Westone Thunder 1A - pre-amp distortion

[Grangur]

I've picked up a nice Westie. I changed the switches and one battery clip and It was playing fine and all was all fine in the world.

Then yesterday I played it and on active the sound was seriously distorted. Seeing other threads and mailing a friend here, I decided to change the other battery clip, but no change. It's still sounding bad.

Any ideas?

Actually, while writing this I'm thinking - remove the pre-amp from the back panel and check all the joints for dry joints.

I'll come back to you and let you know what happens.

[razze06]

If you switch on the active preamp, and turn up all the way the bass boost, the signal may get too hot for your amp. It is a seriously powerful preamp

[Grangur]

I[quote name='razze06' timestamp='1474630203' post='3139378']
If you switch on the active preamp, and turn up all the way the bass boost, the signal may get too hot for your amp. It is a seriously powerful preamp
[/quote]
Many thanks. I've got the volume and tone turned all the way "forward"; so that's max treble.
If I have it in active mode, both the passive tone and the "active tone" pots work. That's to say they do make a difference if I turn them.

Soldering one the back of the pre looks ok.

[hubrad]

I had the guitar version decades ago.. even the treble could really push an amp hard. Can you try it in anything with a gain indicator?
If it's the pre that's at fault, I'd be more inclined to fit a modern, far less battery-hungry unit.
Excellent basses, but probably not so collectable that the original preamp makes so much difference,

[Grangur]

[quote name='hubrad' timestamp='1474631622' post='3139408']
I had the guitar version decades ago.. even the treble could really push an amp hard. Can you try it in anything with a gain indicator?
If it's the pre that's at fault, I'd be more inclined to fit a modern, far less battery-hungry unit.
Excellent basses, but probably not so collectable that the original preamp makes so much difference,
[/quote]

Very fair point. To be honest, the Westone active tone strikes me as being more wacky rather than useful.

There was someone on here who was making Pre-amps for Stingrays. Maybe one of those would fit in there.

[Thunderbird]

Think the person on here was selling the stinger pretty amps mate

Have you investigated the jack plug mate and another thought in my head is the brass screw mounts on the back of the pres may be loose or dirty they are used to help with grounding from what I read some time ago it has been ages since I look inside one of these so memory is a bit rusty

Edited September 23, 2016 by Thunderbird

[Grangur]

[quote name='Thunderbird' timestamp='1474633673' post='3139444']
Think the person on here was selling the stinger pretty amps mate

Have you investigated the jack plug mate and another thought in my head is the brass screw mounts on the back of the pres may be loose or dirty they are used to help with grounding from what I read some time ago it has been ages since I look inside one of these so memory is a bit rusty
[/quote]
This is the one I was thinking of:
[url="http://basschat.co.uk/topic/172964-feeler-would-you-buy-a-musicman-sabre-based-preamp-for-l15-update/page__st__60"]http://basschat.co.u...te/page__st__60[/url]

I've checked out the jack socket - sprayed it and dragged a wad of fine wire wool though it.
I've liberally sprayed the PC with contact cleaner.
Taken the IC out of the socket, sprayed the socket and refitted the IC.
Tightened the mountings of the PC. Although looking at it, the board seems to be insulated from the back, but the green covering over the track on the back of the PCB.
Checked all the terminations for lose connections/bad joints etc.
Looked over the PCB for components' legs connecting to make a short circuit

Something that may be the key is the active output is very much louder than the passive output. So I think the problem is something has gone wildly high-gain-noisey. I don't think I'm seeing signal drop out.

Edited September 23, 2016 by Grangur

[Thunderbird]

Hmmm that's a funny one I can't think of much you've not done hope you sort it mate

[Grangur]

[quote name='Thunderbird' timestamp='1474645660' post='3139581']
Hmmm that's a funny one I can't think of much you've not done hope you sort it mate
[/quote]


You're not ment to say that! You're ment to say, "Ah, change the 3rd capacitor on the left, that's gone open circuit" or summat like that.

[dannybuoy]

If it was fine then it wasn't, have you tried changing the batteries?

[Grangur]

[quote name='dannybuoy' timestamp='1474652145' post='3139685']
If it was fine then it wasn't, have you tried changing the batteries?
[/quote]
Both batteries are putting out over 9v measured on my multimeter.

[steve-bbb]

[quote name='razze06' timestamp='1474630203' post='3139378']
If you switch on the active preamp, and turn up all the way the bass boost, the signal may get too hot for your amp. It is a seriously powerful preamp
[/quote]

+1 the east's are similar by sounds of it - have to keep the volume at 50% and the bass and treble boosts back below 100% as fully boosted they up the signal level quite considerably - hopefully once you wind them back a bit you will find a sweet spot and keep those settings

[Paul S]

I quite liked the active controls on the Thunders. As I recall the centre indent was flat with a bass or treble boost depending upon which way you turned it, together with a passive roll off knob, too. I would usually select just off the centre indent towards bass - deep, powerful yet still punchy.

[Grangur]

The amp I'm using is a Little Mark 3.

I played through the same amp and never had any problems with everything turned up full. I could turn up the volume full and crank the Active tone back and forth all the way and no problem.

A day or so later the active tone is distorted when volume is at 1/4 and whatever I do with the active tone control. It is not a case of my Little Mark 3 at low volume can't handle the gain of the Westone.

The LM3 is fine with all other basses.
The problem is still there when I play the Thunder through either my Roland cube or my Vox headphone plug thing.

Yesterday I got a replacement op amp IC and changed that thinking that had gone high gain. That made no difference.

Thanks guys, but I'm thinking of either go through the wiring for a bad joint, or rip it out and either go passive or fit a new pre amp to have bass-mids-treble.

After all, the WT1A pre is quirky but does anyone actually play using it?

[razze06]

It could be that some of the caps in the preamp has dried out, or otherwise expired. You might be able to get a replacement pre amp from a parts bass quite cheaply, and swaps the pres.

I always used the pre on the thunder i used to have, mainly leaving a little bit counter-clockwise of the notch to give it a conrolled bass boost. In its last incarnation, I had it strung with think flats, and played raggae and dub with it. The pre really made a difference there

[Grangur]

[quote name='razze06' timestamp='1474883391' post='3141182']
It could be that some of the caps in the preamp has dried out, or otherwise expired. You might be able to get a replacement pre amp from a parts bass quite cheaply, and swaps the pres.

I always used the pre on the thunder i used to have, mainly leaving a little bit counter-clockwise of the notch to give it a controlled bass boost. In its last incarnation, I had it strung with think flats, and played reggae and dub with it. The pre really made a difference there
[/quote]
Many thanks. You could well be right. I guess though, if the caps in mine have dried, than most other pre's from Thunders can't be far behind. In an ideal world I would know the values of the caps and buy new, but we don't live in an ideal world.

[rmorris]

[quote name='Grangur' timestamp='1474897746' post='3141327']

Many thanks. You could well be right. I guess though, if the caps in mine have dried, than most other pre's from Thunders can't be far behind. In an ideal world I would know the values of the caps and buy new, but we don't live in an ideal world.
[/quote]

Any electrolytic caps on there ? If so replace those first. Value should be written on the case.

[Grangur]

[quote name='rmorris' timestamp='1475011213' post='3142370']
Any electrolytic caps on there ? If so replace those first. Value should be written on the case.
[/quote]
They're all red drop cap type. Most have values on them. There are some really small ones on there though. I guess the values of those probably wont to too critical though. It's not like it would blow up.

[HowieBass]

Do non-electrolytic (ceramic?) capacitors dry out?

[rmorris]

[quote name='HowieBass' timestamp='1475013895' post='3142386']
Do non-electrolytic (ceramic?) capacitors dry out?
[/quote]
They can't dry out as they aren't 'wet' to start unlike electrolytics. They can still go faulty though but electrolytics are much more likely to show problems especially after 10+ years.

[rmorris]

[quote name='Grangur' timestamp='1475012076' post='3142378']

They're all red drop cap type. Most have values on them. There are some really small ones on there though. I guess the values of those probably wont to too critical though. It's not like it would blow up.
[/quote]
OK. I used to have one of these but have emgs in the bass now. If you can get hold of a multimeter that does capacitance you should be able to measure the value. It may not be exact but should be accurate enough to indicate the standard value used.

[HowieBass]

[quote name='rmorris' timestamp='1475049410' post='3142519']
They can't dry out as they aren't 'wet' to start unlike electrolytics. They can still go faulty though but electrolytics are much more likely to show problems especially after 10+ years.
[/quote]

This was actually my point! Would the low voltages (9v and 18v) be likely to age the capacitors in the preamp?

[Norris]

[quote name='HowieBass' timestamp='1475059356' post='3142658']
This was actually my point! Would the low voltages (9v and 18v) be likely to age the capacitors in the preamp?
[/quote]

I think it's time that does the aging

[Grangur]

OK. I've taken a pic of the board, numbered the Caps. Now to make a list of the writing in each and try to find a replacement for each. Each one only costs pennies, so it's worth simply going for it. Besides if one's gone then the rest can't be far behind it.

Hopefully the guys down Maplin will know what a 1K 103K translates as - for example.

Many thanks for your help, guys.

[quote name='rmorris' timestamp='1475049600' post='3142520']
OK. I used to have one of these but have emgs in the bass now. If you can get hold of a multimeter that does capacitance you should be able to measure the value. It may not be exact but should be accurate enough to indicate the standard value used.
[/quote] Many thanks RMorris. I already have 2 MM's but nothing that does capacitance. I might just go and buy one. I've seen one for about £50. It's no great shakes really and it'll be alot better than the cheapies I have. Besides, I can possibly sell the cheapies.

[BigRedX]

I take it you have already run your soldering iron over that board just to make sure it isn't a dry joint somewhere causing the problem?

Edited September 28, 2016 by BigRedX