#1
Hi GB&C!


about a month and a half ago I bought a used ENGL Thunder 50 combo (loving every single second I play through it) but the reverb didn't work. I didn't care to much because I figured that I wouldn't use it a lot anyway, and it brought down the price.
I do however want my amp to be completely functional, but never got around to fix (or try to ) it.
Until now!


The reverb tank is an accutronics type 9 (specs number 9AB2A1B)
Google tells me that these are also the ones used in for example mesa boogies MK I, MK II, MK III and MK IV, so I figure that it must be of at least some degree of quality.

I took it out of my amp and looked at it, but I couldn't see any loose or disconnected wires.
Does that mean that I can't fix it and that I just have to get a new one?
I figured that I should check for continuity, but I don't know where I should check And yes, I do realise that I sound like a complete retard asking this .


Also, how do I rule out that the problem isn't situated somewhere else?
I don't want to buy a new one and find out that the problem wasn't the reverb tank


Help me please, people of GB&C!
#2
(weren't you supposed to be sick?)

if you can (and know how to, but someone will know here...), check continuity over the reverb tank, if that's alright, the problem lies somewhere else in the amp, and then I'd suggest you take it to a tech...

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#3
The easiest way to see if a reverb tank is good is to install it into an amp that has working reverb. If the reverb quits with the tank that is suspect you know the problem is your tank. If it doesn't quit you know the problem is in the reverb circuitry.

Testing a reverb tank is tricky because it's kind of like a transformer with a primary and secondary coil but instead of a rugged metal core transferring current it uses springs connected to very thin and delicate wires. Because of the nature of the beast you can get the right readings for each coil on the reverb tank but still have a tank that doesn't function due to loose springs.
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#4
It's probably not in the tank itself but in the electronics that drive the reverb. Is it tube driven reverb? check that tube if it is.
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#5
It's still worth testing the tank, loose wires are a common problem on any reverb tank.

Open it up, look for any loose solder connections, especially ones that may have broken free from the body (ground) of the tank.

Check to see the springs are free, and not binding on eachother or something else (I have ssen the little sticker that Accutronics used to put inside their tanks curl up and tangle in the springs).

If you have a an ohmmeter you can check it, give me a minute, I'll dig up the specs on that tank...

EDIT: resistance measured across the sleeve and tip of the RCA jacks:

Input: 10 Ohm

Output: 2575 Ohm

You might not get those values axactly, just be on the lookout for something like a megaohm or more, indicating an open circuit.
Last edited by Rutch at Oct 13, 2009,
#6
@poipoi: I am, but I need something to keep me busy right? :P
@CorduroyEW: I haven't got another amp to test it with, there are no visibly loose wires
@pac_108: it is ss driven

So on in and output jacks, I get continuity on the outer part of the jacks. It's a fluctuating though.
I'm not reading anything when checking the inside of both jacks though.
How do I narrow down the problem? All the cables are insulated.

edit: springs are able to move freely, there is nothing obstructing their movement.
Last edited by Toxc at Oct 13, 2009,
#7
Quote by Toxc
@poipoi: I am, but I need something to keep me busy right? :P
@CorduroyEW: I haven't got another amp to test it with, there are no visibly loose wires
@pac_108: it is ss driven

So on in and output jacks, I get continuity on the outer part of the jacks. It's a fluctuating though.

These are both common to ground, this is good.

I'm not reading anything when checking the inside of both jacks though.
There should be no continuity here.

How do I narrow down the problem? All the cables are insulated.


Are you testing the jacks on the tank, or the jacks on the amp?

You want to test between the inner and outer on input, then the inner and outer on ouput, on the tank.
#8
Was testing on the tank, but doing it wrong I guess :P

I now checked the inner and outer parts of each jack, and the problem is at the output. I'm getting an open circuit there
#9
It doesn't matter if there are no visibly loose wire. This is part of the problem. You can't simply look at it. You need to run a signal through it and measure what comes out the other end. In terms of measuring continuity, do what Rutch has told you.

Quote by Toxc
Was testing on the tank, but doing it wrong I guess :P

I now checked the inner and outer parts of each jack, and the problem is at the output. I'm getting an open circuit there


Open or infinite?
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Last edited by CorduroyEW at Oct 13, 2009,
#10
I did that, see my previous post.

I maybe wasn't really clear, sorry for that. Let me try again :P
On the input jack I get a reading when checking the inner and outer parts, so that's good right?
When I do that on the output jack however, I'm not reading anything.

edit: Open or infinite?
It gives me the same as when I don't touch anything, my multimeter just reads '1'
Last edited by Toxc at Oct 13, 2009,
#11
That would be infinite and indicates that the output coil is broken. Unless your meter is set in the wrong range. It should be set at 200ohm to test the input but 20K to test the output. If it's one of the meters that self selects it's range then you may need to use a different meter.
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#12
1 - DC resistance =/= impedance.

2 - for your tank, you should read a little less than 1 ohm resistance between tip and shield on the driver end.

3 - you should read about 200 ohms resistance on the return end

4 - an open (infinite) reading indicates a break somewhere. either in the coil or a connection to it.
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#13
Quote by CorduroyEW
That would be infinite and indicates that the output coil is broken.


Is this fixable? Would putting in a new one help? If it is even possible :P


Quote by CorduroyEW
Unless your meter is set in the wrong range. It should be set at 200ohm to test the input but 20K to test the output.

That's what I did, I basicly tried both on 200, 2k, 20k, 200k and 2000k :P

edit: I figure that replacing the coil would be to much for me, I should just buy a new tank.
But how do I know for sure that it is the coil and not just a connection to the output jack?

Btw, thanks for all the help you guys gave me, I really appreciate it.
Last edited by Toxc at Oct 13, 2009,
#14
Quote by Toxc
edit: I figure that replacing the coil would be to much for me, I should just buy a new tank.
yep. tanks aren't all that expensive, anyway. about $30~40

Quote by Toxc
But how do I know for sure that it is the coil and not just a connection to the output jack?
Use your eyes and your meter. Do you see solder connections where the wires meet the coil? Do they look broken? Can you measure resistance at the coil itself?
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Quote by SK8RDUDE411
I wont be like those jerks who dedicate their beliefs to logic and reaosn.
#15
If you look inside the tank you will see that the input and output jacks have 2 wires coming from them. 1 wire is green and will be coming from a tab that is folded over from the center (hot) of the jack the the other wire is black and will be coming soldered to a tab that stick strait out of the jack off center. This is the ground. Both wires should be securely soldered. If you follow the wires you will see that they connect to a little plastic quick connect that is plugged into a little coil wrapped in yellow tape. Carefully pull the quick connect so that is disconnects from the coil leaving you with 2 exposed prongs. Touch each prong with the probes of your meter and if it still doesn't give you a reading then you need a new tank. If it does give you a reading then your tank is fixable, you just need to take readings from jack to quick connect pin to see which wire is breaking the connection and redo the connection of that wire to both the quick connect and the jack.
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#16
I'm getting close to locating the problem. If it is what I think it is, I can fix it.

So there's this plug at the coil, the two wires coming from the output jack go in it and connect with the wires coming from the coil.
Now, there's this small bit where the wires coming from the coil are naked, and connect to that plug. I've narrowed the problem down to there by using my resistance meter.
If i look closely I can see a little bit of black on the plastic behind the wires, like it burnt a bit.
I'll try to reconnect those wires and I'll let you guys know

thanks for all the help

edit: Being as dumb as I am I didn't refresh the page before I posted. I didn't see CorduroyEW his post. I'll try that and I'll see if it confirms what I think is wrong. thanks
Last edited by Toxc at Oct 13, 2009,
#17
(Double post: editing doesn't work for some reason, my page just goes blank every time)


I've located the problem for sure now, it's not the coil.
The wires that come out of the coil are burnt where they connect to the pins that go into the quick connect thingy. I'll try to fix it
#18
Quote by Toxc
(Double post: editing doesn't work for some reason, my page just goes blank every time)


I've located the problem for sure now, it's not the coil.
The wires that come out of the coil are burnt where they connect to the pins that go into the quick connect thingy. I'll try to fix it
The "burnt" look might be because of the enamel insulation that covers the wire. This will be difficult to clean and re-solder. You could use a strong solvent like acetone, but you would have to be very careful to not allow any of it to drip onto the coil.
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#19
Sounds like a pain in the ass. I say check electronics inside the amp, make sure all is well. Then put out for a new tank..Accutronics charged me 27 dollars shipped for mine, and it was kickass. Until I sold the amp. Now I'm probably going to put a new one in my Valveking.
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#20
I'll probably have to get a new one, my dad sais that it'll be too hard to fix it because there's really no room for error.

The things is, there's only 1 Accutronics dealer in Europe and it is in Germany.
€39 (excl. shipping)


Thanks for helping me trough this GB&C
#21
You could always call them to see if they'd make an exception and ship direct to you, maybe mention that the one you have already is an accutronics and it f#cked up on you.

Don't be pushy, just ask.

You know, I just realized, Accutronics is right down the street from here...

I might cruise on over on my lunch break just to rub it in TS's face and tell him all about the shiny new 9AB2A1B I saw in the showroom...

Just playin'.

Their number is (847) 639-4646.