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Post subject: Re: Need some advice, with a fender Super reverb.
Posted: Sun Jan 08, 2012 9:29 am
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Morbe, looking more closely at your amp--- you have a CBS 70 watt Master Volume "Super Reverb." It runs nearly 500VDC onto the plates of the power tubes. And should have at least 600VDC rated caps in the power supply. It has solid-state rectification bypassed with "snubber" caps. All of which means the unit needs very heavy duty parts.

Prolly UF5408 diodes in the PS and stacked filter caps (in series with equalizing resistors) replacing the OEM filter caps in order to get good voltage ratings. Maybe go for two 350VDC stacked to get 700 VDC total rating.

You need very heavy duty output tubes. Like original Sylvania STR-415 or Philips mil spec 7581A. No regular 6L6GC will be able to handle the plate voltages for very long.

And the Standby Switch could be a big source of noise. Finding a 600+ VDC rated one is really going to be hard.

Your tech should treat this amp as if it's an ultralinear amp, that really pushes the output section to the max.

BTW... the amp has a hum or pot for adjustment between the output tubes. NOT as bias pot. I highly suggest adding a bias pot to the circuit.

I must credit a little bird from AZ for most of this information. :wink:



http://www.webphix.com/schematic%20heav ... tr_rev.pdf


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Post subject: Re: Need some advice, with a fender Super reverb.
Posted: Tue Jan 10, 2012 12:09 pm
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Not to jump the gun but i purchased the black tolex from the fabric store. Its not the same as fendr black tolex,the grain is a hair smaller but to the naked eye you cant tell. Plus they moved remaining roll over to the remnents section causing the cost to drop to 5 dollars a yard. I got enough to retolex the amp and make an amp cover! Anyhow i'm being told on another site that this amp worth poo but when im done with it its going to be my main rig. Silverface or not its going to rock! Its gonna shine like a diamond in a goats $@!


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Post subject: Re: Need some advice, with a fender Super reverb.
Posted: Mon Jan 16, 2012 8:22 am
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The restore process is under way, The Amp was returned on Saturday morning with all new caps and sounds great. New tubes sounds great. And Saturday early evening the Replacing the tolex started. I did it my self to save cost. Not the greatest job but hey it was my first time. But its a huge improvement to what it did look like.

here are some pics.

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Some before pics

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Taking off the Old Tolex

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Ooops, had a weak joint I had to reinforce

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all the pieces cam off in whole pieces so I could get semi close pattern.

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Also while the wood glue was drying i hit all the rusty metal pieces with a wire wheel.

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The sand down

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The retolex job

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And the finished product.

The corners are cut clean and well, but some how maybe with razor getting a little dull some of the white under material started to show in this pics. maybe i'll just get a black marker to cover them up or something.


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Post subject: Re: Need some advice, with a fender Super reverb.
Posted: Mon Jan 16, 2012 11:46 am
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Nice job! Is the circuit being worked on?

Thanks! And Happy MLK Day.


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Post subject: Re: Need some advice, with a fender Super reverb.
Posted: Mon Jan 16, 2012 2:46 pm
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Yes nice job


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Post subject: Re: Need some advice, with a fender Super reverb.
Posted: Mon Jan 16, 2012 6:01 pm
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Well the circuits were worked on, but as of right now Frank my amp guy said that there was still some internal issues with one power tube socket, with all adjustments and such. one tube still burns hotter just slightly. He gave it his blessing and said play like you normally would and and the problem tube just to make sure it doesn't start to melt down. But he said its perfectly fine to play. dont know if he wants to make more money but he keeps suggesting that I mod it to a Bassman by getting a 50 watt output or power transformer (I forgot which one he said) and let him change a couple of things.

Thanks for the compliments! My first job. you might see some white and this is also where I make lines with a wax pencil for sewing, though I didnt know it was wax until I tried to wipe it off with a damp rag. LOL gotta get that off some how.


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Post subject: Re: Need some advice, with a fender Super reverb.
Posted: Tue Jan 17, 2012 2:55 am
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You are better to replace or repair if you can, this tube's socket. This will go worst with time an cost you more money.
Why don't you trust your amp guy ? You bring some amps to him before ? He do good job or not ?


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Post subject: Re: Need some advice, with a fender Super reverb.
Posted: Tue Jan 17, 2012 5:48 am
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I totally trust my amp guy. I take several amps to him. But the reason this amp is getting fixed one problem at a time, is because i dont have the money to get it all repaired at once. He's a great amp tech and A good person. I am going to get it all done hopefully next month. Its when i get some more cash aloted for music stuff.


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Post subject: Re: Need some advice, with a fender Super reverb.
Posted: Tue Jan 17, 2012 7:10 am
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Morbe, your amp tech is prolly talking about changing the output tranny. To get more of a "AB763-ish" BF tone. Which in this amp is not a simple backwards step.

The whole power supply needs to be redone to yield voltages in the AB763 range. And the gain stages, phase inverter, and global feedback part of the circuit may need re-working. In other words, it could run you more $$$ than just another output tranny.

Is it worth it? Well, if you want the classic BF Super Reverb tone... the changes will get you closer, if properly implemented. But reversing the changes will not be a simple thing.

http://www.webphix.com/schematic%20heav ... tr_rev.pdf

http://www.webphix.com/schematic%20heav ... _schem.pdf


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Post subject: Re: Need some advice, with a fender Super reverb.
Posted: Tue Jan 17, 2012 4:10 pm
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Not a simple change indeed. It's either rebuild to your amp's specs, or think about stripping out everything to change to BF -- you don't want to have half-baked amp.

On doing repairs bit by bit -- I'd suggest doing what I do and save up and do it all at once -- it's usually cheaper and it's easier to fix it altogether vs. piecemeal. It does mean you have to wait longer, but you could do things like your re-tolexing (nice work) while the chassis is with your amp tech.

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Post subject: Re: Need some advice, with a fender Super reverb.
Posted: Thu Jan 19, 2012 9:48 am
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Im going to put it back in the shop so they can futher investigate the hotter tube. But in the mean time, lets talk speakers. Because it needs speakers bad! Im getting told to put in alnico speakers in it. Is there realy a difference? Jensen alnico 10's at 25 watts are 100 bucks a pop! Is there really a noticable difference or is the ceramic speakers vs alnico speakers another endless debate like mexistrats vs ameristrats. Or tube amp vs ss amps?


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Post subject: Re: Need some advice, with a fender Super reverb.
Posted: Thu Jan 19, 2012 3:33 pm
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Really depends on the tone you are after. IN GENERAL, ceramic magnet speakers tend to be a little more efficient than similar sized alnico magnet types. So, a good ceramic magnet speaker will tend to be a bit louder than a comparable alnico--at the same volume level. Alnico TEND to have an earlier and more Bluesy break-up. A bit warmer tone.

You have a powerful amp there. So, I think the qualities of the alnico may suit it better. But, it really depends on what kinda music you plan on playing through the amp. Prolly best to test drive some speaker cabs loaded with various makes and models of speakers, before deciding.

Good luck with all of that!


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Post subject: Re: Need some advice, with a fender Super reverb.
Posted: Fri Jan 20, 2012 1:08 pm
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I will look into speakers as the months pass these speakers still got some life in them. But FINALLY, my amp is getting picked up by the repair man, this time with a clean bill of health! Swapped a resistor and finally both tubes circuts check out fine. Its amazing how a 30 cent part on these things can make a world of difference. It brings a new meaning to "pay me a little now or a lot later." So when the grill cloth is finally replaced then this will move in as my main gigging amp.


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Post subject: Re: Need some advice, with a fender Super reverb.
Posted: Mon Feb 06, 2012 7:04 am
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And the battle restoring this amp goes back a bit as i tried to work on the amp myself. (gotta live and learn i guess) well i had a scratchy pot and desoldered it, removed it took it apart and cleaned the contacts with and eraser, which worked and is something ive done on electronics before. Resoldered and installed it and every thing was good UNTIL. I tried to fix the vibrato. I thought "maybe its the tubes?" So i pulled and reseated all the preamp tubes, reverb tubes and basically all the smaller 12ax7 type. Though when i plugged my strat in it. I got a realy bad high tone buzz. A buzz i dont think was there before i pulled the tubes. At this point the tone selector was activating two pickups so i should have gotten any buzz but it was there. A mid pitched hum. But i could touch the guitar strings and he hum got quiet, still ther but very quiet. Lol i was playing the amp with the strat barefoot on tile floor and noticed that when i lifted my feet off the ground the noise got a little less. So i started thinking, maybe i did mess something up while working on the pot. So after some google searches i then, started to trouble shoot the amp and guitars. And here is what i found:

took chassis out of the box with all tube intact remained conected to speakers and poked around with a drum stick listening for a loose ground connection. (None could be found)

Tried both channels, (hum is evident in both channels)

*this is where i start to suspect maybe its the guitar*

Tried another strat style guitar with same settings, tone knobs high and tone selector in the 4th position. (noise was there but not as loud. Had both kramer style strat and fender strat wired and plugged then in alternating betwen the two the noise is there with both but louder with my fender strat. They both will produce the same level of hum when the fender strat is plugged into the number 2 input and the kramer strat is in the number 1 input. The hum is almost non existant with a true humbucker type guitar.) *i know that last comment will make me seem that i dont know what im doing but i know single coil pickups are noisier than humbuckers, its just that i dont remember it sounding that noisy with two pick ups active. *

Put a cable in my strat with same settings listed above and tested ohms from strings to the sleeve and it peak when i initially at about 400 of course but then stablized a slip sec later. And flattened out dancing from 0-4.

Bofore.i.get all the negative.comments can i please state and ask the following.

Im not as worried the amp has an issue since a true humbucker guitar will not replicate the noise. I plan to replace the pot with a 1meg pot. Since the original is 999k pot. Come to find out the capacitor for the vibrato was not replaced! But i was read that this was the main culprit, the vibrato i dont think ever worked. The cap is a 5mf 50v but i was told that newer capacitors are stronger and i should replace it with a (recalling from memory.may be wrong) 4.7mf 46v capacitor. Does that sound right? Also will copper shielding help with this noise or is that only for single coil noise btw forgot to mention the mid range hum i get from this amp is there in all tone selector positions 1-5


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Post subject: Re: Need some advice, with a fender Super reverb.
Posted: Tue Feb 07, 2012 6:15 pm
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A note first. You are mentioning several unrelated problems. This is not a good way to solve the "big picture." IMHO. Better to go step-by-step:

From the source (guitar)

To the patch cord.

To the amp's power supply and bias stage.

To the amp's input stage.

To the amp's gain stages.

Then, the EFX stages.

Phase Inverter.

Power section (output tubes).

That way you'll catch the issues. It works better for me, than a helter-skelter manner. With one person suggesting this solution. And another suggesting that solution. Also, you'll gain a better understanding of how the guitar and amp electronics work.

Maybe, log onto Merlin Blencowe'S Valve Wizard to help you with matching theory to practice:

http://www.freewebs.com/valvewizard/


OK...You have several issues here.

1.) " I could touch the guitar strings and he hum got quiet, still there but very quiet. " This is either a guitar wiring/pups issue or a problem with the input section of the amp. You body's capacitance is changing the frequency of the hum. Try another guitar or patch cord to isolate the problem.

2.) So i pulled and reseated all the preamp tubes, reverb tubes and basically all the smaller 12ax7 type. Though when i plugged my strat in it. I got a realy bad high tone buzz. Sounds like a socket or two with contacts that need tightening, cleaning, or replacing. Try the old "chopstick test" on the dressing points of the scoket.

3.) The cap is a 5mf 50v. If the bypass cap is bad, you'll have a weak EFX or a shorted circuit (no EFX). There are good non-polar 5mfd caps these days. Maybe try a Russian mil spec PIO. Or go to a Sprague Atom 8mfd/150VDC 'lytic.

Just my suggestions. Make a plan & follow it. Good luck!


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