A fender super reverb MOD that concerns me

GroupDIY Audio Forum

Help Support GroupDIY Audio Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

W DeMarco

Well-known member
Joined
Dec 21, 2005
Messages
455
Location
Cleveland
Hi all,

Studio got a blckface Super reverb that I want to rock, However it belched out some serious stuff the other day, Pure bad noise, didnt sound like a guitar, More like a trainwreck with a dose of reverb. I assumed some stuff was fried but when I opened it up I found a possible short in this mod that came with it. Basically a pot tied into three points on a circuit board. 2 CAPS are involved. I made a webpage that documents the mods and possible short. www.vuturevisions.com/supershort.html I am concerned this could have hurt the circuitry in some way. Any advice. Also should I just get rid of this mod altogether? I don't really need it to be real quiet but distorted for any purpose.

Thanks

Will
 
I would pull that out of there.
Looks like he wanted to change the tone a bit, looks like a 0.01 ceramic to ground via a pot.
Looks kind of dangerous, lousy wiring job, he is coming off tyhe HV after the plate R, so direct contact to HV DC possible.

Drain the pwr caps before ripping out that circuit.
Stock Super black faces sound pretty good without any mods, if ya know what I mean.

I do have a book with "Ten Easy Mods to Make Your Super Reverb Sound Better" from Webers book if you are interested.
The book is at home, so AM.
 
Im assuming all I do is disconnect these three points from the pcb. I would'nt think it would have involved removing some of the circuit to create the mod.

Thanks

Will
 
Pull the red/blk coax, that is not stock.
Pull the Alpha pot and all it's wiring, that is not stock.
Pull the second cap I see a-danglin by the white wire.
This thing might not work after ripping out the mod, but we can put humpty dumpty back together again, there are wiring diagrams for that thing all over the place.

I can't see the face plate, but I fear it has an extra hole in it. :cry:
 
The tube pin in question is a cathode in the vibrato circuit.
I can't tell where the red wire (the junction of the two 220k's, preamp section output?) or the cap is connected (pin 2, input grid of the phase splitter?).

The black is connected to the neg fdbk point.

Some sort of presence boost?

Pull it out now!
 
Yeah mod came with a hole as well. Luckily its on the back side!!

Sounds like a wortheless mod. Its history. Thanks for the advice guys.

:green: W
 
I can't tell if it's there 'cause that big grey mod wire is in the way, but there should be a little disk cap going from the junction of the two 220k preamp summing resistors to the grid of the phase splitter (last 12ax7) via the yellow cloth wire.
 
I went ahead and posted a couple more pics to the webpage. I moved that big ole grey wire to the left and snapped a couple more. Im not sure if the wire you we're speaking of is there or not.

http://www.vuturevisions.com/supershort.html

Same link

Im expecting the caps I ordered to arrive tomorrow. I'm gonna wait and take out the mod when I recap it.

Will
 
So the capacitor is NOT there. I should go from where the red wire is to where your Mod #3 arrow is pointing. It looks like said cap has been re-routed to the pot. This is how a master volume can be rigged, but I don't get why the bottom lug of the pot (Blk wire) is going to the neg fdbk point and not right to ground (the other side of the 100ohm resistor it's tied to).

And no, the end of that cap should not be touching the tube lug.
 
Here's a 70's fender amp with a stock master volume.
The bottom of the pot goes to ground, whereas in your amp it's tied to the other side of the 100 ohm resistor.
http://www.ampwares.com/ffg/schem/bassman_135_schem.jpg

The master volumes that Fender simply added to their original circuits didn't sound good at all, as the preamp wasn't designed to deliver high gain creamy saturation on it's own.
 
Not good huh? This is a poorley modded amp from the sound of things. Again I've had many Fenders but never a mod for master volume. I should be getting caps today so I'll go ahead and post a question on that. I was urged to get orange drops and electros. Pretty obvious where the electros go but shound I be swapping out the discs with orange drops? Or should I just change the electros and not touch the others.

Thanks

Will
 
In some circles, an amp that sounds like a trainwreck with a bit of reverb will fetch big $$$$ :grin:

http://cgi.ebay.com/1953-Fender-Trainwreck-Tweed-Deluxe-NR_W0QQitemZ110064133256QQihZ001QQcategoryZ38074QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

good luck with the project!!!

Andy
 
I'm about to embark on a recapping of two mid-70's Fender Silverfaces (Vibro Champ and Deluxe Reverb) so I've been poking around various places on the web to gather some opinions about the film caps. It seems that most people who like good Fender tone (not hot rodded high gain stuff) leave the blue film caps in. Some of the orange drops are reported to give the amp a somewhat more sterile tone. Like I said, this is all "dancing about architecture" from other people. I'm planning on leaving my film caps alone and just changing out the electrolytics (the big brown ones in your amp).

Good luck with it...

A P
 
Be carefull what caps you use for the PS. Are you sure you need new ones?

Also measure you B+ in STANDBY, interesting voltages
Compare the B+ to the voltage rating of the caps

and now you have higher wall outlet voltages.
 
[quote author="W DeMarco"]Or should I just change the electros and not touch the others.

[/quote]
I'd leave the signal caps alone if they're not leaking DC voltage. I do like a Silver Mica cap on the treble control though.
 
Wow, lots to this, thank God mouser is way late. Im thinkin about the recap because outside of the trainwreck sound effect this was a really flabby sounding amp. Sorry bout that description but the attack on the thing sounded so broken up, the bottom end is super flabby. When your old silver face twin sounds better than your black super something ain't right.

For electros I have chosen atoms and all the values came off the scheme.

Otherwise I ordered a bunch of orange drops(probably not be used).

I have forgotten if I oredered spare resistors but in the reading I have done, apparentley these old carbon resistors slip away after 40 years of hard rockin. Is it a good idea to be swappin the resistors out as well?

Does anyone know of a good site for me to learn about all of these different sections in the amp?

GUS SAID "Be carefull what caps you use for the PS. Are you sure you need new ones? "


Gus I'm not sure if my PS Caps are toast or not. Like I said I got the Atoms for all electros and the written values. Should these be alright? I figure your worried about the voltage out of the walls?

CJ, you mentioned draining the power caps before I get me fingers zapped!! Is there a safe way to do this rather than powering down and waiting for a long time!!

Bryson, I have heard before people talk about Silver Micas in the trable sections, Im assuming that these caps are connected to the treblepots in some way. Like I said tube amp techin is new for me, could you point out the values for these caps or where they physically reside?


You guys are great for helpin me on this one. I'll toast you all tonight with my first beer!!

Cheers :guinness:
 
I am not posting the power supply caps are not bad I like to make sure before I change them so I try to test them first.

I have tested some old power supply caps in fenders and have been surpised a few times the originals measured and sounded good.

Check change the cathode preamp Al electros don't overlook them.

500VDC Atoms I have tested in the past have measured well.

Bad power supply caps sometime give "ghost notes" often with bad power supply hum. The first two the output plate and screen ones seem to be the most important.

Flabby could be worn in/out speakers can you plug in a known good sounding speaker cab?

A tuning trick for some tube amps that get flabby at volume is decrease the cap into the PI
500pf can be a good place to start for the PI input cap

The treble cap is a taste thing some like ceramic some like mica some like poly whatever. The trick ones are sometimes a mix a ceramic and poly in parallel etc about 1/2 the total value wanted or ceramic and mica etc...............
Also a good place to tune is at the PI input the greater signal(voltage) swings generate more nolinear stuff in caps try different one there (look at the Steve Bench site)

Have Fun
 
That mod looks like it may have been to control volume by phase, or maybe a tone control. What did it do? did you use it at all? To drain the filter caps, unplug the unit, connect a resistor, maybe 1k, from B+ to ground, watch voltage decrease with a voltmeter. the resistor is to limit the current. The treble caps are on the board, there are three caps in each tone section, one treble cap 250-500pF, and two .022uF, or one 1uF, and one .047uF. Look at the pos. end of the filter caps for a blister, sometimes they ooze. check the first two filter caps, if they are in parallel, you may want to rewire them in series with a couple 220kohm resistors. also in the phase invertor, I like to replace the two .1uf caps with two .022uf to tighten up the sound.
 
to be honest, i've played silverface amps and blackface amps new and old, and haven't really noticed a trend in the way they sounded for better or worse.

in a lot of ways, i've preferred my brothers silverface dual showman reverb master volume with a 2x15 cab for certain sounds. my blackface bassman and bandmaster are great, but not always. a silverface twin reverb i've played enough times is also a great amp.

also, what is the condition/make of the tubes? despite them having a bunch of groove tubes hype, i've been really wondering about those GE cleartop 6l6 reissues, and the mullard 12ax7 reissues. i'd like to try them out in my BF amps along with a pair of nos telefunken 12at7's for phase splitter that i found (my only good "trash" find)

but yeah.... i too would totally lose that mod. a decent powersoak would be a nice build, not sure if it could be kept tube for 'consistency,' and i haven't actually looked for one, so dont jump on me, i haven't searched yet!

but that would probably be a way better method of controlling mastervolume and tone/breakup for studio work with a blackface amp.

i'd like one, anyway. would be good for ribbons too. and not waking people up.
 
So I went ahead with the re-cap as I had originally planned it. I replaced all electros with atoms, and orange drops for the film. I did this to see if the amp would sound better than pre-fix-the-dumb-mod stage. I left in the mod to evaluate its performance as well. I did shrink wrap the hell out of the sourc of the short.

I was nervous to say the least, as with any buildout, when It came to flippin the mains. Of course I plugged it into a electrical cord that was busted and had a momantary Oh Shit reaction. upon pluggin directly to the wall the jewels started to glow as the tubes did!!

Holy Heck, this baby sounds awesome. Have not yet replaced the tubes but they are ordered. I had the old settings marked that the previous owner played and when we got the amp was the closest we could get too a good sound as well. It went from these settings: Bass 8, mids 4, trebles 5 : Now I set it with everything on 5 and it sounds alot better.

I thought it might be a good idea to recap then begin experimenting with other component changes, things like cap choices and tube choices. For my first set of tube changes I ordered a full kit off JJ tubes.

The mod is basically a master volume. I have not listen too closely to see if it rolls any tone as well.


Thanks again guys!!
 

Latest posts

Back
Top