Need help with my Laney VC100

[Deny]

Hi there everyone, this is my first post here. Sorry it's a cry for help and not a contribution, I'll try to do better on my next posts

Schematics:
http://www.freeinfosociety.com/elect...laneyvh100.pdf

I've had this amp for 10 years or so and after one year the JFETs (?) in the switching board began to burn out one by one. It turns out, according to Laney, the first production units had a design flaw that caused that to happen. They sent me instructions for the fix, which is quite easy - just installing 2 zener diodes. The problem is, I can't find the darn switching transistors *anywhere*. According to the schematics their code is PF3820, but the problem is they're all SMD and I was willing to risk trying 2N3820's but no luck with its SMD version so far either. Any ideas? I'm pretty much giving up hope to be honest, I live in Brazil and Laney doesn't seem to care about my problem.

[Zouto]

Hi Deny I have the same problems with a Laney VH100R
http://music-electronics-forum.com/163818/.
Could you please post the instructions Laney sent you for fixing it with 2 zener diodes ?
The switching transistor T9 for relay5 is on the lower board next to the relay
Thanks a lot
Zouto

[Deny]

Hi Deny I have the same problems with a Laney VH100R
http://music-electronics-forum.com/163818/.
Could you please post the instructions Laney sent you for fixing it with 2 zener diodes ?
The switching transistor T9 for relay5 is on the lower board next to the relay
Thanks a lot
Zouto

Sure thing, here are the instructions:

1. replace switching fets
2. add a 3v9 zener on the signal input pin 5 of HDR1 to ground.
(Cathode gnd)
3. add a 3v9 zener on the signal input pin 4 of HDR3 to ground.
(Cathode gnd)

There's also a diagram which I'm saving as an attachment to this post. Good luck!

[Zouto]

Sure thing, here are the instructions:

1. replace switching fets
2. add a 3v9 zener on the signal input pin 5 of HDR1 to ground.
(Cathode gnd)
3. add a 3v9 zener on the signal input pin 4 of HDR3 to ground.
(Cathode gnd)

There's also a diagram which I'm saving as an attachment to this post. Good luck!

Thanks Deny, it seems that those instructions are for another model, not for
the VH100R from 1997, for there are no J175s as T1 etc., only BC847Bs or
those obscure PF3820s.

Zouto

[Deny]

Thanks Deny, it seems that those instructions are for another model, not for
the VH100R from 1997, for there are no J175s as T1 etc., only BC847Bs or
those obscure PF3820s.

Zouto

The PCB may be different, I haven't even looked yet (since I don't have the replacement 3820s), but the connectors HDR1 and HDR3 are there aren't they? And according to the VH100 schematics, the written instructions point to common terminals for all the PF3820, so... I'm guessing the .pdf referers to the *newer* PCB, and we'll have to solder the zeners directly to the copper leads of our older PCB.