[bloodhawk]

Hey Guy! I just find out what's the problem when double checked the NPN & PNP , although both nothing wrong but I notice those transistor's Collector touching ground, I guess that's the reason why the amp short circuit after 2nd VU meter light up.
I will change some problem circuit and confirm again later

Interesting. I guess it was a good move on my part to have insulated the transistor shield with some thick double sided tape.

Hope fully this solves your issue.

 

[klnglim]

Sounds like that could be the problem. That would probably explain why the headphone protection circuit kicked in too, you were getting very high voltages in the other circuit but I think this may right itself when you've fixed the ground issue.

I would like to know what voltage triggers the protection circuit.

The actual ground error connection with transistor is due to serious bad damage of circuit board. It happened since the day when amp start sparkling light and burnt in a sudden when I listened to music..
Now I have to find the way to fix the PCB carbon conducting ground shortage.

Watch this amp repair video, where I have just learned some knowledge from his playlists

 

[bloodhawk]

And all done -

 

[Whitigir]

This amp do look like a mod heaven, is it worth all the troubles over spending on some real high-end one guys ?

 

[baronbeehive]

The actual ground error connection with transistor is due to serious bad damage of circuit board. It happened since the day when amp start sparkling light and burnt in a sudden when I listened to music..
Now I have to find the way to fix the PCB carbon conducting ground shortage

Hi kinglim, sorry to hear that, I will check out the videos when I have time.

I'm assuming that the copper trace has melted from that area you indicated to ground. If it isn't too much damage you could probably use wire to and from the affected area as a solution.

The circuit board has to put up with a lot of punishment and several of us have had to do this when we have had similar problems including me when I accidentally lifted a trace.
.

 

[baronbeehive]

This amp do look like a mod heaven, is it worth all the troubles over spending on some real high-end one guys ?

I definately think so!

The amp, post mods is approaching TOTL. It has wonderful euphonic tone, soundstage and detail. Pretty much all deficiencies can be fixed with the mods. Whether you like the sound is probably an individual preference of course. I have this amp and a Miniwatt amp, also modded, and both are equally good but each has it areas where it scores better slightly.

Only thing is difficulty working in a confined space when you are adding quality parts inside the chassis!

Others on this thread would probably agree with me about the great qualities of the amp.

 

[baronbeehive]

And all done -

......and all working!!

Very nice clean job bloodhawk! I see you have decided on the "standard" layout lol.
.

 

[bloodhawk]

......and all working!!

Very nice clean job bloodhawk! I see you have decided on the "standard" layout lol.
.

Haha thanks!
I have a feeling my friend is going to want me to do the same to his amp now xD

Figured after moving the caps at the top of the otherside of the board, I'll have more space to slap in the 450V 33uF caps. Sonic's layout really helped along with adding a few standoffs in screw holes to add a gap in the bottom panel mounting.

 

[klnglim]

And all done -

That's nice job and great idea, how it sound like now?

 

[klnglim]

Hi kinglim, sorry to hear that, I will check out the videos when I have time.

I'm assuming that the copper trace has melted from that area you indicated to ground. If it isn't too much damage you could probably use wire to and from the affected area as a solution.

The circuit board has to put up with a lot of punishment and several of us have had to do this when we have had similar problems including me when I accidentally lifted a trace.
.

That damage area has carbonize conductive which cause ground shorted PNP transistor, all other circuit has no issue at all after checked with DMM

 

[bloodhawk]

That's nice job and great idea, how it sound like now?

The changes weren't as dramatic as the ones i had before, as i basically rearranged things around and changed the wiring from before.

But the most apparent and biggest changes were to the separation and the blackness of the background when nothing is playing. Before this, the soundstage had a nice bump going from stock to the new resistors/caps, with the wiring everything is much more "clearer". And the low end is so much more well defined. When compared to my WA22, it sound like this has a layer of cloudyness removed, whereas the WA22 feels like it has something in front of it. (if this makes any sense)

That damage area has carbonize conductive which cause ground shorted PNP transistor, all other circuit has no issue at all after checked with DMM

I had this issue once with one of my desktop motherboards, the only way i could fix it was to first clean the affected area with isopropyl alcohol and then to scrape all the carbon off. Which in turn ruins a lot of traces coming into the affected region, so i had to run wires on both sides of the board. Luckily these amps dont have as many traces as a motherboard, and you seem to have the blue PCB so traces will be easier to spot.
A well lit workbench will go a long way to help you in spotting the affected the traces.

 

[bloodhawk]

@baronbeehive Any idea if its sensible to use 33uF instead of the 15uF driver decoupling caps? If you have tried this, what type of improvement does this yield?

 

[Whitigir]

So, the amp is easily taken apart to work on the PcB guys ?

 

[baronbeehive]

So, the amp is easily taken apart to work on the PcB guys ?

Haha, yes. Don't know quite what to say here. The first time you try it it is difficult, but after one or two efforts you get the hang of it. The PCB slides out but not completely due to the wires on the back.

 

[baronbeehive]

@baronbeehive Any idea if its sensible to use 33uF instead of the 15uF driver decoupling caps? If you have tried this, what type of improvement does this yield?

Yes that would be alright, sorry I thought that was what you meant when you were probably talking about the power tube decoupling. I have 40uF driver decoupling caps atm. Don't know what effect they have though because I've only ever had those caps.