Westone Thunder 1A - pre-amp distortion

[Grangur]

Found some good information on the meaning of the codes. 103K means 0.01uf 10%

We're getting there...

[Grangur]

[quote name='BigRedX' timestamp='1475099091' post='3143132']
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?
[/quote]
All the joints do look ok. That said; I know looks can be deceptive.


I took the board out yesterday. Soldered the wires from the pup straight to the jack. It sounds good passive. It actually sounds better then it ever did with the board in place. It's tempting to go passive, but I also don't want to be beaten by a board. It's a new challenge.

Only thing is, at this rate I never will get to learn to play bass. Instead I'm becoming a "bass tinkerer".

Edited September 28, 2016 by Grangur

[BigRedX]

[quote name='Grangur' timestamp='1475099180' post='3143135']
All the joints do look ok. That said; I know looks can be deceptive.
[/quote]

I was just looking at the rusty area around Cap 7....

[Grangur]

[quote name='BigRedX' timestamp='1475099260' post='3143138']
I was just looking at the rusty area around Cap 7....
[/quote]
That's sound. BUt I have just found a dry-joint on a resister. It's on the feed to pin 1 on the IC.

Pin 1 is the output A

[rmorris]

[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]
The voltages shouldn't be a problem. Really just random failures over time.

[rmorris]

[quote name='Grangur' timestamp='1475100092' post='3143145']

That's sound. BUt I have just found a dry-joint on a resister. It's on the feed to pin 1 on the IC.

Pin 1 is the output A

[/quote]
Def sounds like that might be the problem. Was just going to suggest reflowing all the solder joints - can't always see a 'cold' joint - and/or replacing the ic with a new one. Resistors can fail as well so not necessarily a capacitor problem even if it is a faulty component.

Edited September 29, 2016 by rmorris

[HowieBass]

[quote name='rmorris' timestamp='1475151926' post='3143477']
Def sounds like that might be the problem. Was just going to suggest reflowing all the solder joints - can't always see a 'cold' joint - and/or replacing the ic with a new one. Resistors can fail as well so not necessarily a capacitor problem even if it is a faulty component.
[/quote]

Grangur's already replaced the IC so it won't be that... maybe it is just a dry joint at the output pin!

[rmorris]

[quote name='HowieBass' timestamp='1475152496' post='3143486']


Grangur's already replaced the IC so it won't be that... maybe it is just a dry joint at the output pin!
[/quote]
OK. I thought he had just refitted the existing if but maybe I just missed it in the thread.

Edited September 30, 2016 by rmorris

[Grangur]

Successful evening! I've sorted out the dry joint and checked all the others. Then refitted everything again and its all working well again.

Thanks everyone for the support and encouragement.

[gary mac]

Good work Richard, it's very pleasing to sort this sort of problem isn't it?

[Grangur]

[quote name='gary mac' timestamp='1475210441' post='3144006']
Good work Richard, it's very pleasing to sort this sort of problem isn't it?
[/quote]
Yes, it's been satisfying. All I've got to do now is take it all apart again now to work on the body and get that looking good. This one is a bit moth-eaten.

[gary mac]

Will look forward to seeing the end result

[HowieBass]

I reckon the preamp in the Thunder is also the same as that in my Spectrum LX - as another BCer mentioned you can get a great sound by keeping the passive tone set fully open and then add some bass boost with the active. Flicking between the coil tap options on mine (the dual tone toggle) also changes the sound in a useful way in both passive and active modes. Have fun with it!

[rmorris]

[quote name='HowieBass' timestamp='1475222674' post='3144064']
I reckon the preamp in the Thunder is also the same as that in my Spectrum LX - as another BCer mentioned you can get a great sound by keeping the passive tone set fully open and then add some bass boost with the active. Flicking between the coil tap options on mine (the dual tone toggle) also changes the sound in a useful way in both passive and active modes. Have fun with it!
[/quote]
+1 on the series/parallel switch. I had to change my pickup because it went microphonic. But I recall that switching to parallel was useful to avoid 'mud' when playing chords.