Re: Blackface a Silverface Super Reverb

On Jun 13, 2:48 am, Rich Koerner <ri...@xxxxxxxxxxxxx> wrote:
Ether wrote:

Mike Schway wrote:
In article <4850C639.ADBF1...@xxxxxxxxxxxxx>,
Rich Koerner <ri...@xxxxxxxxxxxxx> wrote:

It does not tell you what silverface circuit. I would guess it would be an
earlier one.

Here are the titles to the 4 steps

1. Rewire bias supply and add two 220k resistors
2. Replace 4 resistors in phase inverter
3. Remove parasitic supression caps
4. Change 5u4 rectifier tube to 5ar4/gz34 and check bias

There is a lot more to it than these few steps.

And, the most important one omitted.

OK, Rich WHICH is the most important one? ;-)

Candidates:
1) P/I input cap value

Very important.

2) midrange tone stack cap value

Somewaht important.

3) bias supply filter (single 50uF instead of 2 stage 70uF)

Why would you want to do that? More filtering = less bias ripple.

3.5) Ditch that wonky semi-cathode biased scheme....only seen in the
AB568.

Definitely.

and
4) rip out all the wiring and do it RIGHT!

Well, yeah, if the lead dress is crap and is causing oscillations.

My vote goes to #1, 3 and 2 (in that order).

1 & 2 -- forget 3.

I'm guessing you're thinking #4 (!!!!!!!!!!!!!!!!) ;-)

--Mike

Rich would. !!!!!!!!!!!!!!!!!!!!!!!!!!

--E

I'm going to have to work up a page on the Super Reverb for my web site down the road.

Not mentioning what SF version is at hand is a problem.

If you have the 70 watt SF Super Reverb.... boy do you have your work cut out for you.

However, setting up of those babies in the right fashion makes for a very KILLER Super Reverb.

<thinking>

For now, let me keep thing in a general context, for the sake of BF and early SF perspective, and
awareness.

From 1964 to 1969, in speakers alone, there are noticeable differences in the many different
speakers that Fender shipped in their Super Reverbs.

Of those, the alnico and the many ceramics, which is your base reference point for the targeted
standard?

Not all these speakers sounded the same. Personally, one of the ceramic swiss cheese framed 10's
were their best.

However, that is just a me thing.

There were also the transformer changes the went along the way in the time line too. Voltage
differences and current draw limits make for differences in a Super Reverb's performance too. These
little things make the differences when compared side by side.

Then, there are the other equally fine points that are most often glossed over as not being that
important for consideration in the SF to BF conversions.

What it all boils down to is, the exact voltages, on the exact tubes, so the exact speakers, with a
power supply response characteristic, with the properly referenced EQ within the different stages of
the Super Reverb. Or, any other amplifier where a similar goal if the point of the quest.

What is omitted from the four points of focus depends on much detail you want to get into. For most
these four points is all it takes. For others, close is not good enough.

If you are one of those cats, you have to have a clearly defined target. Then, the small details
become the things that you have to jump on.

First the exact tubes and speakers are a must.

The proper voltages from the power supply's divider string has to be addressed. Those rascals
changed in the time line. Depending on the transformers sitting in your SF, you either can use the
stock resistor string, or have to calculate new values to get all the voltages to each of the stages
to the proper targeted BF values.

Then, just looking into the time line changes to the reverb alone, is an important consideration
too. If the tank isn't driven right, the reverb isn't going to sound right. The big plate NOS 12AT7
is a nice thing to have in that socket to drive the reverb tank with a 2.2K kathode resistor.

On the way back, make sure all the caps are the right BF values too.

Depending on the type of by-pass and coupling caps that sit in the subject SF Super Reverb, few to
all may need replacing because of value changes.

Slap both bias adj and bal into the amp.

I like the AB763 PI ckt.

I'd use only the 5AR4. (I use SI diodes in mine)

Also,... GE, Sylvania, or RCA for tubes.

After this is done, the suppression caps are pulled, and lead dress is the final move.

If I gave this more thought, I may find some things to add I may have forgotten in the throw
together post.

Regards,

Rich Koerner,
Time Electronics.http://www.timeelect.com

Specialists in Live Sound FOH Engineering,
Music & Studio Production,
Vintage Instruments, and Tube Amplifiers

Hummm. I've got one of the last 45 watters.. A 77..
It's been "blackfaced" but I really don't know what all they
did to it. It was done at some shop in Austin where I bought
it, but I forget to ask the guy who actually did it.
The work was done not long before I bought it.
It's worked and sounded fine, so I never have messed with
it, or even pulled the chassis yet..
"If it ain't broke, I ain't got time to mess with it"... :/
They did totally yank the master volume pot..
Myself, I would have left it in, even if unwired..
But, like I say, I didn't do it..
It was totally recapped, and I assume they went to
blackface values, but I've never looked yet.
Mine is using the S/S rectifier.. I've considered
going back to the tube, cuz I like an earlier
breakup and slightly lower power, but too lazy
to mess with it.
Mine uses the 4x10 Oxford? ceramics..
Many blues players don't care for em, but I've
heard some rockers that like em..
Mine sound fine to me, but I've never tried
the alnico's to compare..
Whatever they did, it's a good sounding amp.
I consider it my best amp really..
It's one mean blues machine..
And my other "decent" amp is a 74 Traynor Bassmaster
mk2.."100 watt version" It's no slouch, but no reverb,
etc..
It's my poor mans plexi clone... I need to get off my
*** and recap it.. All the caps are original, and
it's starting to get a bit funky..
.

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