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Post subject: Fender twin reverb reissue Strange noises, crackles and dead
Posted: Thu Aug 22, 2013 2:47 am
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Hello.
I have a Fender twin reverb reissue and have some problems with it. It started with just a drop in volume from time to time. And then it started to buzz and pop when i didn't play. And now it's "dead". The fuse blows with just a little bit of volume and base. It sounds like fireworks when i go over 3 in volume with no base. If i push up the base the fuse blows.

And also my tubes blinks with even the smallest vibration. A guy told me that he thought it was a power issue. Said something about 2 plates in the transistor (The big black box behind the tubes) But i wonder it its the tubes. Because when i gently pick the main tubes with the backside of a pen the amp starts to buzz more and i can clearly hear the picks.

The tubes were replaced about 2½ years ago.

It seems to be something happening when the amp vibrates on high volume. When i disconnect the build in speakers and connect a external speaker i can play as loud as i want with no issue. Just the buzzing and pops.

Sorry if my English is a bit bad, i come from Sweden
I am going to send my amp for service but i cant do it because i need to save up some money first. And i have no idea what it will cost.

Best wishes Simon


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Post subject: Re: Fender twin reverb reissue Strange noises, crackles and
Posted: Thu Aug 22, 2013 3:51 am
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Welcome to the Forum.

" The big black box behind the tubes. "

They prolly meant the power transformer. But, I'd first check all connections on the amp's circuitry. If they look okay, you'll need a tech to go through the circuit board for problems, before looking into the transformers.

Good luck with the amp!


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Post subject: Re: Fender twin reverb reissue Strange noises, crackles and
Posted: Thu Aug 22, 2013 3:55 am
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Hi semestermorgan,

It might be a power tube or tubes (the four big ones). Do you have a spare set that you can try? If no spares, pull the two inner tubes (middle two of the four), test the amp. If all seems good, one or both tubes that you pulled are bad. If you still have the problem, replace the two inner tubes and pull the two outer tubes (the two on the outside of the four). Test again and see if you still have the problem. Remember to turn the amp off and allow the tubes to cool before pulling them.

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Post subject: Re: Fender twin reverb reissue Strange noises, crackles and
Posted: Thu Aug 22, 2013 3:58 am
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There is no transistors in this amp . The "big box" you talk look to be the filter cap housing.

Check your power output tubes . A bias check and adjust is must too.

One easy test you can do before ;
1- Put new fuse , same power

2- Remove you 4 power tubes

3- Power ON the amp and wait .

a ) If fuse do not blow after , let say , 10 minutes , you need to check and replace the four output power tubes AND adjust bias .

b) If fuse blow , trouble is in power supply section . Resistor , filter caps or just a solder . You need to see a good tech. This do not mean output power tubes are good . They could be bad and damaged something in power supply .


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Post subject: Re: Fender twin reverb reissue Strange noises, crackles and
Posted: Thu Aug 22, 2013 4:00 am
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If you have to replace one bad tube, after 2 /12 year , good job is to replace all of them in same time . Keep the old good tube as spair


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Post subject: Re: Fender twin reverb reissue Strange noises, crackles and
Posted: Thu Aug 22, 2013 4:04 am
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+1 stratele52

We also don't know if the bias was set properly when the tubes were replaced. :?:

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Post subject: Re: Fender twin reverb reissue Strange noises, crackles and
Posted: Thu Aug 22, 2013 4:22 am
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shimmilou wrote:
+1 stratele52

We also don't know if the bias was set properly when the tubes were replaced. :?:


+1,


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Post subject: Re: Fender twin reverb reissue Strange noises, crackles and
Posted: Thu Aug 22, 2013 6:14 am
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Thanks for all the replies and help. I don't have any spare tubes to test with, and i meant power transformer, i think (The big black box). I have checked the circuit board if anything looked suspicious and checked all the cables. But just with my eyes so i don't know if any thing is broken but all the solderings looked okay and nothing was loose. And i have checked the reverb too.

I have no clue about the bias. But the one who changed the tubes was recommended by a music store here in Sweden so i trust him. But you'll never know. I don't know the model of the power tubes, if i understand right you can have different tubes for different sounds. If any one wants a picture here it is: https://plus.google.com/104555561436850 ... an3LS1Fvvv
It's a really bad picture so you cant see that much.

But i can try checking the tubes as described and see what happens. Worth mentioning is that when i knock on the top of the amp or on the power transformer when the amp is off it sounds like there is a little bell somewhere on the left of the amp. I cant pin point the sound but i think its from a power tube. Don't know it that's normal, It's my first tube amp and I have had it for since the tubes were new without any problems.
I can think its not so easy to know the problem without looking at it but any help i can get is deeply appreciated.
And i will take it to a professional who know's the stuff. But i am a bit worried about the cost of the repairs. If it's just the tubes i am safe! If it's other stuff to i will have to save up some money, I've heard it can be quite expensive when more things need repairs on the twin reverb. I am unemployed at the moment so money is a bit hard to get.

Thanks again /Simon


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Post subject: Re: Fender twin reverb reissue Strange noises, crackles and
Posted: Thu Aug 22, 2013 7:17 am
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Please do the test I suggest FIRST

Don' t waist your time with other thing for now . It is not useful .

Amp repair need to be done step by step .

I did not read carefully about the "black" in the statement the big black box . Yes it is a transformer not filter housing


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Post subject: Re: Fender twin reverb reissue Strange noises, crackles and
Posted: Thu Aug 22, 2013 8:11 am
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" there is a little bell somewhere on the left of the amp. "

Sounds like you may have a microphonic tube. If any output tube (the 5881 WXT+ big bottles ) is microphonic, you can get a short in the amp that can blow the fuse. What you can try is pulling all the tubes, except the four 5881 WXT+. Turn amp on and gently tap each output tube with the eraser end of a pencil. See if you can isolate the ringing noise to one tube.

If you have a noisy output tube --- I suggest getting at least a matched pair of new 6L6GC, if not the entire quartet. Personally, I am not a big fan of the Sovtek 5881WXT+. They are really heavy duty 5881 (or 6L6WGB). And not true 6L6GCs. I prefer Electro-Harmonix 6L6GC or Tungsol STR-6L6GCs.

If no noise, try replacing end 12AT7 & 12AX7 tube from left to right in proper postition, one-by-one (amp off with each replacement). Tap each new addtion to see if you can isolate the bad tube.

There is one other issue that can cause a big racket with vibation... bad solder points on the sockets, themselves. You'll prolly need a tech to rule this out.

If you go the new output tubes route, be sure to find someone that can check the bias.

Good luck. Keep us informed.


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