Gretsch 6162 reverb tank dead

[evbrad2007]

As my tech was going through my recently acquired Gretsch 6162 (1966), he found the reverb tank to be dead ("open" transformer-like component if I understood correctly). There is pleny of gain going into the tank but no output. He has learned the tank was made by the Hammond Organ Co. but has had no luck finding one to replace it. Modern tanks he has available and has tried are apparently not compatible.

Anyone have any suggestions as to:

1) how to fix the existing tank?
2) where to find a matching replacement?
3) what would be a compatible alternative?

Another angle may be to use the reverb driver as an additional gain stage. Anyone done this on one of these amps? or have suggestions along these lines?

I understand these reverb tanks sound pretty awful anyway so really no great loss if it is not functional but it would be cool to have it up to original specs if possible.

Any suggestions welcome.

Thanks!

[Lonely Raven]

Unfortunately I can't answer your question, but I have a question for you.

Do you have any photos of the amp? What speakers and speaker wire were in it?

I used to have a '66 6162, and I miss it. I sold it here in the forums, and I'm wonder if it's been making the rounds from TGP member to TGP member.

The reverb on it was fantastic!

[OlAndrew]

Here's a schematic...you can download it (save copy...the little floppy icon in the pdf toolbar):

http://www.prowessamplifiers.com/schematics/gretsch/Gretsch_6162.html

Looks pretty standard, I'd put in a Fender reverb transformer and a Fender tank from Accutronics. I'd have to look up the crazed Accutronics part number. Torres, Mojo or any number of other online outfits sell them both. Accutronics has a site with a description of their various tanks and their part numbers.

[evbrad2007]

Unfortunately I can't answer your question, but I have a question for you.

Do you have any photos of the amp? What speakers and speaker wire were in it?

I used to have a '66 6162, and I miss it. I sold it here in the forums, and I'm wonder if it's been making the rounds from TGP member to TGP member.

The reverb on it was fantastic!

I'll see about posting a photo for you. This is not the piggy back style cab, it's the earlier suitcase cab. The speakers are the original Jensens. Did yours have the cardboard box reverb tank? Word I've heard is that these don't sound good so I'm thinking yours must have had a different tank.

BTW, I think I may have found a gent who works on these and can get me back up and running. More to follow.

[Lonely Raven]

Mine sounded like a Fender reverb...could pull off huge and deep surf.

Mine had Jensens, but I don't recall if they were original. The cloth speaker wire was fried so I replaced it with Monster 16 gauge MX. The guy I sold it to said the speaker wire just ruined it for him and tried to return it (buyers remorse). I simply told him I wasn't store and if he doesn't like the amp, he should flip it here in the forums...I had lots of interest in it, so I'm sure it's made its way around here.

I don't seem to have any photos of the back of the amp, only the top and face. From what I recall, I don't think mine had any logo on the grill either.

[OlAndrew]

Oh boy....the schematic shows a straightforward setup, 12ax7 rigged as a small power tube driving xfrmr primary, xfrmr secondary drives MAGNETIC tank input transducer, spring drives magnetic output transducer, which drives grid of recovery tube through a cap.

However, vintage stuff rarely matches the schematics. A lot of those cardboard box reverbs used piezo crystals for the transducers, and over time they turn to jelly. Problem is, the impedences and power levels of the piezo setup are WAY different than the magnetic. Its a bit of a project to change to magnetic, maybe almost impossible if you need to add tubes.

Some folks have managed to do a Harley fix by taking the piezo elements out of small (about watch-sized) crystal mikes and epoxying fixtures on them to hang the spring(s) on. Doesn't sound all that great, by all accounts, but I have to say, I've never tried it.

[evbrad2007]

My tech is stumped. He tried a couple of new tanks (PRY4AB3C1B and 4BD3C1D)we had been informed have worked for other 6162s but with the same issue...very weak output from the tank. The signal coming out of the reverb driver and going into the tank is virtually identical to the signal at earlier points along the signal path before the reverb driver.

The input going into the tank seems okay but perhaps it's supposed to get a boost...Does anyone know what the input should be going into the tank?

Suggestions?

[Lonely Raven]

My tech is stumped. He tried a couple of new tanks (PRY4AB3C1B and 4BD3C1D)we had been informed have worked for other 6162s but with the same issue...very weak output from the tank. The signal coming out of the reverb driver and going into the tank is virtually identical to the signal at earlier points along the signal path before the reverb driver.

The input going into the tank seems okay but perhaps it's supposed to get a boost...Does anyone know what the input should be going into the tank?

Suggestions?

I'm not a tech, so I'm proably talking out my arse...but did your tech try bypassing the tank altogether and just looping from the out right back to the in?

[OlAndrew]

It takes a good deal of current to make the input transducer "shake that thang", it's not unusual to see both sides of a 12at7 in parallel pushing one.

The tank itself is extremely lossy, output is about that of a guitar pickup, maybe a tad more, so there's usually a high-gain recovery circuit before the wet signal is merged with the dry for output to the power tubes.

If you're getting signal at the tank output, I'd look at things that could effect the gain of the recovery circuit...coupling cap, plate voltage, cathode resistor & bypass, grid stopper or grounding resistor, and like that.

A really bad impedence match could screw things up, too. I'd draw my own schematic from what I see in the amp in front of me, and compare that to 'known' schematics, (Fender, Ampeg, Vox, etc) to see if the circuit is close, and then look up the Accutronics tank for the similar amp.

I've more than once seen where a factory schematic showed a tha thad no resemblence to the amp in front of me. So calling Accutronics and asking them doesn't work, 'cause their tech looks at the factory schematic for his recommendation.

Did you open up that carboard tank and see what lives inside? Most of those were piezo ceramic, and the output and impedance of the piezos is waaay different than magnetic transducers. If you started out with a piezo, you're going to have to do some redesign and rebuilding of the recovery circuit. The London Power book will show you how.

[evbrad2007]

It takes a good deal of current to make the input transducer "shake that thang", it's not unusual to see both sides of a 12at7 in parallel pushing one.

The tank itself is extremely lossy, output is about that of a guitar pickup, maybe a tad more, so there's usually a high-gain recovery circuit before the wet signal is merged with the dry for output to the power tubes.

If you're getting signal at the tank output, I'd look at things that could effect the gain of the recovery circuit...coupling cap, plate voltage, cathode resistor & bypass, grid stopper or grounding resistor, and like that.

A really bad impedence match could screw things up, too. I'd draw my own schematic from what I see in the amp in front of me, and compare that to 'known' schematics, (Fender, Ampeg, Vox, etc) to see if the circuit is close, and then look up the Accutronics tank for the similar amp.

I've more than once seen where a factory schematic showed a tha thad no resemblence to the amp in front of me. So calling Accutronics and asking them doesn't work, 'cause their tech looks at the factory schematic for his recommendation.

Did you open up that carboard tank and see what lives inside? Most of those were piezo ceramic, and the output and impedance of the piezos is waaay different than magnetic transducers. If you started out with a piezo, you're going to have to do some redesign and rebuilding of the recovery circuit. The London Power book will show you how.

Thanks! I'll pass this on to my tech. I have actually contacted accutronics and they may be able to cross reference the stock tank with a compatible replacement, not based upon the amp schematic, but the tank number. We'll see.

[SatelliteAmps]

Maybe I missed something, but in the original post you said what was wrong was the ""open" transformer-like component." If that is what is wrong, then swapping tanks won't do anything to fix the issue. The only thing that will would be to replace the reverb transformer. If it was just the Hammond built tank, there are accurate repro's being made currently that will all work. Might not be as much reverb or more reverb, but they will work if the rest of the circuit is fine.

[OlAndrew]

Just occurred to me, tanks are available with various grounding schemes. IE, the jack ground may or may not be attached to the tank case, and the cable shield round may or may not be attached at the amp end, depending on design.

Now the input end, if its driven by a transformer, will have one secondary lead going to the jack and to one transducer lead inside, the other secondary lead will go to the other transducer lead. Makes a complete little circuit, doesn't need a ground anywhere, really. Might just add noise if it had one.

But the output side, whether its to be grounded or not, is gonna depend on the circuit design. This is why you have to draw a schematic of what's in front of you.

One transducer lead is gonna go to the center line in the cable, and that's gonna go to the grid of the recovery tube. BUT there has to be the other half of the circuit.

USUALLY, the second transducer lead goes to the shield terminal on the jack which is also grounded. The recovery tube will pick up the other half of the circuit through the cathode ground. So this rig needs to have the jack shields grounded at the tank and at the amp jack. Cable shield acts a conductor for half the circuit.

Some circuits will be designed to have the other half of the circuit hard-wired to the cathode, or some other method of completing the circuit (through some controls or something, then to the cathode). This needs the jacks ISOLATED from ground at both ends, with the amp end shield wired to the whatever completes the circuit.

So you can see, if any of the grounds are screwed up, not matching what the circuit design calls for, you'll probably get a small sound, mostly from leakage, but not much, as either the circuit is incomplete, or its being grounded out. Everything looks OK, superficially, but you really have to trace the circuit and figure out what has to be there.

If it was grounded out, I'd expect pretty bad hum, but you can't count on that as an absolute. Especially if the 'extra' ground is on the input side, shorting out part of the xfrmr output.

T'other one is a really bad impedence match, but that you can solve for, by doing the schematic of the actual and comparing it to other known amp designs. That won't hum, but it'll be a pretty faint sound, maybe badly distorted.

[Fretts]

I had a 6162 with a similar problem. You can see it at www.20wattworld.com
I did get the reverb working and it was pretty pathetic, sort of like a faint hint of clanky reverb, nothing like you're used to from Fender. The whole reverb circuit is lame, more than anything, it suffers from a lack of a recovery amplifier stage, so the whimpy reverb barely gets heard under the best of circumstances. I have a couple of spring assemblies that will go inside that cardboard box. I don't think they are an exact impedance match, but they are the identical type mechanically. Let me know if you want to try one for $25. I found them by chance at a surplus place several years ago and bought them all. If your amp has a 6973 tube in the upper chassis to drive the reverb, then it is exactly like mine.

[Fretts]

Also, if yours really is like mine, then there is an unused triode in there that a skilled tech could use to boost the reverb signal back up to a useful level.

[evbrad2007]

Thanks for the responses. I'll pass this info on to my tech. Found a gent on the Gretsch pages who has experience repairing these tanks so sending it off to him for a look. I've read in a couple of places that the verb is not much to get excited about but would be cool to get it back to original specs. My tech tried the reverb tranny swap for good measure but had no impact as he supsected. The bad part in the tank is apparently the transducer, if I understand it correctly. My amp has the 12ax7 reverb driver tube, btw. Will let you know how it comes out. Still haven't had a chance to get by to hear the amp itself....all healthy w/exception of verb. My tech says it sounds really good! Hope to drop by his shop to give it a listen this week.

[evbrad2007]

Finally got the amp back after my tech sent the tank off to a gent who believed he could fix it...after getting the tank back my tech reported it still only showed 2ohms over the input transformer of the tank and made no appreciable reverb. My tech noted no problems in the recovery circuit components. The fellow who repaired the tank stated he got definite reverb out of the tank when tried in another amp. So, still no reverb...

The good news, however, is that that amp itself sounds very, very good!
I really don't know how to describe the tone but it is very appealing....has sort of a bright warmth to it, if that makes any sense...not quite like any amp I've played before. It gets some moderate OD when opened up, the tone control is very useful, and the tremolo is very good. It's a keeper for sure!

If anyone learns of a known workable reverb tank substitute, please let me know. I'm not really big on reverb, but it would be cool to have this feature in the amp given it was designed to have it.

[evbrad2007]

After months of infrequent playing with promises to myself that I would eventually get back into it, I finally resolved myself to the reality that I will likely never play enough again to justify keeping my nice amps. In the process of listing my various amps for sale, I took another look at the reverb in the Gretsch and discovered that the reverb tank is fine; the reverb circuit is fine....the owner, on the other hand, is an idiot:o. I discovered that the reverb can only be activated by the footswitch, which I had not ever tried out. Because the tremolo functions without the footswitch, I assumed the reverb would simply turn on and off from the control panel as well. However, the tank is wired directly to the footswitch jack for the reverb circuit and the reverb knob on the control panel only functions if the footswitch is plugged in and activated...you can imagine how foolish I felt when I discovered this. I have an e-mail into the tech who looked at the amp as I was surprised he did not catch this as he is known to be excellent. He apparently took me at my word when I said the reverb didn't work initially and found values he did not expect when testing the tank as he is not super familiar with these old tanks, plus I imagine the values coming out of the tank were a bit off without the circuit being activated by the footswitch ;). I'm sure my tech will feel silly as well and it explains why the other gent who took a look at the tank stated it made Dick Dale reverb when he checked it out in another amp. Anyway, the amp sounds great and the tank works as it should and makes plenty of reverb, though it isn't a very appealing sounding reverb as those familiar with these tanks know.
If I end up keeping the amp, I imagine I'll try to find an accutronics tank for it. I have the amp up on the emporium for those interested.