[BUILd] PM660 / PM670 SCAmp Booster build and tips help thread

[radiance]

have disconected LM7812 and no short between 2 and 3.

You mean, no short between pins 2 and 3 from the LM7812 right?
Did you check if there was a short on the board as well? It seems there must be a short on the board right?
Also, I see your diode's are mounted tightly on your board. Did you put steel clamps on them when soldering them? To release some heat while soldering?
Maybe you've a faulty diode. They can't handle much heat.

I always mount them 5 to 10mm off the board so there's enough space for a steel clip while soldering them....

 

[lolo-m]

have disconected LM7812 and no short between 2 and 3. When 12 V is connected to meters and relays I can buzz with my multimeter pin 2 and 3.

powered up with 12V disconnected and still here the crackling sound. With no power to SCamp all is fine. All was fine before installing SCamp.

Let me know if anyone spots a problem here.

Thanks for the photo, it's always better to see if there's something wrong or not :
The thing I can't see but I suppose you did it, is the strap close to the first big WIMA...
Another thing I can't see is : what do you use as "MODE" switch ? It must work like a dual ON/ON switch. "MODEA-X"switch and "MODEB-X" switch are mechanicaly linked... This switch should operate as a short between MODEA-X pin2 and pin1 (or pin3) and at the same time MODEB-X pin2 should short pin1 (or pin3).

Stupid question, but sometimes they're needed  ;D: did you set the PSU660 to +17V / -17V before installing the SCAB ?

PS: I see you've done the mod the right way (75R before the diode) 

 

[lolo-m]

rrs,
Other idea, if everything on the previous post is correct:
1°) What's connected to the 12V rail ? Keep under 500mA current consumption here....
2°) Check if the BYPASS PCB roll-off diodes don't make a short when connected...

 

[rrs]

Thanks guys. I will get a chance shortly to do more teasting.
One thing is the short only happens when the 12V connector is connected.

It runs the meter lights and relays. There was no problem before the mod with this. Also the crackling sound occurs still when 12V is not connected so it may be something else also.

Anymore testing ideas are more than welcome expecialy the obvious ones.

 

[lolo-m]

Thanks guys. I will get a chance shortly to do more teasting.
One thing is the short only happens when the 12V connector is connected.

This makes me think about the BYPASS PCB roll-off diodes... Are the relays working ? If not, try the opposite connection on the 12V connector (quickly)...

It runs the meter lights and relays. There was no problem before the mod with this. Also the crackling sound occurs still when 12V is not connected so it may be something else also.

You seam to have a problem on the +17V/-17V rail...
Safe test you can do :
- Disconnect the "ATTACK" connector on the PM660 boards... Tell us what's happening (you won't have any compression BTW)...

Anymore testing ideas are more than welcome expecialy the obvious ones.

On the SCAB, check if the electrolytics are the right way because it's impossible to see the orientation on the photo. Check also if the +17V/-17V is present where it should be (op-amps, transistors...)

 

[rrs]

- Disconnect the "ATTACK" connector on the PM660 boards... Tell us what's happening (you won't have any compression BTW)...

No crackling sound  (12v is connected also).

I guess were onto something. It could be coming from the PM660 board.
Where to from here?

 

[lolo-m]

Your PM660 board's fine, cool  ;D.

Unplugged like this did you checked voltages on the SCAB board (OPamp and transistor supply) ?
If everything is fine :
1°) Try to see if the link between SCAB and PM660 is not twisted...
If it's OK:
2°) Replug the connector, and redo the setting operation, trying to see if the voltage between "TO ATTACK-X" connector pins can become negative or positive. SET it to 0V, of course, in analag's mode  ;D...

I'll be back on the web in about 2 hours...

 

[Kingston]

rrs,

why have you nothing connected to your poorman PCB ground and -17V?

Please people! READ THE WHOLE THREAD BEFORE DOING ANYTHING THAT CAN BREAK YOUR UNITS!

then read them again! all of them!

 

[rrs]

rrs,

why have you nothing connected to your poorman PCB ground and -17V?

Please people! READ THE WHOLE THREAD BEFORE DOING ANYTHING THAT CAN BREAK YOUR UNITS!

then read them again! all of them!

Moby's wiring diagram shows no connection. Is Mobys diagram wrong?

 

[Kingston]

What did I just say?

There's only 5 pages. Is it really too much to ask? 

 

[rrs]

What did I just say?

There's only 5 pages. Is it really too much to ask?  

Well looks like the wiring guide was updated in the last 13 days. I am sorry if my not re-reading this thread every two weeks has offended anybody. Then again if you had just alerted us to the fact the wiring guide had changed I would be giving you a big thanks.
I will see if this makes a difference.

[Edit] Well actually that seems to have done the trick so I guess I do owe you a big thanks anyway. :-*

 

[lolo-m]

Thanks Kingston !!!!

 

[Kingston]

I am sorry if my not re-reading this thread every two weeks has offended anybody.

you only needed to read new posts. in the last page. 2 minutes.

compare that to the amount of time you spent troubleshooting.

 

[lolo-m]

I am sorry if my not re-reading this thread every two weeks has offended anybody.

Nobody has been offended, but it's always stupid to waste time...
Tell us about your progress...

 

[dagoose]

Ok, finally had some time to test some things.
First i wanted to make sure that my pm board itself was ok and so added the 4148's again, 120r res and 10uf, standard. then.. still not working.. dammit.. Then i measured the voltages from the psu and i had both 17v lines but... the -17v was + 17v and so i have 2x +17v lines! 
Then i disconnected the -17v from the scabboard (not the pmboards) and everything worked fine again, even the channel with the scabboard came alive.. but without the -17v connected to the scabboard. Of course that channel is not working as it should but at leadt it gives sound and does compress a bit in both modes... weird..

How can a voltage which should be -17v become +17v?  ???
Anyone? i don't see the logical part of this.

 

[radiance]

Ok, finally had some time to test some things.
First i wanted to make sure that my pm board itself was ok and so added the 4148's again, 120r res and 10uf, standard. then.. still not working.. dammit.. Then i measured the voltages from the psu and i had both 17v lines but... the -17v was + 17v and so i have 2x +17v lines! 
Then i disconnected the -17v from the scabboard (not the pmboards) and everything worked fine again, even the channel with the scabboard came alive.. but without the -17v connected to the scabboard. Of course that channel is not working as it should but at leadt it gives sound and does compress a bit in both modes... weird..

How can a voltage which should be -17v become +17v?  ???
Anyone? i don't see the logical part of this.

So you're saying that without the scabboard connected all your voltages are fine right? You meassure -17v & +17v from your PSU with the scabboard disconnected?
If yes, problem is on the scabboard. Did you check all transistors on the scabboard? No mix-ups here?
No shorts to ground on the -17v or +17v traces?

 

[dagoose]

OK.. when i checked the board i didn't see anything wrong but when i connected it again the voltages where ok and it worked.
The only thing was that one channel was faulty, the 5534 got hot and it wasn't working so i changed all tip's and it works  ;D
So it looked like i had some faulty tip transistors, they where not mixed up or something and i didn't see a short, it just did some really weird things.
The only thing is that i blew up one of the 2n6107's on the pm board now while calibrating the voltages again.. 

Another question about the calibrating of the scamp board; you say that you have to put it into analag mode and then calibrate to 0v between the 2 pins of the attack connecter to the attack pot, am i right here? so you do that without the potmeter (stepped switch) connected or with? i have some voltrages going on there but they are hard to get to 0, it looks like i see discharge of a cap when i measure the voltage, it's really not possible to calibrate. The only thing that happens is that the VU meter is changing it's 0 position.

 

[lolo-m]

Another question about the calibrating of the scamp board; you say that you have to put it into analag mode and then calibrate to 0v between the 2 pins of the attack connecter to the attack pot, am i right here? so you do that without the potmeter (stepped switch) connected or with? i have some voltrages going on there but they are hard to get to 0, it looks like i see discharge of a cap when i measure the voltage, it's really not possible to calibrate. The only thing that happens is that the VU meter is changing it's 0 position.

Happy to know you made such progress  ...
The 0 Volts DC must be between the SCAB "TO ATTACK" pins with no signal applied in Analag's mode... My fault. I noticed and corrected my error yesterday on the first post... I'm definitively human, with all the mistakes a human being can do  :-[...  All my apologies...
You'll see, calibrating is really easy... But not to make any error be sure you can see a change turning the trimmers CW or CCW. And definitely, set it to the 0V position.

PS: As the SCAB "TO ATTACK" connector is linked to PM660 "ATTACK" connector, you can make you measures on both. They carry the same voltages.

 

[rrs]

Wow thanks lolo-m.

This works a treat. Definitly worth doing as the original was a little slow for my taste.
Thanks for the help also.

 

[lolo-m]

Wow thanks lolo-m.

This works a treat. Definitly worth doing as the original was a little slow for my taste.
Thanks for the help also.