Pawn Shop: 1975 Blackfaced Twin Rev (Latest Upgrades)

[Jeff Bollettino]

Also, there is a jack on the right side of the amp that's not marked. What is this for?

Sorry if someone already answered this but take a look down the barrel of that jack and see if it's actually got a slot inside it for a screwdriver. If so I think it's the hum balance.

[Donny Hinson]

Thanks for all the responses/suggestions.

I'm going to try and clean the grille clothe as per your suggestions. I don't think this will affect the value...will it?

No, dirt has no intrinsic value...unless you're into landscaping.

[Don Mogle]

Update! The weird jack on the back (right side) has some sort of screw slot adjuster. This may be some kind of hum balancer or bias adjuster.

Don

[Dave Campbell]

if the caps are paper wrapped mallorys, then they will need to be replaced as they are past their lifespan. usually the coupling caps are replaced at the same time.

the screwdriver adjustable pot may be a some sort of bias mod, which is common on '70's twins. the bias circuit in silverface twins is much different than the blackface twins, and many folks try to mod the circuit to blackface specs.

[Lefty]

This is a post-1971 Twin Reverb.
They added the pull master in response to other amps at the time (Musicman, Boogie). Just leave it all the way up for the clean sound and regulate your volume control.
I would leave the grill as is personally as it shows that it is vintage.
Are those EL-34 power tubes?

Don: I asked this question because they look large like the old Sylvania EL-34's. I have been using Twin Reverbs since 1971. I know that 6L6's are the power tubes. Some people think they are interchangeable with EL-34's, not true for Fenders though.
If you look up the number on the left back of the chassis you can determine the year.
Sorry if you know all of this already.

I bought my wife one 2 years ago (a 72). It had been dropped and one of the top dove tailed joints was popped loose. I rolled the tolex backed and re-glued it. It had two JBL K-120's in it, but one is blown.
I think I paid 450 which was a steal.

You won't go wrong with that amp. Good find.
Lefty

[Don Mogle]

Lefty,

This amp uses 6L6s in the power section and a series of 12AX7s and other assorted tubes in the preamp side. I've confirmed it's a 1975 model from the markings on the transformer(s).

I was able to remove the grille clothe and gave it a good scrubbing with mild dishwashing soap (first pass) and Windex (second pass). I used a toothbrush to gently scrub the fabric. It came out pretty good! I was able to "repair" the hole in the fabric by harvesting a piece off the back (behind the baffle) and "sewing it" into place...material put in back of the rip. This, too, looks much better.

I purchased a metal mesh screen product to rebuild the top back door. I wanted something that would allow for a better airflow around the tubes and dissipate the heat better!

I was able to harvest some tolex from the the back of screw strip in the back of the amp. I will be using this tolex to repair the gouges and other rips. I've successfully re-glued the tolex pieces that were ripped and dangling.

I still need to give the tolex a good cleaning and polishing. California Customs products should do the trick...also have some Armor All, but have read there is alcohol in AA, which I understand is not good for the tolex.

I'm having a devil of a time finding a new SF face plate to replace the current one. I may decide to have it put back to original (or blackface) spec and remove the front toggle and plug it with a carriage bolt. An alternative is to use a new black face plate, but these are very expensive ($95-$100).

I looked at the plate that covers the filter caps and noted somebody wrote: RS 10-10-10. Perhaps someone has already replaced the caps! It would be a HUGE blessing to pull the chassis and find out it has already been blackfaced!!

As soon as it is completed, I will post some "AFTER" pictures.

Thanks for the reply.

Don

[Don Mogle]

OK Fellas,

I just got finished with Phase I of the TR SF restoration project. I think it looks much better than when I started...what do you think?

Most of the rips and tears were repaired, but I left a few scratches and imperfections for all the guys who like the vintage look.

The tolex was treated by first cleaning it with mild soap and water being careful not to allow anything to seep into the electronics. Afterwards, the tolex was conditioned with the California Customs product called LVC--Leather Vinyl Conditioner--that came with a whole kit I purchased awhile back. It looks really great--nice and shiny. The CC product is something you all should consider for your projects.

The grille cloth was cleaned with soap & water followed by a liberal dose of Windex and gentle scrub with a toothbrush.

I rebuilt the top back panel with some material purchased at Home Depot. I cut it in half, wrapped it in some heavy Gorilla Tape to prevent cuts from sharp edges, and screwed it in place. I think the tubes will breathe better and stay cooler with this panel. It's not original of course, but I like it!

Here are some AFTER photos of the completed Phase I. Phase II of this project will involve addressing the issues with the present mods, making sure the filter caps are in good shape, and making sure the electronics are in good working order. I'll probably move the front toggle switch back to where it belongs.

Until then, I think it's ready for prime time at my church gig. I'm going to give the Stereo Steel a break for awhile and start using this amp. I'm sure it will have enough clean power to get the job done!

[Bill Terry]

Great job Don! It's amazing what just a good cleaning will do for an old Fender, and leaving the grill and all the other stuff original definitely helps it retain resale value.

I'd be curious how those Celestions work out for steel, I'm a big fan of the original Greenback 25W'ers for guitar.

[Don Mogle]

Bill,

I'll probably test the 12" Vintage 30's during a practice session to see how they do.

I plan on unplugging the 12" drivers and plugging in two 15" JBL K-130s loaded in Peavey Classic 115 cabinets. Should sound great with those speakers!

Don

[Lefty]

With the onset of Ebay, Pawn Shop prizes are few and far between these days. You did well on this one.

When hooking up the external speakers remember this Twin wants a 4-OHM load.
regards,
Lefty

[Don Mogle]

Yes, the JBLs are 8-ohm speakers. Putting them in parallel will make both a 4-ohm load. Thanks for the heads up though...appreciate it Lefty!

[George Seymour]

Glad to see the stereo steel is holding up! I've got 1973 Vibrosonic with the original orange basket jbl, essentially a twin with a 15 " speaker. For me...way too heavy to lug around with as much as I'm playing, have been contemplating splitting the amp into a separate enclosure. Good find, had my local amp guy revamp the preamp in channel "A" with an octal sn7, hate to mention that to you! Have fun with the old twin!
Geo.

[Leon Champion]

Don Try Reverb . com . do a search for twin reverb faceplate. I have seen them on there .

[Don Mogle]

The Twin is off for an electronics update...stay tuned for more later on phase II of this project!!

It should be done next week!

[Tony Prior]

it's a beauty worth every bit of 5 bills. You did the right thing by leaving it alone and cleaning it best you can. Yes, make sure the circuit ,tubes,caps etc, are up to regular duty task then go out and have fun with it !

I would however ditch that front panel toggle switch and repair whatever was wrong with the original. Maybe just put a "button plug" in the hole after removing the switch from the front panel.

TR people would rather have the button in the hole than an extra switch. Also fact of the matter, these Twins are in abundance so it's not like it's going to effect overall value like an earlier SF ( 68 thru 71) or a pre 67 amp. Easier to explain the button than an extra switch !

Great amp, use it in good health !

[Paul Honeycutt]

That looks really good! Those are workhorse amplifiers. I have a '68 Dual Showman Reverb head and a cab with two JBL K-120's and it's such a great clean tone amplifier. I hope you get many years of enjoyment from yours.

[Don Mogle]

Hey Everybody,

I wanted to give you an update on my Pawn Shop Fender TR.

After playing the Twin for a couple weeks at church, it just died on me. It started to blow fuses. Saddened by this, I had no choice but to get it fixed. While searching the Forum about Twin mods, I decided to go ahead and make a few other changes as well while I had it in for repairs anyway. Here's what I had completed:

** Moved the stand-by switch back to where it was originally; plugged the whole with a button plug restoring it back to original condition. (Thanks AJM & Tony Prior)

** Checked the tubes, sockets, pots, resistors for functionality and excessive drift. Replaced resistors and capacitors that were out of tolerance/spec. Tweaked the amp for best overall tone based upon this specific amp's tonal qualities.

** Replaced the output tubes with new JJs. Biased the amp on the cooler side for more clean headroom (35 milliamps). This will minimize early breakup and prolong tube life. Increased the cap values in the power supply.

** Replaced several preamp tubes with new JJs. Put a new 5751 in V-1 (Gain Hole/Channel #1) for increased clean headroom (70 nominal gain). Changed preamp tubes in V-2 (Gain Hole/Channel #2) & V-6 (phase inverter) since these tested weak and marginally effective.

** Sweetened the Silverface circuit with specialized components recommended by a Forum member

** Changed out the filter caps with higher-value F&T caps making it more steel friendly (for better and tighter low-end performance). Note: the caps had been changed by a previous owner, but these were removed for better (higher value) caps. The electronics were replaced with 4.7 mF cathode bypass caps similar to early Dumble amps. The amp should be less boomy with these changes.

** Added reverb/vibrato to Channel #1 (per Ken Fox's recommendation). Now, channel #1 and #2 are in phase with each other.

** Enhanced the reverb: reduced the cathode caps in the reverb section...biased the input stage a bit colder

** Added a resistor/cap to the original standby switch to reduce THUMP when the amp is turned on

** Insured Channel #1 was EQd to around 800 Hz range; Channel #2 @ 500 Hz

** Placed a push/pull midrange control on Channel #1 for a switchable slope with more midrange flexibility. The 100K slope resistor was changed to 56K. The new midrange push/pull switch will allow increased tonal variations to 33K. Upon testing this, I REALLY like the tonal change this feature offers. I was able to hear a distinct difference in midrange tone.

** Removed the tone-sucking .002 uF snubber/suppression cap(s) on the output (thank you Bill Terry!)

** Replaced the power supply electrolytics (220 uF (X2) and 47 uF (X3))

** Replaced 47 UF bias filter caps (X2)

** Replaced the cathode bypass with 4.7 uF audio grade ones (X6)

** Replaced the 470R screen grid with 1K, 5W (X4)

** Replaced the rectifier/bias diodes with 1n/4007 (X7)

** Wired the two speaker jacks (main and external) in parallel so that the amp will see a 4-ohm load when two 8-ohm speakers are used. (I’ll be using two 8 ohm JBL K-130s)

** Disconnected the ground polarity switch for safety reasons/concerns.

** Confirmed a previous owner completed the traditional Blackface BIAS CONTROL mod allowing for easy biasing of the tubes.

** Confirmed the chassis inside was clean, relatively unmolested, and rust-free. Mods done previously were OK with no safety issues to worry about! Not much had really been done to the amp other than moving the stand-by switch and partial blackfacing!

** Confirmed the slotted screw in the back is a hum balancer. Dustin told me this looked to be original to the amp from the wiring and oxidation that were present. This could have been some kind of transitional chassis. Even the hole where the front standby switch was located appeared to be a clean hole (not a mod job).

** I decided to leave the master volume control alone. I didn't want another HOLE in the front of the amp.


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PHASE III: Looking into a speaker change. Leaning towards Eminence Travis Toy 12s. However, I've been hearing some great things about EVM-12Ls or the Emminence EM-12 clones. This will come later as finances permit. But that's another story to be continued!

Thanks for reading!

Don

[Jim Sliff]

I'm sure I missed a few posts, but I'll make some basic comments related to the original post anyway (even though this one is WAY beyond that).

Caps: Electrolytic caps need to be physically inspected to determine their age, and is over 12 years old tested to check their condition.

"Silverface": there are multiple types of SF Fender twins, and some are honestly *awful*. They run from +/- 80 watts to 135 watts. You DON'T want the latter type!

Price: Twins go for $500 around L.A. every day...usually ones that need major work. A serviced one with stock speakers...mid 70's with is not the worst of the lot...can be found for $600-700. Hardly anybody want them - Deluxe Reverbs sell for far more..

They have to be turned up very loud to "bloom" (open up the tone), they are ridiculously heavy, and are severely overpowered for most gigs nowadays (and pretty much useless at home). A Twin turned up to "2" is NOT a good sounding amp, especially with those Celestions.

An amp like that needs to be inspected by someone who knows what they are doing prior to purchase. Buying it and taking it home/playing it could be a time bomb. It could be in need of $3-400 work very easily even if it sounds OK. Buying a vintage tube amp without knowing EXACTLY what you are buying often turns into a very poor deal by the time you have all the needed service performed. And it's devalued right out of the chute because of the replacement speakers (I've been trying to trade off a Vintage 30 locally for a year - nobody wants an 11.5#, midrange-heavy speaker. Newer models are lighter and FAR better.

I'd pass without seeing the condition, the chassis, verifying part numbers etc. You can easily find another.

So given all that and what you ended up having done, how much did your "good deal" $500 Twin (with an extra hole in the control panel, replacement rear panel and replacement speakers) cost you? Will you be able to recoup your investment if you get tired of it?

[Tony Prior]

E-Caps, regardless, should be changed like you are doing. Unless you know with 100% certainty when they were last changed. The screen resistors as well, like you are doing.

I recently acquired a (virgin) Bassman 50, mid 70's with MV, it too has a HUM balance in the exact same place as your TWIN, as well as the fixed bias pot inside the chassis. This amp is not actually identified by any commonly found Fender schematics, close but not exact so indeed Fender let some amps out the door with some added "stuff".

Years back I acquired an original 1964 BF Tremolux set, it blew fuses. It was an easy fix, one of the filter E-Caps was indeed bad. Had the exact same issue with a 64' Bandmaster set. Fender amps are indeed very easy to repair and get back to excellent working condition. Obviously though in the hands of an experienced tech as there is 435 volts (and more) running around inside the chassis.

MV Twins up to the 135 watt Ultra Linear era, as stated above, in reasonable shape do indeed sell in the 5 to 700 range but sometimes the amp outweighs the market value if you like what you have. Even those amps that sell in that price range either need new E-Caps and screen resistors right now or will down the road. also add a couple of 12ax's and maybe 4x6L6's. It's maintenance.

Jim above says that Deluxe R's sell for more and he would be correct, but it's a totally different market, the TR and DR shouldn't be compared. It's probably 50 to 1 guitar players wanting a DR over a Twin. Guitar only gigs are not the same as Steel gigs.

TR's are great amps, all of them , but indeed they can cost a few bucks to bring them to back to band stand duty. If the amp is brought back to quality condition with the appropriate maintenance, it will be rugged and fully operational for easily another decade, probably longer. If you keep it and use it for 10 years, even if you have $800 in it, thats $80 a year for an iconic amp. An investment analysis says thats one gig a year . What a deal !

Enjoy it ! Who cares if you are a tad over market value right now.

[Don Mogle]

Hey Guys,

Here are some pictures of the electronics repair work and mods in action. I think the chassis looks real clean for a 40 year old amp!



ABOVE: This is looking at the right side of the chassis from behind. The hum balancer is visible on the bottom right side...



ABOVE: Here is the left side of the chassis from behind where you can see the massive output transformer.



ABOVE & BELOW: You can see the new push/pull mid control in place. In the picture below are the preamp tubes sockets all wired up ready for action.



BELOW: Here's the push pull mid control in the out position...



BELOW: The new JJ output tubes are now in place along with the preamp tubes...



BELOW: The new filter caps are in place with higher values for nice tight low-end performance...



Jim: Thank you for your take on this project. I guess hindsight is always 20/20. Yes, what looked to be a great deal is now an average deal. I lucked out in some respects in that a previous owner did some blackfacing already. I could have stopped at just getting it working again, but wanted to optimize it as much as possible after studying many Forum posts on the subject. There may not be many amps (if any) set up quite like this one for steel. I'll be using JBL K-130s live when I play.

I thought the Vintage 30s were a good speaker for this Twin (perhaps even an upgrade). After all, they are used by some great guitar players--Warren Haynes, Slash, Bryan Setzer, etc. They are considered by some to be the SM-57 of speakers. These have a warm tone to them and many have stated these sound great in a Twin Reverb. Strong mids are important for steel use.

I didn't want a museum piece of an amp, but something that could be taken out and gigged. In my case, I will be using it at church so I won't have to move it much. I think I can deal with the weight issue if all I have to do is move it once every 1-2 years! I have a complete Walker Stereo Steel for quick grab-and-go needs.

Tony: Thanks for the comments.

I can't wait to start playing it again. I will come back with a full report on how it performs in a live situation. Until then, thanks for visiting my thread. Take care!

Don

[Don Mogle]

Deleted

[Don Mogle]

PHASE THREE!

SPEAKER UPDATE: I was able to acquire two new EVM 15" speakers. The first is a NOS (still in the box) EVM 15L (full range guitar speaker). The second is a like-new EVM 15B that is more of a bass speaker.





I used these two speakers this morning in church and LOVED the sound I got. I put these in a couple cabinets I built and they performed marvelously. The EVMs are warm with a lot of well defined bottom end and smooth highs.

RIG: Emmons Push Pull --> L'il Izzy --> Hilton Pedal --> Fender Twin Reverb --> two 15" EVMs.



I have some pedals that I will try and add into the signal chain at a later date. For now, I just wanted to experiment with a basic set-up to see what sounds best. This combination sounded glorious! (Note: I tried using the Goodrich 120 and H10K at practice, but the Hilton sounds better)

FUTURE PLANS: I'd like to replace the Vintage 30s with either JBL D-120s or JBL K-120s. The D-120s will bring it back to more of an original state. I'm also toying around with the idea of EVM 12Ls. The 12Ls are great for both regular guitar AND steel. Furthermore, they don't break! Stay tuned for more later!

Finally, will probably go ahead and replace the faceplate with a new SF reproduction (or perhaps a blackface one).

Thanks for viewing!

Don

[Rich Peterson]

Considering the weight of the amp, maybe you should consider having Weber make a couple neodymium speakers with EVM-12L cones. The Electrovoice have huge magnets. But I love the sound of them.

[Don Mogle]

Rich,

Thanks for the tip! That's something to consider.

However, since I never have to carry the amp to a gig, weight is not that much of a factor. On the other hand, if I sell it someday, the new buyer may have a different take on it.

At present, my plan now is to put a Travis Toy TT-12 in a separate cabinet along with...something. I'd love to try the EVM-12L alongside the TT12. I bet that would sound pretty awesome.

Thanks for the reply!

Don

[Don Mogle]

Hey Guys,

I just wanted to give you an update on phase III of my Pawn Shop '75 Fender Twin Reverb modification series.

After watching the SPEAKER SHOOTOUT video Travis Toy did at Mike Scagg's house recently, I decided to install two Double T-12s in my Twin--I wanted TWICE the goodness! Here's a link to this shootout:

viewtopic.php?t=327238&highlight=

I know there have been some questions as to whether the Double T-12s would fit in a Twin Reverb. Let me assure you, they will if there is an offset like on my '75 Twin baffle. [Note: Caution should be exercised if your baffle has each speaker side-by-side with no offset. Notice how my right speaker is lower than the left one. All Twin baffles may not be the same.] In my case it took a little bit of persuasion, but they went in OK with no cabinet modifications. The frames are touching, but I figure that shouldn't be much of a problem. I had to remove the reverb tank to get to the one nut on the right speaker.

They sounded great on the initial test drive this evening. It also made the Twin about 8 pounds lighter than the two Vintage 30s that were in it originally.

Here are some pictures...









OTHER IMPROVEMENTS:

TOP REAR PANEL: I was able to find a new top panel for this amp which makes it look a lot better (not in the pictures). It came from a 70s Twin, so it at least comes from the same era. It dresses up the amp nicely...better than the wire mesh panel that I installed earlier.

SILVERFACE FACEPLATE: In addition, I found a new faceplate to replace the one on it now with the hole in the front. I got it at a great price off Reverb. I will install that sometime in the future when maintenance is required.

BLACKFACING: The jury is still out as to whether to do anymore blackfacing of this amp. I'm not sure it will make a big difference compared to all the other mods and speaker change that has been done. There is PLENTY of warmth now with the Double-T 12s! The speakers used can make a big difference in the sound of the amp.

OTHER: I think I will change out the carbon comp resistors to the less noisy SN70 Dales (?) sometime in the future if/when the amp needs any other servicing.

Thanks,

Don