31 PM

Yeah, I could see why you suspect those. Interesting about the Mackie mixers, also terrible for reliabilty.

wavley · April 29, 2010, 01:07:55 PM

Quote from: Paul Marossy on April 29, 2010, 12:19:31 PM
Yeah, I could see why you suspect those. Interesting about the Mackie mixers, also terrible for reliabilty.

The funny thing about the Mackies was that it wasn't consistent. Some had the original ribbons that worked perfectly and some needed every single revision as it came out. Nobody had an answer, but I suspect it was the environment in which they were used being high vibration or not. You could have a cosmetically beautiful that was a PITA next to a beat up one with broken knobs that worked perfectly, excluding the broken knobs part.

But I digress, considering that it has nothing to do with Fender amps other than the possible unreliability of the ribbon cables.

petemoore · April 29, 2010, 01:18:48 PM

The tank driver could be tested with a known working driver, minding the impedance, something like headphones should make a noise that sounds like when mechanically coupled to springs, would be able to drive the springs, with the reverb turned up.
To check the return..plug in an RCA cable, you should be able to hear 'thumbuzz' or other source] coming through the amp/speaker.
This stuff that can be messed with to get an idea where the problem isn't without having to open the amp.

News:

OT - Fender Twin Reverb Reissue Problem - Reverb and Crackle