Thunder IIA active not working

Hi
I have a Thunder IIA since maybe 13 years ago or so. When i bought it the active curcuit worked, but a while later it became dysfunctional, IIRC it sounded like bad contact before it gave up. The passive mode is still working though.
Now i'm a bit curious to see if i can get it working again, but i'm not really sure where to start and what to check. it seems to be the first active version. The batteries are fresh, and the wires from the batteries are ok, but what should i try next? I've looked at the wiring diagram at westone.info, but i can't really decipher it.
so any help would be appreciated!

Try cleaning the contacts on the jack input with fine wet+dry paper. Also make sure that none of the components on the circuit board have been bent against each other, causing a short.
Which model is it? bolt on neck or fixed?

done, still not working.

it has fixed neck

Have you tried switch cleaner on the active mini on/off switch. (NOT WD 40)

nope. i think we have something translated as "electronic cleaner" somewhere, will try that tomorrow (it's 2:40 am here now and i'm off to bed )

Just squirt it in the top of the switch and switch it like there's no tomorrow.

tried, and still not working.

how do i proceed? I've looked at the wiring diagram (http://www.westone.info/wiring/thunderlead/active1/index.html) but i'm not sure what to check and where to measure voltage levels etc.
any help with that would be appreciated

Check all connections(not that you havn't) for a dry joint. Plug it in and have a 'gentle' fiddle with the connections.
Those old switches can take a lot of cleaner before they contact sometimes. Flood it in and switch like crazy.
Alternatively, guitar shop.

Westbone, it might not be the switch, dogged down the middle play yet again. Valentines day -10 is a coming.

If youve got a meter does the battery voltage get to where it looks on the schematic and follow through when youve switched it?

grogg, time for another whopping. Roll on the 4th. Feb. Might have a chance at the Millennium 54-53
I'm a 'bok' by default and remember a result awhile back 96-13 'think it was.

It's a simple diagram, seems like he's in a bit of a pickle with it though.

I've had this on my T2a. I took the back plate off to check the wiring when I first had it(just being inquisitive), had a peep at the wiring to see all was well, and then screwed it back on again. Nothing, no sound. So changed the batteries. Still no sound. I then took the panel off again , plugged the guitar into the amp and low and behold sound. I then systematically moved the panel into position again and the sound disappeared again. So it wasn't the batteries.

I noticed that several of the components on the board seemed to short out ( no sound) when trying gently to put the panel back in place (its a tight fit against the wiring). Eventually, I identified and gently bent a couple components down and out of the way of the wiring. Not had a problem since.

Westbone wrote:grogg, time for another whopping. Roll on the 4th. Feb. Might have a chance at the Millennium 54-53
I'm a 'bok' by default and remember a result awhile back 96-13 'think it was.

Sorry dont/cant/wont remember that, do remember the Boks losing at the opening game of the Millenium stadium, I was there!
I think England are coming good and Wales will only have a chance if they have no injuries at all, so thats a slim one.

Back on topic, Steves suggestion is good, however the symptons are:- it used to work and now doesnt, works fine in non-active mode. Has it had a bang or other interference? Its either a short, an open circuit, a dodgy switch or a component like the op-amp has died. My solution is dont use the active mode cos its rubbish anyway (my Thunder 1A has the battery removed to stop me being tempted), Matsumoku were good at building guitars, not electronics. If youre looking to sell and dont want this to detract then get a friend with a bit of electronics to help, needs some hands on methinks.

grogg wrote:If youve got a meter does the battery voltage get to where it looks on the schematic and follow through when youve switched it?

Westbone wrote:It's a simple diagram, seems like he's in a bit of a pickle with it though.

I've never looked closer on guitar electronics, so i'm a bit confused where to start. I had hoped someone could say "do you have X v there, there and there?". I know how to handle a multimeter, it's just the other bit i'm struggling with.

Steve777 wrote:I've had this on my T2a. I took the back plate off to check the wiring when I first had it(just being inquisitive), had a peep at the wiring to see all was well, and then screwed it back on again. Nothing, no sound. So changed the batteries. Still no sound. I then took the panel off again , plugged the guitar into the amp and low and behold sound. I then systematically moved the panel into position again and the sound disappeared again. So it wasn't the batteries.

I noticed that several of the components on the board seemed to short out ( no sound) when trying gently to put the panel back in place (its a tight fit against the wiring). Eventually, I identified and gently bent a couple components down and out of the way of the wiring. Not had a problem since.

i've looked at the board and there's no problem with the components shorting out.

grogg wrote:Back on topic, Steves suggestion is good, however the symptons are:- it used to work and now doesnt, works fine in non-active mode. Has it had a bang or other interference? Its either a short, an open circuit, a dodgy switch or a component like the op-amp has died. My solution is dont use the active mode cos its rubbish anyway (my Thunder 1A has the battery removed to stop me being tempted), Matsumoku were good at building guitars, not electronics. If youre looking to sell and dont want this to detract then get a friend with a bit of electronics to help, needs some hands on methinks.

i've had it for maybe 13 years or so, it's been on band practices, in the back of cars (in the hardcase though) etc, so it might have had some hard times...
I've found out that i have an extra wire going from the body of the active gain pot, to the bare wire that connect the 3 switches (nr 3 on the wiring diagram) is it supposed to be like that? it doesn't look like it's added afterwards to me.
How do i test if the switch is bad? or if the op-amp is dead?
I have managed to live with only passive mode almost all the time i've owned the guitar, but it would be fun to at least have the choice between passive and active mode

I'm halfway through school to become an engineer in electronics/computer, so i thought i should be able to troubleshoot the guitar. but once again there is a discrepancy between school and the real world

If you have a multimeter, with the lead out and batteries disconnected check the active switch. Looks like a 4 pole one so each of the the centre contacts should switch between either side, use the multimeter in Ohm measuring mode. As you flick the switch the contacts should vary between 0 ohms and something else. I suspect its not this as the passive would be iffy as well.

Next try measuring the impedance between battery negative and the earth (case of the pots), it should be off the scale, plug in the lead and it should be shorted to 0 ohms. If not theres something wrong with the jack socket or wiring to it.

From the diagram it looks like the op-amp is in a socket so could be easily replaced. On my Thunder its a LA6358. With the batteries in and the lead plugged in measure the voltage between pin 4 and 8, pin 1 is the in the corner with a small blob next to it, count the pins from there clockwise. You should get about the same as the battery voltage.

Are you using a stereo or balanced 3 wire cable? If so, the connection that powers the circuit "on" will not ground and the power circuit will still be open. Try a standard 2 conductor cable.

I took that 12 lug switch apart on my Electra 'cause it was already busted. You'd be amazed at the simplicity of design. However, there are 4 springs that push the contacts from side to side. I would venture to say that these springs could easily fail causing the contacts to fall out of position inside the switch. That is the worst case scenario for the easier job of replacing the switch.

Worst, worst case is that the electronics are bad. If that is the case I am sorry to hear that. And have no ideas. Except maybe replace the chip on the board. yikes that is too much work.

grogg wrote:If you have a multimeter, with the lead out and batteries disconnected check the active switch. Looks like a 4 pole one so each of the the centre contacts should switch between either side, use the multimeter in Ohm measuring mode. As you flick the switch the contacts should vary between 0 ohms and something else. I suspect its not this as the passive would be iffy as well.

i tried this, and the results were a bit weird. don't trust my multimeter though, i'll have to borrow a reliable one and try again i guess.

Next try measuring the impedance between battery negative and the earth (case of the pots), it should be off the scale, plug in the lead and it should be shorted to 0 ohms. If not theres something wrong with the jack socket or wiring to it.

From the diagram it looks like the op-amp is in a socket so could be easily replaced. On my Thunder its a LA6358. With the batteries in and the lead plugged in measure the voltage between pin 4 and 8, pin 1 is the in the corner with a small blob next to it, count the pins from there clockwise. You should get about the same as the battery voltage.

this seemed to be just fine!

so i'll have to test the switch again with a reliable multimeter and then before doing anything else.

vidmachine:
i think i've used both kinds of cable, no difference in the result. might be the switch or some other electronics then...

I'll work on a fault finding / troubleshooting guide for this circuit at the weekend, there'll be a link to it on the page with the wiring diagram on when it's finished, probably on Monday