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Post subject: Re: Need some advice, with a fender Super reverb.
Posted: Fri Jan 06, 2012 9:18 am
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Upate: just got the amp back from an amp tech last night. Over all the amp is in decent shape. Some scratchy pots. There some loose items in the chasis that were tightned up. The amp looks like it had something dropped in it, but luckily it only slighlty damaged the frame and the reverb and tromolo pots. Easy fix to replace a couple of pots. There are no burn scars, burn marks or hot spots in the electrical components. The caps were all original so it was suggested to get them replaced and they are on order and i have an appointment for recapping in a week and a half to two weeks from now. The tubes were an older bottom of the barrel set, though still good they are a little weak when tested but still fine (this amp tech is a bit anal retentive) he said to start looking for low current draw set of power tubes. Because a set i pulled out of an hrd are "to hot" in terms of current draw. But we are going to try again after caps are replaced. The speakers are still in good shape for 31 years of age and was told they still have years left of service. There are a few more little things like needing a new reverb cable, since it was replaced by a non fender non amp part. Over all he said it was a great find. Said the hum could be nothing and shook it off as some old amps just hum. He said i could play through it and encouraged it but since i know it needs caps and power tubes, i can wait. I dont want to get impatient and ruin something. I did have. Few question, i didnt want to sem like a complete idiot though. Will new caps effect tone? And what and where and how do i get low current draw tubes?


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Post subject: Re: Need some advice, with a fender Super reverb.
Posted: Fri Jan 06, 2012 11:07 am
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Just a little note. On EBAY there are a pair of 1996 made Svetlana SV-6L6GC. (11/1996 as the production date = "96 11"). With the old stylized "S" logo. These are the primo of the St. Petersburg made 6L6GC's. Much better QA than newer 2000-2010 made 6L6GC's.

Look for these types. Very good tubes.

http://www.ebay.com/itm/2-Pcs-Matched-S ... 43ac4dc2dc


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Post subject: Re: Need some advice, with a fender Super reverb.
Posted: Fri Jan 06, 2012 4:25 pm
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Will new caps effect tone? And what and where and how do i get low current draw tubes?
-morbe

No cap won't change the tone.
Low current draw tube ??? Any good tubes must work in the amp , with proper bias. I don't know what your tech mean by that. He can't adjust bias ? Or he don't have a set of good tubes ?


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Post subject: Re: Need some advice, with a fender Super reverb.
Posted: Fri Jan 06, 2012 4:29 pm
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He mentioned that some extra tubes i had with correct bias were running a little hot said for me to get low gain tubes?


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Post subject: Re: Need some advice, with a fender Super reverb.
Posted: Sat Jan 07, 2012 2:43 am
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morbe wrote:
He mentioned that some extra tubes i had with correct bias were running a little hot said for me to get low gain tubes?

If you ( he ) talk about low gain output tubes , I never see or read anything about these spec about output tubes. Gain is always for preamp tube. If power tube is defective and draw too much current, you replace it.

I don't know how power tube with correct bias can run too hot unless is defective. Different brand or batch can run with different current drain. That is why we have always check bias.

1-Did I miss somthing ?
2 Are you sure he is a professional tech ? He should know more than you which output tubes will do the job.


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Post subject: Re: Need some advice, with a fender Super reverb.
Posted: Sat Jan 07, 2012 7:34 am
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He knows what he's doing i just dont know how to repeat and interpret what he says. He's been working on amps or a while starting with these older amps. Any how im going to test everything after the caps are replaced. Then if we have to look at the bias circutry well go from there.


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Post subject: Re: Need some advice, with a fender Super reverb.
Posted: Sat Jan 07, 2012 1:42 pm
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stratele52 wrote:
1-Did I miss somthing ?
2 Are you sure he is a professional tech ? He should know more than you which output tubes will do the job.


OKay, I think I got it straight. He says by the way you have to bias them there is no Pot to dial them down, you have to take a reading from the Tube to ground I think he said. And the tubes that I had were at idol and pulling a safe amount of voltage but when its being played the voltage (I think he said Voltage) could peak higher than what the tube was rated for, causing the filaments to glow red hot if I wasn't careful. because I wasn't trained to check bias on new tubes to make sure that they will fall in a safe voltage range at idol and be able to make sure that its low enough to give room to peak in a safe level as well. This is why he suggested I get low gain tubes.
I suggested that he put a bias pot which he replied that he could and its not an issue or that difficult to do. He even said that he could put a bias pot on each tube so that it doesnt matter what kind of tubes I get, matching or non matching because I can could place each tube in the correct range. But He said that even with one bias Pot the amp tone will be effected and I could loose some warmth.
If this is true how much warmth could I loose and will it sound like a completely new amp?

And Dead God in Heaven, How do I get the funk out of this thing?! I've tried Febreeze, vinegar, Lysol, and nothing get the smell of cigarettes and goat $@! out of this thing!


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Post subject: Re: Need some advice, with a fender Super reverb.
Posted: Sun Jan 08, 2012 3:35 am
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morbe,

It is not very easy to understand what you ( or your tech )said and mean about all this. I'm french speaking so not easy for me to translate , sometimes, and understand what people mean.

I can't understand why there is a problem for your tech to find and put good tubes you need in the amp. This is a common and basic job.

And to put a bias pot it is an easy job for a tech.
Sorry but for all those statements, you should see another tech . He his not a professionnal tech


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Post subject: Re: Need some advice, with a fender Super reverb.
Posted: Sun Jan 08, 2012 4:07 am
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Let me add a few notes, to hopefully not further the confusion.

1.) A good working power supply (new caps, in-tolerance resistors, choke, and rectifier) will maintain a proper range on your output tube anode plates. Both voltage and current.

2.) Your amp has a screen resistor which helps keep the screen grid at LOWER voltage than the anode plates. This helps keep the tube from thermal runaway.

3.) A good working Bias Power supply will keep the signal grid at a negative voltage. And control the current flow through the tube. Your Super Reverb comes with a bias pot OEM. So someone must have removed the stock pot, for some reason. And never replaced it. In-tolerance grid-to-ground resistors also help keep the tube operating in proper range.

4.) Output power tubes that pass low current are well-worn tubes. I assume this is what the tech meant by low gain power tubes. And won't sound too good. You want tubes that pass a healthy current that can be regulated by the Bias Power supply. FWIW... power tubes are not gain tubes. Most of the gain is done by the pre-amp (or gain stages). Power tubes pass current and HV energizing the output transformer. With the AC signal riding on top of the HV DC.

5.) You need to bias at idle, the amp in the Class AB1 range to get the best tone and life. If you drop the bias down to the Class B range, it'll sound bad. And no matter how loud you play the amp, it will not rise into the Class AB1 range.

6.) I don't think that you need two bias pots. One for each tube. That just complicates the circuit and unless the tech uses quality pots, it can add unreliability to the unit. Just buy matched pair of output power tubes. And use one pot to adjust idle bias.

7.) The tech never addressed the pre-amp or gain stages. Many times this is where noise and problems are generated in tube amps. Really, going section by section is the best way to get a reliable, noise-free amp... that'll give you long life.

Just my 2¢ worth. Good luck! This is a great amp. I hope you get it working well.


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Post subject: Re: Need some advice, with a fender Super reverb.
Posted: Sun Jan 08, 2012 4:28 am
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I think that maybe the two separate bias pot comments got misinterpreted. The guy Frank who I take it to didn't openly suggest that he wanted to put two bias pots in the amp in order to run unmatched tubes. I think that what he was trying to say that anything can be done, but when you start adding things in the circuitry you get a chance of tone loss.
I'm really seriously thinking about getting a bias pot installed though, the consensus that I've been getting from every one (not just here) is that its worth it. (They don't make tubes like they used to).


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Post subject: Re: Need some advice, with a fender Super reverb.
Posted: Sun Jan 08, 2012 4:46 am
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Bias pot installation won't change tone. Bias pots is very very usefull.


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Post subject: Re: Need some advice, with a fender Super reverb.
Posted: Sun Jan 08, 2012 5:01 am
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By the way I know its hard to tell but, on the lighter no technical side of things I was at a near by fabric store Hancock's (hee hee) Because on the phone they claim to have a pretty decent vinyl section. And can you believe that they had Tolex! Its not actual "Fender Tolex" sold on line for $25 a yard but matching Tolex non the less. They had the exact match of black tolex for $12 a yard! Then I tried to bargain with the lady saying "C'mon discount it a bit, how often do you sell this?" come to find out its a hot!! item there. But she pointed me to remnant area where they had odds and ends of it. I found a perfect 3 yard piece of it for $5 dollars a yard. a $15 dollar piece.....But its not true black. its had a silver hue, I'm assuming its suppose to look aged? buy I want to buy the true black tolex vinyl but I like the price of this one and thought what you guys thought about the "off" color.

Image

Image


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Post subject: Re: Need some advice, with a fender Super reverb.
Posted: Sun Jan 08, 2012 5:12 am
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Great discovery mobe. Hancok's fabric store is in the USA ?

I buy some kind of tolex or vinyl at my local fabric store for amp cab projet I built. Great color and good deal


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Post subject: Re: Need some advice, with a fender Super reverb.
Posted: Sun Jan 08, 2012 5:59 am
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yes hancok's in in the U.S. Here in Texas not sure were else it is. They had a very decent display of vinyl. Lost of textures and colors.


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Post subject: Re: Need some advice, with a fender Super reverb.
Posted: Sun Jan 08, 2012 6:30 am
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Thank's for the answer morbe.
Texas , far from my home , Montreal. I wish to visit your state and also see Dallas and eat big steaks.
I go sometimes in Vermont an New York states , I'll look for fabric store like Hancok, never know what kind of stuff I'll found.


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