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Thread: help valuing parts from 1971 Fender Twin Reverb.

  1. #1
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    help valuing parts from 1971 Fender Twin Reverb.

    Trying to determine what value in North America for full set of transformers, PT, OT, Choke, Reverb. from a 1971 Fender Twin Reverb chassis.

    Currently, works (haven't heard it yet), but many aftermarket parts (resistors, caps), so its not a museum piece.

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    Supporting Member The Dude's Avatar
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    Lots of options there, from expensive Mercury to cheap eBay. It's kind of a loaded question. I just have to ask, though. Why do you want to replace all of the iron?
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    If you'd said "pricing" parts, I'd guess you want to buy them... are you trying to part the amp out, so want know the values of the parts to sell? Well, I got both the PT & OT to a Twin Reverb for the price of "take all of it, it's free, but only if you take all of it!"

    I'm with The Dude here... why worry about the iron? I'd expect lots of parts in an amp of that age to be replaced, especially one that spent a lot of time ON and MAKING MUSIC of the LOUD CRUNCHY kind. Get it sounding great and ENJOY it. Screw what the "collectors" think!

    Justin
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  4. #4
    Old Timer Leo_Gnardo's Avatar
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    Depends on who's buying, who's selling, and why.

    Twins are a hard sell in my neighborhood. One store owner said "can't even give 'em away." Everybody wants smaller more portable amps these days. Although I have a lot of respect for Twins, it usually takes years to find a buyer when I've fixed up a beater for sale. If you happen to have a Twin owner with an amp that needs those parts I'd say about $120 to $150 for the lot is fair. If you think you can get more, go for it, ka-ching!
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    I think Mike is thinking of buying for the iron, not selling. He mentioned not having heard it yet.
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    Thanks everyone. OK, it's blasphemy, but planning my next "build", I can get an OK shape Twin Reverb, late 60's, early 70's for roughly 1/3rd the price of building one from scratch, with all new parts. I priced new iron, something like 300.00 (mid range stuff, not junk, not the cadillac's). As Leo wrote above, twin's are a hard sell these days. Very heavy, way too loud, big. Tonally, not very flexible. Musician friends won't even consider one, they want like a little tiny 1 x 10 Mesa combo, with loads of different sonic options, small and light that they can mic and pipe through a PA if they need more coverage. (and they can pop it and the Strat into the back seat of the Mini and heat home after the gig).

    Anyway, priced new iron, but wondering what the street value of a full set of used iron would be.

    I'm going to pick up a couple of these beaters. Both "play" but rough shape (missing tubes etc).

    The idea is to mix two beaters, futz with the circuit to get like a 35 watt somethingoranother out of it, and sell the excess. I have a couple in mind, both in the 600.00 range, both have complete sets of transformers. The transformer set from the second unit would offset the total cost, which is the plan. One of them has a good working circuit board, with new caps/resistors where needed, so Id only have to make small mods to build a lower powered unit.

    In not too beautiful shape (end bells a little rusty) but good working condition, 150.00 or 200.00 too high (too low) for 70's transformer set?

    (I can't wait to get to work on the FrankenVerb II)

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    As an aside, Ive been studying period fender amp schematics and was very surprised how similar the whole preamp + reverb + vibrato + phase inverter portion of these amps are. A few components.

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    Quote Originally Posted by Leo_Gnardo View Post
    Depends on who's buying, who's selling, and why.

    Twins are a hard sell in my neighborhood. One store owner said "can't even give 'em away." Everybody wants smaller more portable amps these days. Although I have a lot of respect for Twins, it usually takes years to find a buyer when I've fixed up a beater for sale. If you happen to have a Twin owner with an amp that needs those parts I'd say about $120 to $150 for the lot is fair. If you think you can get more, go for it, ka-ching!
    Thanks Leo. I was hoping a little more, but, not very popular amps, and not much else someone can do with those transformers, I guess.

  9. #9
    Old Timer Leo_Gnardo's Avatar
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    You're getting the whole amp, or just a chassis, or just the transformers for $150-200? I s'pose for a project amp it's an acceptable price range. One thing you could do is run output tubes in triode mode for a mellower tone & lower power. And if you do that you can run smaller, lighter speakers. If you don't mind spending $$$ on neodymium magnet speakers you can save considerable weight there, too.

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    Quote Originally Posted by Leo_Gnardo View Post
    You're getting the whole amp, or just a chassis, or just the transformers for $150-200? I s'pose for a project amp it's an acceptable price range. One thing you could do is run output tubes in triode mode for a mellower tone & lower power. And if you do that you can run smaller, lighter speakers. If you don't mind spending $$$ on neodymium magnet speakers you can save considerable weight there, too.
    Thanks Leo. The whole amp, for 600 range. Will have excess parts I won't use. I don't care about size and weight since once built it will sit next to the window in my basement until Im planted 6 feet under. I may move it to the left a bit to vacuum underneath .

    Thanks for the tip on running in triode mode! I'll google around for wiring changes. That would change the output impedance of the tube set, right? I never quite understood what effect changing the output impedance of a set of tubes if the same output transformer is used.

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    Quote Originally Posted by Leo_Gnardo View Post
    You're getting the whole amp, or just a chassis, or just the transformers for $150-200? I s'pose for a project amp it's an acceptable price range. One thing you could do is run output tubes in triode mode for a mellower tone & lower power. And if you do that you can run smaller, lighter speakers. If you don't mind spending $$$ on neodymium magnet speakers you can save considerable weight there, too.
    For half power mode, the screen grid, pin4, is connected through a resistor to the plate? The PLATE?

    We'll need a custom circuit that will have a little hammer on a robotic arm. If the user attempts to flip this switch while the amp is not in standby, the robotic arm will hit the users finger with the hammer.

  12. #12
    Senior Member Enzo's Avatar
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    Yes, connecting the screen of a pentode to the plate makes it a triode.
    Education is what you're left with after you have forgotten what you have learned.

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    Quote Originally Posted by Enzo View Post
    Yes, connecting the screen of a pentode to the plate makes it a triode.
    Thanks Enzo. So I guess this isn't the mod where you have 6 wires sticking out of the back of the amp, and a yellow stickie that says "Twist the greens and blues together for full power, twist the greens and the oranges together for half power".

  14. #14
    Old Timer Leo_Gnardo's Avatar
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    Quote Originally Posted by mikepukmel View Post
    Thanks Enzo. So I guess this isn't the mod where you have 6 wires sticking out of the back of the amp, and a yellow stickie that says "Twist the greens and blues together for full power, twist the greens and the oranges together for half power".
    With the full B+ on those wires that would be definitely the wrong way to go about it. I use a DPDT toggle, and steal the hole where the "ground" switch is to mount it.

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    Old Timer J M Fahey's Avatar
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    Well, yes, exactly that.
    Only you drill a hole in the back panel and add a switch to do the wire swapping thingie.

    Leave the dangling wires, 2 prong mains plug, death cap and original swelling caps to those who want to "keep collector value" .... whatever that means
    Juan Manuel Fahey

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    Quote Originally Posted by Leo_Gnardo View Post
    With the full B+ on those wires that would be definitely the wrong way to go about it. I use a DPDT toggle, and steal the hole where the "ground" switch is to mount it.
    The handful of schematics I found on a quick search, e.g.:
    http://mhuss.com/SmallBox/1987.gif

    used the same resistor prop. soldered to the pin on pin4, so either the plate, or B+ (2) would go through the resistor to the screen grid. But this is a "marshal" like schematic. they used a 1K 1W. For the twin case, is it 'close enough for folk music' to have either side go through the same 4701W? (I think I have a bunch of 470 2W on hand) Or should the resistor on pin4 be different for the two cases, i.e. 470 for screen grid to B+ something else for screen grid to plate?

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    Quote Originally Posted by J M Fahey View Post
    Well, yes, exactly that.
    Only you drill a hole in the back panel and add a switch to do the wire swapping thingie.

    Leave the dangling wires, 2 prong mains plug, death cap and original swelling caps to those who want to "keep collector value" .... whatever that means
    This one's a junker so I'm not worried about collector value. It will never be a museum piece. (There's a pre-cbs version of this amp, a "real" original blackface for sale in our area, asking 3800, has been for sale forever, and ever, and ever and ever ...)

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    Ohh, important question: is the reason that the guy used a 5W on pin4

    http://mhuss.com/SmallBox/1987.gif

    because its switchable, and on one switch position where the screen grid goes to the plate, more current flows through than if it only went to B+ (2)?

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    While I don't think Twin Reverbs are as low in value as many may think (just takes the right buyer in the right spot at the right time), $3800 for a 63/64 TR is a bit heinous. Maybe a white Twin or a Tweed Twin, but not a BF.

    Justin
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  20. #20
    Senior Member Enzo's Avatar
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    Amps are worth whatever someone will pay for them, no more, no less. If I ask $10,000 for something and a guy ponies up the 10k, then it is worth $10k.
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    Supporting Member The Dude's Avatar
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    Ok. Call me silly, but the idea seems a bit counterproductive. I'm not trying to be a critical a$$, but this:

    We want to make a low wattage, lighter, smaller amp so we start with large/heavy iron from a 100W amp and bang the wattage down via triode configuration or other methods? Again, I'm not trying to be argumentative, but transformers are some of the heaviest parts of the amp. It would seem a better idea to just use smaller transformers if the goal is as stated.
    “Yeah, well, you know, that’s just, like, your opinion, man.”

  22. #22
    Old Timer J M Fahey's Avatar
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    True, just that it looks like today´s menu is "beater but repairable" Twin hardware and apparently it won´t be moved much if at all.
    In that case $150/200 for a set of iron, chassis, cabinet and speaker looks interesting.
    Almost forgot: killer reverb.

    Only problem is it´s too loud.

    Personally I hate triode-pentode switches because they knock perceived power very little and they kill bite and punch very much but being an experimental amp there´s many other options, from the variable +V thingie which can tame large amps down to whisper levels to some tasty PPIMV (which shine in "clean" amps such as Fender) to .... gulp!!! ..... some kind of attenuator.

    Many fine ways to keep owner-tweaker happily busy ... which I guess is some of the justification behind it
    Juan Manuel Fahey

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    Quote Originally Posted by The Dude View Post
    Ok. Call me silly, but the idea seems a bit counterproductive. I'm not trying to be a critical a$$, but this:

    We want to make a low wattage, lighter, smaller amp so we start with large/heavy iron from a 100W amp and bang the wattage down via triode configuration or other methods? Again, I'm not trying to be argumentative, but transformers are some of the heaviest parts of the amp. It would seem a better idea to just use smaller transformers if the goal is as stated.
    Well, for some, but for me: I don't care about the weight, or the size, a tank is fine. I only need a way to switch to lower power, but if I cant do that, I have a set of those big aircraft mechanic hearing protectors.

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    Quote Originally Posted by J M Fahey View Post
    True, just that it looks like today´s menu is "beater but repairable" Twin hardware and apparently it won´t be moved much if at all.
    In that case $150/200 for a set of iron, chassis, cabinet and speaker looks interesting.
    Almost forgot: killer reverb.

    Only problem is it´s too loud.

    Personally I hate triode-pentode switches because they knock perceived power very little and they kill bite and punch very much but being an experimental amp there´s many other options, from the variable +V thingie which can tame large amps down to whisper levels to some tasty PPIMV (which shine in "clean" amps such as Fender) to .... gulp!!! ..... some kind of attenuator.

    Many fine ways to keep owner-tweaker happily busy ... which I guess is some of the justification behind it
    Thanks, Ive never run a tube amp with pentode/triode switching. Well, Ive talked to a few people about attenuators and most folks hate them. But not completely against one.

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    Quote Originally Posted by J M Fahey View Post
    Only problem is it´s too loud... many other options...
    Pansies... (Not you, Juan! The "guys in charge")
    My two cents: make the amp work as designed. I've got a variety of amps, from 15 to 100W, I live in a connected house on main street in a "city," and I live with 14 other people in the house. I somehow am able to find a way to get my big ones up about 5 or 6 or sometimes 10...

    I'd pull two power tubes and disconnect a speaker (and only "maybe" on the speaker) and leave it at that. Eventually, you'll get to a bigger room and you'll want an amp that can push air. And if your options really ARE "lower power or hearing protectors," just let the Twin be a GLORIOUS Twin and wear hearing protection. All my opinion, of course...

    Justin
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    Senior Member Enzo's Avatar
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    I think you are not looking for lower power, I think you are looking for lower volume. They are not the same thing.
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    Quote Originally Posted by mikepukmel View Post
    Ohh, important question: is the reason that the guy used a 5W on pin4

    http://mhuss.com/SmallBox/1987.gif

    because its switchable, and on one switch position where the screen grid goes to the plate, more current flows through than if it only went to B+ (2)?
    1K5W is pretty much the standard Marshall screen resistor, the amp in the example is based on a Marshall.
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    Quote Originally Posted by mikepukmel View Post
    Well, for some, but for me: I don't care about the weight, or the size, a tank is fine. I only need a way to switch to lower power, but if I cant do that, I have a set of those big aircraft mechanic hearing protectors.
    Oh, sorry. I got the impression from reading your post #6 that you wanted something smaller and lighter. At any rate, I wasn't trying to be all uppity. I just (apparently) misunderstood the intent of the build.
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    Quote Originally Posted by The Dude View Post
    Oh, sorry. I got the impression from reading your post #6 that you wanted something smaller and lighter. At any rate, I wasn't trying to be all uppity. I just (apparently) misunderstood the intent of the build.
    I didn't take it that way. You guys are awesome.

    I got some more photos of one of the twin reverb's for sale, and its way too nice to tear up. Im going to put in an offer, and just fix whatever small stuff needs and leave it stock. I don't have the heart to tear it up.
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  30. #30
    Old Timer Leo_Gnardo's Avatar
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    Quote Originally Posted by mikepukmel View Post
    its way too nice to tear up. Im going to put in an offer, and just fix whatever small stuff needs and leave it stock. I don't have the heart to tear it up.
    Stock or try a couple of the "stealth" mods that don't change its appearance but do make it more versatile: change norm channel's tone stack, send both chan's to reverb & vibrato. And try the triode mod. Juan's not much a fan of it I know, but I have a number of customers who like it just fine. It's cheap and fast enough to do, then at least you'll know what it does and judge for yourself.

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    Oh, well, if you want lower volume, inefficient speakers is one way to accomplish that...

    Justin
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    "When receiving a shock I emit a strange loud high pitched girlish squeak." - Alex R -
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  32. #32
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    Quote Originally Posted by J M Fahey View Post
    Personally I hate triode-pentode switches because they knock perceived power very little and they kill bite and punch very much but being an experimental amp there´s many other options, from the variable +V thingie which can tame large amps down to whisper levels to some tasty PPIMV (which shine in "clean" amps such as Fender) to .... gulp!!! ..... some kind of attenuator.
    ^^ This.

    I hate triode mode switching. I think it ruins the sound of a pentode and only serves to make an amp sound like ass. I have several commercial amps that used it for marketing, and it sounds great on paper. But in the real world I don't like it. I never use it on the commercial amps that have it, and I don't bother adding it to a build. I see no use in it.

    With that said, there's no reason not to take a Twin Reverb project chassis and build something fun and low powered out of it. Redesign the amp to use two 6L6 instead of 4. Keep the OT and switch the speaker load to match the new plate resistance. You'll find that with that huge iron the amp will sound great. If weight is an issue, eliminate one speaker and plug the other side of the baffle.

    One of the great things about Twin Reverbs is that they are one of the few Fender platforms that provide mid controls on both channels. I can't begin to tell you how important a mid control is if you're playing Jazz. Personally, I'd rather have a master volume Twin Reverb than any other Fender amp, regardless of it's weight. Yeah, I said it. I prefer the Master Volume amps because the two volume knobs can be used to provide very fine control over volume. It's hard to play standards in a piano bar if your non-MV amp has a jumpy response at the low end of the volume pot.

    Another reason that I love twins as modding platforms is because they can be had dirt cheap, just because they're too big for the average guy who wants a small amp for his bedroom or basement. When fender was making these amps back in the 60s-70s, the little amps were inexpensive and the big amps were the ones that cost more. Now we've got the pricing structure for Fenders turned upside down, such that a Princeton Reverb costs as much as a Twin Reverb. Why? Because basement warriors are driving the amp market. Few people need a Twin any more, so they're cheap.

    BTW, $600 is a lot for a project chassis. $350 would be a better price for an amp that needs work. You have to bear in mind that these amps don't fix themselves, and when an old Fender needs work, it needs work because somebody was too cheap to pay to have the work done. When you're looking at an amp that needs repair, be sure to subtract the commercial cost of the repair from what you're willing to bid, otherwise you'll be paying too much.

    As an example of pricing, in the past year or so I picked up a Twin Reverb with original JBL for $700, a master volume mid-70s TR with EV-SRO for about $650, and a Super Twin Reverb that needed tubes and the reverb tank replaced for $350. Your time as a repair tech has value. don't give it away by overpaying for a broken amp.
    "Stand back, I'm holding a calculator." - chinrest

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