It does seem to uses piezo transducers. That accounts for some of the unusual circuit topography. The problem is that piezo transducers fail with age. So if it works at all that is actually impressive. I don't know of any way to repair such a tank and doubt there are any new ones made. A unused old one probably has also failed by now, so that route is out.
So it probably sounded better when new and you just might not be able to totaly restore it.
So it probably sounded better when new and you just might not be able to totaly restore it.
I have actually repaired those piezo reverbs, and believe me it wasn;t worth the effort. I took the piezo element from some tweeter, trimmed it to size, and reconfigured the element holder from two sided to sandwich for connections. Serious pain for a working reverb that sounded like crap when new.
Some pictures of the tank you've got would be interesting and useful. Piezo based reverb units have a poor reputation, probably quite deservedly. That isn't to say that they couldn't be made to work well, just that they haven't been so far. They are efficient transducers, and high impedance, both of which recommend them for a valve amp. Getting them to sound right is the thing though.
Your Teisco has no valve allotted for signal recovery, which is a shame, and if you're not experienced, adding one would be something of a minefield. If there were one, sorting out a suitable tank and matching transformer would probably be feasible, without one, not.
Depending on how interested you are in this, it might be worth experimenting.
If I were going to try this myself, I'd look around for a cheap supply of piezo discs, and maybe an old, dead, spring reverb tank, that would fit inside the Teisco (how much space is there?). If I could find other springs that are long for their width, and could be held taut, so that the coils didn't sag and touch one to the next, I'd consider those too. For experimenting, nothing elaborate is needed, a map pin into a plank would work as an anchor.
Then I'd think carefully about how to couple the discs to the springs, two discs per spring, one at each end. Possibly I'd mount the discs over a round hole in something not very resonant, like hardboard (fiberboard in the US?), so that the centre of the disc can move as much as possible wrt the edges.
A wave can travel along a spring in several ways: As a transverse wave (side to side), a longitudinal wave (end to end) or as a torsional wave (twisting it). How I coupled the disc to the spring would determine which it would be, though with piezo elements and an old reverb tank, I'd try to make it a sideways (transverse) motion.
I'd try using guitar string wire, soft soldered at both ends to connect the piezos to the springs. Steel needs good cleaning before it can be soldered, with a much more aggressive flux than is used for electronics - something like killed spirit, ie zinc chloride. Possibly I'd prepare and tin the point on the spring I wanted to connect to, shape and tin the connecting wire, tin the point on the piezo I wanted, assemble, then solder in place. Soldering piezos needs quick, competent work or they die.
If this all sounds insane, you might well be right, I am mad enough to find this interesting. But I don't have a Teisco amp, and I doubt it's something I could ever sell enough of for it to be worth me developing a viable replacement unit - interesting to think aobut though.
Hope you manage to sort something out - a reverb pedal would be easier of course, just depends what you want out of it. Have a look on youtube for "piezo reverb" there's some entertainingly crazy stuff comes up.
Your Teisco has no valve allotted for signal recovery, which is a shame, and if you're not experienced, adding one would be something of a minefield. If there were one, sorting out a suitable tank and matching transformer would probably be feasible, without one, not.
Depending on how interested you are in this, it might be worth experimenting.
If I were going to try this myself, I'd look around for a cheap supply of piezo discs, and maybe an old, dead, spring reverb tank, that would fit inside the Teisco (how much space is there?). If I could find other springs that are long for their width, and could be held taut, so that the coils didn't sag and touch one to the next, I'd consider those too. For experimenting, nothing elaborate is needed, a map pin into a plank would work as an anchor.
Then I'd think carefully about how to couple the discs to the springs, two discs per spring, one at each end. Possibly I'd mount the discs over a round hole in something not very resonant, like hardboard (fiberboard in the US?), so that the centre of the disc can move as much as possible wrt the edges.
A wave can travel along a spring in several ways: As a transverse wave (side to side), a longitudinal wave (end to end) or as a torsional wave (twisting it). How I coupled the disc to the spring would determine which it would be, though with piezo elements and an old reverb tank, I'd try to make it a sideways (transverse) motion.
I'd try using guitar string wire, soft soldered at both ends to connect the piezos to the springs. Steel needs good cleaning before it can be soldered, with a much more aggressive flux than is used for electronics - something like killed spirit, ie zinc chloride. Possibly I'd prepare and tin the point on the spring I wanted to connect to, shape and tin the connecting wire, tin the point on the piezo I wanted, assemble, then solder in place. Soldering piezos needs quick, competent work or they die.
If this all sounds insane, you might well be right, I am mad enough to find this interesting. But I don't have a Teisco amp, and I doubt it's something I could ever sell enough of for it to be worth me developing a viable replacement unit - interesting to think aobut though.
Hope you manage to sort something out - a reverb pedal would be easier of course, just depends what you want out of it. Have a look on youtube for "piezo reverb" there's some entertainingly crazy stuff comes up.
I found this googling silvertone reverb
Echoes from the past ? the Silvertone Twin Twelve Reverb Project My Tube Audio LLC
IN fact that google search returned MANY replacing the reverb project reports.
I don't have one here, nor do I have photos, but I can describe the basic piezo reverb as used in SIlvertone/Danelectro amps.
The spring is fat as my pinkie and 4-5 inches long maybe. The spring is densely wound, but not taut. Think like a slinky toy. It is just stiff enough that if you suspend it from the ends, the center won't sag into a grin. It isn't stretched like the spring pans we know.
The reverb is built on a base of Masonite. They fashioned a clip for the two piezo pieces. Little flat pieces of strap metal bent into shape on either side of a narrow slit, into which the piezo piece was shoved. The metal strips pushed against either side of the piece, making contact. The piezo had each face a different side electrically. (Piezos taken from like the old Motorola piezo tweet are a sandwich. A metal disc in the center with piezo crystal on either side of it. A jumper wire connects the two sides to each other. COnnection is then made to the center disc and the two side connector.)
The slice of piezo was simply shoved in between windings on the large spring as it sat in its holder. One near each end. The longitudinal wave shook it back and forth. One piezo drove it, the other picked it up. Both pieces were identical.
Echoes from the past ? the Silvertone Twin Twelve Reverb Project My Tube Audio LLC
IN fact that google search returned MANY replacing the reverb project reports.
I don't have one here, nor do I have photos, but I can describe the basic piezo reverb as used in SIlvertone/Danelectro amps.
The spring is fat as my pinkie and 4-5 inches long maybe. The spring is densely wound, but not taut. Think like a slinky toy. It is just stiff enough that if you suspend it from the ends, the center won't sag into a grin. It isn't stretched like the spring pans we know.
The reverb is built on a base of Masonite. They fashioned a clip for the two piezo pieces. Little flat pieces of strap metal bent into shape on either side of a narrow slit, into which the piezo piece was shoved. The metal strips pushed against either side of the piece, making contact. The piezo had each face a different side electrically. (Piezos taken from like the old Motorola piezo tweet are a sandwich. A metal disc in the center with piezo crystal on either side of it. A jumper wire connects the two sides to each other. COnnection is then made to the center disc and the two side connector.)
The slice of piezo was simply shoved in between windings on the large spring as it sat in its holder. One near each end. The longitudinal wave shook it back and forth. One piezo drove it, the other picked it up. Both pieces were identical.
Hmmm?... I appreciate all the suggestions and the help, regarding the reverb cirquit.
The rest of the amp sounds fine.... but will I ever enjoy an amp that sounds fine, when I´ve also built a 5e3 and the marshall 18watt that both sound GREAT. I don´t think so...?
A tesico amp isn´t worth much, even though some might find it "vintage"
At the moment I´m actually considering rebuilding it to a matchless spitfire
I think the transformers could work....the power transformer Should be able to power two el84´s a pair of 12ax7s and a tube rectifier?
Tanks for the help again though
The rest of the amp sounds fine.... but will I ever enjoy an amp that sounds fine, when I´ve also built a 5e3 and the marshall 18watt that both sound GREAT. I don´t think so...?
A tesico amp isn´t worth much, even though some might find it "vintage"
At the moment I´m actually considering rebuilding it to a matchless spitfire
I think the transformers could work....the power transformer Should be able to power two el84´s a pair of 12ax7s and a tube rectifier?
Tanks for the help again though
Looking at this
http://www.ceriatone.com/images/layoutPic/matchlessLayout/SpitFireCeriatone.jpg
It seems the gz34 needs a seperate heater winding on the power transformer, So maybe it´s a no go....
http://www.ceriatone.com/images/layoutPic/matchlessLayout/SpitFireCeriatone.jpg
It seems the gz34 needs a seperate heater winding on the power transformer, So maybe it´s a no go....
A word about piezo drivers. Virtually all of the ones made today are designed for cell phone or sounder (Sonalert) use. I got in a batch of 100 piezo tweeters none went above 8K. Inside were mated pieces of ceramic piezo elements of cell phone type material. I have some old sound level meters that used some of the best piezo (stability wise) of the day. All have faded with age.
So if you want to try to rebuild one, a big issue is where to get the old style crystals. One source might be crystal earphones. I did buy some newly made ones from Mouser a few years back. They were intended for crystal radio use, but my fell was they used the older version of piezo crystal based on how they sounded. (Tinny and distorted!)
So if you want to try to rebuild one, a big issue is where to get the old style crystals. One source might be crystal earphones. I did buy some newly made ones from Mouser a few years back. They were intended for crystal radio use, but my fell was they used the older version of piezo crystal based on how they sounded. (Tinny and distorted!)
What kind of drivers are these Simon? Could you show us a picture? The sort of thing I'm talking about are flat discs, various sizes, including 20mm. I can get these cheaply even in England, so you must have rivers running with them in the US.
8K is plenty high enough for guitar reverb.
Chinese copies of Motorola classic tweeters.
They are cheap, but the original spec which was copied as the supplied devices data sheet showed output well above 20K.
Must admit I've never pulled one of those apart. Annoying for you getting only up to 8kHz - no good at all for a tweeter.
Wanting some low gain bjts (for effects pedals), I've just ordered some chinese ones very cheaply, gambling on the likelihood that there'll be plenty with less than 'C' suffix type gains in there. Noise'll probably get me though...
I just came into a large pile of Western Electric BJTs including some germanium ones. I'll be glad to send you some if you'll pay postage!
sorry to revive the old thread, but its targeted towards my brand. and the same area i dislike. hoping i would find some info on its reverb before i tear it out and use it in my lil baby converted BCrich- its a CRAX-82 now... ecl82/12ax7 hybrid... with an upper crust dial
teisco was designed by an electrical engineer?
this i find hard to believe!
from where the reverb is fed from, to where it feeds back in...woeful. what, does distorted reverb sound good? i always thought that reverberated distortion was the desired outcome...
not that this thing can even distort... my 3.5 watt ecl82 drowns it out...
i was fiddling around with my checkmate 25, reset bias to use the el84's rather than 7189's... and each and every part of this amp is just odd. particularly the schematic inside the case. im looking for the transistors it says are there and i cant find any!
ie, it has a solid state schematic, labelled for that model... but its a tube amp. and google has found me two versions of the tube schematic...i have one of them, and it hasnt been modified by anyone. its stock. cant believe this was a commercial amp...
the tremolo though...that bit IS good, i hate to admit.
my analysis of the whole stinking mess?
strip the chassis down, and copy the traynor guitar mate.
at least when laying it out one can use their head rather than...seriously, what were these guys THINKING? some great components in there, some bits are beautiful but the actual amplifier as a whole is seriously pathetic. gotta love having the mains and the OPT side by side...
hope i offend diehard teisco fans saying this you can have the front grille when i tear it off and deface it...
teisco was designed by an electrical engineer?
this i find hard to believe!
from where the reverb is fed from, to where it feeds back in...woeful. what, does distorted reverb sound good? i always thought that reverberated distortion was the desired outcome...
not that this thing can even distort... my 3.5 watt ecl82 drowns it out...
i was fiddling around with my checkmate 25, reset bias to use the el84's rather than 7189's... and each and every part of this amp is just odd. particularly the schematic inside the case. im looking for the transistors it says are there and i cant find any!
ie, it has a solid state schematic, labelled for that model... but its a tube amp. and google has found me two versions of the tube schematic...i have one of them, and it hasnt been modified by anyone. its stock. cant believe this was a commercial amp...
the tremolo though...that bit IS good, i hate to admit.
my analysis of the whole stinking mess?
strip the chassis down, and copy the traynor guitar mate.
at least when laying it out one can use their head rather than...seriously, what were these guys THINKING? some great components in there, some bits are beautiful but the actual amplifier as a whole is seriously pathetic. gotta love having the mains and the OPT side by side...
hope i offend diehard teisco fans saying this
you can have the front grille when i tear it off and deface it...
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did you separate the trannies a bit?
i find that due to the large ...um...recess at one end for...cable storage? that with the reverb there...theres no space left!
and it wont quite fit my cascade unit unless i trim something down a bit somewhere..
the accutronics i have is possibly longer than the chassis itself. havent checked. and is a completely different unit(to the traynor). shame that.
it never ends
i finally figured this thing out... took some doing, but i got there!
one thing no-one has mentioned is the impedance a piezo requires to drive properly. 10M+ or so if you want decent bass content...
so...after getting a copy of valve wizards "preamps for bass and guitar"...i have ended up with what can only be described as some really nice reverb, using the stock tank. shame i fried one of the drivers by attempting to use it as a coupling capacitor..oops. they smoke when you put 300 volts or so on them.
what did i do?
from the preamp, after the tone and volume, i simply tap off and drive one stage. this drives the piezo circuit, with its own volume control, for "depth". this is rather restricted in bandwidth, for a reason... restrict the low end to about 100hz or so (no need to send powerful bass through a reverb, it sounds like crap i found, the springs start jangling) with a roll off around 3khz. give or take a couple of hundred hertz... also no need for excessive treble or it starts sounding too tinny...
i then reclaim the signal using a bootstrapped circuit, giving me roughly 5M+ input impedance, in line with what a piezo pickup requires. bandwidth restrictions also apply to the recovery side.
then, my "wet" reverb signal is fed to one side of a "common anode" mixing circuit, the "dry" signal from the tone stack and volume pot are sent to the other side of this mixing circuit, with a nice "blending" control between the two cathodes.
this way...i can set depth AND mix, and i get reverb that can only be described as....FREAKING AWESOME! considering its now only driving through one spring rather than the original twin springs... stupid brown smoke... meh, gives me an excuse to try and make my own now i much prefer torsional drivers. these are definitely longitudinal as stock.
though theres still something in the chain that needs a bit of swapping around before im 100% happy... to do with the location of my master volume and the mixing circuit... it already has six knobs, i dont want to go adding anymore!
seriously, after reading through this pre-amp book...ive gutted about five amps, two being hi-fi chinese things (thats an oxymoron, isnt it? chinese hi-fi amplifier!) and done some fiddling, and everything so far is sounding so much better than before! i hate to say it, but if you havent already got it in your library...GET IT! so its directed at guitar amps? if you read it properly, a lot of what is talked about applies to hi-fi as well. (miller capacitances, johnson noise, balanced phase inverters, NFB, the list goes on...) and it is so much clearer than some of the books i already had. you dont need to take a course in electrical engineering to wade through pages of maths. just stick this here, that there, do a small bit of number crunching , viola!
(no, im not getting paid for this.)
no cloning amps or circuits anymore...(get the book, design your own...you learn nothing by copying is now my motto...ie, im posting no schematics!) this teisco is all my own design now... i get crunch, i get clean, i get 30W output... time to think up a good label to stick on the front... "hed-smess" or possibly 'the offender"
never even had to relocate the trannies. after laying out a decent earthing scheme, its virtually silent when idling...
one thing no-one has mentioned is the impedance a piezo requires to drive properly. 10M+ or so if you want decent bass content...
so...after getting a copy of valve wizards "preamps for bass and guitar"...i have ended up with what can only be described as some really nice reverb, using the stock tank. shame i fried one of the drivers by attempting to use it as a coupling capacitor..oops. they smoke when you put 300 volts or so on them.
what did i do?
from the preamp, after the tone and volume, i simply tap off and drive one stage. this drives the piezo circuit, with its own volume control, for "depth". this is rather restricted in bandwidth, for a reason... restrict the low end to about 100hz or so (no need to send powerful bass through a reverb, it sounds like crap i found, the springs start jangling) with a roll off around 3khz. give or take a couple of hundred hertz... also no need for excessive treble or it starts sounding too tinny...
i then reclaim the signal using a bootstrapped circuit, giving me roughly 5M+ input impedance, in line with what a piezo pickup requires. bandwidth restrictions also apply to the recovery side.
then, my "wet" reverb signal is fed to one side of a "common anode" mixing circuit, the "dry" signal from the tone stack and volume pot are sent to the other side of this mixing circuit, with a nice "blending" control between the two cathodes.
this way...i can set depth AND mix, and i get reverb that can only be described as....FREAKING AWESOME! considering its now only driving through one spring rather than the original twin springs... stupid brown smoke... meh, gives me an excuse to try and make my own now
i much prefer torsional drivers. these are definitely longitudinal as stock. though theres still something in the chain that needs a bit of swapping around before im 100% happy... to do with the location of my master volume and the mixing circuit... it already has six knobs, i dont want to go adding anymore!
seriously, after reading through this pre-amp book...ive gutted about five amps, two being hi-fi chinese things (thats an oxymoron, isnt it? chinese hi-fi amplifier!) and done some fiddling, and everything so far is sounding so much better than before! i hate to say it, but if you havent already got it in your library...GET IT! so its directed at guitar amps? if you read it properly, a lot of what is talked about applies to hi-fi as well. (miller capacitances, johnson noise, balanced phase inverters, NFB, the list goes on...) and it is so much clearer than some of the books i already had. you dont need to take a course in electrical engineering to wade through pages of maths. just stick this here, that there, do a small bit of number crunching , viola!
(no, im not getting paid for this.)
no cloning amps or circuits anymore...(get the book, design your own...you learn nothing by copying is now my motto...ie, im posting no schematics!) this teisco is all my own design now... i get crunch, i get clean, i get 30W output... time to think up a good label to stick on the front... "hed-smess" or possibly 'the offender"
never even had to relocate the trannies. after laying out a decent earthing scheme, its virtually silent when idling...
Hey thanks for that, I am looking at modding one of these. The power valves are shot in this one . Apparently a lot of people mod for 6v6 to handle the voltage. Did you go that way?
Nice thinking around the reverb. What were the advantages of a bootstapped stage v's just a simple contact bias of 5 to 10 M?
Cheers
Nice thinking around the reverb. What were the advantages of a bootstapped stage v's just a simple contact bias of 5 to 10 M?
Cheers
hello
I’m looking for a skill tech, my reverb is broken (trasducer) and it works bad with only one spring. This reverb tank is out of production, and I would like to fix it.
pic attached
Imgur: The magic of the Internet
I will appreciate any suggestion, and of course if anybody is be able to repair it.
thanks guys
I’m looking for a skill tech, my reverb is broken (trasducer) and it works bad with only one spring. This reverb tank is out of production, and I would like to fix it.
pic attached
Imgur: The magic of the Internet
I will appreciate any suggestion, and of course if anybody is be able to repair it.
thanks guys
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